[chupathingie]

Hah… win! Love it

[chupathingie]

A wobbly mount isn’t fatal for planetary imaging, you’ll be shooting .avi (or .mov etc) at 30fps. This leaves a lot of room for tracking error. Software like Astrostack and the like will correct for drift between frames, and the amount of drift per frame is very small even if the mount is undriven and the subject is allowed to simply drift across the field of view. It’s common to stack several hundred frames into a final image. I’m still amazed at how much detail the process pulls out of the total data. The images are much sharper and clearer than anything I ever saw in textbooks when I was a kid way back in the pre-Hubble era (lawn, off, etc). The limiting factor really is what type of scope you use… a cheap Newt will yield cleaner images than a similarly priced refractor since it doesn’t require any fancy elements for color correction. Even then, software is available to reduce the chromatic aberration (later versions of PS do this for example).

Now you’ve got me wanting to break out the old mount and tube and try some of that with a Canon Powershot… I’ve got an old Edmund 4 1/4″ f10.6 Newt and an equatorial mount with a single-speed clock drive. It’s above the usual department store fare, but certainly nothing fancy. Heck, if you can’t finagle the school’s gear for a few nights, give it a go with whatever you have. If you’ve got a finder that you can align you can manage some frames I’m sure. If you’re lucky enough to have the slow-motion axis cables on the scope, even better.

I’d be doing this NOW, except everything’s packed. I just bought a house and moved in… my schedule’s pretty much booked solid for the next month with all the things that I need to do around here.

[chupathingie]

HA photography can be done with the IR block in place, but typically the filter blocks ~80% of the near IR so the exposures will be 5X longer than what you’d expect for visual. Canon and Nikon cameras have a lot of help on the net to do that mod, and it can be done “at home” if you’re technically apt. That’s definitely in the realm of “at your own risk”, as it will obviously void any warrantee and requires a complete disassembly of the camera. It will also make necessary a snap-in IR block or processing for every image you take for normal photography as well a neutral clear filter of the same optical density as the original IR block to keep auto-focus working properly. Most folks who do the mod plan on the cam being dedicated astro gear. I may try that with my Rebel once I buy the 5D MKII, or it may get gifted to my niece… The upshot of HA is that it is unaffected by the moon; you can shoot with a full moon high in the sky and still get great results.

Post what you get of Jupiter and friends! Along with processing details… It’s going to be a few months yet for me to do any imaging, sadly… I’ll have to drool over others’ images til then…

[chupathingie]

hmmm… well, I’m new and don’t really feel entitled to vote… but I can manage to be up towards the NW easily enough… I vacation in Idaho each year.

[chupathingie]

The D90 is great for prime focus, it’s just that prime focus is not a viable method for planetary imaging. Prime focus uses your scope at it’s lowest possible magnification.

For planetary imaging, you’ll get the largest image with eyepiece projection. You need a T-adapter that will accept an eyepiece, like one of these: http://www.scopetronics.com/trings.htm

Smaller sensor pixels will yield a higher resolution final image because the image covers more pixels, which is why webcams that have had the lens assemblies removed are so popoular… even tho they have fewer total pixels than a DSLR, they are much, much smaller. A 2MP sensor that is 1/4″ square is more completely covered by a projected image of Jupiter than a full-frame 35mm sensor.

The brighter nebulae you can work with, as long as you don’t try to shoot when near zenith; that’s where your field rotation from the alt-az mount is at it’s worst. 1000mm is pretty long for most bright nebulae. If the D90 is a full-frame sensor, 500mm will just about make the M42/43/Running Man complex fill the frame. Ditto for Andromeda, but worse… it’s apparent size extends out to about 3 degrees. You can piggy-back the DSLR with a telephoto lens, and drop the f-ratio a stop or two if you get a lot of violet fringing (dunno what quality glass you’ve got… the high-end Nikkor stuff has excellent color correction) with a corresponding trade-off in increased exposure times.

