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New scope: Celestron NexStar 8SE

September 20, 2020

London looking through the scope the first evening, when I had it on the AZ-4. His 60mm Meade refractor waits in the background.

Welp, I finally did it. I’ve been low-key lusting after one of these scopes for a few years now. Between 2007 and now, I’ve owned reflectors from 70mm to 300mm, refractors from 50mm to 102mm, and Maks from 60mm to 127mm, but I’ve never had a Schmidt-Cassegrain, and I’ve never had a GoTo scope. I figured it was time to rectify both of those omissions. What tipped my hand was the planets: I’ve had great fun these last few weeks observing Jupiter and Saturn almost every evening, and Mars on many evenings, as we speed toward opposition with the Red Planet in mid-October. Yes, the Apex 127 and the XT10 both do great on planets, but after a while I get tired of nudging them along, especially at high power. Also, the XT10 weighs about 55 lbs all set up and kitted out, and some evenings I wuss out. It will be nice to have something between the 5-inch Mak and the 10-inch Dob for those times when I want a little more oomph and a little less hassle.

If the NexStar 8SE is actually less hassle–I’m new to computerized scopes, or indeed even to motorized scopes, and my first night getting the whole system set up was not without some frustration. But I’m getting ahead of myself.

The first point in this saga is that the NexStar 8SE, like almost all NexStar scopes, and like almost all computerized scopes, and in fact like almost all scopes period, is almost completely sold out right now, from sea to shining sea. This is apparently less about the pandemic disrupting supply lines and more about a completely bonkers demand for telescopes during the era of COVID. A lot of people are looking for hobbies while they are stuck at home, and sales of astronomical gear are, well, sky-high, at least according to the vendors I’ve heard from via email or on Cloudy Nights. So it took some doing to find one. I usually prefer to support friendly local and not-so-local telescope stores like Oceanside Photo and Telescope, Woodland Hills Camera & Telescopes, Astronomics, and Orion, but none of them had the scope in stock when I was looking. Turns out, Amazon had a few, so I put in an order. Aaaaand…nothing. More than a week after I placed the order, the scope still hadn’t shipped, and there was no sign that it was going to do so anytime soon.

During the unboxing. Each big component is sandwiched in styrofoam or ethofoam, inside its own box, and all of them are in two bigger boxes. The square vacuity at the lower right held the box for accessories. Note the ruler sitting on the OTA–this is a big scope, in a big package.

Frequent commentor, sometime observing buddy, and telescope-purchase instigator Doug Rennie came to the rescue, with an AmazonSmile link to NexStar 8SEs that were said to be shipping in just a few days. I canceled the original order and tried again using Doug’s link (which is here — apparently the scope is still in stock). The scope arrived in just a couple of days, which is only surprising because the estimated delivery time was more like five days. It arrived in a big box: 3.5 feet x 2 feet x 12.5 inches.

On the day that the scope arrived, I had no way to power it. I had been planning to order a rechargeable battery pack (this one), but hadn’t gotten around to it; we were out of suitable alkaline batteries at the house; Vicki had the car to work a forensic case so I couldn’t drive to the store; and London and I were still sunburned from a trip to the beach the previous weekend so we didn’t want to walk to a store. I took a page from Uncle Rod (this post and this one) and put the C8 OTA on the SkyWatcher-branded Synta AZ-4 alt-az mount I got back when. The result looks goofy as heck but it works. At 17″ long and 9″ in diameter, the C8 is a voluminous scope, but it’s mostly air, and the OTA is not much heavier than the Apex 127/SV50 combo that I use on the AZ-4 all the time.

C8 OTA on the left, Apex 127 with rings on the right.

Here I hit a snag. The NexStar mount is left-handed, the AZ-4 is right-handed, so the C8 tube went on upside-down. That put the focuser knob above the visual back, diagonal, and eyepiece, rather than below, which was weird but not a deal-breaker. It also put the finder mount–a little Picatinny rail for the included red-dot finder–below the scope’s equator instead of above it. (I had the same problem with the Apex 127 back in the day, as discussed in this post.) I figured heck with it, I’d get by just sighting down the tube. I do it all the time with my other scopes, and it works okay.

Correction: I do it all the time with my other non-Cassegrain scopes, and it works okay because they have short focal lengths and wide fields of view. The C8 has a focal length of 2032mm and a max field of view of a little less than 1 degree. Getting the scope pointed at anything without a finder involved a tremendous amount of faffing about, like 5 to 10 minutes per object. It would have been way simpler to just mount the RDF and crouch down to use it. But like a bloody-minded fool, I persevered without, and managed to observe the following objects the first night out:

  • Jupiter – even at just 63x in not-great seeing, I caught the Great Red Spot easily in direct vision.
  • Saturn – also at 63x, immediately got 4 moons. I’m sure more would be possible on a night with better seeing. I ran the magnification up a bit, but didn’t see any more. That’s how it goes when the seeing is bad.
  • Moon – holy light-collecting area, Batman! At low power, with the entire just-past-full moon in the FOV, I heard a sizzling sound and a beam of moonlight shot out the back of my head. I ran the power up to 169x and saw subtle features in the maria that I’d never seen before, especially inside flooded craters on the margin of Mare Fecunditatis. Focus on the C8 was surprisingly snappy for a non-refractor–one second an object would be out of focus, then BAM, it was in, no question. I decided a star test was in order. But first, on the way to the pole:
  • Mars – brilliant. Even at 81x with the included 25mm Plossl, I could see a wealth of detail on the surface, including the dark triangle of Syrtis Major.
  • Polaris – used this for a star test. Happily, the collimation appears to be dead nuts on. The star test looks excellent. I hauled out a copy of Suiter’s book, Star-Testing Astronomical Telescopes, which is on loan from a fellow club member. Any problems with the optics are below the threshold of my ability to diagnose. This is consistent with the fine details and low-contrast features I was picking up on other targets.
  • Vega – I just used this to get on target at Epsilon Lyrae, but I was happy to see no chromatic aberration. I did catch just the faintest whiff of greenish-yellow on the limb of the moon, but I can’t be sure that wasn’t in the eyepiece. Long planetary and lunar sessions with the Apex 127 these past few weeks have shown me that eyepiece CA is real, and varies a lot between makes and models.
  • Epsilon Lyrae – by now the seeing had turned to crap again, at least in the west. I only ran up to 169x and the stars were still too shimmery to “black-line” split, but I was happy to see that they were elongated into little 8s at 81x, which makes me think this scope will split the Double-Double below 100x on a still night. That’s not any huge achievement, but it’s nice to know the scope is performing within expectations.

In sum, the scope is optically great. I’ve been pretty lucky with most of my scopes, but I’ve had a couple of stinkers, so it’s nice when they turn out better-than-expected, which this one certainly did.

