Archive for March, 2012


Going dark for a while

March 27, 2012

Hey folks,

I am sorry to say that I will probably be around much less frequently for the next two or three months. I have severely overcommitted myself this spring and for the next few weeks I have to pay a succession of pipers. I hope I can find little spaces here and there to post. I will certainly try, but no promises.

In the meantime, I’m happy to see that comment-thread conversations are rolling along just fine without me. I hate to take off when it feels like things are really hopping around here, but that’s the shape of life right now.

Before I go, here’s how David DeLano put his GalileoScope on his SkyWatcher 114N OTA as a superfinder, which itself has a red-dot finder. David was already working on this before I posted about homebrew finders, so I can’t claim any inspirational credit, it’s just a nice example using, in this case, some commercial rings David found on sale.

See you in the future!


SkyWatcher 90mm Maks sold out?

March 19, 2012

Seems to be the case. Amazon has no more, and neither do Adorama and OPT.

So what to do if you’re in the market for a little Mak? Get a C90, stat! As Ed Ting said in his 3-way Mak comparo, “An embarrassingly good telescope package for almost no money. As of this writing they’re practically giving them away. If you’ve been thinking about getting one of these, I urge you to do so immediately before they run out, or before Celestron stops making them.”

On one hand, there is probably little danger that Celestron will stop making them; they’ve had a 90mm Mak in their product lineup for almost as long as I’ve been alive. Now that the SkyWatcher brand has been subsumed into Celestron (both are owned by Synta), it’s likely that the SkyWatcher-branded stuff is being allowed to die off to strengthen the Celestron brand.

On the other hand, C90s have been around for ages in multiple guises, but they haven’t always been this inexpensive. I wouldn’t get one just because they’re cheap–that way leads to a garage full of telescopes–but if you already want a little Mak and you’re bummed that the SkyWatchers are gone, the well-reviewed C90 should be a more than acceptable substitute.

I haven’t posted any new observations with my little Mak in a while because it’s been raining here. Next weekend I’m out of town, so I was hoping to get out to the desert for a Messier Marathon this weekend. Naturally it rained all weekend and today dawned sunny and clear. So it goes.


Thinking about cheap finders–and cheap finder mounts

March 16, 2012

This all started because Orion’s Maks are “wrong-handed” for their VersaGo II alt-az mount. Here, I’ll show you what I mean. Here’s my Apex 127 on the VersaGo II.

If the scope is sitting on its dovetail bar, the dovetail shoe for the finderscope is on the left side of the scope, at about 10:30 (viewed from the eyepiece end). So when the scope is mounted sidesaddle on the VersaGo II, where the dovetail faces left, the finder ends up at about 7:30. The eyepiece of the finderscope is a bit below the eyepiece of the main scope (the effect is exaggerated in this picture, which was taken looking down at the mount). This isn’t terribly inconvenient, it just looks weird, and it can cause some slight balance problems when the scope is aimed up high.

What I’d like is to have the finder sticking straight out sideways from the scope. That way the eyepieces would be at the same height, and the altitude axis of the mount would run through the centers of mass of both scopes so there would be no balance problems. I could achieve that by moving either the dovetail shoe for the finder or the main dovetail rail, but that would require drilling holes in the scope and I’m not willing to do that. A better solution is just to get some tube rings, so I can orient the scope and the finder shoe however I want.

Thinking about that led me to think about how nice it would be to have a small refractor mounted alongside the 5″ Mak. Something in the 70-80mm range could function as both a “superfinder” and rich-field telescope, so on one mount I’d have a low-power, widefield scope and a planet-killer.

Stellarvue sells an 80mm superfinder that some folks use as a stand-alone rich-field and spotting scope, but that runs something like $250. I’m sure it’s nice, Stellarvue gear is top notch, but as always I am interested in less expensive options. Celestron’s Travel Scope 70 is not much smaller,  it’s gotten generally good reviews (at CN, for example), and it can be found for $60-80 (the Amazon price fluctuates a lot, but other vendors usually have it for $60). That would work for a finder, but I’d have to mount it somehow. I could just buy some mounting rings, but adjustable mounting rings for a 70mm scope would cost more than the scope itself. There has to be a better way.

So that’s the first thread: moving up from a 50mm finder without breaking the bank.

The other issue is that I have several scopes that I use regularly, and only one 9×50 RACI finder. So I keep moving the finder around, and this is kind of a pain, because I have to realign it for every scope. It would be nice to just park it on one scope, but that means I’d need finders for the other scopes. As before, I could just buy some more RACI finders, but the 6×30 models are about $60 and the 9x50s, which I really prefer, are $90 or more.

