Sunday, August 30, 2009

 

Digital Setting Circles on the Cheap


I’m lazy. Which should come as no surprise to those of y’all who know me personally, or even those who just read this blog regularly. That doesn't mean I won’t pack up a car-full of gear on occasion and head down to the Chiefland Astronomy Village for nights of hitting it hard with one of my CATs. I even used to do that for brief Saturday night forays to the club dark site. But lately? Not So Much. Since I’ve made CAV a more regular getaway, I don’t feel as pushed to do imaging and other “serious” projects from our good (but hardly perfect) Tanner-Williams, Alabama site. There’s also the weather we’ve had over the past year. There’ve been some good nights, but it’s usually not apparent how good or bad one will be till close to sundown—I hate loading tripods and mounts and CATs and computers and all the other junk at the last minute.

I’ve experimented with several nice-‘n-easy observing alternatives since last spring. First I tried Old Betsy, my 12.5-inch truss Dobsonian. She gives good sky, but at 2 a.m. even her relatively portable mirror box is a complete pain to tote back up the front steps of the Old Manse. How about my 37-year-old telescope? Aside from the need to drag out a GEM for her to perch on, I couldn’t help but wish for a little more aperture. Same goes for the recently acquired and restored RV-6. The aperture need also eliminated my refractors, the StarBlast, another couple o’ Newts hanging ‘round here, and my ETX 125, Charity Hope Valentine (though Sweet Charity is a good choice for those iffy sucker-hole-infested nights).

The obvious candidate? Old Yeller. Well, formerly yellow (baby-poop yellow) anyhow; my Konus 8-inch f/5, who was rebuilt into a groovy and portable Dobsonian by my friend Pat R. I had no doubt this telescope would be up to the task. 8-inches is enough aperture to reveal tons of cool stuff. Even in these aperture-jaded times, I’m amazed at how spectacular Messiers look in an 8-inch from darkish sites, and an 8 can, believe it or not, also take you way beyond the Messier list. At f/5, the scope really lets my beloved Ethoses strut their stuff, too. Pat’s design combines extreme portability and ergonomic functionality, and there’s not too much else to wish for. I haven’t had many opportunities to use Old Yeller since Pat finished it (it was brilliant at the last International Sidewalk Astronomy Night), but I knew the telescope could do great from a dark location. There was only one major problem with it: star hopping.

Don’t get me wrong; I’ve done my share of object finding with Telrad and star atlas. Thirty-five years of it, to be exact. And it can still be fun. Once in a while. It’s not so much that go-to has spoiled me as that I have come to the realization that, given my insane schedule and the vagaries of Gulf Coast weather, I prefer to look at stuff rather than hunt for stuff at the moment. Old Yeller? He had a cute Rigel Quikfinder, and that was it, which wasn't enough. I decided I’d need to shell out a C-note and a half or so for a set of encoders and mounting hardware so I could use my Sky Commander computer with the hound, but I never pulled the trigger on that. Somehow it seemed untrue to the minimalist philosophy inherent in the telescope’s design. OK, OK, you got me. The main reason was that I am stingy in the Scrooge McDuck mold.

And so the idea of using Old Yeller on a more regular basis stalled. Until I spent the better part of an hour breaking down my NexStar 11, Big Bertha, and getting her packed in the car at 2 a.m. for the trip home. This on an evening when I’d seen—maybe—a handful of objects due to unrelenting clouds. “Gotta be something better than this.”

Were there alternatives to equipping the scope with the Sky Commander? I had a Palm PDA, and I knew people were successfully using these as DSC systems. But I’d still need encoders. Buy ‘em used? Used encoders are usually accompanied by DSC computers (which I did not need). “Hmm. What did that dude use with his Odyssey 1 out at the old Dark Site in the 80s?”

Thinking back to the dark ages, I recalled a member of our club regularly amazed us by guiding his 13.1-inch Coulter to object after object with the aid of an HP programmable calculator. His “system,” which quite a few folks used back when DSCs were neither common nor cheap, involved analog setting circles. Analog altitude and azimuth setting circles. I am no stranger to setting circles on equatorial mounts; I still teach my students to use them with their fork-mount non-go-to LX10s. And I've used them on more than one occasion to find objects with the Ultima C8.