In fact, it was a little anxiety-inducing. I really, really wanted the mount to work, too, so I’d have no reason to return the package and lose such a nice OTA. Yesterday (Thursday) I had to run some errands anyway, so I picked up some batteries. By this time I had a rechargeable external battery pack on the way, but not yet in. So I murdered some AAs to try out the mount.

The accessories that come with the NexStar 8SE. Clockwise from the upper right: a bubble level for leveling the tripod before you put on the mount and telescope; a 25mm Plossl (of course!); mirror star diagonal; and the hated red dot finder (RDF).

First thing: you really, really need a finder to get the scope aligned for GoTo. Which means the finder needs to be aligned to the scope, and I foolishly had not done that during the day. Have I ever said how much I hate, hate, hate red dot finders? My first accessory purchase for this scope, after the external battery pack, was a 9×50 RACI, again from Doug Rennie, who had gotten one for his NexStar 6SE but wasn’t using it. Anyway, after some faffing about I got the RDF on and aligned. Did a rough alignment on some distant leaves, then got it dialed in on Capella.

I had just watched a video Doug had sent on the Auto 2-Star alignment (this one), so I did that, starting with Capella. The suggested second star was Vega, which was still visible in the west. Got the alignment dialed in on Vega, then I was off and running.

First object I tried was M27. I couldn’t see a darned thing, BUT it was going down into the light dome over LA, and fighting the light of the nearly-full moon, so…who knows. After that I punched in Mars, and after the scope stopped slewing, Barsoom was in the eyepiece and looking good. Pleiades, ditto, although they spilled well beyond the sub-1-degree field of view. M34, ditto. Neptune, ditto, a tiny ball of blue floating out in the black. Then the moon, and like every one of the others, it was just about centered in the eyepiece. These objects were reasonably well-distributed over the sky, so I was pretty happy with the mount’s ability to get the scope on target. I let the scope just track the moon for a few minutes while I took some notes.

One thing–I had left the tripod legs collapsed for max stability, but even sitting down that put the eyepiece about 7-8″ lower than it could have been, and punishingly low on some high targets. I figured I’d elevate the scope a little more in future sessions. To figure out how much I’d need to raise the tripod, I punched in Aldebaran to get a low-in-the-sky target, and the scope slewed right to it. I spent a few minutes using the hand control to drive around the Hyades, looking for double stars, then stopped to write some more notes. Have I mentioned that I’m including more double stars in my observing these days? Blame the Astronomical League’s Double Star and Binocular Double Star observing programs, for acquainting me with so many fetching targets.

At this point the mount had been on for about an hour. I tried for the double star Eta Cassiopeia, and the scope drove to Cass, but not to the star. I wondered if the batteries were dying–apparently GoTos lose their minds as the power runs out–so I punched in Polaris, hoping to get one last target, but the scope slewed off to the east, in completely the wrong direction, and then stopped moving entirely. I flipped the power switch off and put everything away. The scope ran for a little over an hour on the AAs, which is in line with what others have reported. And also a fairly expensive session!

The NexStar 8SE set up just inside the garage, looking south over the car for some alignment and tracking testing.

So, the OTA was optically great, and the mount worked, did GoTo, and tracked objects. The Talentcell battery pack (this one) arrived the day after the AA-powered session. What I wanted to do was set up in the driveway for a long planetary session, to see how the mount and battery pack work during extended tracking, and to take the whole rig up the mountain soon to see how it would work on a multiple-hour session under darker skies. Unfortunately by this time ash from the wildfires was raining from the sky, and ash is hell on telescope optics, so both the driveway and Mount Baldy were out. Still, I was desperate to know how the whole rig would work together, so I set the scope up inside my garage, which has a south-facing door, and did some tests in the southern sky. After doing a two-star align on Fomalhaut and Nunki, the system was putting objects near the center of the FOV every time. I also tried a single-object solar system align on Jupiter, and that was good enough put objects somewhere in the FOV of a low-power eyepiece, and to track for 20 minutes or so, but definitely not as good as the two-star align.

Why was I pushing to get this scope and mount tested when conditions were so crappy? That will be revealed in the next post.

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Resources for Naked-Eye and Small-Scope Observing

September 12, 2020

Allan Dystrup’s Classic Rich Field, and more

A few years ago, Cloudy Nights user Allan Dystrup started a thread called “Classic Rich Field“. It’s mostly about OB associations, and the early observations were all done with a Vixen 55mm f/8 scope. Later observations were done with classic refractors of up to 4” aperture, and included night vision enhancement. The thread fired my interest in OB associations, and I admire Allan’s commitment to making detailed observations with small telescopes. Also, other experienced observers chimed in with additional information. It’s one of the best threads I’ve ever encountered on CN.

Allan also published an overview of his Classic Rich Field project in Nightfall, the Journal of the Deep-Sky Section of the Astronomical Society of Southern Africa. It just came out this summer, and it’s a free download at this link (17 Mb).

What I did not know until recently is that he has a bunch of other threads going, including “Classic Messier“, “Classic Best NGC“, “Classic Planet Observation“, and “Classic Moon“. Turns out he also has a clearinghouse page with links to all of them, which is here. Go read and be inspired.

Scott Harrington’s DSOs for Small Telescopes, Binoculars, and Naked Eyes

From the wonderfully useful site Adventures in Deep Space, check out these thoroughly awesome observing lists:

100+ Planetary Nebulae Visible with Small Telescopes & Binoculars, by Scott Harrington

250+ Deep-Sky Objects Visible with 7×35 Binoculars and the Naked Eye, by Scott Harrington

Bob King’s Night Sky with the Naked Eye

I spend a good chunk of every dark sky observing session just looking around, with no instruments. So I was excited when this book came out, I got a copy, and I love it. Of course, that was all four years ago, and you’re just hearing about it now because I’m kind of a lousy blogger. But there you go. Here’s the Amazon link.

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Observing Report: SkyScanning on Mount Baldy

September 5, 2020

Backstory: from NEOWISE to Jupiter to the stars

Since I write a monthly column for Sky & Telescope, I can’t ever just quit observing (this is a good thing). But I do go through dry spells where I only observe enough to feed the column. Other times my observing ticks up, usually when something comes along to prod me into getting out more. In July it was comet NEOWISE, then last month it was seeing Jupiter and Saturn so big and bright in the southern sky, with Mars coming along close to midnight. At the same time, I was doing some unrelated sorting and straightening in our home office and I rediscovered some unfinished logbooks for observing projects–the Binocular Double Star and Galileo program logbooks for the Astronomical League (available here), and logbooks I put together for myself for Stephen James O’Meara’s Hidden Treasures and Secret Deep. One of the Galileo club projects is to observe Jupiter’s moons for 17 nights in a row, and use those observations to determine the orbits of the moons. This is a good time of year for such a survey, because we’re pretty much guaranteed 17 clear nights in a row.