Now, I could build my own finder. I have spare 50mm objectives from some cheap binoculars, and I have an erecting prism diagonal, and I could build the tube out of plumbing parts. But that still leaves the problem of mounting, and as before, the mounting rings would set me back almost as much as a new finder anyway.

That’s the second thread: adding 50mm finders without breaking the bank.

It’s been a while since I’ve bought a new finder, and I have to admit that the prices kind of took me aback. I can’t shake the thought that the Celestron Travel Scope 50 runs about $45 and the Travelscope 70 is $60. If only I could find some way to mount them, I could have easily focusable luxury finders for less than new RACIs of smaller aperture! And that’s really the rub in both of the threads of thought outlined above: building a finder-quality scope is not hard. Mounting it solidly, reliably, and conveniently is hard. Part of what you pay for in a commercial finder is a sturdy, easily-adjustable finder stalk with a standard dovetail foot.

Well, what if I built my own finder stalk?

There are examples out there. My favorite, because they look easy to fabricate, are what I call the “half-pipe” mounts that consist of two half-cylinders mounted back to back. Here are a couple from the “Frugal Astronomer” thread on CN:

This one is by CN user Grendel, and is made from cardboard tube–as is the finder, as shown in this post.

I think this one is from the same thread, but derned if I can find the original post now. Anyway, it’s not my photo, I’ll credit it properly if I figure out where I found it,  if it’s yours please chime in, etc. The nice thing about this one is that it’s easily adjustable, thanks to the combination of thumbscrews through the half-pipe and rubber bands pulling the finder against them. Note the zip ties holding the half-pipe mount to the main scope.

So these got me thinking about the possibilities of the half-pipe mount. Here are some sketches I knocked up in GIMP.

The one at the top is simplest, just a V-slot, essentially the same as in the previous photo. The finder would have to be held in with rubber bands, elastic, velcro straps, or zip ties. Alignment could be done with bolts (you could either tap threaded holes or drill simple holes and epoxy nuts on the outside) or shims.

At lower left everything is the same except a trough has been added to cradle the finder, which might make it easier to use. I don’t know that, obviously, just kicking ideas around here.

At lower right is a full ring holder. I figured, if you’re putting alignment bolts through anyway, just make two more holes and you’ve got a six-bolt alignment system just like on the commercial rings (see an example in the photos here).

The key thing isn’t finder alignment, though, since even rubber bands and shims would work there. The key thing is convenient and repeatable mounting and unmounting to the OTA. I got to thinking: with an inverted V-shaped foot, like all of these have, is there any reason it coulnd’t be cut and sanded to fit into the existing dovetail shoes, so that the dovetail retaining screw tightens on one side of the inverted V? If that could be made to work, this kind of finder base could be mounted and unmounted and moved between scopes just as conveniently as one of the commercial jobs.

The end of all of this thinking? I got a piece of ABS pipe when I was at the hardware store to get parts for my sun funnel. I’m going to play around and see what I can come up with. If I find a workable solution, I’ll post it.


Guest post: Sun Funnel built and tested

March 14, 2012

Here’s something new–my first guest post on this blog. It’s by frequent commenter David DeLano, whose DIY astro gear I have featured here once before. David puts a lot of thought into equipping and fine-tuning his scopes to get the best performance possible, and you can see that attention to detail in his sun funnel writeup. He sent this as an email message with permission to post. It’s pretty much as sent, with just one or two additions to clarify things that were already familiar to me from our email conversations. The sun funnel parts list and instructions are here (or in PDF form with background math here), and I previously mentioned it on the blog here. Enjoy!

First off, this is one of the coolest projects I have done lately.  It was easier than I thought, and the results were better than I would have expected.  Thanks for pointing it out!! [I didn’t put him up to that, promise!–MW]

Here are some experience points worth noting.

It was cool to have an EQ mount, even as light as this one is.  I had to do some tweaking on it, and it took several brain sessions to get it aligned properly, but one I got it configured, it helped to be able to tweak one knob to follow the sun.  It moves fairly quickly.  You get maybe a minute to look at any specific thing before you need to adjust the view.  I also had to tighten the Alt down most of the way.  This setup is very heavy on the EP end.  I had to slide the scope a bit back to clear the Alt micro stem, which made it even worse.  I need to find a counter weight to put on the front of the tube.

