Archive for July 20th, 2012

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Suburban Messier project–gear? rules? company?

July 20, 2012

Part 1: Inspiration

I am contemplating a new observing project. It started back in May, when Doug wrote a long comment that ended with:

You know what we need? Really, really need. One of these guys: O’Meara, Sue, Tony Flanders, etc. to write a book complete with sketches, using a Real People telescope in a typical residential suburban setting. A Celestron or Meade or Orion sub-$500 scope from a backyard or driveway in Torrance or Sacramento or Cleveland and do all the Messiers . . . or whatever. Then you’d have something you really could use with goals you had a realistic chance of achieving.

Come to my house, or one like it and do all your observing here. For a year. Sketch what you see through the eyepiece of a real world scope in a real world setting. Then I can say “Ah, so THAT is the pattern I am looking for.” And will recognize when I see it….

Hey, Matt, YOU have real world scopes. And a backyard. So, maybe you?

And I wrote:

Your question inspires me. I had already been thinking about doing a Messier survey with a small scope, just to see what could be achieved. I may fire up that observing program one of these days. If I do, I’ll try my hand at sketching, too. It probably won’t be soon. Our skies here suck in the summer, with lots of haze and smog and not much wind to blow it out. And it’s too hot to go to the desert. But I might do some runs up Mount Baldy, which is acceptably dark but not stupid-dark like the Mojave.

So, at first I was just thinking of doing a small-scope Messier tour, from wherever, including Mount Baldy and the Salton Sea. But I think that would be of limited usefulness. The orange/yellow zone skies on Mount Baldy are something that a lot of folks would have to drive to get to. The blue/grey zone skies at the Salton Sea are way too dark to be useful for what Doug was describing. Not at all like what you’d get in “Torrance or Sacramento or Cleveland”. If it’s going to be a suburban Messier survey, it needs to be from in town–specifically, from my front yard and driveway (my back yard has a verdant canopy of greenery which is beautiful but not good for stargazing).

The other part of this is that I have never sketched deep sky objects. I have often sketched planets, very approximately, to show how many cloud belts and moons I could see, and I have been sketching my way through the AL Double Star Club observations, but c’mon, that requires drawing 2-4 tiny circles. I haven’t sketched DSOs, and I think it’s a skill I should cultivate.

My desire to learn to sketch DSOs has been intensified by observing with Terry Nakazono, who sketches, and by seeing the really nice sketches done by fellow PVAA member Justin Balderrama (who blogs here). Justin is in his teens, but you’d never know it to flip through his observing logbook. And these guys don’t make a big deal out of their sketching–it’s just part of their observing technique. I dig that. I’d like to do that.

Part 2: The Rules

Okay, so I’m going to observe and sketch all the Messier objects from my yard. Using what?

For a while I toyed with the idea of getting one of Orion’s $100 tabletop scopes, the SkyScanner 100 or GoScope 80, just for this project. But lately I’ve been cutting back on scopes–I just sold Shorty Long and Stubby Fats–and I’m loathe to turn around and start piling them up again. The scope is going to have to be one I already own.

My current lineup includes:

  • XT10 (10″ or 254mm)
  • Apex 127 (5″ or 127mm)
  • Skywatcher Mak (3.5″ or 90mm)
  • Travel Scope 70 (2.75″ or 70mm)
  • SV50 (2″ or 50mm)

Since this is a small-scope project, the XT10 is out. I’m throwing out the Apex 127, too. Using Doug’s original “sub-$500″ criterion you could buy the OTA, but you couldn’t mount it securely, not unless someone was having a ridiculous sale on mounts. And, fer cryin’ out loud, Uncle Rod uses a 5” Mak as his back-up deep-sky scope (which is one of the reasons I got one for myself), so I think it’s big enough to also be disqualified for a small-scope challenge.

On the other hand, the SV-50 is too small. Reeling in all the Messiers with it would be an interesting challenge from a dark site, but from town it would be straight-up murder. Plus, I doubt too many amateurs these days are starting out with a 50mm scope. Anyone who can afford a 50mm scope can probably afford 10×50 binoculars (currently $25 at Amazon for a decent pair), and those will frankly be a lot easier to use.

