05-12-10 – Happy Farktography Anniversary 5

Forums Forums Farktography General Chat This week’s contest 05-12-10 – Happy Farktography Anniversary 5

Viewing 15 posts - 61 through 75 (of 80 total)
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  • #27430
    Elsinore
    Keymaster

    Yep got it when I went looking for Deaconblues’. Found yours and a number of other photos actually.

    #27431
    olavf
    Participant

    Thanks. I seems like it’s a uber-heavy night. But, I think I’m going to have to make a push this weekend and get the new server in place by next week. W00.

    #27432
    orionid
    Participant

    Late to the party, and commenting from work (where Flickr is blocked because it’s part of Yahoo).

    Re: Astro-stacking. I’ve done quite a bit of research and info-gathering, haven’t had a chance to put the scopes to good practical use, though. There are a lot of techniques, that when combined together, can produce stunning images from earth-bound scopes. The yellows can be brought out through channel stacking. Taking multiple exposures through each of a Hydrogen-A (specific wavelength of red unique to an electron drop from the n-3 to the n-2 layer around a hydrogen nucleus, unique to stars and nebulae), Oxygen III (specific wavelength of green unique to electron capture in doubly-ionized oxygen, also unique to nebulae), and Sulphur II (specific wavelength of blue unique to electron capture in ionized sulphur, also unique to nebulae) filters and stacking them separately leaves you with three clean, sharp images that can each be used as an alpha channel and combined in photoshops channel mixer (or other software). Because these spectra are almost exclusive to nebulae, they can be very specifically isolated, almost entirely eliminating atmospheric and cosmic light pollution. If you assign the Ha alpha map to red, the OIII alpha map to green, and the SII alpha map to blue, a striking image in psuedo-false color can be achieved. Anywhere the green and red channels overlap without blue, will give you yellow. Based on Intolerant Jerk‘s posted info, this is exactly what he did, with 10-17 30 minute shots stacked for each spectra/channel.

    Further false color manipulation can be created by assigning the spectra to opposite channels, ie – Ha to blue, SII to green, and OIII to red or using other spectra like near IR, UV, Hydrogen-beta, etc. NASA does this for spectral analysis.

    A dig through flickr will find images similar in quality to IJ‘s image, although they are rare, and the photographer is usually quick to say exactly how he/she did it. Most contain the above described filters, methods, and a large ($4000+) scope in a clean-air (desert, hawaii, etc) environment.

    You can also take things one step further, for nebulae that cover 4 or 6 stops of light like the Orion Nebula, do two sets of exposures, one with relatively short exposures (say five minutes) for detail in the trapezium (while underexposing the surrounding nebula) and one with relatively long exposures (say 30 minutes) for detail in the surrounding nebula while burning out the trapezium. You’d then place both final images in PS as separate layers, then create an alpha-mask out of the over-exposed layer, allowing the under-exposed to show through in the burnt-out portion. Sort of the Astro equivalent to HDR.

    re: OBO’s. Thanks, Kat!

    #27433
    ravnostic
    Participant

    Orionid; like I said, I need new toys.

    On that note, I just purchased online a reducer for the scope. It seems that in prime focus, my setup is the equivalent to an f-10. This, in addition to a very limited FOV, means that the 4 minute exposure came out pretty dark. The reducer drops me to an f-6.3, and widens my FOV considerably. That will shorten my exposure time by a factor of 3, and allow me to capture more nearly the entire Orion nebula (and dang if it isn’t moving right towards the sun as we speak! Oh well…). I’m hoping, as they are shipping USPS priority, that I get it Monday (if it ships today, maybe), so I can try it out. As my original Whirlpool nebula was plenty big enough, I’m hoping the reduced exposure time allows for less star travel during exposure, yet also allows for a brighter, less noisy picture. We’ll see.

    You are correct about the filters. I gotta get me some filters! Those and a wedge mount and some decent software and I’ll perhaps be golden to rival IJ’s photos. I do have one red-spectrum filter, but without the polar mount setup, I’ll never get the exposure time I’d need to make a decent picture. My retail seller of my scope has the wedge kit and the extra kit for easier fine-polarity alignment for $395. It’s on my list (if overtime at work holds up, I’ll have it by the end of June.)

    Between all these things, I could possibly rival IJ’s pictures, and I look forward to that possibility. But regardless, it’s a fun process to have have already done more photographically than I’d ever done before, and I look forward to whatever strides I make in improving upon the results.

    #27434
    justkat
    Participant

    Elsinore – we’ve got broken images (at least one) going on again. I’m so sorry our server is being dicky. Please to fix? Thanks.

    #27435
    ravnostic
    Participant

    Elsinore – we’ve got broken images (at least one) going on again. I’m so sorry our server is being dicky. Please to fix? Thanks.

    Not to quibble, but you guys need to buy your own domain for $10, complete with free hosting account (and I KNOW you would know how to use it). This hardly ever ever ever happens to me (maybe twice in the past 5 years.)

