Observing report: the transit of Venus in Claremont

Here, just one day shy of being one month overdue, is my post on the transit of Venus on June 5. As promised, I took scopes downtown and did some sidewalk astronomy, and eventually some rooftop astronomy. As with the solar eclipse on May 20, the primary instrument was my son’s Astroscan with a homemade sun funnel, and once again it performed beautifully.

My partner in this enterprise was fellow Claremont paleontologist Matt Benoit. He was there for the whole thing, and helped keep scopes on target and help people understand what they were seeing. We hit a grocery store beforehand for soda and snacks and basically made an extended party out of the event.

I wanted to see the transit, period, but I was especially keen to watch the entry of Venus onto the solar disk to see if I could spot the “black drop effect” that bedeviled transit-timers in previous centuries. Sure enough, as Venus started to pull away from the limb of the sun there was a persistent dark blob or zone that seemed to connect the planet to the black space beyond, like surface tension keeping a drop of water from falling off the faucet. The black drop effect was once thought to be an effect of the atmosphere of Venus, but it’s not, because airless Mercury shows the same effect during its transits (the next of which is coming up in 2016, by the way). It’s nothing to do with our visual perception, either, since it’s easily recorded photographically, as you can see above. It’s now understood to be an effect of diffraction when a vanishingly thin line of light separates two darker spaces or silhouettes. You can see it by holding your finger and thumb up to the light and bringing them together–just before they touch, the black drop effect will seem to bridge them.

Along with the Astroscan and sun funnel, we had along the Celestron Travel Scope 70 with the aperture mask and solar filter described in this post, for direct viewing. Here’s my friend Marcy, who was there with friends for about half of the transit, getting her first look.

Although we both put in time on both scopes, for the most part I drove the Astroscan while Matt minded the Travel Scope. He also helped people get some photos through the eyepiece, as he did here with Marcy’s DSLR.

The view through the filtered scope was not as detailed as in the sun funnel, but the warm yellow color was more aesthetically pleasing, and many of our visitors appreciated both views.

Like the eclipse, the whole effect of the transit was a little unreal. In addition to the scopes, we also had eclipse glasses and a piece of welder’s glass. Every few minutes we would look up with our naked eyes and see a little black dot on the sun, and know that it was a whole world. And not just a world, but a twin of Earth. Someone on Mars watching a transit of Earth would see something very similar–our whole planet, all our evolutionary and human history, everything we’ve done or built (except for the handful of tiny things we’ve sent away)–all shrunk to a point, no larger, to the naked eye, than the period at the end of this sentence.

We had a steady stream of visitors downtown until a little after 6:00, when the theater blocked the view of the sun from the public square. So we decamped to the top of the parking garage across the street. Some people followed us over from downtown, and some found us up there on their own. One guy said that he found us because he had Googled for Venus transit events in Claremont and found my morning-of invitation post, which is nice, because that’s exactly why I put it up. In all, about 85 people saw at least some part of the transit through one of our scopes.

My son, London, watching the very tail end of the transit with the welder’s glass.

Venus was still crossing the face of the sun when they set together. As with the eclipse, I managed to get a shot right when the world crossing the sun touched Earth’s horizon. A moment later, it was gone, and the last transit of Venus until 2117 was over. I’m glad I got to see it, and to share it. I hope you had the opportunity to do the same.

More low-cost solar observing

In preparation for the transit of Venus tomorrow, I did a little hacking and tinkering late this afternoon. Although the sun funnel worked well enough for watching the eclipse, as we’ll see below it is not perfect for photographing the sun in any detail. My full-aperture solar filter still hasn’t arrived, but I got to thinking about how to make a safe direct viewing setup.

I recently acquired a Celestron Travel Scope 70, a little 70mm (2.75 inch) f/5.7 achromatic refractor. Like a lot of small refractors, the dust cap for the objective lens has a smaller removable cap in the middle, in case you want to stop down the scope for more pleasant viewing of bright targets like the full moon. The diameter of the small hole in the middle of the big cap is 40mm, so with big cap on but the small cap off, the scope functions as a 40mm f/10.