That leaves the 90mm Mak and the 70mm refractor. And here I’m just going to make a command decision and go for the 90mm Mak, for a lot of reasons. The biggest is comfort. If I’m really logging, sketching, and taking notes, I reckon I’ll need about a half hour per object. Multiplied by 110 objects means 55 hours of observing time, minimum, spread out over the next year or two. If I’m going to spend that much time with any one scope, it has to be comfortable for both eye and body. The optics on the Travel Scope 70–on my example, anyway–are swell up to about 20x, acceptable up to about 40x, and frankly pretty gross after that. In contrast, I’ve had the little Mak up over 200x regularly with no image breakdown, and it’s got a nice flat field that is essentially free of aberrations.

The “body” side of the comfort equation is why I’m not using my son’s Astroscan. For him it’s fine sitting on a folding chair or even on the ground. For me it needs a table, which is never as stable as a tripod, and more of a pain to move around late at night in the dark. And like the TS70 it is wonderful for bright, wide, low-power scanning, but runs out of magnification pretty fast.

My one reservation about using the 90mm Mak is the long focal ratio–1250mm, or two inches longer than the XT10 even–which means high minimum powers and a narrow field of view. The max true field in this scope is only a little over 1 degree (compared to a max true field of about 4 degrees for the TS70), which is not enough to fit in the largest Messier objects. I’m not worried about the Pleiades–I’ll just scan around to see them all–or M31, where I’m unlikely to see more than just the core from town. It’s M33, the Triangulum galaxy, a large not-quite-face-on spiral galaxy, that makes me sweat. It’s going to be hard enough to see from town in the first place, let alone in a scope that won’t fit the whole thing into the field of view at once. But no scope is perfect for every job, and I want this to have some element of challenge, so I’ll stick with the little Mak.

I’ve also decided to eschew fancy eyepieces for this project, and just use ordinary Plossls, probably my 32mm (39x) and the three that came with the scope: 25mm (50x), 12.5mm (100x), and 6mm (200x). I strongly suspect that the 25mm is all I’ll need for most objects. A lot of DSO hunters recommend a 1-degree true field for finding objects and a 2mm exit pupil for observing them. In the 90mm Mak, the 25mm Plossl gives almost exactly those values:

True field of view (TFOV) = Apparent field of view (AFOV)/magnification; in this case 52 degrees/50x = 1.04 degrees.

Exit pupil = aperture/magnification; in this case 90mm/50x = 1.8mm exit pupil.

As with the fancy eyepieces, using the nice Astro-Tech dielectric diagonal feels like cheating.  I sold the 90-degree prism diagonal that came with the scope–I couldn’t get it out of the house fast enough. That leaves either a 45-degree erect-image prism diagonal that I just discovered I had the other day (which is the only reason I haven’t sold it yet), or an $8 mirror diagonal I bought off Cloudy Nights. Either is probably a good match for what would come with a beginner scope, but I’m going to use the cheap mirror diag. More Maks are sold with prism diagonals, but whatever, I can’t put myself through that many hours of looking through a low-end prism, and I don’t think substituting a piece of gear that costs less than ten bucks will corrupt the replicated beginner experience.

Now, the big question: what finder should I use? At first I was thinking I would just roll with the 9×50 RACI. It’s my favorite and most-used finder, and observing with it would be a cinch. But I am reluctant to do that, for two reasons. First, I know how to find stuff with a 9×50 RACI. It’s not going to push me or teach me anything. Also, I think it sort of violates the spirit of observing with the stuff that Joe Newbie would have available. A 9×50 RACI is a big upgrade, close to half of what I paid for the 90mm Mak in the first place. That leaves other three finders that I have lying around that I could potentially use:

  • The 20mm erect-image finder that came with the scope. Gag me with a stick. I know that a lot of 90mm Maks ship with these things, but they shouldn’t. This finder is good for two things: gathering way too little light, and making people hit their face on the scope when they try to get their eye behind it (you can see a close call here). For the love of Pete, if your scope came with one of these and you can’t afford anything better, get over to Telescope Warehouse and get a 6×30 finder with a bracket for $18-20 or a dot finder for $14 (also, if you just flat need a scope, they have 70mm achromatic refractors for $22 and 90mm achromats for under $40, although you’ll have to rig a mount).
  • The 6×26 straight-through erect-image finder that came with the Apex 127. I forgot this existed until I found it in an unlabelled box when I was cleaning up the front room.
  • The red dot finder that came with one of my other scopes at some point, which I never got around to selling.

