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Great deals at Sky & Telescope today only!

November 30, 2014

Hey, just a heads up that among all the other Black Friday/Cyber Monday/whatever-we’re-calling-this-season-now discounts out there, the ShopAtSky store at the Sky & Telescope website has some screaming deals. If you use the promo code BLKFRIDAY, you get 30% off storewide and free US shipping. But the promotion ends tonight (Nov. 30), so get on it!

Caldwell Objects cover

Of personal interest to me is that they have new copies of Stephen James O’Meara’s Deep-Sky Companions: The Caldwell Objects. I like all of the Deep-Sky Companions series (see my review of Hidden Treasures here) and I’ve been collecting them one by one, but I didn’t have this one. It’s been out of print or at least hard to find for a while, and used copies have been going for upwards of $60 on Amazon. The book is normally$39.95 at ShopAtSky, currently discounted by 20% to $31.95, then discounted today by an additional 30% if you use the promo code, which brings it down to $22.something. I know some folks aren’t wild about the Caldwell list but there are a lot of great objects in it and if you like O’Meara’s writing, this book is a must-have. There may never be another chance to get new, hardcover copies of this book this cheap, so if you’re remotely interested, do the right thing.

Oh, and if you don’t already have Hidden Treasures, ShopAtSky has it for $19.95 before the 30% promo today, so you can get this book right now for under $15 and with free shipping. That is just astonishing.

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Another visit to the Palomar Observatory

November 28, 2014

Palomar 2014 - London with the dome 1

London had the whole Thanksgiving week out of school, so I took some vacation days to spend it with him. On Monay we went to Anza-Borrego Desert State Park to camp and observe – more on that in the next post. We’d never been there before, and in planning our route I noticed that we’d go pretty close to Palomar Mountain. I asked London if he’d like to visit the observatory again, and he jumped at the chance. Our only previous visit, in September of 2012, had left a big impression on him.

Palomar 2014 - 18-inch model

The visitor’s center had gotten a major upgrade to its exhibits in the intervening two years. Out in the entrance lobby, a small display case showed this model and photo of the 18-inch Schmidt camera, which was the first operational telescope on Palomar Mountain. It entered service in 1936, a full 12 years before the 200-inch Hale telescope first opened its shutters in 1948. The 18-inch Schmidt had a long run – Carolyn and Eugene Shoemaker and David Levy were using it in 1993 to find and catalog near-Earth objects when they accidentally discovered Comet Shoemaker-Levy 9.

Palomar 2014 - 18-inch front

The 18-inch Schmidt has since been retired, and now it’s on display in the visitor center. This is a huge upgrade to the exhibits there – when we visited in 2012, all there was to see were the lighted plates along the walls of the room. Now the 18-inch Schmidt sits in a plexiglass island that is surrounded on all sides with photographs, signage, a touch-screen that shows short movies about the history of the observatory, and display cases with equipment used to operate the camera, including the hand-operated press that punched 6-inch circles of film.

Palomar 2014 - 18-inch back

Here’s the back end of the scope. As you can see, it has no eyepiece and no provision for one. Where an amateur Schmidt-Cassegrain telescope has its secondary mirror, the Schmidt camera had a piece of film (and maybe later a CCD?). On top is what looks to be a 6- or possibly 8-inch guidescope, which does have an eyepiece. Until the advent of computerized autoguiders, taking long-exposure photographs meant that an astronomer had to sit at the guidescope for hours, keeping the crosshairs centered on a guide star and tweaking the alignment of the telescope by hand. Sounds thrilling, eh? I wonder how much more productive professional astronomers are as a group, now that they don’t have to spend so many hours guiding telescopes.

Palomar 2014 - Hale dome with book

But of course the real attraction at Palomar Observatory is the 200-inch Hale telescope, which was the world’s largest fully-operational telescope for almost half a century. Astronomy books from before the early 90s talk about the Hale telescope in the same glowing tones reserved for the Hubble Space Telescope today. And for good reason – the 200-inch scope served roughly the same purpose as the HST and the twin Keck telescopes today. Until the space race of the following decades, the construction of the 200-inch telescope was probably the closest thing to a ‘megaproject’ in science and engineering. The story of how the telescope came to be is a decades-long saga of obsession, invention, science, engineering, and politics; if you’re interested in that story, I highly recommend The Perfect Machine: Building the Palomar Telescope by Ronald Florence. Here’s the 200-inch dome alongside its portrait from London’s Golden Book of Stars and Planets (1985 printing).

Palomar 2014 - London with Hale model

Famously, much of the design of the 200-inch scope came from the mind of amateur astronomer and amateur telescope maker Russell Porter, who built this scale model in the 1930s.

Palomar 2014 - Hale telescope

And here’s the scope itself. We didn’t get to go inside the dome and walk around the scope like we did last time. Those tours only run from April to October. But we were able to look in at the scope from an observation gallery.

