Archive for the ‘Gear’ Category

h1

Dr. Phonelove, or: How I Learned to Stop Worrying and Love Astronomy Apps

October 6, 2020

Warning: long, navel-gazey confession inbound. To wit: I used to be a bit of a snot when it came to planetarium apps. When I put together my “Astronomy Wish List for Beginning Stargazers” post back in 2014, I wrote:

Yes, you can get a free app for your phone that will show you thousands of celestial objects. If you get one with a good night-vision mode AND turn the brightness way down on your phone, it might not destroy your night vision, but it will still only show you a small slice of the sky at one time. At best, you’ll be outside under the stars and still looking at a dadgummed screen. Here’s a thought: put all the devices away, get out a lawn chair or just lie down on the grass, grab a planisphere, and spend a quiet half hour picking out the constellations. One of the chief advantages of a planisphere over an app is that you can see essentially the whole visible sky displayed at once, so you can figure out how the constellations relate to each other. 

Ugh! That was written out of ignorance and prejudice, and I cringe to read it now. Especially the bit about how an app would supposedly only show “a small slice of the sky at one time”. I didn’t own a smartphone at the time and I hadn’t actually used a planetarium app, I’d only seen other people use them, so I didn’t know about using two fingers to zoom in and out, which by now has become such second nature that it’s like looking back and realizing I didn’t know how to turn a doorknob.

My favorite constellation: Cassiopeia.

In any case, no, every planetarium app I know of will show as much or as little of the sky as you want. And most offer a red-based night vision mode for preserving your dark adaptation, which combined with the native screen brightness controls and night vision modes on most smartphones mean that you can use the apps under dark skies without sacrificing all your dark adaptation. (Another easy solution: close your observing eye when using the phone, and ask any companions to look away.)

So what pried me out of my self-dug hole of stupidity regarding astro apps? Direct experience. In 2015 I got my first smartphone, and in 2016 I got the job of writing the ‘Binocular Highlight’ column for Sky & Telescope magazine. I decided it was time to drag my ass into the 21st century, and since I was finally in a situation in which stargazing was bringing in money instead of consuming it, I could afford a decent astro app. I went with SkySafari 5 Pro, and it didn’t take long for it to eclipse almost all of my other astronomy tools put together in terms of how often I referenced it and how much I relied on it. Four years later, I’m on to SkySafari 6 Pro, and I’m sure that when 7 is released I’ll trade up.

For the Binocular Highlight column, we plan for and illustrate a 5-degree circle, and the ability to zoom the SkySafari screen to show a 5-degree field is extremely useful for planning my observing and my writing.

Also, I started noticing at public outreach events and star parties that basically everyone else was using planetarium apps. For people just starting out, they offer a ton of functionality that a planisphere doesn’t. Allow me a metaphor. I firmly believe that Wikipedia is how encyclopedias are supposed to work, and that the beloved World Books and Encylopedia Britannicas that I grew up with were about the best possible implementations of that idea in paper, but hobbled by not having hyperlinks, not being available via wifi, not being continually updated, etc. Similarly, even thought I love planispheres, I can admit that they are basically physical planetarium apps that restrict you to one latitude, one magnification, and a tiny subset of stars and deep sky objects. The digital apps are more intuitive, period, and not just for beginners. Experienced folks use them all the time, too, and for the same reasons: faster, easier, more information. Nowadays I find myself hauling out my phone almost every observing session–to check the positions of Saturn’s moons, or the classification of the components of a double star, or, most often, simply to find the distance to a celestial object.

I’ve enjoyed chasing the moons of Saturn this summer, and SkySafari has been clutch for making identifications — only after I’ve made my own sketches, to avoid spurious detections.

My app use in the field took another jump when I got the NexStar 8SE. Before I got that scope, I was pretty darned proud of my knowledge of the sky. I didn’t quite know all the Messiers by heart, but I could find probably 3/4 of them without even checking an atlas. But the NexStar taught me a hard truth: I may know most of the constellations backwards and forwards, but I know very few stars by name. Caph? Nunki? Alpheratz? Might as well be Farsi, Swahili, and Linear B to this monolingual doofus. So when it comes time to find alignment stars, out comes the phone, because with a handful of exceptions–Polaris, the Summer Triangle, the Winter Hexagon, and a few favorite doubles–I don’t know what these darned things are called.

Oh, hey, there’s Nunki!

(Aside: in a way, this reminds me of what it was like when I first started stargazing in the fall of 2007. Every month, new stars and constellations were up in the eastern sky. I still remember vividly the first time I got up before dawn to see the spring constellations. I’ll get a taste of that in the coming year, as I have to keep familiarizing myself with new alignment stars.)

So to sum up, actually using planetarium apps myself, and seeing how much they opened up the sky to other people, forced me to belatedly pull the stick out of my butt.

The bright, popular double star Eta Cassiopeiae consists of a Sun-like yellow main sequence star and an orange dwarf, which lie only about 19.5 light years from Earth. I didn’t know that until the star party at the park last Saturday, when someone asked if the Eta Cass companion was a red dwarf, and I was able to look up the answer in SkySafari.