I don’t have any loose solar film to make a 70mm solar filter or even a 40mm solar filter. But I do have a stack of eclipse glasses, each of which has two 1×1.5 inch eye holes covered with solar film. So I cut one of the eclipse glasses in half, made a round 25mm aperture in a square piece of cardboard, and mounted the eclipse glasses ‘lens’ (solar film still surrounded by two sheets of thin cardboard) and the 25mm aperture stop on the back side of the big dust cap. I didn’t think to take any pictures of the inside of the dust cap to show how it all goes together, but hopefully the general idea is clear enough. With the big dust cap on and the small dust cap off, the scope admits a 25mm beam of fully solar-filtered light to the objective, turning the scope into a 25mm f/16 solar refractor. And because the solar filter is on the inside of the big dust cap and protected by the small dust cap (in front) and the second piece of cardboard with the 25mm aperture stop (behind), I can leave it in all the time. Take the big dust cap off, the scope functions normally. Take only the small one off, I’ve got a 1-inch solar scope.

Two other design decisions to note. First, the finder–and I use the term advisedly–that came with this scope is without doubt the worst finder I have ever seen on a commercial scope from a brand name manufacturer. It looks like a 5×20 straight-through magnifying finder. However, right behind the (single, plastic) objective lens is an aperture stop with only a 1-cm hole in the middle. So in fact it’s a 5×10 finder with a plastic singlet objective. The immense irony is that the scope doesn’t need a finder at all; throw in a 32mm Plossl and you get 12.5x and 4-degree true field of view, so the scope effectively functions as its own superfinder. So I unscrewed both ends of the finder and dumped out all the plastic optics, turning it into a hollow sight tube. Why is this important right now? Because it’s really dumb to leave a magnifying finder on a telescope being used for solar observing; it’s too easy to forget what you’re doing and accidentally looking through the unfiltered finder and cause serious eye damage or blindness. There’s a good reason that every commercial telescope comes with a “don’t point the scope at the sun, dummy” tag or sticker or both. This is not something to mess around with. If you’re going to observe the sun with a telescope, cultivate the same habits of awareness and deliberate action that you would use around loaded firearms and power saws.

Oh, the included 45-degree prism diagonal is also rubbish and the light tripod looks pretty dodgy. Today I used my standard small-scope setup–an AstroTech 90-degree dielectric star diagonal and a Universal Astronomics DwarfStar alt-az head on a Bogen/Manfrotto tripod–and I’ll doubtless do the same in the future.

The other design thing was the sun shield. At first I tried going without but look into a dark eyepiece to catch a filtered (= comparatively dim) view of the filtered sun while unfiltered sunlight was hitting the top of my head and my upper eyelid had me squinting and developing a minor headache almost immediately. The plastic dewshield on this scope pulls right off, so I got a handy piece of cardboard (part of the packaging of a picture frame), cut a hole just big enough to admit the front end of the scope without the dewshield, slid the cardboard sunshield on and used the plastic dew shield (and dust cap with solar filter) to hold it in place. I also cut a second, smaller hole to let light in to my sight tube sun finder.

If you do something similar, make sure that the sun shield can’t get blown off and take the solar filter with it. In my case, the dewshield slides on a long way and grips both the sun shield and telescope tube firmly; a strong enough breeze might upend the whole setup, but it couldn’t blow off just the shield and filter. Again, eye safety is paramount; don’t take any chances.

Okay, so how did it work in practice? Pretty darned well. I had already aligned the sight tube with the telescope, so all I had to do was rotate the sun shield a bit to make sure the second, smaller hole lined up with the sight tube. Then I could point the scope roughly at the sun and pan around until a perfectly round beam of sunlight (projected on my hand) emerged from the sight tube. That always put the sun in the field of view of a 25mm Plossl (16x, 3 degree true field of view). The view of the sun at the eyepiece was reasonably bright–for an astronomical object, not compared to the unfiltered sunlight streaming down all around–and razor-sharp. The sunspots with their umbrae (dark centers) and penumbrae (lighter borders) were striking, like they’d been etched on stained glass.