Palomar 2014 - Hale concrete mirror blank

Outside the dome is this 200-inch concrete disk, which was used as a mass simulator to make sure the mechanical structure of the telescope worked before the actual mirror was installed. The mass blank has apparently been sitting out in the elements, right across the road from the dome, since 1948. It looks little worse for the wear, and it gives visitors a visceral sense of just how big a 200-inch mirror actually is.

Palomar 2014 - London with the dome 2

One last shot from this visit: London just off the path that leads from the visitor center to the dome. I had to take this one to replicate the picture below, from our last visit in 2012. It’s part of what is apparently now an ongoing series of pictures of London at different ages in front of the same telescope – see him with a replica of Galileo’s telescope here.

London at Palomar Mountain

Next up: crazy-dark skies at Anza-Borrego. Stay tuned.

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My first telescope-building adventure: a 3-inch reflecting travelscope

November 20, 2014

I got my first telescope, an Orion XT6 dob, back in October of 2007. It wasn’t an impulse buy – I had spent almost exactly one month reading the telescope recommendations in books and magazines, on Cloudy Nights, and on countless other webpages, including Ed Ting’s amazing scopereviews.com.

Inevitably during this time of rapid, omnivorous consumption of all available telescopic information, I came across many websites that dealt with amateur telescope making (ATMing). Even more interestingly, I found that lots of folks had built little scopes, mostly reflectors, that could fit in a carry-on bag for airline travel. Probably the most exciting to me was Bob Bunge’s 4.25-inch f/4 reflector, which he named “Pringles” – exciting because it looked like something I could actually build. Although I have not to date built any scopes along those specific lines, Bunge’s little scope showed that it was possible to get good, useful results from a fairly humble structure.

I should mention that I was fascinated with airline-transportable telescopes mostly because I was living in Merced at the time, in California’s central valley. It was a fairly depressing place to be a stargazer. The central valley is ringed by mountains and in the summer, smog from vehicle traffic and dust from agricultural work just pile up in the atmosphere. I actually experienced worse smog in Merced than I do here on the edge of the LA basin. (It didn’t help that the only astronomy club within 50 miles of Merced had gone defunct a year or two before I got there.) Anyway, Vicki and I grew up in Oklahoma and that’s where most of our extended family lives, so we go back to visit once or twice a year. I was really keen to get out under dark Oklahoma skies with a telescope, but I figured it would have to be a telescope I took with me.

So that’s me in the autumn of 2007: mad about telescopes, unhappy with my skies, interested in building something airline-transportable. Then one day I was following London through the toy section of a department store and saw a 3-inch National Geographic branded reflector telescope on sale for about forty bucks. I’d seen a lot of travelscopes in that aperture range online, so I bit.

National Geographic 76mm reflector

I did at least try to use the scope as sold. It was a decidedly mixed bag: the tripod was actually fairly sturdy, and the 6×30 finder, although 100% plastic (even the optics), actually worked. But the whole thing went to hell in the last four inches of the light path. The 0.965-inch plastic focuser was the roughed rack-and-pinion unit I’ve ever used – trying to focus was like driving down a washboarded country road in an old pickup with no suspension. The drawtube was so loose that when it was racked out you could move it from side to side by almost half a centimeter. The final insult, though, is that to make the plastic focuser look like metal they painted it silver – inside and out. That meant that when you looked through the focuser you get all kinds of horrible reflections from inside the focuser drawtube! With an insane amount of effort, one could get something into the field of view, only to be rewarded with the mushiest, most chromatically-aberrated views I have ever seen in a Newtonian, which I blamed (correctly, as it turned out) on the beyond-crappy, entirely-plastic eyepieces. Now I understood why every piece of advice for beginning astronomers included a warning about department store trash scopes. Shame on National Geographic for lending their imprimatur to such an unusable instrument, which was good for only two things: making newcomers hate astronomy, and spare parts. I promptly disassembled mine.

my travelscope v1

Here’s the v1 test rig I lashed together as a proof-of-concept. The scope is held onto a tripod by a 1/4-20 T-nut embedded in the bottom strut. The helical focuser is made from plumbing parts, which are stuck to the upper tube assembly (another plumbing fitting) with Automotive Goop.

my travelscope v2-1

Here’s the v2 incarnation. I shortened the upper tube assembly and painted the whole thing. The grooves at the back of the struts are so I could slide the mirror back and forth to get in the neighborhood of focus, then touch up with the helical focuser. That also meant I had to recollimate, but I had to do that anyway.