In fact, theoretically, alt-az circles might work even better than those on an equatorial. In alt-az, I’d be freed from the need to do a close polar alignment, the usual bug-a-boo when it comes to equatorial mount setting circle accuracy. Also, since I’d be making ‘em myself, they could be nice and big, and in the world of analog circles, “bigger” goes a long way toward “better.” The more I thought about it, the more I began to believe analog setting circles would be effective and would encourage me to use my 8-incher a lot more. I rung-up Pat to suggest he do the same for his nearly identical 8-inch, and shortly we were brainstorming.

I know what the  title up top says, but what I was proposing to Pat was not really a DIGITAL setting circle system. Maybe half digital. It would be analog in part, since I would be using an analog circle for azimuth, at least. The other one-third of the system, the computer, would be digital. I eventually wound up with a digital solution for the altitude axis, too; which makes it a 2/3rds digital setting circle system, I guess

Since I’d seen the concept work before, it was just a matter of implementation. One thing was sure, the big stumbling block of yore is gone: the need to have a computer on hand to figure out the altitude and azimuth of objects at any given time. In the old days, you could use a programmable calculator, an expensive and far from user friendly calculator. Or you could use a PC. Almost nobody had a notebook in those days, so people resorted to wacky dodges like a program that would speak the coordinates of an object.

You ran inside, picked the DSO of interest on the PC, and hung a computer speaker out the window. The program would, in a Majel Barrett Roddenberry voice, then continually update the object’s position: “15 DEGREES, 40 MINUTES, 15 DEGREES 41 MINUTES, 15 DEGREES 42 MINUTES.” I don’t know how well that went down with the neighbors, but it did work. Now, of course, not only does everybody have a laptop or netbook, there are even more convenient ways to get alts and azes.

That way is the PDA, a Palm or a Pocket PC. There are plenty of effective and inexpensive applications that will run on one of these calculator-sized gadgets and get the job done. The two I've used most over the near-ten years since I got a Palm, though, have been Astromist and Planetarium for Palm. Both of ‘em do far more, of course, than just report the altitudes and azimuths of objects. Either will tackle about anything a planetarium on a full-size PC will—display thousands of objects and hundreds of thousands of stars, furnish detailed data on those things, even display pretty pictures of DSOs. Astromist can be had for both the Palm and the (Windows Mobile) Pocket PC—and I believe even for a few cell phones—while the slightly less fancy Planetarium for Palm is for, well, the Palm only.

Funny thing, y’all, while the PDA still seems Buck Rogers-futuristic to me, it’s really yesterday’s news. Oh, you can still get mobile phones that run the Palm OS (the heavily advertised new Palm Pre will not run the programs we’re discussing here) and the Microsoft equivalent, but the no-phone-PDA is an endangered species. That’s not all bad, since it means you can get Palms and PPCs more than powerful enough to run astronomy programs for a song on eBay for chump change. But it also means you are saddled with devices that, much as I love my faithful Tungsten E2, ain’t exactly state of the art.

Firstly, while some are better than others, the screens on most PDAs are real small. That, as you might expect, becomes ever more a problem for your Old Uncle with each passing birthday. Also, there’s that stylus, which you need for everything from entering data to making simple menu selections. Oh, it seemed high-tech and all ten years back, but quickly lost its allure after I’d dropped one in the observing field grass (and Prude Ranch dust/horse manure) a time or three.

A little consultation with my tech-savvy daughter, Lizbeth, revealed there were numerous alternatives to the tired old Palms. For starters, in the form of Apple’s iPhone. I considered getting one. I had heard there were already quite a few astro apps available for the thing, and our cell service was already with ATT. B-U-T. Being as cheap as y’all know me to be, the charge for monthly connectivity (Internet and all) was more than I thought I’d feel like paying, since all I really want to do on a cell is yak with my buddies, and my antique Nokia does that just fine, thank you.

Lizbeth stepped unto the breach once more, “Well, how about an iPod Touch, Daddy? It’s got a big screen and more memory than the iPhone and runs the same applications.” Hmm. I recalled a buddy at the club, Joe Kuhn,  mentioning his interest in one of the things, which, he said, would shortly be able to run a go-to scope wirelessly via wi-fi. (Or was that Bluetooth? Anything past SSB is confusing to Rod, who is still locked in the 1970s and considers 8-track players high tech.) Anyhow, I began to seriously consider whether I should open my wallet and let a couple hundred dollar bills fly out.