Happily, the filtered scope yielded nice, even light all over the surface of the sun, no matter where it roamed in the field of the view. My one beef with the sun funnel is that it can be hard to get really good photos because of the inherent granularity of the screen material. Inevitably some part of the projected sun is brighter than another, and if you manage to get the light perfectly centered, it can easily wipe out the sunspots. The best way I’ve found to avoid this flashlight-beam effect is to photograph the sun from a bit to the side, out of the direct path of the projected light (that’s how I got this very sharp photo), but then the sun is out of round–not ideal if you’re hoping to combine images into a composite or movie, or even get a nice, square-on shot of a circular sun.

For example, in the photo above the sunspots on the left are sharp enough–the big one even shows the umbra and penumbra clearly–but the dimmer two on the right are lost in the flashlight glow of the sun lighting up the screen material from behind. And in this view the sun is already way out of round.

Also note that this image is flipped horizontally compared with the image from the refractor. In fact, this image is correctly oriented. Normally Newtonian reflectors show things rotated by 180 degrees, but projecting the image on the screen undoes that and gets everything back to normal. The solar filter on the refractor just cuts down the intensity of the light, it does nothing to reorient the image, so the image at the eyepiece is right side up but, because of the 90-degree mirror, flipped left-to-right.

I didn’t go to all of this trouble just for the transit of Venus. I mean, I happily would have, had the transit been the only game in town. But it’s not–the Astronomical League has a Sunspotters observing program, and now that I have the gear for solar observing, I might as well start logging. I’ll keep you posted on that.

Now, I should point out that the flashlight-beam effect washing out the sunspots in the sun funnel is mostly a photographic concern. For visual appreciation, even solo, I think the sun funnel still wins. A 4-inch image scale and the ability to put your head and eyes wherever you want–and even wear polarized sunglasses to observe–can’t be beat. But for photography, I prefer the filtered direct view–even in a one-inch scope.

Fortunately I’ll be rolling with both tomorrow. Now if the weather just cooperates…

Banner photos, part 1: the little boy with the telescope

Once when I was a kid Mom and Dad and my brothers and I sat out in lawn chairs until midnight or maybe later to watch a total eclipse of the moon. We only did it once, but it’s always stuck in my mind as Reason #4,769,341 why My Parents Are Awesome (that’s actually a pretty high rank, considering how many museums, zoos, turtles, cats, chickens, model rockets, hikes, skinned knees, dirt clod fights, movies, puzzles, trips to the bookstore, vacations, homeworks, county fairs, kolaches, and giant pans of lasagna went into our upbringing).

The night of February 20, 2008, there was a total eclipse of the moon. It started at 5:45 PM and ended a little after 9:00 PM. We were living in Merced at the time, and I’d only been into amateur astronomy for a few months.

London and I watched the eclipse from the back porch, and Vicki came out a few times to look, too. The “baby red telescope” (a used Edmund Scientifics Astroscan) was my Valentine’s present from Vicki that year. London loves it and at the time he was very possessive about it, but we talked about it and he decided to share. He was just three when these pictures were taken; he’s seven and a half now.

I passed this Astroscan on to a friend, but I got another just for London. They are nearly indestructible scopes. The newest versions from Edmund Scientifics have red-dot sights, but the old ones have a metal peepsight, so there is typically zero user maintenance. That doesn’t sit well with everyone–for one thing, there’s no provision for collimating the mirrors so if they slip out of alignment, you’re basically stuck. Unless you want to disassemble the telescope, that is. For the brave, Gary Seronik posted instructions on how to disassemble, collimate, and reassemble the Astroscan.

The tank-like build of the scope is a big selling point. We often take London’s Astroscan when we go camping, because we can always find enough room for it in the car and we don’t worry about it getting banged up. I have read about people who leave their Astroscans in the trunks of their cars on a semipermanent basis so they’re never without a scope, and about Astroscans that have tumbled off tables and tripods and been none the worse for the wear.

One of my favorite observing sessions with the Astroscan was in Yosemite Valley with some ecology students on a field trip. A group of us drove out into the middle of the valley to get out from under the trees, set the Astroscan on the hood of the truck, and spent a couple of hours just cruising the skies. One of the students had never seen Saturn before with his own eyes. It was tiny in the Astroscan–the short focal length limits the magnification–but very sharp, and he stayed hunched over the telescope after everyone else had gone off for some naked-eye stargazing. I will never forget that night; I was so glad I had a scope along and could show people a little of what’s up there (this was about a year before I started doing sidewalk astronomy).