There’s another, larger point, which is that I think it’s stupid to criticize how anyone else enjoys the night sky. I’m glad I missed the GoTo wars of the 90s and early 2000s, and I have no time for the limited conflicts that are going on right now over Electronically Assisted Astronomy–essentially, looking at the night sky with night-vision googles, with or without a telescope–and smart telescopes like the Stellina and eVscope. It was always pretty selfish and short-sighted to worry about how anyone else was engaging with the night sky. It’s not like people who have different preferences regarding their gear or observing habits are hurting anyone. Surely we should be able to focus on what matters–our shared love of the cosmos, and getting out to enjoy it–and not whether anyone else is doing stargazing the “right” way. And that’s especially true now, in a year that sees the world shambling among catastrophes like a shell-shocked orphan. With all the horribleness going on, I just don’t have it in me to be upset at other people when they’re not hurting anyone else, especially over something as innocuous and ultimately positive as stargazing.

To the (near) future: the moon will visit Jupiter and Saturn on the evening of October 22.

So I say, bring on the technology. Cameras, electronic eyepieces, smart scopes, light enhancement devices, and the things that no-one has yet thought of. There is plenty of room out there in the dark for those things to coexist with traditional stargazing, and if they bring a few more folks into this wonderful pursuit, so much the better. If the expense bothers you, go look at what people spend on boats and motorcycles, let alone gambling and drugs, and also, check out what serious astrophotographers spend on the rigs that get their photos into Sky & Tel and Astronomy, and also, seriously, just mind your own beeswax. If dealing with the computerized gizmos isn’t your cup of tea, or you feel like using night-vision goggles is cheating, fine, I’m pretty sure no-one will ever force you to use them. I’m also pretty sure that no matter how fancy the hardware and software gets, there will be times that I feel like heading out with nothing but a manually-driven scope or some trusty old binos for “unplugged” observing. But I’m going to try to not close myself off to any more observing experiences a priori, without even trying the new things to see what they have to offer. That was dumb.

h1

Unboxing fest, part 2: Celestron f/6.3 focal reducer-corrector

October 3, 2020

Even before I had decided to get the NexStar 8SE, I knew that if I got a big SCT, I’d want a focal reducer-corrector for it. SCTs and Maks have secondary mirrors, which partially obstruct incoming light. This implies a necessary tradeoff: make the central obstruction small, which results in a long focal ratio–typically f/10 to f/15 for commercially-available SCTs and Maks–or get a shorter focal ratio by using a larger secondary mirror, which blocks more light and degrades the contrast.

There is a third solution, which is to use a focal reducer to make a steeper light cone and a shorter focal ratio. Astrophotographers use these all the time to making their scopes optically ‘faster’ so they can get brighter images with shorter exposure times. For SCTs they are useful because they bring the focal length of the scope down to something more reasonable, and increase the true field of view. As shipped, the Celestron C8 OTA has a focal length of 2032mm, so even a 32mm Plossl gives 63.5x, and the included 25mm Plossl gives 81x. The max true field of view with 1.25″ eyepieces is about 0.7 degrees, which can be a little claustrophobic. You can juuust fit the Double Cluster in a 32mm Plossl, as long as you don’t mind clipping the edges of both clusters. You can get M81 and M82 at the same time, as long as you don’t mind parking them on the extreme edges of the FOV.

The Celestron f/6.3 reducer-corrector turns the C8 from an f/10 to an f/6.3, with an effective focal length of 1280mm, which is pretty close to the mid-sized commercial Dobsonians–the XT6, XT8, and XT10 and equivalent models from other companies are all 1200mm scopes. That pushes the max true field to something like 1.2 or 1.3 degrees, which is a big jump over the native 0.7 or so. That’s enough to put some of the larger celestial objects, like the Pleiades and M44, back in a single field of view, although the Pleiades will be cutting it mighty fine (I will test this and report back!).

As the name implies, this unit is not just a focal reducer, it’s also a corrector, which makes the field flatter for better image correction across the entire field of view. In other words, stars at the edge of the field should still look round with this thing in, as opposed to oblong. This isn’t a factor for me–I don’t photograph stars, and the stars at the edge of the field in the C8 haven’t bothered me so far–but it’s nice to have if either of those things change.

Here’s the gizmo, out of its (unsealed) bag, with its custom dust caps. I got mine from Astronomics (here), and evidently it was one of the last they had, because the availability listing there says “More on the way”. Amazon has it, too (link), I just like supporting brick-and-mortar telescope stores and specialized astro-gear dealers whenever I can.

Why am I bothering to do an elaborate unboxing post for such a trivial piece of gear? Mostly because it took a lot of digging for me to figure out how one was used. What I wanted was a photo essay that showed how “this part goes here, that part goes there”. When I couldn’t find one, I decided to create my own.

Here’s how the NexStar 8SE OTA comes as shipped, with a 1.25″ visual back on the rear port. When I was first getting into this, it took me forever to understand what a “visual back” was. Did it mean anything other than the bit where you stick the eyepiece or diagonal? And if not, doesn’t every telescope have one?

The answer is that not everyone sticks an eyepiece or diagonal at the back of a scope. Some people put a camera, or a spectrograph, or who knows what else. So if you are going to use the scope visually, you need a doohickey that holds the eyepiece or diagonal, and that’s the “visual back”. It was just new to me because non-SCTs aren’t generally described as having a “visual back” (some high-end astrograph refractors excluded), they just have focusers.

ANYWAY, the focal reducer-corrector threads onto the rear port of the scope, after the visual back has been removed.