For the Galileo club, there is no limit on aperture but there is on magnification: to count, observations have to be made at 20x or lower. My longest focal length eyepiece is the 32mm Plossl, so any scope with a focal length over 640mm is out. In practice that only disqualified the XT10 dob (1200mm) and Apex 127 Mak (1540mm). The C80ED just slipped in–with a focal length of 60mm, it gives 18.75x with the 32mm EP. In the end I made a few of the observations with that scope, and a few more with the little SV50 that I mounted side-saddle with the Apex 127, but my most-used scope for the Galilean moon survey was my serendipitously-purchased and much-modified SkyScanner 100. I didn’t have time for a big observing session every night, but I could grab the SkyScanner with one hand, plop it on the hood of the truck, and be on target in about as much time as it took to compose this sentence.

During this period I was also periodically faffing about with London’s 60mm Meade refractor, and also with the 80mm “reflactor” I nicknamed the Ferret (see this post). I need to do a full writeup on that scope soon. But the point for now is that over a span of about three weeks, I was using most of the scopes in my arsenal:

  • Apex 127 for high-power views of Jupiter, Saturn, the Moon, and Mars
  • C80ED, for the same targets
  • London’s 60mm Meade, for the same targets
  • SkyScanner, for low-power observations of Jupiter’s moons
  • SV50, for the same
  • the Ferret, for evaluation purposes

About the only scopes I didn’t haul out during this period were the XT10, Bresser AR102s, and Tasco/Vixen 9VR. The upshot is that I had the opportunity to compare the SkyScanner to a lot of other small scopes, of varying designs, apertures, and focal lengths. I kept coming back to the same thoughts:

  1. The SkyScanner pulls down a lot of light; 4″ is a formidable aperture for a 6-lb scope (with mount!) that is easily carried in one hand.
  2. The focal length is short, so magnification is limited, but the images are bright and the field of view is wide.
  3. With the collimation dialed in, and at the low magnifications I was using, the images were very sharp and contrasty.

Then I realized a few more things:

  1. These are all the same attributes I love about the Bresser AR102s–which is, for its aperture, the finest deep-sky scope I’ve ever owned–but in an even smaller package, capable of even wider fields.
  2. In four years of owning the SkyScanner, I’d mostly used it for quick peeks at bright stuff from the driveway, and I’d barely used it on the deep sky at all.
  3. Despite all my yapping about small scopes (exhibits A, B, C, and D, for starters), I’d never done a serious observing program with one.

Clearly, I needed to get the SkyScanner out to a dark site and spend some time chasing DSOs. A Messier survey seemed like just the ticket, to get a handle on the capabilities of the scope, and to ease myself back into deep-sky work. Also, although I look at the best-and-brightest Messiers almost every time I’m out, the lion’s share of my Messier observations have been made in the spring, in preparation for or during a Messier Marathon. It would be nice to reacquaint myself with those objects at a different time of year.

A Perfectly Imperfect Start

Normally for deep-sky work I’d head to the desert, someplace like Anza-Borrego Desert State Park or Afton Canyon if I wanted super-dark skies, or Owl Canyon or the Salton Sea for convenient, decently-dark skies. But it’s hotter than two hells in SoCal right now–out at Owl Canyon this weekend, it’s still going to be 86F at midnight. Even here on Mount Baldy the nighttime low was supposed to be 75F, but that’s at least doable, and I’ve done plenty of observing from Cow Canyon Saddle and Glendora Ridge Road. It would work. Except that when I got up there last night, Glendora Ridge Road was closed because of the extreme fire danger, because of the extreme heat and the fact that it’s the middle of our dry season.

Oh well, no worries, I know of a couple of turnouts that are deep enough that I could set up 50-100 feet from the road, and put the scope on the far side of the truck to block most of the headlights. So I went to one of those and got all set up: SkyScanner on a tripod, binoculars to hand, charts and logbook on a folding table, plenty of water and snacks.

Then the moon came up.

Normally for deep-sky work I’d head out near the dark of the moon, but the fact is, I was impatient. So I decided to go out last night, knowing that the waning gibbous moon would rise at some point, but figuring that between the transparent mountain air, local hilltops and ridgelines to put me in shadow, and the fact that moon is waning, I’d be okay. Then I spent too much time messing around at the house, and I didn’t actually get set up on the mountain until 10:15, about 3 hours after sunset and a full hour and a half after astronomical twilight. The moon was already lighting up the ridgeline to the west, and before midnight it had crested the ridge to the east, and was falling directly on me. I could almost read the charts without a flashlight.

I had to laugh, because my very first observing session using a SkyScanner was with Doug Rennie back in 2012, when we’d been out 3 nights after the full moon. It was the same this time, almost to the minute: the full moon had been at 10:22 PM on September 1. But I was also encouraged, because Doug and I had a great time then chasing DSOs under a bright sky with a small scope. Would I be able to replicate that success?

Aside: Training the Eye vs Stressing Over Gear

Also, in general, my observing philosophy is “go for it”. Amateur astronomers can be a neurotic lot, agonizing over setups and field of view and light throughput and a thousand mechanical and behavioral minutiae to squeeze every last photon out of every last carefully-deployed dollar of gear–I know, because that’s what about half the posts on this blog are about. But there is also freedom in setting all of that aside, being grateful for optics that Galileo or Messier would have eaten their own legs off to get hold of, and just looking. So the conditions are imperfect. So your optics are suboptimal, cheap or small or chintzy or some combination of the above. What’s better, observing, or not observing? The astronomy police aren’t going to come lock you up for doing it wrong. Some of my most memorable observing sessions have happened with suboptimal gear under suboptimal conditions, which raises the question of what “suboptimal” even means in this case. Did you see stuff in the sky? Did you have fun, or find the experience educational or rewarding, or get to share it with another human being? Good enough.

Before someone misunderstands my point, I’m not saying just run out and buy any old things. As I’ve said about choosing vs using binoculars, there are loads of things you can and should consider when you purchase an observing instrument. But if you’re going out to observe, use whatever you have to hand. Don’t worry about its quality, get out there under the stars and let it show you what it can do.

A couple of quotes come to mind here. One is something I read some time ago on Cloudy Nights. I thought I had it saved somewhere, but to my immense irritation, I can’t find it at the moment, so I don’t know who said it or when. Nevertheless, it went something like this:

“I realized that most serious observers go after objects that are near the limits of their instruments. Even for a small telescope, that is hundreds or thousands of objects. And I’ve been happily pursuing small-scope observing ever since.”