my travelscope v2-2

Lots of things require explanation in this picture. First, my super-simple all-axis adjustable spider is just a pencil with an eraser on either end, wedged into the upper tube assembly. There’s a ridge inside the UTA right where the erasers needed to bite, so I ground it down with a Dremel. But I only discovered that after I painted everything, which is why there is a patch of bare white plastic showing. The back end of the scope is the metal-and-plastic mirror cell from the original scope, complete with spring-loaded collimation screws. I had removed the mirror, drilled three equidistant holes in the side of the mirror cell, and glued in 1/4-20 nuts for the eyehooks to thread into. The red rubber band around the mirror cell was to give the struts a bigger, no-slip contact patch. At the front end, you can just make out an extra 1/4-20 nut between the bottom strut and the UTA. I actually had one of these inboard of each strut, because the UTA was slightly smaller than the mirror cell and I needed the nuts as spacers to keep the struts straight. Finally, there is simply a boatload of hardware here: 6 eyebolts, 6 thumbscrews, 6 washers, 3 extra nuts up front…gah.

DIY 3-inch travelscope reborn

Here’s the scope in its final – or at least current – version. The first simplification was to go from three struts down to two. Second was to realize that since I was collimating by sliding and rotating the mirror cell anyway, I could ditch the oversized original mirror cell and just stick the primary mirror in a drain endcap that would match the diameter of the UTA. Third was to realize that I could get by with a lot less hardware: just 4 thumbscrews and 4 washers for a total of 8 bits, and I could even glue on the front washers if I was so motivated. And the wooden struts are even the right width to fit into a Vixen-style dovetail, so I can attach the scope to an astronomical tripod with no extra parts, although one strut is still threaded with T-nuts for attaching to a camera tripod (you can see it mounted that way in this post, in a photo from 2008!). Still rocking the pencil spider. I should at least paint that thing black.

So, how does it work? Surprisingly well, given that there’s almost nothing to it. I had it out last night for a quick spin around the sky, and took in the Pleiades, the Ring Nebula, Albireo, the Double Cluster, and Stock 2. None were spectacular, but all were recognizable. I’ve never rigged a shroud, so scattered stray light definitely gets into the mirrors and eyepiece and cuts down the contrast, which isn’t good since the scope gathers so little light to begin with. I actually got a noticeable improvement in contrast just by cupping my hands above the mirror cell. I should really make a decent shroud and give this odd little duck a fair shake. I’ve only used it a handful of times, always more for testing than for actual observing, and I’ve never flown with it, so it’s never gotten to serve its intended purpose. On the plus side, in addition to throwing up an acceptable image, it makes a great model for demonstrating the principles of a Newtonian reflector. And it’s still the only complete telescope (minus the optics) that I’ve built from the ground up on my own.

The main legacy of this scope was to convince me that I was a telescope user, not a telescope maker. That may change someday – I do tackle the odd DIY project here and there - but it was definitely the right decision in my first year as an amateur astronomer.

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How to build a stand for a Dobsonian telescope

November 19, 2014

DIY dob stand 1

London got an Orion XT4.5 for his birthday last week. We’ve had it out a couple of times and it is an awesome scope. It strongly reminds me of my old XT6–the XT4.5 is a bit smaller, but probably not as much as you’d think from looking at photos of it. It’s solid, moves well, and the optics are great.

It is, however, too short. Even for London, and he’s just a bit over 4 feet tall. Clearly, we needed to get the scope up off the ground. The first night out, just to test potential setups, I put the scope up on an old plastic milk crate. This is the heaviest, sturdiest milk crate I’ve ever seen, and the scope still rocked back and forth on it. We needed a 3-legged solution.

Now, Orion makes a dedicated Dob stand that is really nice. It has grooves instead of divots to accommodate Dobs of many sizes. It also costs about $145, which I think is stark raving lunacy for 4 pieces of wood that any idiot could screw together.

DIY dob stand 2

The Dob stand I am about to show you will also accommodate any size of Dob, as long as you build it that way. It also costs next to nothing. For me it was precisely nothing since I used old crap I found in the garage: wood from a long-defunct futon (the same futon that gave some of its physical body to my old DIY Dob base), some metal shelf supports from a project that never got off the ground, screws from my “spare screw” box, and the modest tools I already owned, namely a saw and a handheld drill.

Step zero was to have London sit in one of the folding chairs that we use when we go camping or up Mount Baldy to stargaze, then set up the XT4.5 in front of him on the floor, pointing straight up, and measure the vertical distance between the eyepiece and his eye. As always when building anything to do with a Dob, it’s better to skew low–it’s always easier to bend down an extra inch to get to the the eyepiece at the horizon than it is to lift your butt an extra inch when the scope is pointed straight up. My rough target height for the stand was about 6 inches.

Conceptually this thing is dead simple: it’s just a ‘T’ of wood, reinforced on either side with the shelf supports. I figured out the dimensions by putting the XT4.5 down on a big sheet of paper and tracing the feet, and then laying the wood down on the paper sheet and tracing the cuts that I would need to make.