Then the visual back screws into the focal reducer.

Then you put eyepieces or diagonals into the visual back, as usual. Everything is just scooted back 3/4 of an inch or so by having the focal reducer interposed between the scope and the visual back.

Incidentally, this is something to keep an eye on for NexStar users: when the scope is pointing high, the diagonal already comes pretty close to the base of the mount, depending on how far forward the OTA is scooted in the dovetail clamp. I’ll have to mess around with the system, but I might have to start mounting the scope a smidge farther forward to make sure the diagonal clears the mount when observing up high.

And here’s where the last post and this post come together: the Baader Hyperion 8-24mm clickstop zoom eyepiece, riding in an Astro-Tech dielectric diagonal, inserted in the stock 1.25″ visual back that came with the C8, screwed into the f/6.3 focal reducer-corrector. All saddled up and ready to go (er, minus the finders). Now all I need is for night to fall.

I have one more piece of gear to write about, but it hasn’t come in yet, so the next post might be an observing report–hopefully, a first-light report on the focal reducer and the Baader zoom. Stay tuned.

h1

Unboxing fest, part 1: Baader Hyperion 8-24mm clickstop zoom eyepiece

October 3, 2020

It has been a long, long time since I got a new eyepiece. Three and a half years since I got my Edmund 28mm RKE, and just under five years since I got my Meade 5mm MWA, which was the last “premium” eyepiece I picked up (the 28mm RKE is one of my all-time favorites and most-used eyepieces, but at $85 I don’t think it counts as “premium”–for however much or little that is worth!).

I have been wanting to try this Baader zoom for years and years. It has an almost unbelievably positive reputation on Cloudy Nights, where at least some observers report selling off a lot of their premium fixed-focal-length eyepieces after acquiring the Baader zoom.

Does it really live up to the hype? Thanks to a bolt of consulting money coming in last week, I’m about to find out.

I found it in stock at Woodland Hills Camera and Telescope, and one arrived on my doorstep a couple of days later, extremely well-packed. Since I ordered mine, Woodland Hills seems to have run out of the standalone eyepiece, although they still offer it bundled with the matching 2.25x Baader barlow, which I skipped, for a little more dough (here). Amazon has it in stock, but for a little more than most other outlets–$325 right now, versus $289 or so most other places (here).

There’s no instruction book inside the box–the box itself is the parts inventory and instruction manual. I really dig this. I think every other eyepiece I’ve ever owned has come in an unadorned box, some of them quite fancy and nice enough to repurpose as gift boxes for birthdays and holidays (looking at you, Explore Scientific). This box is functional. Every surface is illustrated, and most of the sides show you how to use the eyepiece in various situations.

Even when you open the box, there are more instructions on the newly-revealed surface! Who does that? As a catalog-junkie who likes looking a photos of gear, this box ticks all my, er, boxes.

Now this is kinda awesome, and kinda hilarious. Instead of coming in a bolt case, like my two Bresser eyepieces; or clamshell foam, like all of my Explore Scientifics; or a sturdy plastic can with a screw-on lid, like the Celestron 8-24mm zoom; or just dust caps inside the cardboard box, like all of my Orion eyepieces, the Baader Hyperion 8-24mm clickstop zoom comes in a rugged nylon pouch with a velcro closure and–as you can see in the inventory photo on the side of the box–a belt strap. And it’s high-visability yellow so you won’t lose it.

This is pretty cool, and definitely functional, and also amuses the heck out of me. This is the kind of case I expect for a multi-tool, or a handheld GPS unit, or some other thing you might take hiking, not a telescope eyepiece. I guess if you ever wanted to bushwhack across Utah or Patagonia with a high-end telescope eyepiece on your hip, or clipped to the side of your pack, now you are prepared. I imagine I’ll keep mine in my eyepiece case, like any normal person.

Here are the eyepiece and the extra bits, out of their respective bags. The four things in the extra bag are (clockwise from top) the winged rubber eyecup, the fold-down eyecup, the spotting scope adapter, and the dust cap that goes with the fold-down eyecup. The eyepiece itself comes in the bag with the larger dust cap on top of the adjustable eyecup, which rotates up and down, and with the 2″ adapter and its dustcap on the bottom end.

I should mention right here that both plastic bags were open, not sealed, which is good, because it prevents dew formation. The one for the accessories had one of the little silica gel packs, which I always steal to throw in with my meteorites. (Note to self: blog about new meteorite storage system soon.)

Pull the dustcap off the 2″ adapter and you find inside the smaller dustcap on the 1.25″ adapter. You could use the eyepiece in a 2″ focuser or diagonal with both the 1.25″ and 2″ adapters in place, and I’m not sure if there’s any benefit to taking the 1.25″ adapter off.

Here’s the adjustable eyecup in the down position…

…and twisted up. I’m a fan of these things–I notice that civilians are much less likely to stab the eye lens with a greasy finger* if there’s something in the way. Plus it’s nice to be able to signal to people where they should put their eyes, something that can be surprisingly tricky with eyepieces that have long eye relief.

* I’m not mocking n00bs or people who come to public star parties. To astronomical optical surfaces, all fingers are greasy.

Here’s the Baader compared to my Celestron 8-24mm zoom. The Celestron has been in service for a few years and eventually the knurled rubber wrap around the middle of the eyepiece split and fell off, which doesn’t impact the function whatsoever.