EDIT: Of course, within about an hour of posting this, I’d found the quote–in one of my own previous posts! The post of mine is “Big fish with light tackle“, the quote was from CN user blb, originally posted here, and here’s what he actually wrote, quoted at a bit more length:

“No matter what size telescope you use, it seems that you are looking at objects that are on the limits of what can be seen with that size scope. Once I realized this and read, some years ago now, what Jay Reynolds Freeman had to say about his observations, I came to realize there were way more objects to be seen in a small telescope than I would probably see in my lifetime. Having come to this realization I made a list of the galaxies that could be seen in a small scope. I included all the Messier, Caldwell, Herschel 400, those listed in Stephen O’Meara’s books, and a few more that others said were possible to see and you know what? Given dark skies and good dark adaption using averted vision, tube tapping, heavy breathing and all the tricks a good deep sky observer uses, there were well over 600 galaxies that could be seen. Now that does not include globular clusters, open clusters, planetary nebula, bright nebula, reflection nebula and dark nebula. What about double stars? There are over 10,000 that can be seen in a 4-inch telescope, most of which are seldom observed. Now add to all that the ease of portability, setup, and use, you see why I have used primarily these two small telescopes the past couple of years.”

The other is from Stephen James O’Meara’s introduction to Walter Scott Houston’s Deep Sky Wonders:

“Scotty had a light touch and avoided being distracted by technical details. You don’t find any invidious comparisons of different telescope or eyepiece brands in his writing or much about the nitty-gritty of equipment at all, because Scotty knew that the most important piece of equipment was the eye, and its training the most important activity; all else was trivial by comparison. Time wasted arguing the virtues of one eyepiece over another was time not spent honing your observing skills.”

Heck yeah. Let’s go misuse a telescope!

The SkyScanner Messier Survey, Part 1

So there I was, set up on a dusty highway turnout, bathed in moonlight, about to go chase Messier objects with a scope that actually would fit in a breadbox. I didn’t want to mess with my whole eyepiece case so I’d just taken five:

  1. a 32mm Plossl for max field of view;
  2. a 28mm RKE because it’s my favorite;
  3. a 17mm Kellner I found in a box of miscellaneous astro-junk and have been evaluating;
  4. a 12mm Plossl that is wonderfully clear and sharp;
  5. and a Celestron 8-24mm zoom.

However, very quickly after I started observing I narrowed down to just two: the 28mm RKE, which gives 14.3x and a true field of just over 3 degrees, and the 12mm Plossl, for 33x and about 1.6 degrees. I don’t have a magnifying finder for this scope, and the moon was wiping out a lot of the dimmer stars, so my usual program was to use a green laser pointer to get the scope on a bright star, then star-hop from there.

And now, finally, on to my observations, mostly verbatim from my logbook. Times are indicated here and there, whenever I remembered to check. Scorpius and Sagittarius were still up when I started, but squarely in the light dome over the Inland Empire. I’d scanned them with 7×50 binos and seen nothing, and I didn’t try with the scope. Instead, I turned to the west, to catch some things before they set.

M13 – an easy catch at 14x, didn’t try at 33x. (10:45 PM)

M92 – same.

M57 – visible in averted vision at 12x with 32mm Plossl, a bit easier at 14x in 28mm RKE, easy and with a hint of donut-osity at 33x with 12mm Plossl.

M56 – visible at 14x, better at 33x.

M71 – barely there at 33x. Suspected in 28mm RKE, though. (11:20 PM)

M27 – easy in 28mm RKE even in these skies. Need to do some comparison tests from home.

M29 – easy catch in downtown Cygnus.

M39 – very easy.

Then I got up, walked around, drank some water and some caffeine, and sat on a boulder to eat a snack. Breaks like that are important in a long session. When I got back to the scope, it was time to head north.

M52 – suffering under this moonlight. Suspected at 14x, confirmed at 33x.

M31 – MUCH reduced, basically down to just the core, but the core was easy.

M32 – suspected as a fuzzy star at 14x, confirmed at 33x.

I didn’t even try for M110, it really suffers under any light pollution, including that of the moon. Instead, I tried for M76. I got to the right field, but I could see nothing at 14x. I suspected it at 33x, barely, maybe, but not enough to count it. We’ll have a rematch under better conditions.

M103 – surprisingly easy at 14x, but still not a nice as nearby NGC 663.

Here I spent some time using the Double Cluster, Trumpler 2, and the Alpha Persei Association to star-hop to M34.

M34 – big, bright, detailed, easy, even at low magnification.

At that point I’d gotten all the easy northern ones. The Pleiades were not quite up yet, on account of a close hill to the east. Instead, I turned south.

M11 – probably the worst view of it I have ever had, but it was there, at both 14x and 33x.

M15 – dead easy at 14x, even with the moon behind me shining right into the eyepiece when I move my head.

M2 – bright, easy, maybe even easier than M15. Have I been neglecting a great glob just because it’s kind of a pain in Messier Marathon season? I repeated the star hop from M15 to M2 with the 7×50 binos and again thought that M2 was a little easier catch. Definitely going to have to spend more time with this object. (1:15 AM)

On the star-hop from Sadalsuud (Beta Aquarii) to M73 and M72, I stopped at NGC 7009, the Saturn Nebula. It was visible at 14x but I had to go up to 33x to confirm that it was non-stellar.

At 1:30 I happened to be glancing at the ridgeline to the west when I saw a very bright meteor going past Saturn, from northwest to southeast. It was a fireball, and as I watched it visibly broke up into a handful of gradually-diverging chunks that individually flamed out and went dark. It was easily the best meteor I’d seen in years.

M73 – kinda stupid, since it’s just 4 stars, but not that hard. Spotted easily at 14x, but had to go to 33x to confirm that it was non-stellar.

I tried hard to get M72. I was dead on and using every trick in the book, including cupping my hands around my observing eye to bock stray light and breathing deeply, but I could only barely suspect it at 33x, and not well enough to count it. It was way down in the murk over LA and the Inland Empire. I could see the mag 9.3 star next door, but not the mag 9.4 cluster. Sometimes visibility hinges on such tiny increments (that, and the fact that the cluster’s light is distributed across its face, leading to an even lower surface brightness).

M30 – could not see it at 14x, then it was easy at 33x, and then when I went back to 14x it was tough but doable; I just needed to know where to look.

I went after M75 and after star-hopping across literally the entire constellation of Capricornus I found that it had just set–I missed it by 2 degrees, or 8 stinkin’ minutes.

Enough chasing tough stuff in the southern sky. Taurus and Auriga were up, so…

M45 – awesome, even in these bright skies. Nicely framed at 14x.

M38 – same story as M30. Could see nothing at 14x. At 33x, the cluster was not just easy, but partially resolved, with its characteristic duck’s-foot shape. Once I knew exactly where to look, I could catch it at 14x–barely.

M36 – obvious, big, even partly resolved at 14x. Great at 33x.

M37 – faint but there at 14x, as a hazy patch. Wonderful at 33x: partially resolved in direct vision, with many more stars momentarily popping into view in averted vision.

