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Seqenenra posted:Is that some kind of artifact in the center of your picture? The dark circle? It shows up in every night photo from my backyard where I point up into the sky. It might have to do with my neighbors' lights in their yards. I forget the term for it, since I took physics so long ago, but my thought is that the light from my neighbors' yards is coming into the lens. But in the middle of the lens, the light is hitting at an angle such that it's not entering into the lens, being reflected, or if being refracted in the lens, isn't making it to the sensor. v  v
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Mar 6, 2014 04:58
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| # ? May 29, 2024 23:00 |
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 The story goes this was found in a grade one classroom in america. But you know, the internet.
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Mar 6, 2014 05:48
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Rotten Cookies posted:It shows up in every night photo from my backyard where I point up into the sky. It might have to do with my neighbors' lights in their yards. Looks like you need to shoot flat frames.
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Mar 8, 2014 07:42
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Atimo posted:Looks like you need to shoot flat frames. Someone mentioned that it could be from LR's vignette correction. I turned off any lens correction and slid the vignetting correction slider, and even still the ring seems to be slightly there. Also, this term "flat frames" is new to me. After googling, I've never seen it before. Not surprising. Is this a common procedure, or is it somewhat unusual? God drat the weather this weekend. It was supposed to be pretty clear this Saturday night, and now it's going to be mostly cloudy. gently caress me.
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Mar 8, 2014 08:18
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Flat framing is both common and highly effective, add taking darks and bias frames to complete the package.
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Mar 10, 2014 17:23
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At least in my experience, flat frames are basically required- I'm surprised you haven't seen it before.
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Mar 11, 2014 02:58
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Luneshot posted:At least in my experience, flat frames are basically required- I'm surprised you haven't seen it before. I meant that I had seen "bias frames" but not flat frames. Asking about how common it is was supposed to be a separate thought. Well, it wasn't too far off the mark, since I didn't really know much about them, whatever name is used. I did only start taking pictures of the stars like a couple of weeks ago. v  v
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Mar 11, 2014 06:57
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Jekub posted:Flat framing is both common and highly effective, add taking darks and bias frames to complete the package. Flat frames are to correct for imperfections in the optics, so are they something that you only take once?
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Mar 11, 2014 10:09
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Unfortunately not, you need to take them at the end of your imaging run, and without adjusting anything, every time. If anything in the imaging train changes before you take the flats then they probably wont match the defects in the actual images. It's usually the last thing you do before packing up for the night if you have a flat panel to use, if not you need to carefully move the camera and scope / lens to a place you can take flats and hope you don't move anything on the way. In the past I have used a white painted wooden board lit with bulbs, a homemade lightbox, an evenly illuminated white wall and now I've gone all fancy and have a Gerd Neumann light panel. However you do it the plan is the same. Take a series of exposures of an evenly illuminated white surface, expose to about half the maximum saturation value based on the center of the image (normally around 1 to 1.5 seconds). You are basically taking a picture of the defects in your imaging train, mostly vignetting and dust donuts. Once you have your flats your image integration software can use them to subtract those imperfections from the light frames hopefully giving you a clean, flat image.
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Mar 11, 2014 13:34
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Jekub posted:Unfortunately not, you need to take them at the end of your imaging run, and without adjusting anything, every time. If anything in the imaging train changes before you take the flats then they probably wont match the defects in the actual images. It's usually the last thing you do before packing up for the night if you have a flat panel to use, if not you need to carefully move the camera and scope / lens to a place you can take flats and hope you don't move anything on the way. And along with this, you also take darks? No light into the OTA, just taking an exposure of your CCD imager to get the noise?
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Mar 11, 2014 15:07
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If someone knows of a good guide to stacking (i.e., what are flat frames, dark frames, light frames, bias frames, why/when you should be taking them, etc) that'd be great. I never seem to find a good comprehensive article when I look.
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Mar 11, 2014 15:46
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Mr. Despair posted:If someone knows of a good guide to stacking (i.e., what are flat frames, dark frames, light frames, bias frames, why/when you should be taking them, etc) that'd be great. I never seem to find a good comprehensive article when I look. Well, as far as the different frame types, I JUST found this, and it helped me a bit. http://deepskystacker.free.fr/english/faq.htm
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Mar 11, 2014 15:50
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I don't do imaging myself (don't have a setup) but I've worked with research data, so here's my understanding of the different frames. Bias frames are a "zero-length" exposure. The purpose for bias frames is simply to remove readout noise from the CCD itself. This is generally a 'flat' level of noise across the chip, so these should not be scaled for exposure time- often what I need to do is begin by removing the bias from all other frames, including darks and flats. Dark frames are long exposures with no light hitting the CCD chip. They are temperature dependent, and represent the thermal noise on the chip- doing dark subtraction correctly should get rid of your hot pixels. Although they technically depend on exposure, we can usually get away with scaling by exposure time as long as the temperature is right. Flat frames are images of the imperfections within the optical system itself- dust on the lens, vignetting, sensitivity variations across the chip, etc. Methods of taking flats vary- some people do an image of the twilight sky, some have a setup like Jekub up there. As long as it's evenly illuminated, it should work fine. For amateur imaging, that should be all you need. The astronomical spectra I worked with required a lot more processing- comp frames, wavelength calibration, transformation (the spectra have to be perfectly straight), overscan subtraction, sky subtraction, etc. Images are a lot simpler than spectra.
