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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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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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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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Mr. Despair posted:There is one but it's not this thread You do realize you just linked back to this thread, right? Or am I missing a joke here?
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May 15, 2014 03:15
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What about a used CG-5 mount? I see them going for less than $500 fairly often on Cloudy Nights Classifieds, and I'm wondering if there's a reason a computerized motorized mount would be that cheap compared to new.
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Jun 3, 2014 13:49
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Ah, ok. It's all hypotheticals right now, because I blew all my cash on a Z12. Which is great, except that the collimation commits suicide any time I so much as look at the telescope. :v But 12" for less than $450 is worth it to me.
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Jun 3, 2014 17:41
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I think a 10" is the upper limit of portability unless you have a truss dob, and it's still got plenty of aperture to look at faint things. I have a solid tube 12" and I honestly have to convince myself to haul it out on clear nights- the view is great, but carrying something the size of a hot-water heater outside is annoying as hell. A 10" is perfect.
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Jun 15, 2014 22:57
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Observing report: Got a chance to go out with my 6" and look at stuff before the Moon came up. I got a nice view of PANSTARRS C/2012 K1 in Leo Minor, although even though the comet is like magnitude 7.8 it's right next to a brightish star so it was hard to view the dimmer bits of it. Also got a quick view of M51 (which was interrupted by a bright satellite streaking right through the FOV and ruining my night vision for a few seconds). I spotted M106 as well, which is mostly just cool to me because that's the galaxy I'm doing research on at the moment. A successful night, methinks.
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Jun 17, 2014 05:11
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Trampus posted:I know this isn't exactly what this thread is for but I'm hoping you guys can help me out with my telescope. I have an 8" dob that I use in the Phoenix area and due to light pollution and laziness, I really only look at the planets and Orion's Nebula. I'm taking it on a road trip with me to the middle of nowhere in Missouri this week and would love to take advantage of the dark skies there. Can someone recommend a good cheat sheet or guide for finding stuff in the Summer sky? Amateur astronomy thread- that's pretty much exactly what this thread is for! The summer sky is just as interesting if not more so than the winter sky, IMO. You've got the huge clusterfuck of galaxies in Virgo, some really nice galaxies in the Ursa Major/CVn area, the summer Milky Way rising in the east if you wait around for it, fucktons of nebulae and star clusters... My personal favorites that you should try for:
For finding them, I'd suggest Stellarium, probably my favorite free astronomy program. For bonus points, check http://heavens-above.com/ for ISS passes, Iridium flares,other satellite passes, and other fun things like that.
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Jun 30, 2014 17:56
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Trampus posted:Thanks, this is exactly what I was looking for. Even if I can only find a third of the stuff you suggested I'll be happy. Thanks again. No problem, be sure to keep an observing log so you can write down the stuff you did manage to see! A lot of those objects are fairly easy to find by star hopping or even just guesstimating by looking for bright stars nearby, so once you start remembering where stuff is you'll be able to find it in no time.
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Jul 2, 2014 05:39
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If you use binoculars, it might be worth it to get a tripod. Your mileage may vary, though. Some people can use them with no problems, but my hands are so shaky that it's literally impossible for me to see anything through binoculars.
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Jul 16, 2014 19:20
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Trampus posted:I wanted to follow up and tell you the telescope was a big hit with my family. Many of them had never looked at the moon or Saturn through a telescope and many minds were blown. Unfortunately, I wasn't able to locate any Messier objects =( I tried using the SkyMap app on my phone to find the general locations but when you have a line of impatient people waiting to see something, five minutes is forever. I'm going to take the time and practice finding things from home before I take the scope out in the public again. Glad to help! Saturn is always an instant crowd-pleaser and usually the one that makes the most impact- most people aren't quite as interested in looking at a fuzzy blob, no matter what that fuzzy blob is. If you're familiar with the constellations/asterisms, it's much easier to find Messier objects. On some clear nights, it's worth it to go out without the telescope and with a planisphere/star charts and just try to identify bright stars and constellations- soon enough you'll be able to find stuff without even trying. For example, M57 is nearly exactly halfway between two of the bright stars in Lyra. M13 is located in the "armpit" of Hercules. The Lagoon Nebula (M8) is above the "spout" of the Sagittarius teapot. M51 is below the last star in the handle of the Big Dipper/Ursa Major. Once you get a good handle on where objects are in relation to bright stars or constellations, you can usually find them in less than a minute.