DIY dob stand - top close-up

Once I had the basic T-shape together, I set the XT4.5 on it and traced the feet again, directly onto the wood, then used a spade bit to drill out some depressions. The spade bit has a triangular tooth at the center that cuts a deeper hole, and that became the pilot hole for the screw that holds each leg on. So the legs are precisely below the feet of the Dob for maximum strength and stability.

DIY dob stand - foot close-up

In addition to the big screws that run down their long axes, the legs are reinforced with small angle brackets. These are probably overkill, but I wanted to build this thing once and then not worry about it for the next decade or two. In retrospect, angling the two “back” legs toward the center might have been smarter than making them parallel to the cross-bar. But like I said, this thing is probably over-built as it is.

DIY dob stand 3

The last step was to paint it with a couple of coats of black primer, which I also had lying around in the garage. The black paint definitely classes it up a bit. From a few feet away in the dark, you might even mistake it for something that had shipped with the scope.

How does it work? Wonderfully. I took care when I used the spade bit to cut the depressions so that the feet of the XT4.5 just fit inside their outer edges. Once the XT4.5 is settled in place, it will not slide or rock at all; it practically snaps in. You’d have to knock it over to get the ground board to move. You can grab the tube and swing it all over the sky and the ground board and stand stay put. And there’s no detectable vibration. The legs are each 5 1/4″ long and the T is 7/8″ thick, so the height is acceptably close to my “roughly six inches” goal. More importantly, London is able to observe comfortably while seated, whether he’s looking at Polaris low in the northern sky or the Andromeda galaxy dead overhead (and it was the other night, too, darn near straight up).

DIY dob stand 4

There is one final addition I want to make before I call it done: I want to sink a cap nut into the bottom of each leg. That way I can screw bolts of various lengths into the legs to make smaller feet. The stand as built does not rock on any surface on which I have tried it (driveway concrete, grass, and gravel so far), but the bottoms of the legs are long enough that it potentially could. Using bolts as feet would make the contact patches smaller and reduce the opportunity for rocking. Plus, that way the stand can grow with London: as he gets taller, we can swap out the foot-bolts for progressively taller pieces. I’d use cap nuts instead of T-nuts so the support bolts couldn’t punch through and damage the wood.* With a bigger Dob, I might put on casters. In fact, the swiftness and ease with which this thing came together–I did essentially everything but paint it in one afternoon–has got me thinking about building a rolling unit for the XT10. If that ever happens, you’ll read about it here.

* It just occurred to me as I was finishing this post that if it wouldn’t have upset London to start hacking on his brand-new scope, I could have sunk cap nuts into the ground board of the XT4.5 itself, and put long threaded bolts straight into them to make feet. If I ever get an XT4.5 of my own, I’ll probably do exactly that.**

** It further occurred to me after the post went up that the ground board already has threaded holes for the rubber feet, which have embedded bolts and screw in from the bottom. So in fact if I had thought it through I probably could have skipped the whole Dob stand entirely and just screwed 6-inch-long bolts into the ground board; if the included rubber feet are loafers, those long bolts would be stiletto heels. I haven’t actually tested that setup, mind you, but it seems like it ought to work.

If you don’t have a bunch of crap lying around in your garage, you can probably still build something like this for under $20, maybe less than half that if you can scrounge the wood. If you don’t have metal shelf supports and don’t want to spring for them, you could cut pieces of wood to reinforce each side of the ‘T’ diagonally. Painting is optional, the thing works just as well in its unpainted ugly state. If your woodworking skills are like mine–nearly nonexistent–you can also use the unpainted unit to make your carpenter friends cry. Have fun!

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An Astronomy Wish List for Beginning Stargazers

November 14, 2014

One of my main goals with this blog has always been to make amateur astronomy accessible to newcomers. So it’s probably past time that I post a list of the top 10 things I think a beginning stargazer needs. I’ve ranked them here roughly by my perception of how important or useful they are, especially for people just starting out. Almost everything on the list is something I’ve either owned or used myself, and the important exceptions are noted.

chandler_planisphere

1. A Planisphere

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. Planispheres aren’t just for newbies, either – I know a lot of experienced observers, myself included, who keep one handy to do a quick check on what’s up, or will be up, at a given time. There are lots of planispheres on the market but I prefer the simplicity and utility of The Night Sky series by David Chandler, which come in different models for different latitudes. I suspect that most readers of this blog will want the 30-40 degree one (link) or the 40-50 degree one (link); if you’re outside that zone, search for one that matches your home latitude. Cheap alternative: print out the free Evening Sky Map for this month (here), which in addition to a star chart has lists of objects for naked eyes, binoculars, and telescopes.