    #27436
    Elsinore
    Keymaster

    justkat: Got ’em

    #27437
    olavf
    Participant

    ravnostic, this is actually the first time I’ve had an issue like this in a good long while – and the first time with this server. Before last night it hadn’t even been rebooted in nearly a year – and that was when we lots power long enough that the UPS ran out.

    elsinore, I’m going to have to let those two broken links stay broken. Not sure if it’s too much, or if there’s something funny with one of those files, but the moment that Fark breaks them, the whole system runs happier :/ Thanks anyway.

    #27438
    Curious
    Participant

    I have never printed out anything of mine on anything larger than A4 photopaper, and I am not sure if my 10 Megapixel 4/3 mount camera can go much larger without seeing a significant drop in picture quality.

    if you’re still reading this thread go to sam’s (or cosco possibly or any place that has one of those roll printers) and try it out. i had a 3008×2000 pixel 3.78MB photo blown up to 16×20 and it turned out great. was using a 5 megapixel DSLR camera.

    the folks at sam’s told me the size was too small to do that. ha, fooled them. and it was <$20.

    #27439
    LeicaLens
    Participant

    I have never printed out anything of mine on anything larger than A4 photopaper, and I am not sure if my 10 Megapixel 4/3 mount camera can go much larger without seeing a significant drop in picture quality.

    if you’re still reading this thread go to sam’s (or cosco possibly or any place that has one of those roll printers) and try it out. i had a 3008×2000 pixel 3.78MB photo blown up to 16×20 and it turned out great. was using a 5 megapixel DSLR camera.

    the folks at sam’s told me the size was too small to do that. ha, fooled them. and it was <$20.

    Thanks. I will check at my local camera stores to see what type of printer they are using.
    The websites I looked at seem to suggest that the limit with 10 megapixels is 12.91″ x 8.64″ at 300ppi (about A4 size), but that seems a little conservative to me.

    I’m quite curious about print sizes. I currently scan a lot of 35mm film negatives at 4800 ppi (or is that dpi?), which creates a bigger file with more pxiels than images taken on my digital camera, so I am wondering how big I can go with prints.

    #27440
    Elsinore
    Keymaster

    The thing is, as print sizes go up, the dpi/ppi count can go down some, but you won’t notice it in the final print partly because you just don’t necessarily need 300dpi, and partly because viewing distance goes up with print size (e.g. you aren’t viewing a poster sized print with your nose 2 inches from the print–you stand back further to take it in). So for a 16×20, you don’t really need 300dpi. Think of all the billboards you see. Those aren’t shot with 100MP cameras, but they still look fine. They actually have extremely low dpi (in the teens or even single digits IIRC), but because you’re viewing from so far away, it looks fine. My Guitar Triptych was shot with an 8MP 30D and printed at 20×30. The final dpi worked out to about 116dpi, but even up close, you’d never know. Mpix typically tells me that 20×30 is the largest I can print from my 30D, but looking at the results at 20×30, I suspect I might actually be able to go up to 24×36. At some point, I’ll try and see.

    As for your 35mm negs, I’m not entirely certain, but at some point you may run into a format/lens resolution issue in terms of enlargements. Past a certain point, the image will be softer because you’re enlarging past the point where the lens/camera system resolves/records details. But again, that will probably still be pretty large, because your viewing distance goes up with the print size. 24×36 (or whatever the similar international ratio is) will probably be no problem. Possibly even larger.

    #27441
    justkat
    Participant

    I’d like add my apologies to kestrana, orionid and everyone who wanted to vote for them to this forum as well as fark. It’s not my/our fault, but I still feel really bad that the OBO hosting went sour. Some one of those pix was corrupted or some such and gave our server existential fits. We couldn’t even get into the directory I’d placed them in without going to a level of computer expertise that Olav thankfully has, though I don’t. It totally changed our plans as to which of our network computers we were going to replace. 😯

    I tried, I failed, I’m really really sorry. 😥

    #27442
    Elsinore
    Keymaster

    Congrats to soosh this week!

    (That’s a shame about the image files 🙁 )

    #27443
    LeicaLens
    Participant

    The thing is, as print sizes go up, the dpi/ppi count can go down some, but you won’t notice it in the final print partly because you just don’t necessarily need 300dpi, and partly because viewing distance goes up with print size (e.g. you aren’t viewing a poster sized print with your nose 2 inches from the print–you stand back further to take it in).

    That’s very true, and I hadn’t really thought of it like that. I have been toying with the idea of getting the local camera store to print out a photo or two on A3 size, just to see how it comes out (and we need some decoration on our walls), now I think I will go ahead with it. Thanks! 😀

    #27444
    orionid
    Participant

    I’d like add my apologies to kestrana, orionid and everyone who wanted to vote for them to this forum as well as fark. It’s not my/our fault, but I still feel really bad that the OBO hosting went sour. Some one of those pix was corrupted or some such and gave our server existential fits. We couldn’t even get into the directory I’d placed them in without going to a level of computer expertise that Olav thankfully has, though I don’t. It totally changed our plans as to which of our network computers we were going to replace. 😯

    I tried, I failed, I’m really really sorry. 😥

    No worries. Thanks anyway (for both the hosting and the nudging to put something up this week. Interwebs come back to the house tomorrow so this week is a go. And flickr will be barraged with photos from our trek.

Viewing 15 posts - 61 through 75 (of 80 total)
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