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Jul 21, 2014 18:37
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Rip Testes posted:Good to come across the thread. I live in an urban area and my skies are poo poo due to light pollution, reducing me to really only planetary and lunar observing. I've been trying to get into the planetary imaging for a couple of years now and have sunk a bit of coin into that without justifiable results, the problem being the seeing conditions are really disappointing where I live generally. Undaunted I recently decided to throw even more money into the money pit that is amateur astronomy and bough myself a dedicated solar scope, figuring that not only is the Sun around a lot more than things in the night sky, but it generally works well with my sleeping schedule (as in not interfering with it). After looking through a hydrogen alpha scope a couple of years ago for an eclipse I knew I needed one of those. Then I started looking at the prices on that and got really dissuaded, tho recently I was able to score some good kit for a few thousand off retail. Holy gently caress this is gorgeous. I never knew you could get this kind of results with the Sun with amateur equipment.
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Sep 29, 2014 04:03
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If you want to do photography through a telescope for long exposures, you'll probably need an equatorial mount. Unless you have a field derotator, a dobsonian mount won't work because the field of view will rotate as time goes on. It's slow, but it's enough to mess up long exposures.
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Oct 7, 2014 18:11
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Golden-i posted:It seems like you get it calibrated to your time/location and it uses arrows on the computer screen to direct you where to point the telescope, so it's not actually motorized. Slightly misleading, it seems. I have one like this. It works decently, but it's not exactly high end. Also, just to clear things up a bit more: A dobsonian/altazimuth mount can be motorized to track the stars, but it's still not suitable for astrophotography- it has to track in two axes, and the field of view will rotate as the night goes on. It works great for visual observing, but it's not meant for long exposure photography unless you have a field derotator, which is pretty expensive. If you want to do long exposure astrophotography of objects like nebulae and galaxies, you absolutely need an equatorial mount, because it only needs to track in one axis and the field won't rotate over time. Unfortunately, computerized equatorial mounts are not cheap. That's not to say that you can't do astrophotography with a Dobsonian- I'm just saying that you will be time limited no matter how good your tracking is if you have any sort of altazimuth mount. There's also the option of a homemade equatorial platform/barn door tracker, but that requires more work. I'm not sure what the time limit exactly is on how long you can use an altazimuth mount and still get decent results, but my guess is that you may start seeing the effects of field rotation as early as 5-10 minutes into an exposure. Luneshot fucked around with this message at 20:07 on Oct 7, 2014 |
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Oct 7, 2014 20:02
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Golden-i posted:That's great info, thanks. I'm having a hard time finding a reflector/refractor on an equatorial mount that's in my price range and computerized, maybe I'll wait until I have a little more money to spend. Yeah, astrophotography is an expensive hobby unfortunately. I've always preferred visual observing so it's not really an issue for me, but I've picked up enough from others and my own experiences to have a decent idea about the cost and effort involved. If other people here are more experienced with it, feel free to chime in. One possibility is to buy the mount and scope separately- that way you can pick and choose what fits your needs.
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Oct 7, 2014 20:12
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Here's my best shots: 
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Oct 9, 2014 04:13
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Generally, you have three choices for cameras for astrophotography. 1. DSLRs. These are what most people start with, and they're plenty capable on their own for basic astrophotography. This has the advantage that your exposures are already in color, and most people who know their way around cameras should get the hang of using a DSLR for astrophotography pretty quickly. You do have to buy a T-ring and such to mount it, but in general this is the simplest option. 2. Low end CCDs- starting at a few hundred dollars. CCDs are a different beast altogether from DSLRs. Most CCDs are monochrome (although there are color ones), meaning that to get color images you'll need to use a filter wheel or manually change the filters to get three images in R, G, and B. CCDs also have more thermal noise, require dark subtraction and/or flat fielding, and are more prone to cosmic rays. However, they provide a good introduction into higher-end imaging and they can give great results. The ability to merge exposures and such to remove defects has benefits too. 3. High end CCDs. These can cost several thousand dollars- you probably shouldn't even consider one of these until you've owned a lower end CCD, because you'll probably have no clue how to work with it well. If you know what you're doing, though...these things can have utterly breathtaking results. These usually have more features than the lower end CCDs, more detector pixels, more even sensitivity across the chip, better cooling, and so on. e: beaten on some stuff
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Oct 10, 2014 03:23
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AstroZamboni posted:So I just bought this, and I figured you nerds would want to know it exists too. Finally, a shirt that perfectly encapsulates my financial philosophy. Bought it immediately.
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Nov 16, 2014 04:46
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Oh man, I'm super jealous. Phil Plait is my role model. That's awesome! I want a meteorite someday. 
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Nov 23, 2014 18:08
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Something to note with telescope mirrors is that in general it's best to clean them as rarely as you can. A fine coating of dust won't hurt your seeing too badly, so I wouldn't worry about it. Remember that a primary mirror is a precision instrument, and cleaning it carelessly can do more harm than good. The general rule of thumb is "when in doubt, leave it alone". If you absolutely need to clean your mirror, Google for some good guides online. S&T had an article several months ago about cleaning optics too, but I can't seem to find that particular issue right now.