M35 – very large. Not super-obvious at 14x, but it was there. Highly resolved and quite beautiful at 33x.

Tried for M1, could not get it at any magnification. (2:49 AM)

Spent some time looking at the Moon and Mars. Mars was a tiny bright dot at 33x, with no details visible, but I didn’t feel like getting a more powerful eyepiece. The Moon looked great. I love moon-gazing at low magnification, when the whole disk fits in the field of view with plenty of space around it. It looks like a world–which, of course, it is.

The Stingray asterism, which includes the open cluster Collinder 65, traced on chart 7 from the Beginner’s Star Atlas; the latter is a free download here.

I went back to the Pleiades for what was going to be my last look before I packed up, but then I noticed that Orion was very slowly climbing over the ridgeline to the east. I cruised along the local horizon and observed Bellatrix, the Orion OB-1a association (in the vicinity of 21, 23, and 25 Orionis), Meissa, and the Stingray asterism I wrote about in the January 2018 Binocular Highlight column. Which reminds me, I should blog about a few things: Allan Dystrup’s “Classic Rich Field” posts on Cloudy Nights (here), the Beginner’s Star Atlas (here), and about the asterisms I’ve written up for Sky & Tel (uh, in the pages of Sky & Tel).

While I was waiting for Orion’s Sword to come over the hill, I got up to walk around a bit and get some circulation going. Coming back I was startled to see a large animal move out into the moonlight just 50 feet away. It was between me and the Moon, so it was just a pool of black shadow casting a smaller black shadow on the ground, but it was big. I froze. There are bears on Mount Baldy, and mountain lions. I tensed, preparing to either run for the car or at least grab the folding chair to defend myself. I needed to know what this thing was. I reached up and flipped on my headlamp, which goes red first, then to bright white light if you keep pushing the button. The red light came on and I saw two red eyes shining right back at me. Gulp! Then the white light came on and I saw that it was just a deer. Whew! My heart was still pounding. I switched the light off to stop inconveniencing the deer. It didn’t spook, and in fact it spent a few minutes just walking around out in the open, stopping to nibble a tuft of grass or a low bush now and then. The wind had died down for a moment, and the night was so quiet that I could hear its hooves softly clattering on the rocks as it walked. I felt an utterly unexpected rush of embarrassment–not because I had gotten scared, it’s perfectly sane to be alarmed when you realize there is a large animal close to you in the dark–but because I was suddenly aware that I was on the deer’s turf. It was supposed to be there, I was the interloper. So I stayed still until it wandered off.

The sky had still been turning overhead while I watched the deer–or, more accurately, the Earth had been spinning eastward, carrying me with it–and Orion’s Sword was almost over the ridgeline. I sat down at the scope and did something I can’t remember ever having done before: I watched through the eyepiece as the Orion Nebula rose over the local horizon, at 3:20 AM. The wind had come back up, and the seeing was particularly ragged in the east. I could only get 3 members of the Trapezium at 33x. I checked and I was seeing M43 as well as M42. I tried for M78 but it was a no-go. I went back to the Belt and Sword for one last look, and shut down.

Taking Stock

I set up at 10:15 PM, started the Messier observations at 10:45, and continued in that mode for 5 hours, including breaks. During that time I logged an even 25 Messier objects. I got to the right field for five others–M76, M72, M110, M1, and M78–but couldn’t see them under the conditions I had. Along the way I also observed 3 meteors, the Moon, 3 planets, 7 double stars, and 14 non-Messier DSOs, for a total of 53 objects. It was my longest observing session since the Messier Marathon in April, 2019.

The SkyScanner rocked. When I couldn’t see certain objects, I knew it was the skies, not the scope. Many objects looked fantastic despite the moonlight–the open clusters M34, M35, M37, and M45 stand out. I had never before caught the dwarf galaxy M32 in such bright conditions. Yeah, the moon was a pain, but that just meant I had to push my observing skills a little, and it made the tough catches that much sweeter. I found a few new things to write about for Sky & Tel, saw a fantastic meteor, and had a close encounter with the local wildlife. All in all, a wonderful observing session, good for the mind and the soul.

I’m going to finish the Messier survey with the SkyScanner. It’s a splendid Messier hunter–easy to use, wide field of view, and sharp enough to dial in on the tricky ones. It’s one of my favorite scopes, and easily the one I’ve recommended the most times to people thinking about a first scope. For 100 bucks you get a capable, convenient instrument. If you hate it, at least you gave observing a fair shake, and you’re not out much (compared to other available options). If you love it, it can keep you busy for a long time–potentially for a lifetime, depending on your interests–and it’s a great grab-n-go scope if you move up to a bigger instrument. It’s not perfect–I hacked the heck out of mine to make it work like I wanted it to–but I think it is probably unbeatable in terms of capability per dollar. I’m glad circumstances conspired to make me finally get one, and I expect to get many more nights of enjoyment out of it.

Until next time, keep ‘Scanning!

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Scopes you can build: AstroMedia Newtonian reflector

September 4, 2020

I just realized that although I’ve built several AstroMedia kits, I’ve never given them more than a brief mention here and there on the blog. If you’re just here for the link, click here. If you want more info and pix on AstroMedia kits and what it’s like to build them, read on.

AstroMedia is a German company that makes primarily astronomy-related kits. That’s not all they do–they also have kits to build heat engines and musical instruments, and they carry meteorological and physics gadgets like Galileo’s Thermometer and Einstein’s Drinking Bird–but as their name implies, the lion’s share of their products are related to astronomy. That includes not just telescopes, but also a sextant, a handheld spectrograph, a sun movement simulator, a working orrery that includes the Sun, Mercury, Venus, Earth, and the Moon, and other things besides. But also, telescopes, including Galilean, Keplerian, and achromatic refractors, and a Newtonian reflector.

Of the AstroMedia kits that might be used for serious (or at least semi-serious) observing, the ones that stand out are the Plumber’s Telescope, shown here, and the Newtonian Telescope. I have built both. The Plumber’s Telescope is pretty cool: it includes the 40mm objective lens, lenses to make an eyepiece, cardboard mounts for the lenses, and a wooden mounting block for attaching the scope to a tripod. The tube and the eyepiece housing are made from plumbing parts, hence the name of the scope.

I built one of these for London a few years ago–here’s a photo of him using it at the 2014 All-Arizona Star Party. At this remove, I can’t remember if the scope natively accepts 1.25″ eyepieces and accessories, or if I built London’s with that capability. I put in a 45-degree correct-image diagonal to make it more intuitive for him to use. The scope focuses with a sliding drawtube, like an old-time spyglass.

I’ve thought several times about digging this scope out of storage and giving it a whirl from a dark site, but I haven’t actually gotten around to doing that. I talk a lot about small-scope observing, but lately it’s been more mid-scope observing, with the C80ED, SkyScanner 100, and Apex 127. More on that soon, probably.