Orion Redbeam flashlight

2. A Red Flashlight

Yep, I’m giving this the number two spot. Why? Because you’ll need one right away, and you’ll never stop needing one as long as you’re stargazing. For my first month as an amateur astronomer, all I had were a planisphere and a red flashlight, and I still had a lot of fun out under the stars. As with planispheres, there are lots of models available. I like this one from Orion (link) – it’s small enough to keep on you at all times and just bright enough to be useful (a lot of red-beam flashlights are too bright). Cheap alternative: get a regular flashlight and tape some red cellophane over the end, or even some brown wrapping paper or part of a paper bag. If it’s still too bright, do what I do and tape a coin over the bulb to block more than half of the light.

Nightwatch cover

3. Nightwatch

That’s right, not just any beginning astronomy book, but this particular one (link). Why? I wrote a whole post about that (here), but here’s the short version: no other single book covers so many aspects of amateur astronomy, from the kinds of celestial phenomena to naked-eye, binocular, and telescopic observing – and what kinds of binoculars and telescopes to consider buying. It even has star charts to get you started as an observer. The Backyard Astronomer’s Guide (link)treads similar ground, with more detail on the gear and how-to side at the expense of star charts or guidelines for finding specific objects. Cheap alternative: see if you can find a used copy, especially of one of the older editions (the current edition is the 4th) – some of the specific gear recommendations may be a little dated, but everything else will be just as useful.

4. Binoculars

I put binoculars ahead of a telescope for two reasons. First, if you’re on a tight budget, you can get decent binoculars for a lot less than you can get a decent telescope. Second, like the red flashlight, they’re something you’ll never outgrow. I am a committed binocular observer, but even if you’re not, binoculars can be a huge help at the telescope, mainly for finding your way around the sky before you attempt a star-hop in the ‘scope, but also for appreciated big extended objects like the Pleiades, the Hyades, the full extent of the Andromeda Galaxy, and so on. There are tons and tons of binoculars out there. Here are a couple of models that I own and use a lot, that I think are good values: for a general instrument, the Celestron UpClose 10x50s have decent optics and build quality and cost only $25-$30 (link). I spent one of my most rewarding nights of stargazing using only this instrument, a red flashlight, and a book I’m about to recommend (Gary Seronik’s Binocular Highlights) – here’s that observing report. If you’re really into binos and want to try some big guns, the Celestron SkyMaster 15x70s are a nice first step (link). They’re light enough that most folks can hand-hold them, but they’re easy enough to mount on a tripod if you’d like a steadier view. I use mine a LOT – I’ve seen almost all of the Messier objects with them, and probably close to 100 non-Messier NGCs and other deep-sky objects. Cheap alternative: whatever binoculars you already have lying around, or that you can pick up at a thrift store, or borrow from a friend. It was a view of Jupiter and its moons in the cheap 7x35s I’d had since high school that first got me hooked on stargazing. Any binoculars will be a useful and probably mind-blowing step beyond what your naked-eyes can show. That said, avoid binos with red-tinted “ruby” lenses if you can – they look and sound high-tech, but the tinting is pointless and crappy and only there to cover other optical faults.

Orion Starblast

5. A Decently-Sized, Solidly-Mounted Telescope

I imagine a lot of beginning stargazers must get frustrated when they ask what telescope to buy, and more experienced people keep saying, “Get a planisphere and some binoculars and learn the sky first.” We say that because you can get months or years out of enjoyment out of those things, for an outlay well under $50, whereas most of us would have a hard time recommending a telescope under $100 as a rewarding instrument. But if you’re here for scope recommendations, I have some.

A word about the qualifiers I put in the heading: by “decently-sized” I mean something with an aperture in the neighborhood of 4 inches (100mm) or larger. Yes, people can and do get a lot of enjoyment out of smaller telescopes, and some of us have a possibly unhealthy fascination with tiny telescopes. But if you’re just starting out, you need some early wins, and a 4- to 8-inch scope will make everything bigger and brighter. “Solidly-mounted” is crucial; on many objects rewarding magnification starts at 50-100x, and at those magnifications, every little shake in the scope or mount is going to be magnified 50 to 100 times. A shaky mount can make an otherwise decent telescope essentially unusable. I suspect that frustration with shaky mounts has probably killed more budding observing careers than any other single factor.

So what should you get? If you know you’re in for the long haul, follow the standard advice and get a 6- or 8-inch Dobsonian. I’m a big fan of the Orion XT6 (6 inches, ~$300) and XT8 (8 inches, ~$370), but Dobs are hard to screw up and you can’t really go wrong with any of them. If you’re less certain, or have less dough to throw around but still want a decent scope, get a smaller Dob or tabletop scope on a Dobsonian mount. Popular choices that don’t suck include the Orion SkyScanner 100 (4 inches, ~$125, observing reports here and here), Orion StarBlast 4.5 (4.5 inches, ~$200), Orion XT4.5 (4.5 inches, ~$260), and the Astronomers Without Borders OneSky (5 inches, ~$200, observing report here [as the Bushnell Ares 5 – same scope, different branding]). Personally, I’d avoid the Celestron FirstScope and Orion FunScope (3 inches, $35-70 depending on model and outlet), for reasons explained in this post. Cheap alternative: already covered – binoculars and a planisphere! Yes, you can probably find some rickety undermounted disaster on eBay or Craigslist for less, but it will almost certainly not be a good choice for a beginner. As a beginner you need something that Just Works, not a project scope. Wait to rescue one of those trash-heap darlings until you know what you’re doing.

