Friday, September 22, 2006

 

The Astro Holga

"Uncle Rod, how much do I have to spend for a camera before I can take good deep sky astrophotos?"

That used to be a simple question to answer. You spent 100 – 300 dollars for a 35mm camera body and prepared to spend thousands on film and processing. In addition to money, you'd also have to be willing to invest hundreds and hundreds of hours in learning and trying before you began bringing back recognizable pictures of deep sky objects.

Oh, that’s all changed now, of course. Technically minded amateurs will probably be able to get at least recognizable images of deep sky objects on evening one with a new CCD cam. But there’s always a catch, ain’t there? Yep. Now you have to spend thousands UPFRONT before you can take your first fumbling image.

"Thousands? Really?"

A lot of that depends on what you consider “good.” At the top of the line for most amateurs, at the SBIG ST11000 level, your camera alone will run you something in the neighborhood of 10,000 of those li’l green pieces of paper you work so hard for. What do you get at that price point? A big chip and results (in the right hands) that can potentially be far better than anything you could have done with medium format film a few years back.

If 10,000 dollars—or e'en three or four thousand for one of SBIG's very capable midground cams—is too much according to mama (or papa)? If you’ve got a passel of kids needing new shoes, a mortgage, and a new car payment to deal with? You could go the DSLR route. If you’ve already got a Canon Digital Rebel or one of her Nikon sisters that you bought for snap-shooting hubby or wifey and the kids, you are in bidness. You won’t get results like you would from a big SBIG or Starlight Xpress, but you’ll get good deep sky pictures eventually, and it may be a little easier to learn how to do that with your DSLR than with a “real” CCD cam. You are, in other words, in like Flynn.

You wanna take pictures and can’t round up the cash for a DSLR? Have you considered an astro-Holga instead?

You know what a Holga is, don’t you? It’s a plastic 120 format box camera that has become the darling of art photographers (http://en.wikipedia.org/wiki/Holga_camera). The Chinese-made Holga is simple and it’s junky—to the max—but in dedicated hands it can take astonishingly beautiful images. The astro Holga? I’m talking about the Meade DSI, the orginal color version, of course.

The “DSI C” is a one-shot color, uncooled camera that, assuming you have $299.00 to spend and a computer of some kind you can use at the telescope, can get you taking all kinds of deep sky astrophotos in a hurry. NO, you won’t be making Jack Newton sweat, but you will be bringing back full-color images of amazingly distant marvels. When you see the delicate spiral arms of M101 jump off your monitor screen for the first time, you’ll be made a believer in this simple and good little cam in a right quick hurry, that’s for damned sure.

"Cheese…an uncooled camera, though? How is that gonna be? How about all the NOISE?"

Yeah, the DSI-C is completely uncooled, and that means thermal noise will always be a factor in its images. I won’t lie to y’all. The DSI’s pictures, especially those done with shorter integration times for subframes, are a little noisy, but it's subtle enough in final, stacked images that you can probably learn to live with it.

How good your DSI results will be depends mostly on how much time you’re willing to spend learning how to process images. Careful, skilled processing can make the pictures that come outa this basic CCD camera look pretty snappy. Spending time learning image processing is a Good Thing, anyway, and will stand you in good stead if you move up to the astrophoto major leagues some day.

If you want to spend a lot of time larning how to tweak images with a computer, that is. If you don’t, you can, like your old Uncle Rod, just be content to consider that the less than perfect images you turn out are your your “cosmic postcards,” little mementos of your personal deep sky voyages. One thing’s fer dang sure: no matter how fumble-fingered and lazy you are with the DSI, you’ll still come home with much more detailed images than you would have in the film days.

Don’t let me give you the impression that the DSI is totally incompetent as an astrocam. It is not by any means. One was used, for example, to produce the discovery image of the recent supernova in M51.

One really good thing about the DSI is that it greatly minimizes the importance of mount and guiding quality. If your scope can manage untrailed thirty-second exposures, at least every few frames, the software that comes with this camera can easily produce good final images.

"How about the other DSIs? The new ones. The DSI Pro and DSI II cameras?"

Yeah, they produce better images, images more like the mainstream CCD cams SBIG and Starlight Xpress sell, but, in some ways, I think that’s gilding the lily. Accept the DSI as the Holga it is and be happy with that if you can. If you find you just can't be happy with your DSI's slightly noisy and pixel-crazed images? If you need more-better-gooder than what the 299 buck basic DSI can produce, you might want to save them pennies for a, say, ST2000 and the MAJOR improvement one will bring to your imaging instead of spending for a somewhat better DSI Pro or II.