If you want to read up on the Astroscan, the review at dansdata is funny, Tony Darnell has an inspiring writeup here, and Ed Ting’s review is both thorough and charming.

If you actually want to buy an Astroscan, you have a choice of paths. The new Astroscan version with the red-dot sight is called the Astroscan Plus, and Edmund Scientifics will sell you one with two eyepieces and a shoulder strap for about $250. For an additional $180, the Astroscan Deluxe package includes a third eyepiece, a sun-projection screen, a tote bag for the scope, and a full-size tripod for getting it up off the ground.

However, you can probably have an Astroscan for a lot less dough if you want. The scope’s basic indestructibility and absence of things for users to fiddle with means that, apart from the switch from the metal peep sight to the red-dot finder, 20-year-old Astroscans are about the same as the ones rolling off the assembly lines today. And the scope has been in production since about the time I was born, so there are a lot of used ones out there. I’ve bought two used Astroscans, the one I passed on and the one London still has, and I found them the same way: put ‘Astroscan Craiglist’ into Google and see what comes up. You might have to do this on a regular basis over the course of a few weeks to find one that is (a) in your area and (b) in your price range, but they do turn up with surprising regularity. You can also find them on eBay sometimes, but usually being sold more dearly. Expect to pay $100-150 for a used Astroscan, although I have seen the occasional one pop up at $75 or even $50 if someone finds one in the back of the closet and just wants it out of the house.

In terms of price and aperture, the Orion StarBlast 4.5 ($180-200)and SkyScanner 100 ($110) are clearly intended to compete with the AstroScan, and if you’re just looking for a reasonably sturdy, portable, 4-inch widefield reflector, either of those would do nicely. But the Astroscan is more maintenance-free (in that it has no provision for user maintenance–whether this is a bug or a feature is up to you); solidly built to the point of near invulnerability; and has a distinctive charm all its own. I suspect that at this point most people don’t end up owning an Astroscan because they wanted a small telescope, but because they wanted an Astroscan specifically. If that’s you, go nuts. It’s an awesome little scope.

A Cheshire Cat on the moon

It’s been an interesting week.

I got a new scope…

That was sort of by accident. I really wanted the mount for my 5″ reflector, because it’s a bit too heavy for my current mount and tripod. Orion sells that mount as the VersaGo II for $199, but right now OPT has the SkyWatcher-branded version of that mount, the AZ4, and a nice 80mm refractor with finder and eyepieces for the same price. So by going through OPT I essentially got the scope and accessories for free. I originally planned on selling off the scope, but I keep hearing about people falling in love with the crisp views through refractors (which unlike reflectors and catadioptric scopes have no central obstruction), so I decided I’d give this one a fair shake before I got rid of it.

I’m glad I did. It’s a keeper–it has very sharp optics, gives a nice, clean, contrasty image, and is very fun and easy to use. It doesn’t pull down as much light as my bigger scopes, but it’s easier to handle and it cools down in no time, which is a big plus at this time of year. (One  of the biggest sources of image distortion at the eyepiece is heat waves coming off lenses and mirrors that haven’t reached ambient temperature.) Frequent commenter David DeLano has this scope as well, and he warned me that if I wanted to sell it, I shouldn’t look through it, because I’d get hooked. You called that one right, David!

I gave it a name, too. Some people name their scopes and some people don’t. I also talk to myself and to inanimate objects when I’m alone, and I suspect that those traits are highly correlated with naming scopes. Anyway, there’s a bit of back story behind this one. When I was a kid, my cousin Michael had a good friend, also named Michael, who was quite a bit taller than he was. They felt dumb calling each other by their own name, so my cousin Michael dubbed the taller one “Shorty Long”, and tall Michael retaliated by calling my cousin “Stubby Fats”. That’s never ceased to crack me up. And now I’ve got two shiny black SkyWatcher scopes that will be sharing a mount, one a long skinny refractor and the other a short fat reflector, so it made sense to name them Shorty Long and Stubby Fats.

With the moon and Jupiter both high and bright in the evenings this week, it didn’t pay to go after fainter fare, and I hadn’t put in any serious time on the moon in a long time.