Field Map of the Moon

6. A Moon Map

Depending on your tolerance for light pollution and willingness and ability to navigate when there are few visible stars in the sky, most other astronomical objects look less than stellar for at least one week each month, and maybe two, centered on the full moon. Also, the moon is one of the few objects that looks fantastic in almost any telescope. And you’ll enjoy looking at the moon more if you have some idea of what you’re looking at. Plus, moon maps are so cheap ($5-$12 for all of the models listed here) that there’s not much reason to pass on getting one. Sky & Tel have a couple of models available, their basic laminated moon map (regular, reversed) and the much nicer Field Map of the Moon (regular, reversed). As the links indicated, both are available in two versions, one showing the moon as it is in the sky, and the other with the moon reversed from left to right, to match the flipped orientation in most refractors and CATs. Cheap alternative: if not a moon map, how about a moon app? My favorite is Moon Globe by Midnight Martian. The basic app is free, and Moon Globe HD is a worthwhile upgrade for a couple of bucks. You can ignore my griping about apps wiping out your night vision, because the moon is bright enough most nights to wipe out your night vision all by itself. And for your computer, Virtual Moon Atlas is the reference standard (link); it’s been continuously updated for more than 10 years and is a very mature piece of software.

Turn Left at Orion

7. Books That Show You the Way

You can get a really good start with free resources like the Evening Sky Map and Stellarium (free planetarium software, get it here), but a lot of beginning stargazers find it helpful to have a book that not only tells you what to point the telescope at, but also tells you how to get there. Turn Left at Orion (link) is the standard recommendation here and indeed it will show you a lot; I own a copy and it was very helpful in carrying me along until I could fly for myself. A not-so-obvious choice that I also recommend a lot is Gary Seronik’s book Binocular Highlights (link) – almost every one of the 99 objects he shows you how to find in that book are dynamite targets for telescopes of all sizes, and the finder charts are very clear and well thought-out. Although I haven’t used it myself, Peter Birren’s Objects in the Heavens (link) is another popular choice–frequent commenter Doug Rennie calls it “the best observing guide out there”. If you’re a little more seasoned or just want more of a challenge, Sue French’s books Celestial Sampler (link) and Deep Sky Wonders (link) have zillions of things to find, organized by constellations or small areas of the sky, with targets appropriate for scopes of all sizes (Sue does most of her observing with a 4-inch refractor and a 10-inch reflector). Finally, the Deep Sky Companions series by Stephen James O’Meara is nicely organized and presented, with 109 objects per book plus a few bonus objects at the end; the individual titles are The Messier Objects (link), The Caldwell Objects (link), Hidden Treasures (link), The Secret Deep (link), and Southern Gems (link). Cheap alternative: a used copy of one of the above. Heck, used copies of the 2000 edition of Turn Left are currently going for a buck and a half on Amazon – observing guides don’t get much better or cheaper than that.

Pocket Sky Atlas

8. The Pocket Sky Atlas

Wait, if I just recommended books that will drive you to dozens or hundreds of objects in the sky, why do you need an atlas? Because no matter how nice the path that other authors have blazed for you, sooner or later you are going to want to step off it, and go wander in the wilds of the sky on your own. When you take that step, you’ll need an all-sky atlas.

Once again I’m skipping past a lot of other possible contenders to recommend a single book. There are lots of sky atlases out there, which cover a wide range of “depths” in terms of numbers of stars and objects shown. Some, like the Bright Star Atlas (link) and the Sky Atlas for Small Telescopes and Binoculars (link), simply show too few stars and objects to help you get on target with a telescope, although they are both fine binocular atlases. Others, like the Sky Atlas 2000.0 (link) and Uranometria (link), are overkill for a beginner – you’ll know when you need to move up to something like that. The Pocket Sky Atlas (link) hits a happy medium: for most of the hundreds of objects that beginners are likely to go after, it shows enough stars to get on target, but it’s still conveniently sized and intuitively laid out. The PSA has been my guide for the Messier objects, the Caldwells, the Astronomical League’s Deep Sky Binocular, Urban Observing, and Double Star observing programs, and the first 40% of the Herschel 400, and I’m still very far from exhausting the 1500 or so plotted deep-sky objects. (For the record, I also own the Bright Star Atlas, Sky Atlas for Small Telescopes and Binoculars, the Cambridge Double Star Atlas, and Uranometria, and I have used the Sky Atlas 2000.0; I recommend the PSA because it’s my most-used atlas, not my only one.). For a dissenting view and an alternative recommendation, see this post and its comment thread for a discussion of Eric Karkoschka’s Observer’s Sky Atlas (link). Cheap alternative: there are several nice sets of free, printable atlases that cover the entire the sky; these have the advantage that you can print only the pages that you need, and at the level of detail that is best for your equipment. My favorites are the Mag 7 Star Charts (link) and the TriAtlas (link); this last one is actually three atlases of varying sizes and levels of detail.