The mother of all AstroMedia telescope kits is the Newtonian Telescope, shown here in an AstroMedia photo with the optional full-aperture solar filter made with Baader solar film. I built one of these a few years ago, and documented the process in photos, I just never got around to posting about it until now.

The primary mirror is spherical, and as shipped it has a diameter of 70mm and a focal length of 450mm, for a focal ratio of f/6.4. But in the assembled kit, the outer 5mm of the mirror are masked by the telescope’s front aperture and by two additional light baffles inside, which make the operational diameter 60mm, for a focal ratio of f/7.5. This is getting up into the range where spherical mirrors perform almost as well as parabolic ones, and that factor alone might explain the decision to mask the mirror down to 60mm.

I knew right out of the gate that I wanted my scope to be a little stronger than the default cardboard tube, so I got some wooden dowels and punched holes for them in the bulkheads/baffles that separate adjacent tube sections.

Here I did a test fit of the tube, without glue, to figure out how long I needed to cut the wooden reinforcing struts. You can see a page of the instruction manual at the upper left corner. I should say here that the AstroMedia instruction manuals are in English (at least from AstroMediaShop.co.uk), and they are excellent. Very detailed, with illustrations, clearly written by people who have actually built these kits firsthand and recently. In the depressing swamp of crappy telescope instruction manuals, AstroMedia a rare point of light.

Here’s the tube going together.

And the final product. You can see a bit of dowel sticking out the back of the OTA. The primary mirror is glued (or maybe double-sided taped? I can’t remember now) to a hexagonal piece of cardboard that forms the back of the OTA. That piece of cardboard can be left loose, so that fine adjustments can be made to achieve collimation. I went a step further and made a simple collimatable cell, with push-pull collimation using three bits of dowel that stick out of holes on the back of the tube. Friction of the cardboard mirror cell against the walls of the tube are enough to keep the mirror in place once it’s collimated.

Here’s a view down the hexagonal focuser drawtube. The white circle is the reflection of the primary mirror, sitting inside a slightly larger dark square that is the flat secondary mirror on its two-vane cardboard “spider”, and containing a smaller black reflection of the secondary mirror, within which is the black and blue of the case, body, and camera aperture on my old iPhone 5c, which I used to take this photo. As you can see, collimation is not bad; everything is at least roughly in alignment.

The two eyepieces can ride in little carrels on either side of the base. The kit includes 2 eyepieces, a 15mm Ramsden (30x) and a 28mm Steinheil (16x), which is a 3-element eyepiece type I was not previously familiar with. Focus is achieved by sliding the eyepieces up and down in the focuser tube. Possibly 0.965″ eyepieces would work as-is with the scope, although you’d have to be careful about their weight either pushing down the front end of the scope or deforming the tube.

How does it work? The mini-Dobsonian mount works great, as does the straight-through peep-sight finder–at least for the bright stuff that you’ll probably use this telescope to look at. Optically, it has the limitations you’d expect from an obstructed 70mm spherical mirror in a cardboard tube with plastic eyepieces. Which is to say, it’s good enough to demonstrate the principles of a Newtonian reflector, but I’ve not undertaken any serious observing projects with it. It should be good enough for a Messier survey, for someone with sufficient fortitude. For me, it was a fun project and it looks cool on the shelf, but I’m unlikely to press it into service as long as I have more convenient options available. Also, right now the kit goes for about $27 for just the telescope, and $30 for the scope plus solar filter, so you’re not risking much if this sort of thing appeals to you.

I have heard of people buying this kit just for the mirrors, and building mini-reflectors around them using wood, plastic, metal, and more exotic materials. A few years ago I found a webpage where a group of amateur astronomers in Germany all bought these kits and formed a “70mm club”, with each person building their own take on a 70mm reflector. There were some really creative designs on that page, which to my intense irritation I can no longer locate (if you know if it or find it, please let me know in the comments!). So if you’re in the market for small Newtonian optics for a STEM project or demonstration, this kit is an inexpensive way to get a decent primary and secondary mirror set, whether or not you build it as shown.

Verdict? You have to look around a bit to get a good Plossl eyepiece for the cost of this kit, which gives you a whole working telescope. I’m a big fan of people either buying cheap astro gear and taking it apart, or building their own–even if the results are ugly, as mine often are–both to understand the principles of astronomical optics better, and to demystify the process for the day when they need to take apart a scope they care about, either to clean it or repair it. Plus this one is fun and the results are pretty cool. Recommended. Here’s the general AstroMediaShop homepage (link), the one specifically on this and other telescopes (link), and the one on the package with this scope and the solar filter (link).

skyscanner-100-before-hacking

If you have built this and want a step up, or want something like this without having to build it, the Orion SkyScanner 100 is a serious piece of kit that will show you a lot for about $100. Its elder sibling, the StarBlast 4.5, is a little bigger, a little easier to use, and a little more nicely appointed. You really can’t go wrong with either one.

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Crazy scope deal: Newegg.com is closing out the Bresser Messier AR102S Comet Edition package

August 29, 2020

Yes, the awesome RFT with the strange design and incredibly long name is still around. Amazon is selling the package for $399 (link), BUT as of right now, Newegg.com has it for just $240 (link). You have to log in to see the price, which I did before making this screenshot. Considering that the tripod is actually stable with this scope, that the binoculars are actually good (don’t tell the bino snobs, but these came-with 7x50s are my favorite low-power glass!), and the eyepiece is fine as long as you don’t look at anything bright (on Saturn, it showed CA in my Maksutov, but it’s fine for deep sky), that is a cuh-ray-zee deal. The scope itself is a fine low-power, wide-field sweeper. It’s not a planetary scope, although its planetary performance can be improved with a sub-aperture mask. But for what it’s designed for–rich-field viewing of the deep sky–it’s terrific. If someone told me I had 5 minutes to grab gear for a Messier Marathon or they’d shoot me, I’d grab that scope, the 28mm RKE, a folding chair, and a water bottle, and be out the door with minutes to spare. You can find the rest of my blatherings about this scope under this tag (link).

If you have any interest in a rich-field telescope, pounce on this deal while it’s still around.

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Summer observing: planetary nebulae

August 25, 2020

Messier and Caldwell planetary nebulae, modified from the Caldwell object star chart produced by Jim Cornmell at https://commons.wikimedia.org/wiki/File:CaldwellStarChart.svg. Both the original file and this modified version are released under a Creative Commons Attribution Share-Alike license (CC BY-SA 3.0).

This all-sky chart shows the planetary nebulae from the Messier and Caldwell catalogs. Horizon lines are for southern California for the next couple of weeks. I put this together for a little observing feature I’m writing for Nightwatch, the monthly newsletter of the Pomona Valley Amateur Astronomers. I don’t know how well this map will reproduce, which is why I’m stashing a high-res copy here, so I can link to it in the newsletter feature. I will eventually post the observing feature here, too, probably sometime next week after the PVAA members have had a chance to see it in Nightwatch.