I like the Celestron a lot. It’s been one of my most-used eyepieces, and along with a 32mm Plossl it is hands down the eyepiece that I’ve recommended the most. Long-time readers may recall that when I flew to Texas in 2017 for the Three Rivers Messier Marathon, the only eyepieces I took were the 28mm RKE and this Celestron zoom, and they proved to be all the eyepieces I needed.

In fact, it was my positive experiences with the Celestron zoom that convinced me to venture the money for the Baader zoom. I rarely splurge like that for a piece of gear in a class I’ve never tried. In normal times, the Celestron zoom runs $65-$75. With the temporary shortage of astronomy gear because of increased demand during the pandemic, the price has spiked a bit, at least at some retailers. I see it going for just over $90 at Amazon (link).

If I have one knock on the Celestron zoom, it’s that it is ever-so-slightly less sharp than the best of my fixed-focal-length eyepieces. The difference is subtle–I would not have been able to spot it in my first 3-4 years of observing, and even now it takes a determined effort for me to see it–but it’s there. (As always, your eyes, your experience level, and your sample of this piece of equipment might vary from mine, and probably do.) Which is another reason I wanted to try the Baader, with its sterling reputation for clarity and sharpness. If it lives up to that, I will be using it a lot.

I haven’t pulled out a ruler, but the eye lenses of the two zooms look about the same size.

My kitchen scale says the Baader zoom weighs 10.4 oz, or 296 grams.

And the Celestron zoom weighs about 3/4 as much, 7.7 oz or 218 grams. I was pleasantly surprised by the lightness of the Baader; at least to me, it looks like it might weigh a little more.

With any luck, I’ll have a first-light report along soon. And there’s more unboxing coming soon–stay tuned!

h1

Why I prefer RACI finders to straight-through finders and red-dot finders

September 26, 2020

My Orion 9×50 RACI finder mounted on my son’s XT4.5, at the Salton Sea.

Intro

A commenter on the last post asked why I hated red-dot finders. I wrote a short comment by way of explanation, but I realized that I had a lot to say on this issue, so I’m coming at it again with a full post.

Right off the bat we need to get something straight, and that is the difference between facts, on one hand, and preferences or opinions on the other. If I say that red-dot finders tend to be smaller and lighter than magnifying finders, or that straight-through and red-dot finders require users to put their heads lower than right-angle finders, those are statements of fact. I may be right or wrong about them, and if I’m wrong, I expect to be corrected. If I say that I don’t mind the extra weight and bulk of a magnifying finder, or that I hate crouching to look through a finder, those are my preferences. I can’t be wrong about them, any more than I can be wrong about liking egg salad and long solo drives. If you have different preferences, great! You can’t be wrong about them, either. It’s a big world, and there’s room for all kinds of preferences. Where we often get into trouble is when we (a) mistake preferences for facts, and (b) expect others to fall into line with our preferences. Maybe egg salad and RACI finders just aren’t your cup of tea. That’s fine, I can’t tell you that you are wrong.

So I will try to be as clear as possible in this post between the objective facts and my subjective preferences, and I expect to be called out if I get any facts wrong, or get any of those facts and preferences on the wrong side of the line.

With all that in mind, here are some issues that arise when we consider finders:

  1. Straight-through versus right-angle viewing
  2. Magnification
  3. Size and hassle
  4. Longevity

1. Straight-through versus right-angle viewing

The main difference in preference here seems to come down to just a handful of things: with a straight-through finder, whether magnifying or non-magnifying, you’re looking in the same direction as the telescope tube is pointed, which some people find more intuitive, and if you want you can use both eyes and overlap the image through the finder with the image through the other eye, whereas with a right-angle finder you’re looking in the same direction as the telescope eyepiece, which typically requires less head and body movement, and less crouching to get your head down behind the finder.

Sighting down the tube of my Apex 127 to get the finder aligned, using the top of a palm tree as a target.

One criticism that might be leveled at right-angle finders is that people using manual mounts often end up sighting down the tube anyway to get the scope in the right neighborhood, and as long as you are down there with your face against the tube, you haven’t actually saved yourself any ergonomic benefit over looking through a straight-through finder. My counter is that I’ve gotten good enough at “shooting from the hip”, just aiming the scope up at the patch of sky I want without sighting down the tube, that I can almost always put the target somewhere in the field of view of a 9×50 RACI finder. So I hardly ever sight down the tube. I realize that’s a personal experience and preference, not a universal one. (You can also get away from sighting down the tube by using a laser pointer as a finder, as discussed below.)

I prefer to sit when I observe, and I often observe things when they are high in the sky, and there’s no getting around the fact that if you do those two things, using a straight-through finder means crouching or kneeling on the ground. The only ways I know of to get around that are (1) putting the scope higher, which means either standing or using a really tall observing chair, (2) not observing near the zenith, which means giving up the darkest part of the sky, or (3) using go-to, where you only need to use the finder at all during setup, assuming the alignment is good and the pointing is accurate.

2. Magnification

Some people prefer magnifying finders, and others don’t. I prefer them, for a few reasons. First, a magnifying finder offers an intermediate step between naked-eye and ‘main telescope’ viewing, which I find especially useful for star-hopping. Particularly in dark areas of the sky, or under light-polluted conditions where big areas of the sky have all the naked-eye stars wiped out of visibility, I often need something between my eyes and the scope to help me get on target, even with the aforementioned sharp-shooting. Not everyone does, so that counts as a preference.