Seeing in the Dark

9. Books About the Why

Many books will tell you what’s in the sky and how and where to go find it, but only a few capture the “why” of stargazing. A lot of committed observers end up spending a considerable amount of time alone in the cold and the dark – what is it that keeps drawing us back out there? I am certain that there are almost as many sources of inspiration as their are stargazers, and what works for one may not work for the next. But this is my list and I have to recommend something. The two books that crystallize for me the wonder and romance of observing the night sky are Leslie Peltier’s Starlight Nights (link), and Timonthy Ferris’s Seeing in the Dark (link). The former goes in and out of print. Sadly it is out of print right now, and used copies are going for ruinous prices. Happily there is a Kindle edition that is not too steep. Seeing in the Dark is one of my favorite books of all time, and I wrote a whole post about it, which you can find here. Cheap alternative: used copies of Seeing in the Dark start at $0.01 plus shipping, so you’re not risking much by giving it a try.

Universe the definitive visual guide

10. An Almanac of What’s Up There

For cloudy nights and quick reference, it’s handy to have a book that just has tons of data. Say you want to find out how many moons in the solar system are bigger than Mercury*, or the orbital period of Neptune**, or the distance to the Orion Nebula***. Yes, you could just look all of that up on Wikipedia, but sometimes it’s faster and easier to use a book. Plus, everyone needs stocking stuffers, right? Now, there are shedloads of books that cover this ground, and if you have access to a Barnes & Noble or other large brick-and-mortar bookstore you can probably find any of half a dozen likely candidates on the bargain rack. I have a couple of favorites to recommend. First, the pocket-sized Smithsonian Handbook: Stars and Planets by Ian Ridpath (link) has a special place in my heart, because it was the first astronomy book I bought back in 2007 when I was first getting into the hobby. Although I couldn’t have known it at the time, I got lucky: the book has a simply amazing amount of information in a very compact package, and I’ve keep it close by ever since and referred to it often. If you want a big fat book to curl up with on a rainy evening, Universe: The Definitive Visual Guide is hard to beat (link). If there’s an important topic in astronomy that’s not covered, I don’t know what it might be. I wrote a whole post about this book, too – go check it out. Cheap alternative: A used copy of one of the above. Universe seems to be out of print now, but you can get new copies for under $20 and used copies for about a buck and a half, plus shipping.

Conclusion

Well, those are my top recommendations. If there’s something awesome that I missed, let me know down in the comments. And in the words of Cloudy Nights user gnowellsct, “May peace be upon your high end consumerism”.

- – – – – – – – – – – – – -

* Two: Ganymede (the largest moon of Jupiter, and the largest moon in the solar system) and Titan (the largest moon of Saturn).

** 164.9 Earth years.

*** Approximately 1344 light years.

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Timothy Ferris on galaxies, the universe, and time

November 12, 2014
Abell 2744 from Hubble

Abell 2744, Pandora’s Galaxy Cluster, from the Hubble Frontier Fields. Click through and get lost for a while.

This passage has been lodged in my head since I first read it years ago, and it is still the best short explanation I’ve read for the scale of galaxies and the universe. From Seeing in the Dark, pages 253-254:

Were the Sun a grain of sand, Earth’s orbit would be an inch in radius, the solar system the size of a beach ball, and the nearest star another grain of sand four miles away. Yet even on that absurdly compressed scaled, the Milky Way galaxy would be a hundred thousand miles wide. Galaxies are so big that once you get up to their scale, the universe starts to take on an almost country-cottage intimacy. The larger galaxies in clusters like the Local Group, to which Andromeda and the Milky Way belong, typically lie only a couple of dozen galactic diameters apart from one another – comparable to dinner plates at the ends of a twenty-foot-long dining table. Add in the galaxies’ halos of stars, globular clusters, associated hydrogen clouds, and dark outer disks, and they almost impinge on each other. On the same scale, the Virgo supercluster, of which the Local Group is an outlying member, comprises ten thousand plates scattered across an area not much larger than a football stadium, and the entire observable universe has a radius of only about twenty miles. From a galaxy’s point of view, the universe isn’t all that large.

Andromeda_galaxy_2

The Andromeda Galaxy in ultraviolet light, from NASA’s Galaxy Evolution Explorer. You want to click through for the full image – trust me.