If I wanted to get all arty on y’all, I’d suggest your goal as a 21st century imager shouldn’t be to strive for photographic-quality or photographic-looking results anyway, but to instead relish images that are obviously a product of the digital age. And the DSI’s sure are that, in spades.

Again, I won’t gloss over the truth. My ST2000 is capable of producing pictures that blow the DSI out of the water—er… "sky.” In some ways the 2000 is easier to use, too. No fiddling with short exposure stacking. Want a picture of 10 minutes exposure duration with round stars? Hook the 2000’s autoguide output up to your mount and shoot away. What will you wind up with? Tiny round stars. That’s what three grand buys you.

Yeah, SBIGs and Starlight Xpresses are great, but. You might enjoy spending some time with the DSI, even if you own a “better” camera. the li'l Meade is capable of going surprisingly deep with a very simple setup, and sometimes “simple” can be a refreshing break from the astrophoto highlife. The image of the Helix at the top of this entry is a completely uncalibrated one—no darks, no flats. It’s also an unguided one shot through William Optics’ remarkable little 66mm APO refractor. The WO rode piggyback on a C8 mounted on one of Celestron’s inexpensive ASGT CG5 mountings. Total exposure time was 10 minutes in the form of twenty thirty second exposures. What did I do? Started the exposure and wandered around the field to annoy my fellow observers--no fuss, no muss, the DSI and its software do all the work.

The Helix image? I like it for what it is. Is it art? Maybe in a Holga sort of way it is.

If you’d like to see more of my Holga-style imaging, see my “Instamatic” astrophoto page at http://skywatch.brainiac.com/deepweb/index.htm

Sunday, September 10, 2006

 

How Not to Spoil a Star Party

The Fall star party season will soon be in full swing for us Northern Hemisphere observers. Maybe now is a good time to reflect on not just what you should bring to a star party, but how you should act at one. Yeah, “How you gonna act?” How are you going to ensure you and the people around you have fun?

The key to behaving well at a star party? Remembering why you came. Sure, we go to star parties for dark skies, but that’s not the whole show. In fact, that’s not even a major part of it for many of us—most of the time, anyway. Yes, when you invest the family’s yearly vacation in something like the Texas Star Party, superb skies are perhaps a major part of the deal. But your average east-of-the-Mississippi regional star party? I suspect most of us have a club dark site comparable in sky-quality to what you'll find at many of these venues. No, when we go to one of these star parties, we’re going for the PEOPLE.

Yes, people. To hang out with our fellow amateurs, to renew acquaintances with the good folks we only see a time or two a year, and to hear what those more experienced than us have to say about our magnificent obsession. In short, we go to star parties to have fun with our friends old and new. With that in mind, the following are a few of my semi-random thoughts on the behavior of that that least shy of all beasts, Amateurus Star Partius North Americanus.

Star Party Choices: Since you’re mainly at a star party for the experience of being with a group of like-minded folks, don’t turn your nose up at a star party that’s got less than perfect skies. I’ve had a tremendous time, for example, at the Georgia Sky View. Sure, you’ve got that Atlanta light dome to the north, but you’d be surprised at what you can still see. And that other part of the star party "bargain" is well in force: wonderful people.

People: Since people are such a large part of the star party experience, are you mindful of the way you treat your fellow partiers? When somebody pulls up on the field right next to you and starts setting up, do you give ‘em a scowl that says, “I was saving that spot for a lawn chair,” or do you give ‘em a smile that says, “Howdy pardner, welcome! We’re gonna have a great time!”

Cabins: Along the same lines, do you treat the folks sharing a cabin with you with respect? Think back to the way you learned to live in a college dorm or military barracks. Feel hot? Ask your fellow residents before you open a window. Clean up after yourself, especially in the bathrooms; Uncle Rod ain’t your mama.

The Next Morning: Maybe you don't like to observe till dawn. Lots of us do. If you turn in early and thus awaken early, KEEP IT QUIET. Your friends are trying to sleep. You loudly humming the theme from Spongebob Squarepants is not going to help.

Pets: Some star parties permit them. Even if they do, leave Fido at home if possible. The observing field is no place for a dog. You know that no matter how carefully you watch him, Rover is going to leave a "surprise" on the field, start barking and keep on barking long enough to annoy everybody, and will inevitably frighten somebody or somebody's kid (I absolutely love all dogs—I do not believe there is any bad in them—but plenty of folks feel just the opposite). Since I hate to generalize, I'll say some dogs (and at least one prairie dog of my acquaintance) are wonderful and well-behaved at star parties, but this is the exception.