The Apex 127 with a little SV50 mounted as a luxo-finder and mini-RDF. The wide-field, low-power views in the little refractor complement the narrow-field, high-power views in the larger Mak.

I have also come to appreciate using a magnifying finder as an observing instrument in its own right. The finder offers a larger true field for big objects that might not fit in the FOV of the scope, and under sufficiently dark skies the finder serves as a miniature rich-field scope. From the Salton Sea, Anza-Borrego, and dark places out in the Mojave, Utah, and the Oklahoma panhandle, I’ve seen virtually all of the Messier objects in a 9×50 finder. As an enthusiastic binocular observer, I think of a 9×50 finder as a 9×50 monocular that I can park, and which I don’t have to worry about holding steady. I also find a magnifying finder useful for educating newcomers—I can have them compare the views in the finder and the main scope to learn about the tradeoffs of light gathering, magnification, and field of view.

3. Size and hassle

Here the point goes to the red-dot finder, and in fact most non-magnifying illuminated dot or ring finders. Even Telrads are voluminous but not heavy. So if size and weight are considerations, the RDFs come out ahead.

Also, dot- and ring-finders can typically be aligned with just two or three adjustment knobs. The spring-loaded finder brackets used for a lot of magnifying finders these days are equally easy to adjust, but the older two-rings-with-three-screws-each setups can be pretty tricky by comparison. They’re not exactly hard, especially once you get used to them, but they have a slightly steeper learning curve over the very simple alt-knob-plus-az-knob alignment of most red-dot finders.

I’ll say this for RDFs, they are much less hassle when you’re trying to balance a scope.

4. Longevity

Red-dot finders require batteries. So do illuminated magnifying finders, but non-illuminated magnifying finders don’t, so that’s a slight convenience win for them. More seriously, in my experience red-dot finders are the component of a modern scope with the shortest lifespan; in fact, they’re the only component that usually wears out at all (although reflectors eventually need their mirrors recoated). We use Orion StarBlast 4.5 scopes in the Claremont Library Telescope Program, which has been running so long now and with so many scopes that I have about 20 cumulative telescope-years of experience with that model. The RDFs always fail early in the lives of the scopes. After a couple of years of trying to fix or replace them, I started pulling the batteries and rewrote the instruction manuals to direct people to use them as peep-sights, and that has solved the problem to everyone’s satisfaction. So at a base level, I don’t trust RDFs because I expect them to eventually fail, and that’s not something I feel about any other piece of kit that I own or work with.

I see you, red-dot finder, but I don’t trust you.

The third way: what about laser pointers as finders?

I have to admit, I use a green laser pointer a lot as an auxiliary finder. Several manufacturers make GLP mounts that can be precisely aligned with the main scope. I tend to just pull my GLP out of my pocket and slap it alongside any straight edge on the telescope, mount, finder base, or focuser, and that’s good enough to get the 9×50 RACI on target–or the whole scope on target, in the case of the SkyScanner, which I modified with a bespoke wooden trough to hold a GLP. On my other scopes, I can do without a mount for the GLP precisely because I use a magnifying finder, which takes over where the rough laser alignment leaves off. I can certainly understand, though, why some people prefer permanently-mounted GLPs as finders, and if I didn’t like using mine freehand so much—or if I was willing to buy a second one—I’d be awfully tempted to do the same. I wouldn’t give up a magnifying finder, though, so I’d have to dual-mount.

Cheap GLP in the wooden trough I built for my SkyScanner 100. I got the idea from fellow PVAA member Ken Crowder, who had done something similar for his 8-inch SCT!

Conclusion

In summary, I don’t like the ergonomics of any straight-through finders, red-dot or otherwise; I don’t trust the longevity of the cheap came-with red-dot finders, and I’m unwilling to invest in better ones because of the ergonomic issues; I strongly prefer to have a magnifying finder as a second telescope mounted alongside the first; and I don’t mind the extra size, weight, and hassle that comes along with 50mm finders in particular. In fact, if 70mm and 80mm finders were cheaper, I’d probably have them sprouting from my telescopes like mushrooms. A 9×50 RACI finder was the very first add-on I got for my first telescope back in 2007. I’ve moved it around as needed to almost every other scope I’ve owned, so I’ve been using one for so long now that if I don’t have one on a scope, it feels like I have a limb missing. (The SkyScanner 100 gets a pass here, because with a 32mm Plossl in the focuser, the scope itself serves as a 12.5×100 right-angle finder, albeit with an inverted image, and the same goes for other super-widefield scopes like the Bresser AR102S.)

Every one of those things is a preference, not a fact. Obviously many other folks have other preferences—just witness the devotion to Telrads, which IMHO are about 10 times as large as they should be to do what they do. And using my new NexStar 8SE is gradually eroding my hate for RDFs. I have to grudgingly admit that the RDF is a handy tool for the initial 2-star alignment, especially because I tend to select alignment stars near opposite horizons, so I don’t have to crouch too much to use the RDF. I still do the first round of centering using the Celestron illuminated 9×50 RACI that I bought from Doug Rennie, and I check the finder on about half the targets just to see what they look like in the smaller instrument. But the RDF is clawing for a place in my kit, and possibly when I’ve used one as much as I’ve used a 9×50 RACI, my preferences will have changed.