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Mar 12, 2014 00:06
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Sweet, that's exactely the sort of thing I need to know. I've got a triggertrap showing up tomorrow, so hopefully I can take the startracker out again tomorrow night and try some 5+ minute exposures. Should make it a lot easier to get 30+ minute exposures stacked together in the end.
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Mar 13, 2014 00:20
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Awww yissss
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Mar 13, 2014 20:58
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The primary mirror in my 16 year old 6" dob has seen better days, and some tests showed it to be down to around 72% reflectivity. Not entirely surprising since I've had the thing since I was a freshman in high school. So a couple of days ago I packaged up the mirrors and sent them off to be stripped and recoated and a catseye center spot is being applied too. I should be getting them back in about a week. The shop doing the work is a small operation in NJ called Majestic Coatings. They have a really good reputation and they do all the coating work for Teeter Telescopes and D & G optical. That alone is about as good of a recommendation as you can get. Also, their coatings are about 6% better reflectivity than the mirrors had when they were brand new. While the mirrors are gone I'm upgrading the mirror cell and the secondary spider, tweaking the focuser and improving the bearing surfaces. When all is said and done it'll be like a brand new scope. Woot!
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Mar 22, 2014 23:06
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What pair of binoculars do you guys recommend for someone interested in getting started in stargazing? I'm in the UK if that makes any difference.
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Apr 1, 2014 19:03
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kim jong-illin posted:What pair of binoculars do you guys recommend for someone interested in getting started in stargazing? I'm in the UK if that makes any difference. I've been using a pair of Bushnell 10x50 binoculars for a while, and they've been pretty great. I think they're linked in the OP? They're most definitely under $50. I think I got mine for $20?
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Apr 1, 2014 21:19
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Welp, my photography tripod I use for the refracting spotting scope I inherited broke. Are there adapters for spotting scopes to use astronomy mounts?
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Apr 1, 2014 22:33
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Welp, I've got a publication date locked in for my article! "Making the Case for Structured Observing" by Tristan Schwartz (AstroZamboni's real name) will be appearing in the July issue of Sky & Telescope. The timing couldn't be more perfect. It'll be hitting newsstands about 3 weeks before Rocky Mountain Star Stare, where I'll be giving a talk based on it. I'll also be receiving my freebie copies and getting paid for it RIGHT AROUND MY BIRTHDAY. The timing is beyond loving excellent.
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Apr 3, 2014 22:59
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That's awesome! I'll be sure to look for it when I get the issue.
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Apr 3, 2014 23:05
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Great news. I just re-subscribed so I'll keep an eye out for your article.
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Apr 4, 2014 02:48
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Count myself as another one who's excited to read your article. I did a talk on something similar at our last astronomy club meeting when demoing our new website. It pretty much turned into myself trying to encourage our membership to use more modern and public means of communication other than an old mailing list. Neil deGrasse Tyson was in town a few weeks ago for a big engineering event at the local university, and we were able to get a lot of exposure with students there were weren't just into observational astronomy, but folks who are working on stuff like high altitude robotics, microsats, and even aerospace firms like Magellan. I saw a lot of fresh faces at our meeting last month, so I hope we can keep up the momentum.
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Apr 4, 2014 04:22
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Made a few upgrades to my setup. Better ballhead mounted to the tracker, and a Nikon 180/2.8 ED lens. Also have a dirty cheap Canon Rebel XT in the mail... that's had the IR filter replaced with plain optical glass.   Camera won't be here til monday but I can at least test this lens tomorrow night. As a bonus here's some tiny rear end gears  
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Apr 4, 2014 04:58
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Somebody sent me this yesterday. This guy has to be the luckiest bastard on the planet for getting this meteorite on film and not getting killed at the same time. http://www.nrk.no/viten/skydiver-nearly-struck-by-meteorite-1.11646757 Edit: found a link to the actual news site. Seqenenra fucked around with this message at 06:29 on Apr 4, 2014 |
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Apr 4, 2014 06:25
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Ehh, moon was too bright to really do anything fancy but it was still good practice tonight. Orion nebula with 2 sats flying through the frame (was ever so slightly out of focus on most of my shots I realized later, or maybe a touch over exposed? Not real sure, but I'm going to experiment tomorrow)  And the moon 
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Apr 5, 2014 05:41
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I think it's a touch overexposed. The Trapezium of M42 is kind of burnt out. Might want to dial back your red channel a bit as well in post. Looks pretty nice otherwise though!
