Perseids?

[CauseISaidSo]

Jealous. As. Fuck.

http://davidharveyphotography.blogspot.com/2010/08/sky-is-falling.html

I’m with you on that one. That is truly an awesome composition. Although I think I have to agree with the comment from another user on his site: “You can’t tell me that shot ever existed in the camera as shown though.”

From my viewing area here, I’d had to have had a 30+ MINUTE exposure to capture that many streaks, much less coming from the same section of sky. Maybe it’s a layered composition (that would also explain the clarity of the stars)?

None of which I’m saying to take anything away from the pic. I’d really like to learn how it was composed, so if anyone has any tips on how to make a shot like that happen, please share.

[ravnostic]

CISS; I’m inclined to believe it’s pretty much as it was. Mt. Lemmon has fantastically dark skies. The telescopes in the domes have to be very dark to capture decent shots (i.e., light pollution from the inside). Today’s cameras can have fantastic ISOs, and to have the dome lit up like that from the inside tells me that the camera must have been super-sensitive to any light. Since there’s no moon, its easy to have the interior of the dome, however dim, be well-above brighter than the exterior, which would be lit solely by stars. The stars themselves would be phenomenal. A fortunate 10-20 second exposure could have captured that, given a sensitive camera and the right moment. Timing is everything. When they do happen, Perseid meteors often happen in groups of 2-4 at once, and sometimes are followed within seconds by another group. Serendipity happens, I’d say.

But that’s just my opinion. Everyone else’s mile rating may vary.

[chupathingie]

According to the EXIF data attached to the image: 5D mkii, 6400ISO, f2.8, 16mm @30seconds. I can’t see any visible trailing in the stars or any artifacts from the landscape to indicate a stack of lights (doesn’t rule it out tho). The image is in Canon’s native 3:2 aspect, but it has been reduced from the original size (5Dii won’t shoot at that low a rez). It’s been run thru photoshop, but he may do his RAW conversion and resizing there. The file name has “sum” appended to Canon’s default naming scheme, indicating that he did some combining of layers, but combining darks with your light(s) is practically required for getting astro shots without hot pixels.

I think it’s a straight reduction rather than a crop. The vignetting is symmetrical, and the coma from his lens is also symmetrical.

Can’t tell much from the noise present, between the reduction and the jpg artifacts it’s just about impossible to make any assumptions based on noise as to whether it’s a composite of lights or not. 6400ISO in the 5Dii makes for quite a bit of noise, and darks don’t reduce the noise by much.

If it’s a single shot, Perseus surely smiled upon him that night. Over a dozen in 30 seconds is very lucky indeed.

[CauseISaidSo]

Interesting analysis, chupathingie. Can you (or anyone else) recommend some good (hopefully open source or freeware) software for combining astro shots to reduce noise?

[CauseISaidSo]

OK, question answered. I just checked his site again and he posted this in response:

Dean – yeah – Ok – a sum of 12 images shown here – but it was put up only an hour after the last shutter click in the series . . . pretty warm. ~Dave

[chupathingie]

OK, 6 minutes makes much more statistical sense.
CauseISaidSo, I can do a quick write-up on some basic stacking in Cinepaint (works in PS and others, same principles) but it will be later… been working my day off since before dawn and I need to run and catch dinner before they call me again (double-time, HUT! I’m a greedy little so-and-so).

[chupathingie]

While the wife gets ready (after rushing me into the shower… 😛 ), the idea of noise reduction is to average the images together. the easiest way to do this is to stack all of your images (please shoot in RAW and stack the huge-ass TIFFs…although JPGs do actually benefit from this as well) in separate layers, then apply transparency to each layer in the following order: base layer=100%, second layer=50%, third layer=33%, fourth=25%, fifth=20%… in the fashion of transparency value = 1/layer# starting with 1 for the base layer. I stack in groups of five, so for 25 images you’d do this process twice… once with the originals, and again with the flattened results from the first set.

Keep in mind that you do this AFTER you apply darks (and possibly lights made with a lightbox or equivalent) to mitigate hot pixels and vignetting, respectively.

I’ll cover the basics there after dinner, hopefully. 🙂

[ravnostic]

I’d sure like to learn the trick of how to make the starry sky stand still for 6 minutes while one composes a picture…that’s quite a feat. So I’ll check back later.

[chupathingie]

ya know, I could do a write-up, but rather than re-invent the wheel, this guy:
http://www.covingtoninnovations.com/dslr/EOS300Dastro.html
has a pretty good write-up.

As far as software goes, that depends on your desired learning curve… software like Astrostack, Registax, et al automate a lot of things and work in high bit-depths. Don’t bother with any software that is only 8-bit. You need at least 16 bits per color channel to do any worthwhile level-stretching with astrophotos. 8-bit software will simply leave you with a heavily posterized image after only a few stretches or curves adjustments. Some of the software out there uses 32 bit float formats. You’re going to need a lot of RAM and as much processor as you can scare up. Expect images you take with a DSLR to consume 50-120MB PER IMAGE in 16bit. Double that for 32. You’ll be stacking upwards of 20-30 images for each final if you want them to look clean and sharp. Do the math, it’s quite easy for a project to consume several gig of ram while you’re working.