Tuesday the moon was waxing gibbous. I got this shot through Shorty Long with my Coolpix 4500:

It doesn’t show everything there was to see. Sinus Iridium, the Bay of Rainbows, is the C-shape, open to the bottom, at the very top of the moon in the above picture; it’s an old impact basin mostly flooded by the later basalt flows that formed the maria or lunar seas. Just past Sinus Iridium I saw a couple of mountain peaks that the sunlight was just reaching, and they glowed like a pair of eyes staring at me from beyond the terminator. Here, I’ll show you:

Kinda spooky lookin’, eh?

It got better. As I stared back, the rising sun (from the perspective of those mountains) lit a couple of lower peaks, below and between the first two, and then a ridge running beneath all of them. It looked for all the world like the face of the Cheshire Cat, with two bright eyes, two nostrils, and a big wide smile. The nostril peaks and the smile ridge were too faint to show up in any of my photos, but a helpful guy on Cloudy Nights produced this image with the Lunar Terminator Visualization Tool (yay, more free astro software!) using my location and the time of the observation:

One of the nostril peaks was too dim to show up even in the LTVT shot, but other than that the face looks pretty much like what I saw Tuesday night. There is even a suggestion of eyebrows.

The peaks turn out to be the aptly named Harbinger Mountains. I asked around on Cloudy Nights and no one has reported seeing the Cheshire Cat “lunarism” before. I’m going to do a little more research on the features involved and report back.

That wasn’t the end of my weird moon adventures for the week. Last night I was back outside for the full moon:

I had basically just gotten set up when I saw a small, perfectly round object float by in front of the moon. I figured it was probably either a weather balloon or a satellite. Turns out that a CN user got video of the thing; the video is now on YouTube, here.

[Almost Immediate Update: the thing in the video is not the same thing I saw, or at least not the same pass, because that video was made about three hours before I made my observation. I just learned that in the CN thread, which is here.]

It’s probably a satellite; another CN user got video of a similar thing flying in front of the sun, and reports seeing them on a regular basis. So don’t get out your tinfoil hats just yet. But do get out and have a look at the moon when you get a chance. As this week has shown, you never know what you might find, even with this closest and most familiar of celestial objects.

Telescope tradeoff: aperture vs portability

In a comment on the last post, Jon Lindberg brought up some good points about the aperture/portability tradeoff with telescopes. It’s fertile ground for discussion, because there is always a tradeoff.

The big up-front ground rule for this discussion is that when it comes to portability, your mileage may vary. Some people consider 8″ or even 10″ scopes to be “grab-n-go”. For me, scopes break roughly into two categories: those that require one hand and one trip–my definition of grab-n-go–and those that require some more setup, either two hands or multiple trips or other fiddling. And at any given time, there is only one scope in each category that I’m using heavily.

Right now my big gun is a 10″ Orion dob. It weighs about 55 lbs assembled, which is about half in the tube and half in the base. I can move it while it’s assembled, but usually not without having a few twinges in my back the next day. So I usually carry the base to where it’s going to be set up, then put the tube on, then set up  some kind of  chair next to the eyepiece. Including a trip for my eyepiece case and some charts, it’s usually about four trips. But that’s okay, because I only tend to set it up when I’ve got some serious observing to do, or when I want to impress houseguests.

My old “big gun” was my first telescope, a 6″ Orion dob. It weighs about 33 lbs assembled, and I always carry it out in one piece. But it lives out in the garage with the 10″ and also requires a chair, so I’m still making two or three trips to get it set up. If I’m going to go to that much effort, I might as well get out the 10″ and get the benefit of nearly three times the light-gathering ability and almost twice the angular resolution. So I’ve barely used the 6″ at all since I got the 10″.

The 6″ is also facing competition from the other end, from my 5″ Skywatcher reflector on a homemade Dob mount. That one weighs just under 20 pounds and is short enough that I can use it sitting on the ground, so it’s more grab-n-go-able and still delivers most of the performance of the 6″ scope.

One of the lessons of all of this might be that I have too many telescopes. The more broadly applicable point is that the goodness or badness of a telescope for any particular application depends on what else you’ve got in the stable. When I only had one telescope, it was of necessity both my big gun and my grab-n-go scope. But my enthusiasm for hauling out a 30 lb scope on short notice declined markedly when I had something under 10 lbs to use for quick peeks.