What pushed me over the edge was that a little reading on the Interwebs informed me the iPod would, in addition to holding my music (I really love my Classic iPod and use it every day; CDs are almost a thing of the past for me), take over the non-astronomical duties of my Palm—calendar, contacts, etc.—and liberate me from the Tungsten’s microscopic screen. Before I lost my nerve, I headed to BestBuy, and, as you might have guessed, left closer to four-hundred than two-hundred dollars lighter. Gotta have a case. The widget I used to play my old iPod over the car radio turned out to be—who woulda guessed?—incompatible with the Touch. Surely it would be best to have the model with MORE MEMORY, too? I was a little bitter, yeah, but from the first I was impressed with this doo-dad.

What tickled me? The screen was easy for me to read. Without my glasses. The display itself is a thing of beauty; the colors are rich, and even video looks just outstanding. Best of all, no stylus; the touch screen is a joy to use. After transferring my contacts and setting up my calendar (it interfaces with Outlook: Yay!), I set about getting the astronomy-end nailed down. That is, I went to the iTunes store and downloaded Carina’s program.

While SkyVoyager v1.2 is still pretty early in its development cycle, it’s impressive even so, and I am sure it will only get better. Not only did it do what I needed for my particular project, give altitudes and azimuths of a goodly number of DSOs, in its capabilities it’s quite competitive with any planetarium for any device. When Carina releases their wireless module to allow the pod/phone to communicate with go-to scopes, I suspect lots and lots of amateurs will be salivating over SkyVoyager. Despite the recent misstep by Carina in offering this and their Voyager (PC/Mac) software for free for one day—for the Apollo 11 anniversary—but then bein’ utterly unable to supply it to everybody who wanted it (they shoulda taken note of KFC’s free grilled chicken debacle; me, I got no chicken nor did I get Voyager), I have some right warm fuzzies about the company.

All that remained was to equip the scope with circles. How would I do that? I planned to use a mechanical level indicator (three bucks from Harbor Freight) for altitude. But I wasn't sure how to go about making an azimuth circle. Luckily, I’m a Cloudy Nights addict and stumbled across a thread, “Degree Circles” in the Equipment Forum. There were plenty of good ideas on the subject of making and using Dob circles from lots of nice CNers, but my salvation was thanks to Rob Willett. This kind gentleman has put up a website that will create a .pdf picture of an azimuth circle in any size you need. How do you print it? Unk has access to a large plotter, but a print shop (Kinkos, etc.) will print you one for just a few dollars. Save the .pdf file Rob’s site generates to a CD, bring that to ‘em, and that is all there is to it. They will also laminate it for another couple of bucks. A good thing if you, like me, live were the dew is more like rain.

I’d covered the computer end, bought a couple of cheap altitude angle indicators, and printed out the az circles for our scopes. Now it was up to Pat to figure out how to mount the azimuth circles on our Dobsonians’ bases. The simple and elegant solution he came up with was to affix the circle to the ground board and cut a small window on the inside of the rocker box for viewing. This preserved the telescopes’ sleek-looking exteriors. Because of the shape of our scopes' mirror boxes (not box shaped), it's easy to see this window no matter what position the scope's in. He added pointers (a couple of tines from a plastic fork), and I sussed-out illuminators (LED booklights from WallyWord red filtered with some of the wrapper I saved from the box of Valentines candy the lovely Miss Dorothy gave me this year). Only other thing the scopes needed was a small strip of ferrous metal on their “top” truss poles. That would allow us to mount the altitude angle indicators, which are equipped with magnetic bases, on the aluminum tubes.

Now to try it. It looked like it ought to work, but lotsa bad ideas look like they oughta work. I didn’t get to try my scope until just the other day, but Mr. Pat had been able to experiment with his not long after the construction was done on a night when a few bright stars briefly peeked out of sucker holes. He reported that he was hitting them, no problem. But how would the circles do on a remote observing field? I was encouraged by Pat’s experience, but he had the comfortable surroundings of his observatory to work with, which included, most of all, a nice, level spot to set the scope. The telescope, you see, must be level for this idea to work well.