When you mount the screen on the funnel, make sure the back, inside, is as clean as you can get it.  I had an annoying spot on mine, and I ended up taking it apart, cleaning it, and putting it back together.  One of the directions says to put the shiny side inside the funnel.  I agree.  This side is easier to clean, as it’s slicker.  Try to keep the clamp as close to the top as you can, as it will want to slip down as you tighten.  After a while, though, the grabbiness of the cloth will keep it in place.  Pull the cloth down from under the clamp as you go, and try to eliminate any creases.  After a while, the sliding down will just tighten.  I tightened mine until I could ping the top like a drum.

I don’t have a shade yet, but what I’d suggest more is a shade umbrella or tent.  A beach umbrella clamped to the mount, or even a chair would be nice.  It gets hot observing the sun.  In fact, this is probably conducive to sitting in a chair to observe anyway, since you don’t have to be hunched over the EP.  The only part of the scope that got noticeably hot was the front of the funnel, from the outside, not the inside.

The Solar Scope

Pardon the leaves…that’s another project for this week.  This is a Bushnell 50mm F12.5.  The ideal EP is around 17.5mm, but the closest I have is 15mm (OWL), and it works fine.  Note that this diag is either 90* or 45*.  I didn’t try 45*, but that might be nice for sitting in a chair.

The Solar Finder

This is a nifty and very inexpensive solar finder that David came up with and described in a couple of previous emails. He wrote:

Something finally worked and was darn easy.

I took a clear-ish film canister, with a grey lid, and punched a hole in the center.  This was the hardest part.  I used my centering punch to fight the little nib and get a hole a close to the center as possible.  (If you don’t have one of these, get one.  They are cheap, and you can use them for all sorts of things.  You put the point where you want to mark and press down. It’s spring loaded and will “pop” when enough pressure is applied.  You are under control up until the pop, so you can’t miss making a small indent exactly where you want it.  Pop it several times to make a deeper dent.  I use this for starting screws, getting a drill bit to start where I want, etc.)  I ended up with a bit if a smile hole, but in testing it worked.  I did go back up and clean up the hole with a 1/16″ bit.

I bought two nylon spacers, zip tied them together, punched holes in the bottom of the finder, and put the spacer set on with a zip tie.  I zip tied the assembly to the end of the scope.


Notice the dot of light on the back of the canister in the second picture.

The film canister finder works very well.  I has some movement, but it really easy to align.  It didn’t need to be shimmed, only twisted by a minute amount.  This is actually the second one I made, and I tucked the first one away and am not quite sure where.  The hole is just punched.  It looks like it’s overkill to drill the hole out.

The Solar Funnel Eyepiece


I keep a cap on the end of the EP when not in use.  I’m not sure where/how I’m going to store this, as it’s relatively large.

The View

Note that this looks like you are looking inside something.  But, it’s a flat surface.  You can make out some sunspot activity about halfway out from the center to the left.  I’ve looked through solar scopes before, and this setup shows most of the details that I’ve seen in those scopes, though the scopes can zoom.  The surface of the sun even roils in this view.  One note – don’t try to focus on the edge of the sun, as it’s moving.  Try to pick an interior detail if possible.  Now, some close-ups so you can see the real deal.

This is a big picture–click to thermonucleate!

The dark fleck about an inch up from the bottom is a speck on the back of the screen.  You can easily see three sunspots, and in fact, I could see six.  At one point I thought I saw a brief flare, but it didn’t last very long.  There is also a nice sunspot on the right edge, that you can see better in the next pictures.  I left the fleck out of the picture so that it isn’t confused as solar detail.


Here is a cut of the sunspots that are on the left side of the picture.

One question that might be asked…how do you know the other spots aren’t on the screen.  Well, for one, they move with the sun as it goes across the screen, and second, they can be focused.  Anything on the back side of the screen is always in the same spot, and always in focus.

Many thanks, David, for a very clear and compelling writeup, and for permission to share it here. Now I want to build one more than ever.


The King of Planets courts the Goddess of Love

March 13, 2012

For the next few nights, Jupiter and Venus are going to be as close together in the sky as they’ll get this year. I took this picture this evening from my driveway with my old Nikon Coolpix 45oo, about a 1 second exposure. Jupiter is on the left.

If you have optics, even small ones, you should be able to see the moons of Jupiter and see that Venus is a half-lit D-shape instead of a round ball of light.

I was out for a bit this afternoon and again this evening with the 90mm Sky Watcher Mak. I am learning to live with the finder, and the scope itself continues to impress. This is one of the sharpest bird photos I have ever taken:

The seeing was better tonight than it has been in a long time. I put the little scope on Jupiter and dropped in a 6mm eyepiece for 208x. Jupiter was razor-sharp and zebra-striped with cloud bands. In the steadiest moments, the South Equatorial Belt showed a ragged edge, and a small white storm notched its southern border. It was one of the most mesmerizing things I have ever seen with a small telescope.