Eyepiece projection is certainly the way to go for small, bright objects or lunar shots. I’ve been wanting to try my hand at it for a while, but a DSLR isn’t well suited to the task. A point-and-shoot with the optcal zoom fully engaged might work well though, especially since most PNS cams can shoot video.

If you use a PNS, get a bracket mount. easiest to install and use, really, and won’t care what kind of cam you have as long as it has that 1/4 20 threaded hole in the base.

Basic list of parts: range of eyepieces, a 2X or 4X barlow, bracket mount for EP shooting, T-adapter for prime-focus.

I did some prime focus shots a few years ago with Saturn through a 4 1/4″ f10.6 (1150mm focal length) newt with the Rebel. Tiny image, but discernable.

[chupathingie]

I started doing digital AP in DFW. 800ISO f5.6 at 30 seconds was my limit in town (Arlington). It’s enough to get images, but not enough to really get any detail. Longer exposures simply saturated the red channel.

I took to driving out to Aledo on the western outskirts of Fort Worth. One of the offices that I maintained sat in a field about 1/2 mile south of I-20. The skies there were at least dark enough that my limiting factor for exposures was my mount’s ability to track. I started getting 3-minute subs, and I even shot a few 5-minute sets one night (had to throw the vast majority out, though… I have to toss 1/2 my 3 minute subs out on this old mount as it is).

One thing you can try with that fish-eye: do the math and figure out what the angular size of your camera’s pixels are with that lens in the center of the field. Don’t shoot exposures longer than 4 minutes per degree of the pixel’s angular size to avoid trailing (unless you’re on a mount with a clock drive, of course). As fast as a fish-eye typically is though, you should get a lot of detail even at 30 seconds or less.

If you plan on stacking sub-exposures, you have no choice but to track since the distortion of the lens will not allow the subframes to align. If you know how to flatten the field though, share the wealth! That would make it possible.

[chupathingie]

On mirror slap: Use the “hat trick”… hold a piece of black cardboard over the scope’s line of sight for 5 secs after tripping the shutter. Another trick is to hang a long cloth sack with sand in it around the tube and re-balance. Adding mass deadens the vibrations considerably. The sand trick also helps with less-than-robust tripods.

[chupathingie]

Several software packages are avaialable, both free and commercial. I’m one of those funny FOSS types, so I prefer the free stuff… leaves more money for the tangible toys 😉

You can check out qtpfsgui here: http://qtpfsgui.sourceforge.net/

There are others, but that’s all I’ve been using for now. It’s designed primarily for stacking bracketed images, but the tonemapping function will also work on a single image. I’ve been in the habit of setting exposure on the sky for a landscape for instance just to avoid clipping the histogram on the high end and then using tonemapping to bring the darker areas up. If your camera has good noise characteristics, the end result is pretty decent. Sample here: http://www.facebook.com/album.php?aid=2003979&id=1571595696&l=ba1792e6a9 showing the unprocessed RAW, mild and overboard tonemapping. I’ve got a bunch of examples floating around, but I need to organize… Also, that was taken with a Rebel, which has the noise you would expect from an entry-level DSLR. To be replaced soon! YAY!

I’d like to try some other software at some point, the interface and controls in qtpfsgui are less than intuitive. But playing around for a while does manage to lead to getting a feel for what the sliders do.

It’s no substitute for proper HDR bracketing, but it will give the appearance of a much broader dynamic range to an image. If you’re gentle with it, you can bring out the details without crossing the line into the HDR “look” and keep things very natural looking.

[chupathingie]

Rules: works for me.

Side note, I graduated high school up in the Adirondacks some number of decades ago. Awesome clear skies when the conditions are right. Likely the best skies anywhere in the northeastern US, especially in the winter, if you can stand the cold.

The D90 has a larger sensor than what one normally uses for planetary imaging, but the pixel size aughtta be low enough to do some decent imaging with a barlow. Probably need a bracket mount for that, prime focus on small objects just isn’t practical. If you have a long FR on that scope tho, say f10-ish, you’ll have half the battle won.