Automated software is available, and from what I’ve seen some of the most consistently beautiful results come from folks using IRIS, although some of the “easier” software still manage stunning images. IRIS has a steep learning curve, but it’s capable of accurately handling anything you throw at it. Professional astronomers (read: NASA, JPL, most major universities) use IRIS to process their images. Someday I’ll take the time… for now I’m lacking hardware (the droolworthy Losmandy) and the time to make the effort. Someday *sigh*.

Arm yourself with some 16-bit manipulation software. Cinepaint for Linux and Mac (free). You’ll have to google for what’s available in windows, I’ve been off that money treadmill for a couple years now. Photoshop of at least CS2, but there are others that will allow editing/layering in 16bit out there. You’ll use it for more than astro stuff, working in high bit depth works wonders for regular photography as well for expanding apparent dynamic range for example.

[ravnostic]

Registax, for my experience, sucks. I can 3-point align on three stars and it’s useless. I’m probably doing something wrong, like not having each and every got-dammed pixel in a row, but it doesn’t recognize and adjust anything; it just overlays one pic on another–there’s no alignment process that I can determine to correct for any variables. Result: triple star images, all field rotated. I can overlay in my 1998 Roxio Photosuite at least as well (better–I can rotate the images), and without the processing time, so I’ve given up on that program (and I tried, many times). Plus, the ‘user manual’ is barely spanglish, if even.

I’m hesitant to download new software stuff only to find out it can’t compensate for my lack of know-how or equipment. Basically, I’ve given up. What I want will take the points specified and overlay them correctly, regardless of field rotation (it is TIFF or RAW, for cripes sake–are we living in the days of CRAY-I?!?). If I knew how to do this stuff on my own–I’d be doing it instead of bitching about what I can’t do in a forum. A decent instruction manual that amounts to something like a class would help, but I haven’t seen that in freeware.

Forgive the gripe session; in a pissy mood anyway. Sucks to know one doesn’t have photo skills beyond color saturation and gamma correction, and there’s no freebie software to cover up that lack of knowledge. Must be nice to be an engineer with $thousands of disposable income to spend on toys.

p.s.; good article link; I’ve bookmarked it for reference. But I’m still bitchy.

[chupathingie]

I understand the bitchin’; been there, and damn near bald as a result LOL

Doing this manually in PS or an alternative is very tedious, but will get you to grips with the basics. Or you could blow $150 on Registar.

Registax you’re not alone with… it works well for AVI files of solar system objects (that’s what it’s designed for) but I’ve never had it exceed what I could do manually with darks, flats and data in a PS alternative.

Deep Sky Stacker and ImagePlus are another couple of programs I hear folks using.

All I use is the free stuff, and I’m running linux so the high bit-depth manipulator of choice is Cinepaint.

Samples:
http://www.flickr.com/photos/44012674@N04/sets/72157624734692512/
Yes, they look like shit. All but one was taken with a cheap 300mm on the original Digital Rebel back in about 2003 on an amazingly poor quality Edmund Scientific GEM from circa 1977. I’ve since graduated to a much better camera and better glass. Unfortunately, I still have Barney Rubble’s mount; so little else to show til I manage a better transport system for the camera. Also, these are the images I wound up with while just starting with digital AP. Don’t get discouraged. There is a LOT of technique to learn in this hobby, but what I managed was enough to hook me.

Take a series to stack (at least 20) some night, even on a cheap mount, and look me up on skype and we’ll toy with them… won’t take you long to see results.

[ravnostic]

I will take advantage, Chup I have the scope, I need the mount. Once that’s in place (and it’s been delayed, delayed, delayed), your expertise would be invaluable in making a nice composition.

[chupathingie]

I’ll have a car note paid off early next year, and I’m seriously thinking about making a mount and a 10″ conical a priority. I’ve been working up plans for a truss tube with a dovetail to mount to a GEM so that I can break down the OTA for portability. Now if I can find someone who can weld aluminum…

[CauseISaidSo]

Thanks much for the write-up and software pointers, chupathingie. I’ll give your link a read and check out the software you recommended.

When you say “mount”, are you referring to a star-tracking mount (i.e., one that will automatically move to keep the celestial objects in the same position versus time)? Sorry if that’s a stupid question, but I’m more or less a complete noob when it comes to astrophotography.

[soosh]

Thanks much for the write-up and software pointers, chupathingie. I’ll give your link a read and check out the software you recommended.

When you say “mount”, are you referring to a star-tracking mount (i.e., one that will automatically move to keep the celestial objects in the same position versus time)? Sorry if that’s a stupid question, but I’m more or less a complete noob when it comes to astrophotography.

Hey, just out of curiosity, where are you going out of town to view stars? I grew up in Tulsa from 1968-97, with the exception of a few years down in Norman at school. One of my favorite places to go at night was the overlook at Turkey Mountain above the river at 71st street, though you had to dodge the police helicopters and the county sheriffs out looking for criminals. That’s also one hell of a place to watch a summer sunrise or a full moon rising. They hang just huge on the horizon to the east with all that flat land compressed in front of it.

There’s also a really cool raised area north of town that I don’t know the exact spot of, but you can find it if you take one of the main streets near downtown just straight north until you get into the countryside. There’s a big dome-kind of hill that’s paved to the top, and at night, you have a panoramic view, more or less, 360? of the countryside around you. I’ve watched some spectacular thunderstorms roll in from there, and it’s amazing watching the clouds overhead send out lightning arcing out down below you.

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