The trouble is that it’s difficult – probably impossible – for a human to make the mental leap to galactic scale. The very concept of space is inadequate for dealing with galaxies; one must invoke time as well. The Andromeda galaxy is steeply inclined to our line of sight, only fifteen degrees from edge-on. Since the visible part of its disk is roughly one hundred thousand light years in diameter, the starlight reaching our eyes from its more distant side is about one hundred thousand years older than the light we simultaneously see coming from the near side. When the starlight from the far side of Andromeda started its journey, Homo habilis, the first true humans, did not yet exist. By the time the near-side light started out, they did. So within that single field of view lies a swath of time that brackets our ancestors’ origins – and that, like the incomplete dates in a biographical sketch of a living person (1944-?), inevitably raises the question of our destiny as a species. When the light leaving Andromeda tonight reaches Earth, 2.25 million years from now, who will be here to observe it? We think of Einstein’s spacetime as an abstraction, but to observe a galaxy is to sense its physical reality.

Andromeda galaxy by Isaac Robers 1899

Andromeda as photographed by Isaac Roberts in 1899 (borrowed from Wikipedia)

…As objects of study, galaxies are bottomless. If we spent eons observing the Andromeda galaxy with ever better equipment, we would, presumably, learn a great deal – indeed, one hopes that this will happen – but there would always be more to learn, if only because so many things keep changing there. To pick a literally glaring example, it is estimated that more than fifty thousand stars have exploded in Andromeda in the past two million years: The light from all those supernovae is already hurtling through space toward our telescopes, part of Andromeda’s past and our future. A galaxy is not so much a thing as it is a grand, glorious exemplification of the scope of cosmic space and time.

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The lunar ‘Cheshire Cat’ revisited, and problems of contrast

November 3, 2014

2014-11-02 London moonwatching

Just a quick post before I head off to work. London has the telescope bug and he has a birthday coming up, so we were looking at various scopes on Amazon and other places. He wasn’t clear on the distinction between the three main telescope designs, so we hauled out the DK Universe book and looked at the ray diagrams the three kinds (refracting, reflecting, and catadioptric). He was familiar with refractors, like his 60mm Meade, and reflectors, like his Astroscan, but was less familiar with catadioptric scopes, which is not super-surprising since I’ve used my Maks hardly at all in the last year and a half, other than last year’s All-Arizona Star Party. The sky was clear and the moon was high, so we popped outside and set up my 90mm SkyWatcher Mak for a quick look at the moon. Astonishingly, I had not had this scope out in more than two years, since July of 2012.

2014-11-02 waxing gibbous moon - snapseed

Here’s my best iPhone photo of the moon from last night. Up near the top of the terminator you can see two glowing dots like eyes peering over the limb of the moon. If you click through to the full-size version, you’ll see that the eyes have a wide mouth below them and that one nostril is showing. Yep, that’s the lunar “Cheshire Cat”, which I first identified back in November, 2010. It was nice to see it again.

While I was processing that photo I noticed something alarming: a circle of glare around the moon that was bright enough to make the eyepiece field stop visible. It’s more apparent in this over-brightened version:

2014-11-02 waxing gibbous moon - light scatter

I was shooting through the Celestron 8-24mm zoom, just like Saturday night. Since I had a comparable shot with the same eyepiece through the C80ED from that evening, I dug out the raw photo and tried brightening it up to see how much glare would appear.

2014-11-01 waxing gibbous moon - light scatter

The answer is “almost none”. I used the same tool in GIMP (‘Curves’), and I brightened the image way beyond what I did with last night’s shot through the Mak, and the space around the moon is still pretty black in the C80ED shot. Not grey, as in the Mak shot. And this was only with tweaking the brights up, and not moving the darks down, which would be cheating since it would mask the problem.

It’s tempting to read this as a refractor-vs-Mak thing, but it might not be so straightforward. In this case the refractor has very good optics and coatings, so it’s near the upper end of what refractors are capable of in terms of control of stray light. But the Mak does not have fully multi-coated optics–this SkyWatcher version only has ‘coated’ optics, which means possibly as little as one coat of MgF2 on only the outer surface of the corrector. I have heard from someone (Doug or Terry, maybe?) that this particular model of SkyWatcher 90mm Mak has poorer contrast than the comparable but fully multi-coated Celestron C90–irritatingly I cannot find that post or comment at the moment, but I’ll post it if it turns up. Also, the C80ED has a long-ish dew shield which helps control stray light entering the objective, whereas the Mak does not; you can buy or fashion such things for Maks, but I haven’t taken either of those steps. Finally, I’ve seen some threads on CN about glare from the baffle tube in Maks and SCTs, so that’s another possible culprit here.

An informative test would be to pit the C102 against the Apex 127 on the moon, with a homemade foam or cardboard dew shield on the Apex to eliminate that variable. If I get time this evening or next, I may just try that.

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