When I finally got out to our dark site with Old Yeller, I thought I was well and truly screwed. The grass had not been cut and was about 6 – 8 inches high. I didn't see any way I could get the scope even close to being level. Oh, well. A miss is as good as a mile, and I smooshed the rocker box into the grass as best I could and kept on trucking. When Polaris showed himself, I nudged the scope’s ground board until the star was centered in an eyepiece with the azimuth circle pointer on zero. Then it seemed like it took forever to get dark enough to try for a real target. Eventually it was time, and I inserted the 13-mm Ethos, fired up SkyVoyager, and poked my finger at M3 on the screen. Once I had the numbers, I wheeled the scope ‘round to the indicated azimuth, and, recovering my reading glasses, carefully set-in the correct altitude. Holy spit! There it was, not centered, but in the field.

Gratified, I decided to do a tour of Sagittarius. M22, M28, M8, M20, M69, M70, M54, M75, M17, M16 all appeared in my eyepiece one right after the udder. All were beautiful in the splendiferous 13 and 8mm Ethoses. M75, in particular, was a beautiful surprise. And I’d been able to concentrate on lookin’ instead of huntin’—not once did I turn on the Quikfinder the whole time I was down Sagittarius way.

Was the system perfect? No. The altitude indicator was a bit of a pain. The numbers were small and hard to read, dew tended to obscure them, and the pointer needle took a while to settle down on one after the telescope was moved. How about my fears concerning leveling? That was indeed a problem, but only near the zenith, really. Due to the geometry of the situation, performance with alt-azimuth circles on an off-level scope gets worse and worse the closer you get to zenith. It really wasn't so bad, though. Most of the time I was able to avoid the area around Dobson’s Hole, and when I just had to go there, a little slewing around and an occasional peek through the Quikfinder nailed my quarry. F/5 and 100-degrees of AFOV meant my aim did not have to be too precise, after all. I probably observed 35 objects on this evening, and I really wasn't trying to race along. I gave each wonder plenty of time in Ethosland.

To put it mildly, I was satisfied with the outcome of our project. I had no doubt the 8-inch would now be my telescope of choice when I was overcome by sloth (often). It was such a guilty pleasure to have my Dob back in the car just as my buddies were beginning to disconnect power supplies and unbolt scopes from tripods. Not that I thought I couldn’t improve my setup.

The first thing I've done after First Light is ditch the mechanical clinometer for a digital angle indicator. While stingy ol’ me hated to part with the bucks for one, the fare for a nice unit from Harbor Freight, less than 30 simoleons, didn't hurt too much. I haven’t had a chance to use it yet, but I expect its nice, large numerals and .1 degree accuracy will be a substantial improvement. I also plan to devise a means to level the scope—maybe place it on a little platform with some leveling feet. Other than that? I figured out how to dim the iPod’s display and invoke a night-vision color scheme in SkyVoyager, so I might even be able to see some of the stuff I find—assuming I ever get some clear skies again, that is. I will keep you-all posted.

You and your Dobbie want to follow the same path as Unk and his Dobbie? First thing to do is bounce over to Cloudy Nights and read the long aforementioned thread on the subject (it’s permanently stationed near the top of the list on the Equipment board). There are plenty of good ideas and examples on every facet of the subject. If you have any questions, I’ll be happy to try to answer them, and so will the folk on CN, who are, most of ‘em, as nice as nice can be.

Comments:
It is super seeing this topic handled for alt/az mounts. Almost every article I found during an internet search dealt with equatorial mounts. Good info.
 
Nice post. I had a friend do the push-to setting circles on his 8" dob and it helps us find all sorts of things from downtown Austin's mag 3.5 skies.

One thing I'll mention is you might consider getting a Richard Solo battery backup for your iPod Touch. It's a handy thing to have because you'll probably be leaving it on for most of the night.
 
I purchased SkyVoyager for my ipod touch only
to learn afterwards that the Apple store version requires iPhone OS 3.0 or higher. My ipod touch was purchased in December, 2008.
 
Is that a problem? I believe I had to upgrade mine (for a modest fee)...
 
You're right. I have made the upgrade
and am good. I have a GM8; the SkyVoyager
software will come in handy when using the setting
circles.
 
Post a Comment

Links to this post:

Create a Link



<< Home

This page is powered by Blogger. Isn't yours?


stats counter Website Hit Counters