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Apr 5, 2014 05:47
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Awesome night for gazing, I've got my telescope out acclimating, and I'm running to the station for a sixer. Getting ready for next week's lunar eclipse, gonna be a good weather night then too.
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Apr 10, 2014 02:20
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Coxswain Balls posted:Count myself as another one who's excited to read your article. I did a talk on something similar at our last astronomy club meeting when demoing our new website. It pretty much turned into myself trying to encourage our membership to use more modern and public means of communication other than an old mailing list. You're talking about the Winnipeg RASC aren't you? PM'ed
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Apr 11, 2014 21:10
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I wanna get my first scope, but want a dobsonian to do second scope duty. I'd rather save up a little more and just get a scope that'll not only be extremely portable but have an EQ mount with the option for a motorized one later on. So far, I think I've pretty much narrowed down to the Celestron Omni XLT 127 It's TINY. Gorgeous. Read good reviews for the optics and everything. Light enough that, I figure if I ever start astrophotography junk, it'll piggy back easy enough on the mount. Seems like a good compromise between aperture and size. (5 inches seems okay, and cassegrains have good refractor qualities for planets, right?) $600 on BH. Should I steer clear? Just settle and get a 8inch Dob? Just get a pair of binoculars or the astromaster 114eq (which is 150 bucks right now, but has tons of issues I hear. Poor finder, terrible mount, grease issues, etc etc)
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Apr 15, 2014 01:14
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The Omni 127 is a loving excellent scope. I've used them several times and came away impressed each time.
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Apr 15, 2014 02:33
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Anyone getting some shots of the eclipse tonight? I would, but I'm seriously backed up on homework.
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Apr 15, 2014 06:43
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I'm waiting for the clouds to part (which they're just now starting to do), so hopefully I can see the moon in a few minutes.
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Apr 15, 2014 06:50
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I was going to be photographing it, but it's 20 degrees with lots of moisture in the air. My equipment is now covered in an impressive layer of frost.
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Apr 15, 2014 07:06
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No hope with these clouds 
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Apr 15, 2014 08:03
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Perfectly clear out here, and we can see it pretty well from our balcony. We left our telescope at a friend's place, so no pictures tonight, unfortunately.
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Apr 15, 2014 09:12
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 http://imgur.com/TnMqXAX I see the Blood Moon arising. I see trouble on the way. Canon 550D, EF28-135mm @ 135mm, ISO800 F5.6 2.0s Brisbane, Australia, 1854hrs A little noise reduction and vibrance but otherwise straight out of the camera
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Apr 15, 2014 10:31
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The internet is being flooded with eclipse photos right now, so here's a couple of mine. I haven't processed many of these yet - just grabbed a few and sent them to Flickr so I could justify to my coworkers why I was late this morning. I'll get some better, sharper ones up soon I hope. Full moon, pre-eclipse  SDM_5157 by sdmacdonald, on FlickrTotality  SDM_5220 by sdmacdonald, on FlickrFull set here: http://www.flickr.com/photos/habilis/sets/72157644002379223
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Apr 15, 2014 19:43
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Recently dug out my old 6" newtonian from almost a decade of storage, and I am enjoying getting back into some viewing. I'm enjoying great views of Jupiter lately, although I would like a little more magnification/detail than the supplied 10mm plossl allows. I have purchased a Barlow, but I'm not sure it's the highest quality optically, and the view with it and the 10mm is less sharp than the 10mm on it's own. I'm thinking of an eyepiece upgrade, maybe to a 6/7mm like this: http://www.telescopes.com/telescope-eyepieces/125-inch-eyepieces/celestronxcellxtelescopeeyepieces.cfm Is this overkill for my scope? Am I hoping for more than can offered, and really I need an aperture upgrade? Edit: Looks like there's a astromeet near me tonight so I will see if I can borrow some to try out. Slimchandi fucked around with this message at 12:50 on Apr 19, 2014 |
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Apr 19, 2014 01:01
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| # ? May 29, 2024 23:00 |
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I've always loved looking at the night sky, but never used anything to assist in my viewing. I also live in Los Angeles which I know limits my viewing with light pollution. I've ordered the book in the OP, but my question is I have a pair of newish 10x42 Bausch & Lomb binoculars, are those fine or would I be better off picking up a pair of 10x50 listed in the OP? I don't mind buying another pair, but if there is not much difference, then I would rather not have the extra set. Or should I just mess around with what I have and the book for a while then upgrade later?
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Apr 19, 2014 17:58
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