Hawaii: My wife spent last summer there in Puako watching her sister’s cat. What a deal, 3 months in hawaii with a free place to stay on the beach. I had to stay in Rooster Poot and work. She never made it up to Mauna Kea, tho I begged her to go and take some pics for me LOL

[chupathingie]

Bumping this one… No one has mentioned Cinepaint, which I’ve been using in Ubuntu to handle high bit depth RAW processing. It will handle up to 32b/channel, but since RAW files for canon and nikon DSLRs are either 12 or 14 bit, 32bit is overkill. The big plus over the gimp is that the extra color space allows for some pretty aggressive level stretching. I use it for astro pics, and the extent that I wind up stretching color/contrast posterizes 8bit/channel images long before I get useable data out of them.

[chupathingie]

Nice to see some replies, judging by recent post count, I was wondering if the forums had become a ghost town LOL

Edit: After I posted this, I went in search of some info on rules for Farkstronomy contests… You guys already know most of the stuff I posted, so apologies. I’m leaving the comments up just for the benefit of anyone else who might read this and join the addiction…

Orionid, nice collection of shots… I’m guessing you recently took a vacation in HI? VERY nice wide-field Milky Way. Was that a single exposure? What cam, exposure time etc etc…

The alt-az mount is going to make long exposures impossible due to field rotation, I’m afraid. But if you’ve got a cam that can shoot AVI with some level of manual exposure control (webcam, point-and-shoot, etc) you can shoot through an eyepiece and get some stunning solar system images. Anything bright you can stack frames from AVI or MOV files and really increase the effective resolution/decrease turbulence. Plenty of free/affordable software for that. If you want to do long exposures, look into a barn-door mount… relatively easy to build and cheap, plus guides well enough for exposures up to several minutes for wide-field (<300mm thereabout).

soosh… you’ve got an excellent camera for astrophotography. If you’ve got a scope on an equatorial mount (or access to one) all you need is a $20-$30 T-adapter to fit the camera. Most come with barrels to fit a 1 1/4″ and a 2″ eyepiece tube. On SOME scopes you may have to move the primary mirror an inch or 2 up the tube to be able to reach focus. I’ve got a few shots done with a Rebel here: http://www.cloudynights.com/photopost/showgallery.php?cat=500&ppuser=2673&amp; all the astro-shots were taken with a cheap 300mm Canon lens except the Lagoon and Trifid shot, I managed to borrow a 200mm L-Series lens for that. I used a lighting clamp and tripod head to attach the camera to the telescope mount’s cradle and left the scope itself at home. There are LOADS of objects up there well within range of anything under 400mm. I can’t recall if the 20D is a full-frame sensor or not, but if it is you’ll get a similar field of view to those images. You can see a lot of violet fringing on the stars in the images done with the cheap lens. If your lens is an L-Series, you’ll get tack-sharp stars with very little chromatic aberration, L-Series lenses are well worth the $ for astrophotography. White pinpoints against the blackness of space will make any flaws in your glass readily apparent, and good quality lenses really shine for this use.

So many of the objects up there are much larger than most think, the Andromeda Galaxy for instance is easily 3-4 times the apparent size of the full moon. The shot in the above gallery of M57 is an example of a difficult target for a zoom lens, especially with cheap glass, light pollution and a poor quality mount. Matter of fact, all of those images are pretty ugly LOL, but it was enough to make me save my pennies for some quality gear.

One thing I’m wondering about… Farktography contests frown on post-processing beyond global tweaks, but digital astrophotography demands a lot of post-processing in the form of stacking multiple images to knock the noise floor down and combining multiple exposure durations to prevent blowing the cores out of galaxies and nebulae… do they bend the rules for astro images?

[chupathingie]

You can simply tone map the RAW file, I’ve been using qtpfsgui. The results can be nice, if you have a camera with good low-light noise characteristics… otherwise the shadows tend to be grainy. Reducing the rez on the final image helps with that.

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