What do you roll with, and why? The comment field is open.

h1

Anyone tried the AstroBox yet?

June 5, 2017

http://www.astrobox.rocks/

Just learned about this. Am seriously considering springing for the eclipse box. If I do, I’ll post a review when it comes in. If you or someone you know has gotten one of these, lemme know how it worked out.

h1

Young crescent moon, pleasant surprises, the Bresser gets a name

March 1, 2017

earthshine-feb-28-2017-450

Got out tonight for a few short burst of observing amidst other things. I set up the C80ED and caught the young crescent moon as it was going down. Above is my best shot. It is still wildly inferior to the one I have up in the banner image, to the right of the blog title. That one I shot with my XT6, which had about three times the light gathering ability and almost twice the angular resolution of the C80ED, and I got that shot one night earlier in the lunar cycle. That was back in the early days, when we were still living in Merced. From my driveway I had a straight shot almost to the horizon, so I could catch a 2-day old moon. Here I have lots of trees and buildings in the way, so I generally have to wait an extra night to get a shot at the moon from the driveway.

Then I was out again in the half hour before midnight to try some things with the Bresser Messier AR102S Comet Edition. First, I put it on the lightweight Manfrotto CXPRO4 tripod and DwarfStar alt-az mount that I have previously only used for much smaller scopes (example 1, example 2). Orion was going down over LA so it was pretty stinky, but I still had a long look at both the belt and the sword, and I powered up to split the Trapezium and Sigma Orionis. Then I swept up to hit M35 in Gemini, then back down to Meissa at the ‘head’ of Orion. I finished on Jupiter, using the 60mm aperture mask to knock down the CA.

bresser-on-dwarfstar-1

I was deliberately bouncing around the sky, looking at a variety of targets at a variety of magnifications, to see if the Manfrotto/DwarfStar combo would keep up. I’m a pretty forgiving observer – witness my near-pathological devotion to cheap scopes and stuff made out of junk – but one thing I just can’t handle is an undermounted scope. My first Mak was a 4″ which I hated and sold away before I realized that I hated it because I’d never put it on a solid mount. That experience left me traumatized when it comes to rickety mounts.

The Bresser/Manfrotto/DwarfStar rig doesn’t look like it should work. It looks like the definition of a spindly undermounted disaster. But it was fine. I never had any problem slewing, tracking, or focusing. It helps that the Bresser is lighter than it looks, and carbon fiber is a lot stronger than it looks.

(In the photo, I have the optional eyepiece rack attached to the DwarfStar – I don’t think I’ve ever shown a photo of the mount with it in place. It’s useful.)

I was also pleasantly surprised by the views I got of Jupiter. To get to a decent magnification I used the 8.8mm ES82, both natively (52x) and Barlowed (104x), and a Celestron 8-24mm zoom dialed down to 8 (57x). In both eyepieces I could see the North and South Equatorial Belts and stacks of minor belts marching away toward the poles. There was some CA, but I could minimize the effect by keeping Jupiter in the center of the field, and my eye centered over the eyepiece. The view was so good that I slipped out of gear testing mode and just stared for a few pleasant minutes. I was also happy to find that with the rubber eyeguard removed, I could see the entire field of the 8-24mm zoom at all magnifications while wearing glasses. Which I have to do now. In fact, the other night at the Salton Sea I made almost all of my observations with glasses on.

And lastly, the Bresser Messier AR102S Comet Edition – whew! – finally has a name. I posted on Cloudy Nights about the Messier survey I’m starting with it (thread here), and CN user ‘Glob’ wrote,

mwedel, I read and enjoy your blog, let me suggest nicknaming the 4″ “The Ferret” as King Louis XV called Messier.

I responded:

That is a lovely suggestion, and it put a huge smile on my face. One thing I haven’t blogged about yet is that basically by serendipity I managed to pick up an 80mm prototype of the Bresser ‘reflactor’. So now I have two, big and little, otherwise nearly identical. Ferrets are mustelids (weasel family), along with wolverines, badgers, skunks, fishers, martens, stoats, weasels, and otters. My late grandfather was an accomplished taxidermist and one of his stuffed badgers is sitting on top of a bookcase about four feet from me as I type. It’s just about the same size as the 4″ reflactor. So I’m going to take your charming suggestion, with one modification: the 80mm will be the Ferret, as I anticipate some effort to ferret out all the Messiers with it, and the 4″ is henceforth the Badger, because it can just knock them around with all that aperture. Thanks for helping me solve that long-standing and vexing problem!

So, it’s official now: from now on, the Bresser AR102S is the Badger, and the 80mm will be the Ferret. More info on the Ferret one of these days. I’m going out with this family photo of the two – Badger’s up front, Ferret looms behind:

bresser-ar102s-comet-edition-and-80mm-prototype-1

h1

From sub-aperture mask to replacement dust cap

February 23, 2017

aperture-mask-2-4-length-comparison

Here’s something dumb. The Bresser AR102S Comet Edition is optimized for two things: widefield, low-power scanning, and portability. At 20″ for the OTA it’s just within the bounds of airline carry-on-ability, but you can unscrew the dewshield and shave off another 4″, at which point the options for storage and transport expand wildly.