EDIT: I’m too lazy to reformat the observing feature for the blog, but I will link to it: here you go.

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Hideously belated observing report: Mercury transit on November 11, 2019

August 22, 2020

Not a ton to say about this other than that we saw it. London was home from school for Veteran’s Day. It was sunny, warm, and bright, and neither of us fancied spending a ton of time standing in the sun, so we limited ourselves to a few quick peeks rather than continuous observation.

About the only notable thing about the transit was our observing rig, which is probably the redneckest job I ever threw together. Most of my good gear was packed away at the back of the garage and I didn’t fancy digging it out, so I taped a pair of cardboard eclipse glasses over the front of the SkyScanner 100 to create a subaperture mask, taped some spare cardboard from a torn-up Amazon box over that to block all the filter-less areas, and set the whole rig on our green-waste bin. It was decidedly low-tech, but not as sketchy as it sounds–I taped everything very securely to the tube so none of it could fall off, because the risk of direct, unfiltered sunlight through a scope is nothing to joke about. Then London and I took turns shading each other’s faces so we wouldn’t be squinting against the sun while we observed.

I didn’t take any pictures, we just watched the crisp little BB of Mercury drift across the face of the sun. The “lenses” of the solar glasses are about an inch in diameter, so basically we turned the 100mm f/4 system into a 25mm f/16 system, and a light cone that long is pretty forgiving. Which reminds me, I’ve just been reading about people experiencing a pseudo-3D “marble” effect when viewing the moon through telescopes of 40mm aperture or less. I should make a 40mm aperture mask for my C80ED and see if I get that effect.

Anyway, thus ended the transits of the twenty-teens. I was fortunate to catch them all: the Venus transit on June 5, 2012 (observing report), one Mercury transit on May 9, 2016 (observing report), and this second Mercury transit on November 11, 2019. The next Mercury transits won’t be until the 2030s: November 13, 2032 (I’ll be 57), and November 7, 2039 (64). Then 2049 and 2052, 2062 and 2065, and 2078. I’ll be 103 if I make it to that last one. The next Venus transit won’t be until 2117, 142 years after my birth, so barring some kind of technological miracle I don’t reckon I’ll be seeing another. It was a privilege to see the one that I did.

Now transit season is over for a bit over a decade, so we’ll have to find other things to keep busy with. Fortunately the sky has much to offer. Stay tuned.

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Hideously belated observing report: another Messier Marathon at the Salton Sea (from April 2019)

August 16, 2020

Although you’d never know it from the complete dearth of posting from October, 2018, to last month, I neither died nor gave up stargazing. I even had some pretty cool experiences, I just didn’t summon the energy to blog about them. I’m now going to engage in some retrospective pothole-filling, starting with my 6th and most recent Messier Marathon.

Terry getting his 5″ f/8 Meade reflector set up for an evening of deep-sky observing.

Terry Nakazono had gotten in touch and we decided to make a run to the Salton Sea on the evening of Saturday, April 6, 2019. After logging over 2000 deep-sky objects with telescopes of 4.5″ and smaller, Terry had finally allowed himself to indulge and had moved up to his 5″ f/8 Meade reflector, which he had mounted on an AZ4 alt-az.

I was feeling lazy and didn’t want to dig a bunch of gear out of the back of the garage, so I brought London’s XT4.5, which is just an astoundingly comfortable and convenient scope. It normally sits near the front of the garage and these days it probably gets hauled out more than all the other scopes we own combined, just because it’s so quick and gives such good views. If London takes it with him when he moves away someday, I will definitely get one for myself. You can see it here on the homemade stand I made for it a few years ago, to get it up to a comfortable height for seated observing.

I wanted to do a Messier Marathon, but April 6 is getting right to the end of the season, so I figured I’d have some trouble with the early evening objects like M74 and M77. In the actual event, it was way worse: between the light pollution from LA, Palm Springs, and Indio, some clouds in the northwestern sky, and some trees in that direction, I missed not only M74 and M77 but also the Andromeda galaxy (M31) and its satellites M32 and M110, as well as M33. So I started the marathon six objects down out of 110, and the best I’d be able to do if everything else went smoothly was 104 Messiers. Still, I figured what the heck, I’d done my first three marathons (linked here) without getting that many, and there was no shame in ending over 100, especially if I had an enjoyable night under the stars doing it. So I went for it.

How’d it go? Other than losing those six galaxies at the start, it was my easiest marathon ever. I had the Jumbo Pocket Sky Atlas and the Year-Round Messier Marathon Field Guide, a handwritten checklist (like my other last-minute Marathon, back in 2013), my favorite 7×50 binos, and a super-convenient scope. I only used 3 eyepieces: a 32mm Plossl for max FOV, a 28mm RKE, and a 12mm Plossl, which in the XT4.5 yielded 28x, 32x, and 75x, respectively. Once I was rolling, I used the 28mm RKE almost exclusively. The reputation of this legendary eyepiece is well-earned; for the kind of relaxed, low-power deep-sky work I prefer it is unparalleled. All the gear just sort of disappeared and I was cruising through the sky, having fun and enjoying a beautiful night out under the stars.

The dark horse: London’s XT4.5. The white knight: Terry’s 5″ f/8 Meade. Photo by Terry Nakazono.

A highlight of the evening was rocking through the Virgo-Coma galaxies. Ever since my first marathon, way back in 2010, I have always tracked how long it takes me to get through this area. That first time out it took an hour and a half, but I hadn’t logged many Messiers at that point so it was my first time seeing most of them. The next year it only took me 23 minutes, and since then it’s never taken me more than 17 or 18 minutes. My record is 16 minutes, set in 2011 with binos only, and I tied that this time out with the scope.

Our chariots to the stars. Photo by Terry Nakazono.

I knocked off at 11:30 with 64 objects logged, and slept until 3:00–easily my longest and most relaxing mid-Marathon break. I was back at the scope at 3:10 to log M57, and from then on it was smooth sailing through the morning objects. I set a new record for myself in the Sagittarius/Scutum area, logging 13 objects in 6 minutes. And honestly, a good chunk of that time was just writing them down. Once you know the positions of the objects, you can basically just sweep the scope or binos across the area and count them off as you go.

How I roll in the middle of the night: atlases and logbook on a folding table, water bottle on the ground where it’s not taking up valuable real estate. Photo by Terry Nakazono.