As always, I am amazed that a little hunk of metal and glass the size of a 2-liter bottle can do so much. I have really missed having a little Mak around, and I don’t intend to be without one again.


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

March 10, 2012

London with Astroscan

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.

2008-02-20 Eclipse 03

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.

2008-02-20 Eclipse end

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.

2008-02-20 Eclipse with London 02

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.


Sidewalk astronomy with SkyWatcher Mak 90

March 9, 2012

I took the little SkyWatcher Mak downtown tonight to do some sidewalk astronomy. I haven’t blogged about sidewalk astronomy in a long time because I haven’t done any in a long time. And that’s been bumming me out. I was away from it for too long.

I got started doing sidewalk astronomy back in 2009, as part of the global 100 Hours of Astronomy event during the International Year of Astronomy. It’s a pretty straightforward gig: take a telescope to a public space and give passersby free looks at stuff in the sky. The moon and planets are good targets, because people are familiar with them (not everyone knows what the Pleiades are), they’re naked-eye visible so you can point them out to folks, they punch through city light pollution just fine, and they look great in small telescopes. I know some sidewalk astronomers take big telescopes, and more power to ’em, but I have found that my inclination to go do it is proportional to the size of telescope I have to lug downtown (about five blocks from my house).

For the first long while, my sidewalk scope was my original 90mm Mak, the Orion Apex. It was perfect for the job: compact, lightweight, able to be set up and torn down in about one minute on either end, sharp optics, easy for newbies to focus… Then one night at an astronomy club outreach I reach out in the dark and turned the wrong knob on the mount, and dropped the telescope. On the way down it hit a tripod leg and my foot, but neither absorbed enough energy to keep it from hitting the ground pretty hard. The impact spalled a bit of coating (at least, and possibly some glass underneath it) off the primary mirror. I sold it cheap to a fellow amateur who thought it was salvageable.

My next sidewalk scope was another 90mm Mak, an old orange-tube Celestron C90. I had always wanted one, ever since I saw my  first telescope catalog back at age 12. They are sweet little scopes, build like tanks, and since they focus with a rotating barrel like a camera lens there is not much that can go wrong with them; if the focuser ever gums up you just unscrew the front part of the tube, re-lube the threads, and screw it back together.

It turned out, though, that I liked the idea of the C90 better than the actual thing (this was a far different beast from the modern C90 that is on sale at Amazon and elsewhere). The rotating barrel sounded good in theory, but in practice it was a huge pain to focus the scope while keeping it pointed at an object, especially at moderate to high powers, and especially for people with no experience. I used the C90 for sidewalk astro once or twice and then sold it.

(Aside: one of these days I’ll blog about the joys of buying and selling used telescopes. The bottom line is, scopes hold their value pretty well. If you are judicious and buy used you can usually sell them for what you paid for them, so once you’ve ponied up the initial investment you can essentially try out new [to you] gear for free.)

Then I went through a phase of doing sidewalk astro with bigger scopes: a 5″ f/7 reflector on a homemade mount, a 5″ f/5 reflector (Stubby Fats), and an 80mm f/11 refractor (Shorty Long). These are all fine scopes for showing people stuff in the sky, but not so hot for having to lug five blocks. I needed a dinky scope, something bigger than my 50mm refractor (which is too small for that kind of work) but smaller than my other scopes. Frankly, what I needed was a 90mm Mak, I’d just put myself in the position of not having one.

Until now. Suitably armed with the SkyWatcher Mak, I went forth into the warm spring night, and between 7:35 and 8:45 I showed 48 people the moons of Jupiter. The seeing was godawful, as bad as I have ever seen it. Jupiter was a visibly waving ball of fire, when normally I can see at least half a dozen cloud bands (as shown in the previous post). But the Galilean moons were all visible, strung out in a ragged line to the west of king of planets, and everyone who stopped to look seemed bowled over by the views, so who am I to complain?

I didn’t take the multi-mount that came with the scope, just the little Universal Astronomics DwarfStar alt-az mount that I used to use with the old 90mm Maks (shown in the picture at the top of this post). I left the finder and diagonal on the scope, put it nose down in the included backpack, put spare eyepieces in the side pockets, put all that on my back and carried the folded tripod and mount in one hand. It was great, just like old times.

John Dobson argues that the only measure of a telescope’s value that is worth a damn is the number of people who have looked through it. By that metric, I reckon this little Mak may end up becoming my most valuable scope. I’ll keep you posted!