BUT the stock dust cap for the objective is dome-shaped, for no good or obvious reason, which means it sticks out about a full centimeter longer than necessary. When you’re thinking about flying with a scope, that is one centimeter more stupidity than you should have to put up with.

There’s another problem with the stock dust cap: when the scope gets cold, it gets loose and falls out easily. Nothing unique to this scope about that – I’ve had to shim the majority of my scopes’ dust caps for the same problem, including the C80ED and XT10. One cheap package of sticky-back green felt has kept me going since 2010. I think I’ve used almost a third of it.

Now, I already have a nice 60mm sub-aperture mask for this scope (construction details here). If I could plug the central hole securely, I’d have a replacement dust cap that would be shorter, would get tighter rather than looser if it shrunk in the cold, and would serve double-duty as both a dust cap and a sub-aperture mask. The problem was finding a plug the right size, with a good lip on it to keep dust out, that would grab the edges of the mask hole securely.

aperture-mask-2-1-tootsie-roll-can

And it’s the dollar store to the rescue again, with this container of Tootsie Rolls that is intended to double as a coin bank. The hard plastic lid snaps down into the cardboard tube very securely, and the plug bit is just a shade over 60mm in diameter.

aperture-mask-2-2-external

I used the Dremel and some sandpaper to enlarge the hole in the sub-aperture mask ever so slightly, and voila. There’s a small lip that runs around the top edge, and even a little recess in which to hook a finger and pull out the plug.

aperture-mask-2-3-internal

Here you can see the ridges on the plug. By sanding in short increments, I was able to fine-tune the hole diameter until the plug snapped in very securely, without stressing either piece. I need to put some tape or a little epoxy or something over the perforated slot, which is intended to be punched out so the candy container can become a coin bank. Or cut out the center and replace it with another, smaller plug, so I’d have a dust cap and two aperture masks in one package…

aperture-mask-2-5-dust-cap-replacement

Boom. Now the scope is a centimeter shorter for travel, and I don’t have to keep the sub-aperture mask in my eyepiece case.

What I really want is for someone with even rudimentary 3D modeling skills to create a series of nested aperture masks, like Russian dolls, in 10 or 20mm increments, which could be 3D printed on demand in whatever combinations people needed. Most of them could be standard sizes, with only the outermost adapter for each telescope model needing to be custom. Then you could order the adapter for your scope and whatever set of nested masks you wanted, or maybe all of them to simplify, so your 100mm scope could also be an 80mm, a 60mm, a 40mm, and even a 20mm (the “Galileo model”) if you liked, just by taking out the relevant bits from the dust cap. Sure, it would be gross overkill for most people, but for those of us who like playing “what if” (“what if my C80ED was a C40ED?”) it would be a godsend. And with 3D printing no-one would be stuck with a bunch of useless stock when the idea inevitably bombed.

Anyway, if someone would to that, it would save me the trouble of building my own “Mask-ryoshka” dust cap out of junk from the dollar store. But if I’m being totally honest, avoiding building my own stuff out of junk from the dollar store was never the point of the exercise, was it?*

* With apologies to Adam Savage.
h1

The 28mm RKE in action

February 20, 2017

Still cloudy here, but we got a gap earlier this evening, a persistent sucker hole right over Orion, and I got a whole 10 minutes of observing in. I was using the Bresser AR102S Comet Edition and for eyepieces the 20mm 70-degree that came with it, and my new 28mm RKE from Edmund.

Both eyepieces will just fit in the belt of Orion, with Alnitak and Mintaka in the last 5% or so of the field on either side. So the belt turns out to be a good test of edge characteristics. The 28mm RKE is way sharper at the edges, by the way. You might think that its 45-degree apparent field of view would feel positively claustrophobic after the 70-degree field of the Bresser eyepiece.

But it doesn’t, because of the magical floating stars effect. It’s real! It’s one of the most arresting things I have experienced in almost a decade of observing. As your eye gets closer to the eyepiece, you begin to be able to see the image. As you move in until you can see the entire field, the point where the eyepiece barrel disappears from view coincides exactly with the point where you are far enough to see the field stop of the eyepiece. If you hold up right there, you see the image created by the eyepiece floating in space, with a thin ring of unresolved darkness around it, which if you back out a bit will be the eyepiece barrel, and if you move in a bit will be the eyepiece field stop. In either case, the eye relief is great enough that you can still see the rest of the scope in your peripheral vision, past the thin ring of darkness at the edge of the field.

I have never, ever seen anything like this. It is exactly as cool and immersive as the legends have it. I can imagine building a whole observing kit consisting of this one eyepiece and a series of Barlows of various magnifications.

Anyway, if you have been on the fence about this eyepiece like I was, just get it. It’s amazing.

h1

Me and the ‘Stig

February 19, 2017

This story started a few nights ago. I had been monkeying around with the AR102S, both at its native aperture and stopped down, and I decided to see how it compared to the C80ED. In particular, I wanted to compare the rich-field views of both scopes (such as they are here – I was observing from the driveway after all), so I was looking at the belt and sword of Orion. The results of that comparo were not very surprising – with it’s wider aperture and shorter focal length, the AR102S goes significantly wider and brighter, but the longer focal ratio and low-dispersion glass of the C80ED produce a better-corrected image.