But let’s get on to the meat of Jon’s question, which I am going to interpret as, at what point as you go down in aperture do you start noticing the compromises?

Again, the answer will be different for different observers. Some people think that anything smaller than 8″ is a waste of time. Obviously I disagree. I think that the vast majority of observers would say that a 3.5″-4″ telescope is probably at a threshold between noticeable compromise and being to see most familiar targets–moon, planets, Messier objects, the occasional comet–with rewarding vibrancy and detail. I base that in part on the massive commercial success of 90mm Maksutovs and 4″ refractors, especially apochromats. Also, some of the best deep-sky observers in the world like Stephen O’Meara and Sue French use 4″ refractors as their primary scopes.

That’s not to say that smaller telescopes aren’t popular as well. Refractors in the range of 60-80mm have always sold well and probably always will, especially short focal length, widefield scopes like Orion’s ShortTube 80 (pictured above). And you can have a lot fun pushing these little scopes to their limits, as Jay Reynolds Freeman did when he completed the Herchel 400 with a 55mm scope. But achievements like that get noticed because nobody expects to be doing serious deep-sky work with a tiny telescope. Sub-3″ scopes are almost always intended to be either introductory-level instruments or purpose-built grab-n-go and travel scopes.

So what’s the real word? My little SV50 is well into the realm of trading away performance for portability. So far it has shown every Messier object I’ve tried for, but all but the biggest and brightest have been faint fuzzies at the eyepiece, without a great deal of detail. And a scope that small absolutely requires dark skies to do any meaningful deep-sky work. Here in town it just doesn’t have the horsepower to cut through the light pollution. But that’s okay, because I didn’t get it to use here in town. I got it mainly for airline travel, and if I’m flying, it’s usually to someplace darker than the LA area, so it fills its very specialized niche admirably.

One thing that the little scope excels at is putting a truckload of stars in my eyes. Bigger scopes with longer focal lengths have smaller fields of view, that’s just an inescapable fact of optics. I’ve noticed that when I’m using bigger scopes I’m usually hunting for particular targets. With the SV50 I have a lot of fun just panning around the sky. It is the only scope that I have used that delivers the same super-wide field of binoculars, but with the advantages of being solidly and comfortably mounted (image crouching behind a pair of  mounted binoculars when they’re pointed at a target more than 45 degrees above the horizon) and having variable magnification.

For a little more than double the weight and volume, the C90 is still very portable and delivers a LOT more light and a LOT more detail. But for me it has two distinct disadvantages compared to the SV50. First, it’s just big and heavy enough to require a bigger tripod, so the whole kit-and-kaboodle won’t fit into a tiny bag that I can stuff into the bottom third of my backpack. So if I’m traveling with it, it becomes one of the focuses of my packing, instead of something I just shove in the bag and forget about until I reach my destination. Also, the folded light path gives the C90 a very long focal length for its size–900 mm–which makes reaching high powers a breeze. That makes it easy to power up on planets and specific deep-sky targets, but it also means that the scope has a fairly narrow field of view. So my mindset when I’m using it is more along the lines of, “what individual small thing am I going to look at next”, and not, “let me pan around the sky and see what I stumble across”. If you want the latter experience in a more capable scope than the SV50 that still only weighs about 5 lbs and is eminently airline portable, consider a Short Tube 80.

If you’ve got a little more space and don’t mind a little more weight, a 4″ Mak or a 5″-6″ Schmidt-Cassegrain will put a lot of aperture into a decently small space. Something like a Celestron C5 is about the size of a big coffee can but gives you enough light grasp and resolution to go after just about anything you want, especially if you have dark skies. The caveat I’ll add from my own bitter experience is that at this size of scope you have to put as much or more thought into the mount. When I got my first Mak, a 4″, I put it on a cheapo camera tripod from Wal-Mart. That was a disaster–the mount was so shaky that using the scope was an exercise in almost terminal frustration. Moving down to a 90mm scope didn’t really help, and my little scopes didn’t get much use until I got a decent tripod. And by “decent” I mean “costing as much or more than the telescope itself”.