For the last few objects, I was basically waiting for them to crawl over the eastern horizon. Here are the times for the final five:

  • M72, 4:14 AM
  • M73, 4:15
  • M2, 4:17
  • M15, 4:20
  • M30, 4:50

Yes, I got M30, the squirrelly devil, and finished with a total of 104 objects, having bagged every single Messier beyond those six starting galaxies. In the long downtime between M15 and M30 I looked in on Jupiter and Saturn, and after the Marathon was over I plinked around in the summer constellations, checking out NGC objects until about 5:20, when the sky was getting bright. Then I hit the sack and slept for another four hours.

My log, handwritten in a Field Notes 4.75″x7.5″ notebook.

Thoughts afterward? More than any previous Marathon, this one was just fun. Maybe because I knew right out of the gate that I wasn’t going to break my previous Messier Marathon total (108 objects, in 2013 and 2016), I just relaxed and had a blast cruising around the sky. I’ve done enough Messier Marathons now that the process feels familiar, and it’s nice looking in on objects that (full confession) I don’t often check in on otherwise (looking at you, M73).

The secret to sleeping in late in the desert is to park the vehicle perpendicular to the rising sun and put your cots on the west side. That’s me sacked out closest to the truck, sleeping like a baby after a successful Marathon. Photo by Terry Nakazono.

Of course, I’m still hungry to log all 110 in one night. I think I might need even darker skies and better horizons than the Salton Sea, so I am seriously considering hauling myself eastward for the All-Arizona Messier Marathon. Maybe next spring, if this damned pandemic ever subsides.

Many thanks to Terry Nakazono for being a sterling observing buddy, and for taking many of these photos and giving me permission to post them. Until next time!

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Comet NEOWISE

July 18, 2020

I’ve been out to see the comet a couple of times now. Tuesday evening London and I went to the top of the parking garage in Claremont and caught the comet in binoculars and London’s monocular. Then yesterday evening London and I went up Glendora Ridge Road with some friends. Cow Canyon Saddle was packed so we drove another mile and a half down the road and found an empty turnout. Got up there about 8:40, spotted the comet right away with binoculars and then a minute later with naked eyes, and it just kept getting better until about 10:00 when it went behind the mountains. I did some pen sketches in my notebook while we were up there, and this digital sketch after I got back home.

If you haven’t seen the comet yet, it’s only getting better and easier now. The comet is getting higher in the sky every evening, and so far it’s staying quite bright. As the comet climbs up out of the near-horizon murk, it becomes relatively brighter against the darkening sky.

NEOWISE path traced in Stellarium - large

Here’s a chart for the next week that I whipped up using a screenshot from Stellarium (link) and finder charts from Sky & Telescope (here, here, and here)–irritatingly, some of the S&T finders don’t show many stars, and the big one that does show lots of stars lops off the Big Dipper, which is the most important celestial landmark for finding the comet right now.

NEOWISE path traced in Stellarium - bright

EDIT: only after seeing the published version of the post on the screen did I realize that the lines on my chart are pretty darned subtle. Here’s a brighter version, and below I added an inverted version for easy printing.

NEOWISE path traced in Stellarium - invert

The best tool for casual comet-watching is a pair of binoculars. Whatever you have will work. If you need suggestions on things to keep in mind when buying binoculars, see this post (link), and for recommendations on specific models, see this one (link). Why binoculars and not a telescope? First, the comet is large–the tail spans several degrees of sky. Very few scopes have a wide enough field of view to fit it all in. Because the comet is so large, you don’t need a lot of magnification–in fact, in questionable skies too much magnification can hurt, by spreading out the light of the comet and making it look less impressive. What you really need is low magnification and a wide field of view, and binoculars are perfect for that.

(If you have a scope, by all means haul it out and put it on that comet! It does look great in a scope. But if you don’t have a scope, don’t feel like you have to run out and buy one to get good views of the comet. Buying a scope in a rush is not usually a recipe for success, and binoculars will do fine here. If you are bound and determined to get a scope, I have some recommendations here [link].)

Happy hunting!

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My meteorites: moldavite (2g)

October 4, 2018

I didn’t even know moldavites existed until last year. One of the highlights of my trip to the 3RF Messier Marathon in the spring of 2017 was seeing Jeff Barton’s meteorite collection. He set it out for us to peruse one day, and it covered a classroom’s worth of tables. I barely knew from meteorites back then–hadn’t caught the bug yet–but a few things stuck in my head. One was his collection of Chelyabinsk meteorites from the 2013 airburst. Another was his collection of tektites. I knew what tektites were in general, but I’d never seen any firsthand. Jeff had a really nice, good-sized moldavite and he encouraged us to hold it up to the light so we could see that it was translucent glass. I got a few snaps of that and I definitely remembered it.

A couple of months later I was driving back from a museum visit in Mesa, Arizona, with a colleague, and we stopped for lunch and gas. There was a rock shop across the street so I thought, “What the heck” and went in. Amongst the other treasures was this little moldavite in a little display case. I checked it out carefully–there is a burgeoning market for fake moldavites, but most are easy to spot as cast glass. All signs point to it being genuine, so I bought it as a souvenir of the trip.

Fifteen million years ago, a massive impact in what is now southern Germany created the Nördlinger Ries crater, which is 24 km (15 miles) across and still up to 150 meters (~500 ft) deep, despite considerable subsequent erosion. The impact scattered showered tektites over a vast area of east-central Europe, including parts of southern Germany, Austria, and the Czech Republic. Moldavites are typically green. They draw their name from the Moldau River in the Czech Republic, where the first pieces to be scientifically described were found.

This moldavite is one of my favorite pieces in my little collection. At outreach events I encourage people to hold it up to the light, and it never fails to impress. It’s strange, but satisfying, to hold a piece of glass 15 million years old.

Before I started reading up on meteorites earlier this year, I assumed that tektites must be pretty common, since they are impact glass from big meteorite impacts, and the Earth has had hundreds or thousands of crater-forming impacts in the last few hundred million years. But most known tektites can be traced to just four impacts:

  • an impact near southeast Asia or Australia, about 780,000 years ago, that produced the Australasian strewnfield (australites, indochinites, philippinites, rizalites);
  • the Lake Bosumtwi impact in Ghana, about 1 million years ago, that produced the Ivory Coast strewnfield (ivorites);
  • the Nördlinger Ries impact in Germany, about 15 million years ago, that produced the Central European strewnfield (moldavites);
  • the Chesapeake Bay impact on the east coast of North America, about 34 million years ago, that produced a North American strewnfield (bediasites, georgiaites).

There are exceptions:

  • a Central American strewnfield in Belize, with tektites dated to 820,000 years ago, which only started to be reported in the 2010s;
  • Darwin glass, an impact glass associated with the Darwin Crater near the west coast of Tasmania, estimated to be about 810,000 years old;
  • Libyan desert glass from the eastern Sahara, inferred to be the result of an impact or airburst about 26 million years ago (strictly speaking, probably a surface melt rather than melted material thrown through the air).

If you know of a tektite strewnfield or impact glass site that I’ve missed, please let me know in the comments.