There are actually valid arguments for both the 6×26 and the RDF. Most entry-level scopes these days ship with RDFs, including all of the Orion tabletop scopes, so for replicating the beginner experience it is probably the most legit. With a max true field of 1 degree in the scope, though, it will make for some punishing star-hops. The argument for the 6×26 comes from Jay Reynolds Freeman’s essay “Finding deep sky objects rapidly”:

I use magnifying finders instead of unit-magnification ones because I need to see more than just naked-eye stars to point the telescope accurately, and the extra light gathered by magnifying finders provides them. I use straight-through ones because I can keep both eyes open and use the finder cross-hair as a reflex sight, fused by the brain with the view through the other eye.

I don’t know that trick, but I’d like to.

Both the RDF and the 6×26 will be irritating in that they’ll force me to get my head behind the scope, but I reckon it’s time I learned more than one way of finding so I’m willing to make the sacrifice. Anyway, I’m still undecided on which one to use, but maybe you can help me out with that.

Part 3: Audience Participation

Now, gentle reader, I have three questions for you. Before we get to them, let’s review the plan:

I will (1) observe–or attempt to observe–and (2) sketch (3) all of the Messier objects (4) from my front yard/driveway (5) using my 90mm Mak and (6) inexpensive eyepieces. I don’t have a fixed schedule in mind, but doing the whole list in a year does not seem prohibitively difficult or time-intensive; that’s only 2 objects per week, on average.

The one hang-up there is that the dimmest objects will probably have to be observed when they culminate (get as high in the sky as they’re going to from  your latitude), possibly after midnight when a lot of folks shut off their lights and the LP slacks off a bit, which dictates a particular season. For the big mess of galaxies in Virgo-Coma, that means springtime, when the weather is iffy. I have gotten several of the Virgo-Coma galaxies from my driveway with 15×70 binoculars, but I wasn’t sketching or taking extensive notes, which will eat up observing time. In some cases it might not be a matter of going on dawn patrol to catch ones I missed, because in a small scope under LP they might only be visible near the zenith, late at night, during a narrow seasonal window. I’m going to try to get it done in a year, but if it slops over into a second year I won’t be devastated.

Now, if you’ve managed to hang with me this far, I have questions for you:

  1. Following the discussion in the previous section, which diagonal and–especially–which finder do you think I should use? Do you care? Is your interest more in seeing the beginner experience replicated from top to bottom, or just in the descriptions of the objects through a modest scope under light-polluted skies, in which case the mode of finding doesn’t really matter?
  2. Can you think of any other rules or conditions that would make the survey more informative/relevant/legit/challenging?
  3. Would you like to join me?

I’m dead serious on that last point. If you’ve never seen all the Messiers before, feel free to use whatever scope you like, from whatever observing site you like. Or use your big scope from home, or your small one from a dark site, or whatever–set whatever conditions you like for your Messier project. Sketch or don’t sketch, although it would be cool if you did, because then we could compare notes.

I’m planning to set up a sidebar page for this anyway, and scan and post my sketches and observing notes. I’d be happy to host yours, too, if you send them to me. I get 3 gigs of space on this blog, and so far in all of my time here I’ve only used 1/12 of it, so I’m not worried about running out of space by hosting too many images or PDFs or whatever.

I’d like to set an arbitrary start date of August 1 for my own survey, but if you happen to stumble across this post a few months from now and want to join in then, feel free.

Any takers? If so, let me know in the comments.

Clear skies!