I brought up the Short Tube 80 and all of the catadioptric scopes (Maksutov-Cassegrains and Schmidt-Cassegrains) first because they’re probably the most airline-portable of the bigger scopes. If portability is important but you don’t plan on flying with the scope, at least not regularly, the Orion StarBlast 4.5 and Edmund Astroscan both put some serious aperture into a one-hand telescope. Both are bulkier than a 5″-6″ SCT, but in both cases the bulk includes a base so you don’t have to worry about buying a separate mount and tripod (although you may want something, even a picnic table, to get them up off the ground). The StarBlast has better optics and a better focuser, but the Astroscan is almost indestrucible. As with any optics purchase, read around to find out the good and bad about them both before you make any decisions. The links to telescope reviews on the sidebar are good places to start.

Most telescopes are made in China and Taiwan these days, and the same models that are sold by Orion and Celestron in the US are usually available from SkyWatcher or Konus in the rest of the world. Happily, just about all of the scopes I’ve discussed can be had for $200-300 or even less if you’re willing to shop used (for example, at the Cloudy Nights Classifieds, where I’ve bought and sold just about all of my astro gear). If you have any questions, feel free to ask in the comments. I’m always happy to talk about telescopes.

UPDATE March 11, 2013: Here’s Doug Rennie’s StarBlast 6 hanging out amongst the flora–see comments for explanation!

 

Small telescope quest complete

When I caught the astronomy bug in the fall of 2007, my first priority was to get a decent scope. I spent about a month doing research in print and online and just about everyone said the same thing: get a cheap 6″-8″ Dob and some serviceable binoculars and start learning the sky.

This I did. My first scope was an Orion XT6 that I named “Shaft”. For two and a half years, Shaft was my workhorse scope.

But Shaft was still getting broken in when I decided that I needed something more portable. An XT6 is about 4 feet tall and weighs 33 lbs. It’s easy enough to  take the tube off the base and stow them both in the car for camping or a trip to the mountains, but I wanted a scope small enough to fly with. My parents live in rural Oklahoma under very dark skies and I knew all too well what I was missing here in the light-polluted swamp of California.

So began my quest for a grab-n-go scope. Not just any grab-n-go scope–some people consider a 6″ Dob to be grab-n-go. What I was really looking for was my “no excuses telescope”: a scope that would be so triflingly small and light, and yet so capable and easy to use, that I would never have an excuse not to have it along, whether I was driving up the mountain for a quick peek or flying to another hemisphere.

I’ve always had a thing for Maksutov-Cassegrains so my first venture was a little Mak, an Orion Starmax 102, that I picked up used. And it was a great scope. But I realized that a StarMax 90 would deliver most of the performance of the 102 but it would be a couple of inches shorter and a couple of pounds lighter (3.5 vs 5.5, if I remember correctly). So I got a Starmax 90, found it delightful, and sold the 102 (that’s my ad photo above).

The Starmax 90 was my small scope for a long time; it’s the scope I waxed lyrical about in this post. But I also thought that the old orange-tube Celestron Cassegrains looked pretty sweet, and I was entranced by the tank-like build and simple operation of the C90. Same aperture as the Starmax 90, but it was another couple of inches shorter. So I found a used one on Cloudy Nights and sold the Starmax 90.

The C90 has been a very fun little scope. It is even more rugged and versatile than I expected, and it fits in an insulated plastic-lined six-pack cooler, to boot. Nothing like getting an armored scope case for $5.99 at Wal-Mart (the black thing laying over the tube in the photo above is the finder, wrapped in one of the soft cloth bags that come over my wife’s favorite shoes).

But on some level I’ve known for a long time that the C90 would be at best a temporary stop on my quest for the smallest reasonably capable telescope. Because a couple  of years ago when I was surfing Cloudy Nights I discovered the Stellarvue SV50.

As I understand it, the SV50 started life as a high-end finder for larger telescopes, and one version is still sold that way today. I fully support that; one of my first upgrades for Shaft was a 9×50 finder that made star-hopping a lot easier. But people started using the SV50 as a telescope in its own right and it developed quite a following. It is now sold as “The Little Rascal”, a stand-alone spotting scope with a clamshell mounting ring, eyepiece, and in the latest guise, a carrying case.