Chow: If meals are being served on site, don’t pitch a fit if they are not four star restaurant-quality. Think before you whine. Think about the challenge inherent in arranging for and serving 300 or so meals a day. Did you volunteer to help? Will you volunteer next year if you think you can do better?

Vendors: they usually travel a long way and invest a lot of their own money to be on-site at a star party. Do them and yourself a favor (if you want them back next year): BUY SOMETHING (do I really have to twist your arm on this?).

Speakers: Like the vendors, these folks, whether well-known authors and scientists or just your fellow club members with something to say, have come a long way and invested substantial time and resources to help YOU. Attend every presentation you can, and take a moment to thank the presenters.

Prizes: Yeah, everybody’s mouth waters over the raffle prizes. Remember the reason for ‘em, though. Their purpose is almost always to accrue money to help finance next year’s event. Look upon buying a ticket as "insurance" you’ll have another wonderful time next year. Don’t act poor-pitiful-me or bad mouth the star party staff if you don’t win that purty RCX.

Weather: Everybody talks about it; nobody does anything about it. If star party weather turns bad, many folks will not show. For some folks, even the threat of less than excellent weather will make 'em stay home. This is understandable. But, as above, observing is only a small part of the experience. Your attendance, rain or shine, clouds or no clouds, shows your support for the star party and helps ensure its continued good health. In fact, one of the best times I’ve ever had was sitting out on the field at the Deep South Regional Star Gaze in the middle of a torrential downpour, drinking Rebel Yell, and talking over the state of the Great American Telescope (you know what that is) with fellow members of the Yahoo SCT Users Group. That sure was a hell of a lot more fun than sitting home in front of the boob tube.

Yeah, people sure can be annoying; especially at star parties. My cure for the little annoyances other people always seem to inflict on me? Recognize the same annoying behavior in myself and resolve to do better.

Now, get out there and party!

Monday, September 04, 2006

 

Heavens to Murgatroid! A Galaxy Filter?

Yeah, ol' Snagglepuss shore would be surprised that somebody’s making this claim. I know I am. What claim? D&G optics is about to begin selling an LPR (light pollution reduction) filter designed for viewing galaxies. What’s wrong with that? Well, heretofore, we’d always considered a galaxy filter akin to a “cloud filter;” that is, something theoretically not possible.

LPR filters work by using multicoated surfaces to reflect away wavelengths of light produced by earthly sources before these harmful photons can enter the field lens of an eyepiece. Layered coatings of different reflective materials fine-tune a filter for whatever range of wavelengths you want to accept/reject. This obviously works very well for nebulae. Just about every modern amateur, even those with access to dark sites, owns an OIII or a UHC.

While LPR filters work great for emission and planetary nebulae, however, they suck righteously when you try to use 'em to observe galaxies. With a UHC or OIII attached to your eyepiece, not only does the galaxy of your fancy not look better, it’s likely to disappear. Unfortunately, the wavelengths of man-made light sources, all those thousands of mercury vapor, sodium, and incandescent lights, fall in the same range of wavelengths as the light of the stars.

The bottom line is that light pollution filters are very effective at blocking man-made light, but that also inevitably means they dim or even extinguish starlight. That’s why they are no good for observing galaxies, star clusters, and reflection nebulae. All three of these types of object shine either by direct or reflected starlight. Too bad: no galaxy filter for you!

That's what your Old Uncle has always said, anyhow.

Not that I've been unchallenged in my assertion that "there are no galaxy filters." Some amateurs have insisted there most certainly is a galaxy filter—of a sort. They are talking about mild, broadband LPRs like the Lumicon Deep Sky and the Orion Skyglow. These filters, the story goes, darken an eyepiece field background enough to increase contrast with a galaxy without dimming the target object so much that any improvement is lost. So they say. I’ve tried this “trick” more than once, and my opinion has always been that any galaxy is always worse “with” than “without.” The only benefit is that the filter makes HII regions show up fairly well without completely cutting off the main galaxy. But, then, HII regions are nebulae, aren’t they?

Then, the other day as I was hanging out on the Yahoogroups, I noticed a couple of posts about a filter called the “GCE”—that, I soon discovered, was an acronym for “Galaxy Contrast Enhancement.”