What was not only surprising, but actively alarming, was that at low power I was getting ugly star images in the C80ED. Even in the center of the field, stars were not focusing down to nice little round points, but to crosses and shapes like flying geese. I wondered if my diagonal might have gotten banged up, so I swapped diagonals. The problem persisted. The scope will not reach focus without a diagonal or extension tube, and I don’t have an extension tube, so I couldn’t try straight-through viewing. Still, it was exceptionally unlikely that both of my good diagonals got horked in the same way.

I didn’t know what to make of that. I figured maybe the scope had gotten out of collimation somehow, and I was pondering whether to mess with it. It’s always been optically excellent and mechanically solid (overbuilt, in fact), and I was loathe to take it apart (as opposed to the TravelScope 70 and SkyScanner 100, both of which were crying out for disassembly).

Then a few days later I ran across this thread on CN, in which a guy was having the same problem I had. It sounded like it was more likely astigmatism (aka the Stig) in the eyes than in the telescope. Apparently it’s worse at low powers where the exit pupil is large, which makes sense – astigmatism is caused by having corneas that are out of round (football-shaped rather than basket-ball shaped), but as the exit pupils get smaller, the less of the cornea is involved in vision, and the more likely it is that the ‘active’ portion will approximate a radially even curvature.

astigmatism-of-the-eye

One commenter recommended making a little diaphragm between thumb and forefinger to stop down the exit pupil. I tried that, but it was awfully difficult to hold my finger and my eye all steady and in alignment. Then I had the idea of using a collimation cap from one of my reflectors. That stopped down the exit pupil to a 1mm circle, which made the image d-i-m, but the star images cleaned right up. Then I took away the collimation cap and tried the view with and without glasses, and the glasses also cleaned up the star images.

It wasn’t the scope, it was me. I have astigmatism, and it’s bad enough that stars look ugly at low power unless I wear glasses.

On one hand, that’s a big relief, because the C80ED scope has always been a rock-solid performer. Along with the Apex 127, it’s my reference standard for good optics. I was feeling a bit queasy at the thought that it might have gotten out of whack.

On the other hand, I now need to prioritize eye relief in my eyepiece collection. I have a bunch that are too tight to show the whole field when I’m wearing glasses. So I have some decisions to make.

That was the first major discovery of the night.

The second was that the AR102S can take 2″ eyepieces with the most minor tinkering. The 2″-to-1.25″ adapter at the top of the AR102S focuser drawtube screws right off. I had been worried that it might be permanently affixed, but when I tried turning it, it spun with remarkable ease. Once I had it off, I dropped in the 32mm Astro-Tech Titan, which is my only 2″ eyepiece, and the views were pretty darned good. Way wider than with any of my 1.25″ eyepieces, and pretty clean as well, although I need to a little more head-to-head testing on that score. Possibly the star images looked good because they were so small at only 14x.

bresser-ar102s-with-2-inch-ep

In any case, the 32mm Titan gives a significant boost in true field, from 3.6 degrees in the 32mm Plossl and 24mm ES68, to a whopping 4.88 degrees.

I don’t think there would be any advantage in going wider, at least in the AR102S. Astronomics seems to be out of Titans, but the equivalent 70-degree EPs are available through Bresser and Agena. The next step up would be a 35mm or 38mm, giving 13x and 12x, but those would push the exit pupil to 7.7mm and 8.5mm, and that’s just wasted light. At least in the AR102S – in the C80ED, longer 70-degree eyepieces would yield the following:

Focal length / magnification / exit pupil / true field

  • 35mm / 17.1x / 4.7mm / 4.1 degrees
  • 38mm / 15.8x / 5.1mm / 4.4 degrees

Either of those would be a good step up from the 3.7-degree max field that the 32mm Titan gives in the C80ED, without pushing the exit pupil uselessly wide.

Anyway, I’m just noodling now. The big news is that the C80ED is fine, I need to prioritize long eye relief in future EP purchases (and maybe thin the herd a bit?) so I can observe with glasses on, and the AR102S can take 2″ EPs after all.

h1

Unboxing the Edmund 28mm RKE

February 17, 2017

rke-unboxing-1

Look what came in the mail today.

rke-unboxing-2

Something small, in a gold box.

rke-unboxing-3

An eyepiece wrapped in paper, and a rubber eyeguard.

rke-unboxing-4

And here they are.

rke-unboxing-5

That is a big honkin’ eye lens. And that’s why I got this eyepiece. The 28mm RKE from Edmund is legendary for its “floating stars” effect where the big eye lens, the sharply raked barrel, and the long eye relief combine to create the impression that the eyepiece has disappeared and the image is simply floating in space. I’ve never experienced this, because I’ve never gotten to look through one of these before. But the reputation of this eyepiece, illustrated by several glowing threads on Cloudy Nights (like the ones that follow), was enough to convince me to take the plunge:

rke-unboxing-6

It didn’t come with a case, so I made my own out of an old prescription pill bottle. A little bubble wrap stuffed in the bottom and taped inside the lid, and I’ve got a nice padded case for free.

new-eyepiece-curse

And I need that case, because the new gear curse is in full effect. How does this eyepiece work in practice? No idea yet – with any luck, I might find out next Wednesday, when the clouds are finally supposed to part. I’ll keep you posted.