My SV50 was a present to myself for finishing my summer teaching. I bought it from Oceanside Photo & Telescope on the last possible day that I could have done so and still have had the telescope delivered before I left for Uruguay. I was on the phone for maybe 5 minutes tops and in that time the sales guy (whose name I’ve unfortunately forgotten) answered all of my questions instantly and authoritatively, processed my order with admirable efficiency, and even managed to find me a discount I hadn’t known about. If that’s not good customer service, I don’t know what is.

This is a tiny, tiny scope. The aperture is 50mm, the focal length is 205mm, the magnification with the included 23mm eyepiece is 9x. So you could think of it as one half of a pair of 9×50 binoculars. Except that it’s not.

For one thing, it accepts any eyepiece in the standard 1.25″ barrel size, so you can vary the magnification. And it is really, really well made, as one would expect from StellarVue. There are binoculars out there that are made to equal or better specifications, and there are binos that have interchangeable eyepieces, but they’re out of my price range so they don’t come in to this story. And you can put it on a tripod and look at things directly overhead without breaking your neck.

Also, having had the opportunity to compare the performance of the SV50 with that of my admittedly low-end 50mm binoculars, the image in the SV50 seems brighter.  Possibly because it has fewer internal reflections to steal light from the path, possibly because it’s just a better made instrument, possibly because my binoculars are cheap. Whatever. I’m deliriously happy with the SV50.

The SV50 is 9.5″ long and weighs 1.5 lbs. By comparison, the C90 weighs 3.9 lbs fully loaded (i.e., with diagonal, eyepiece, and finder), and the Starmax 90 weighed 4.6 (the less said about the positively Brobdingnagian Starmax 102, the better). Crucially, this means the scope is light enough to ride comfortably on my little Manfrotto 785 tripod, which only weighs a couple of pounds itself.

And that’s good because the folded tripod is the same length as the scope, so it fits into a roughly equal space. I found a little travel shaving kit at Target that holds the scope, doubly wrapped in bubble wrap; the tripod; three eyepieces; the handle for the alt-az head that goes atop the tripod; my mini red flashlight (a mini Maglite painted over with red nail polish); and a small notebook and pen for recording observations. The only thing that doesn’t fit in the bag is the alt-az head itself, a DwarfStar from Universal Astronomics. Close enough, says me.

By comparison, the ~4 lb C90 and StarMax 90 require the beefier Manfrotto 190CXPRO4, which weighs 3 pounds and folds down to 21″. Which, okay, means you can still get away with scope, accessories, DwarfStar, and tripod for just under 9 lbs. But why settle for 9 when you can have 4.5? More importantly, I have not had the courage to put the bigger (and much more expensive) tripod in my carry-on luggage. For the love of Pete, I use a netbook as my primary computer because I hate carrying heavy stuff through airports. Anything that gives me adequate functionality at half the volume and mass, I will be on in a heartbeat.

For eyepieces I’ve been using the included 23mm eyepiece, yielding 9x; a 10mm Orion Plossl giving 20.5x; and a 6mm Orion Expanse giving 34x. At 9x the SV50 functions as its own finder and requires no other. At 20.5x the scope just gets out of the way and lets me observe. It is honestly one of the most hassle-free setups I’ve ever used. At 34x the optical train is starting to pant a bit. A focal ratio of f/4.1 is hard on eyepieces, especially widefields. The view is still acceptable but focus gets to be very touchy. Fortunately the built-in helical focuser is super-smooth, with no backlash, and is a real joy to use. At the end of the day the three eyepieces get rolled up in a Ziploc bag to fit into the small empty space between the scope and tripod.

So far my SV50 has only seen serious use away from home. In Uruguay I used it to do all of the observations for the Southern Sky Telescopic Club, and this weekend in Big Bear Lake I spent a pleasant hour chasing some Messiers. In fact, I’ve decided to re-observe all of the Messier objects with this scope. I don’t know how long it will take because it will absolutely require dark skies, which I don’t get to as often as I’d like, but I’ll just chip away at it as opportunities present themselves. In any case, I think my quest for the “no excuses telescope” has finally come to a happy end.

I don’t know what I’ll obsess about next, but if you stick around you’ll probably find out. Clear skies!