What the—was this a joke?

At first I thought so, but then I learned that these filters are made by a very well-respected outfit, D&G optical, who are no doubt familiar to you as the long-time producers of very high quality achromatic refractors and classical cassegrains. A bit of looking around turned up a website:

http://www.omegafiltersebuyer.com/servlet/the-GCE-Filters/Categories

The company that owns this page, “Omega Astro Filters,” is a new one on me, but they say they are a well-known supplier of optical components to the aerospace industry. So what do I know? Just because I haven’t heard of them doesn’t mean they are not top drawer. If they haven’t been selling to amateurs, it’s not likely that I would have heard of ‘em.

Anyhoo, if you don’t want to navigate to this page, I’ll tell you what it says. First of all, the blurb on the GCE, which is accompanied by the image above, is headlined “Coming Soon!” How soon? Don’t ask me. Beneath the header, it says “September 1, 2006.” Alas, it still said that the last time I looked, just now, on September 4. ‘Twas the Labor Day weekend, of course, so I’ll keep checking back to see if it is updated.

Whatever. What do they say about the GCE? Not too much; this is all of it:

The Galaxy Contrast Enhancement filter aids in the visual observation of galaxies and Milky Way dust clouds and dark lanes. The GCE filter takes a different approach to enhancing galaxy observation by allowing high transmission through nearly the entire visible spectrum while rejecting only the harmful light pollution wavelengths. Because of those attributes it also is a very good general purpose LPR filter, unlike traditional wideband filters (that) exclude most of the red portion of the visible spectrum.
How does the GCE do this? Something that no one seems to have been able to do before? Doesn’t say, and don’t ask me, Bubba. I can think of a couple of scenarios, I guess, but that would be pure speculation. I will admit that in the 20 years since LPR filters started becoming really popular, there is no doubt that the art and science of optical coatings has come a long, long way.

A little digging on my part turned up some more info in the form of a press release from D&G, which included both some words of wisdom on how D&G and Omega fit together, and further details about the filter itself:

As of 8/20/06 DGM Optics began a partnership with Omega Optical of Brattleboro VT. This partnership involves my LPR/Nebula filters which will be manufactured, and sold through Omega Optical. In addition to the NPB (Narrow Pass Band) and VHT (Very High Throughput) nebula filters we have 2 new filters which will be available within the next 1-2 weeks. First is an OIII and the second, and most interesting, is the GCE (Galaxy Contrast Enhancement).
OK…but how the H-E double L does this thing work?

The GCE filter takes a unique approach to galaxy observation by using a "rejection band" design. A rejection band design essentially allows all of the visible spectrum to transmit while blocking only undesirable wavelengths. The resulting filter has the most total throughput of any LPR filter I'm aware of, and as such, has a very neutral impact on star brightness and color.
Maybe some of ya’ll know what that means or implies; I sure don’t.

So, what else? The news item from DGM goes on to say that the GCE has been tested, and that it has delivered good results on M31, making the dust lanes “somewhat” more visible, and that M33 is “improved.” The release also notes that the filter works best with the Population II rather than the Population I regions of galaxies. What that means to you and me, Elmer, is that the cores of galaxies are more improved than their arms.

Sigh. Wouldn't you know it? It’s the arms that are the problem in light pollution. I can haul the C11 into my urban backard and easily see lots of galaxy cores. The release further puts on the brakes by saying, “However because galaxies (sic) spectral profiles are generally broadband in composition. do not expect them to jump out the way nebula do with the NPB and VHT filters.”

Where does this leave me/us? Well, bubbas and bubbettes, back at square one, I reckon. I went from knowing there was no such thing as a galaxy filter, to hoping someone had made a breakthrough, to believing said breakthrough may be minor in nature. On the other hand, according to the informantion from D&G, the GCE works well as a plain old nebula filter. The price of the thing is quite reasonable, 80 US$ for the 1.25-inch and 160 US$ for the 2-inch, in line with what you’ll pay for Lumincon’s or TeleVue’s mainstream LPRs. Frankly, if this filter offers even a little improvement over the Skyglow/Deep Sky “trick,” I’d consider that money well spent. Hail yeah.

Do I expect much from the GCE? Can't say as how I do. Howsomeever…I’m always one to warn against burying the patient before he’s pronounced dead. I intend to take a wait and see on the GCE filter until I’ve got one in my hands or hear from someone I trust who's got one in her/his hands.

Yeah, I’ll admit it: I want there to be a galaxy filter!

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