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Dec 1, 2014 04:33
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Collimation is easy to do yourself, and with enough practice it becomes a 5-minute affair.
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Dec 1, 2014 05:42
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I have a really nice pair of astronomy binoculars- and they're completely unusable for me because my hands are ridiculously shaky. Just a heads up that if you have shaky hands a tripod will probably be mandatory.
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Jan 12, 2015 03:38
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GutBomb posted:Yeah I've had people ask me too but then I start nerding out about the moon or some poo poo and they stop listening. It's like they hope I'm a creepy rapist. It's pretty terrible that people consider that sort of thing funny in the first place.
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Jan 14, 2015 04:29
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I got a chance to go out and see Lovejoy using my 6". No pictures except a noisy wide-angle tripod shot in which it's barely detectable, but it was distinctly green through the telescope. Even got a chance to show it to a cop who stopped to see what I was doing.
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Jan 16, 2015 16:30
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smarion2 posted:So my binoculars came in! I couldn't wait to go find a dark spot so I just went out side my apartment complex to see what the sky looked like. I found Jupiter! Could easily make out like 3 moons around it. I also think I found Orions Nebula? It wasnt the cool redish orangish color like I see in the pictures though so I'm not sure if thats what i"m looking at. Except for bright objects like planets and the occasional bright comet (e.g Lovejoy right now), you'll never see color through a telescope. Our eyes aren't adapted well for seeing color in the dark, so fainter stuff like nebulae and galaxies will always just appear like grey smudges. (Of course, the real excitement is knowing what that grey smudge really is.) An iPhone app will work in a pinch, but I'd make sure you turn on the red filter to save your dark adaptation.
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Jan 18, 2015 03:17
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Venusian Weasel posted:The other night I had the oddest sensation that I was seeing a dim red and blue tint to the Orion Nebula, which I've never had happen before. It's usually greenish, I wonder if the sky transparency was letting just enough light in to pick up color. But yeah, color is a pretty rare thing. Basically limited to planets and bright stars. Goddamn that's beautiful! I see you even caught the Flaming Star Nebula in there too. Really nice work, I can't wait until the day I finally get a camera and mount I can do that with. smarion2 posted:Ok that's good to know. I'm pretty sure I found the nebula then! It was milky looking I couldn't really get much detail out of it but it didnt really look like a star cluster. I found a really bright yellow star around there as well I'm assuming its Betelegeuse? The darkness of your sky doesn't really affect what you can see for planets, most of them (except Neptune) are all bright enough that light pollution doesn't do anything. For planets and bright star clusters, your limiting factor is going to be 'seeing'- basically, turbulence in the atmosphere. The lower down the object is in the sky, the worse it'll be- hence why stars near the horizon twinkle more. For diffuse objects like nebulae and galaxies, seeing doesn't matter that much but light pollution is extremely important, along with transparency (the amount of water vapor in the atmosphere). Those basically affect contrast, meaning that dim objects will blend in more with the sky background and make it much harder to see. The moon is a real factor in seeing dim things too, it reflects a lot of light into the atmosphere and basically acts as light pollution you can't get away from at all. If you live in North America, I highly recommend Clear Dark Sky, a site which can tell you the expected observing conditions for any site defined as an observatory (although you usually find private sites on there too!) Find one near you and take a look at it- it usually updates twice a day.
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Jan 18, 2015 03:48
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Vladimir Poutine posted:There are a few interesting sky events this week. On the 24th there is a triple eclipse on Jupiter (starting at 1:27am US EST) and on the 25th Uranus and the moon will be close enough together to be in the same FOV of binoculars, making it pretty easy to spot a planet that's normally not visible with the naked eye. There's also a (relatively) large asteroid flying past Earth on the 26th, about 3 lunar distances away. Should be visible in binoculars from what I hear.
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Jan 21, 2015 00:29
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look if you ain't processing your exposures using IRAF you're not doing it right (  )
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Jan 23, 2015 02:42
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Went out last night for some visual galaxy observing and did way better than I expected! Nailed M51, M81 and M82, M65 and M66 (couldn't seem to find the other one in the Leo Triplet, but I wasn't looking too hard), M87, M104, M106(my favorite), and M63.
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Apr 24, 2015 15:41
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I can usually find most "independent" galaxies (e.g. M51, M81, M106) by visual search, but with the Virgo cluster I don't even try- I just use a motorized mount because I don't have much experience in that area of the sky. This is actually probably the time of year that I go out the least, so I've been missing out on a lot of great objects.
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Apr 25, 2015 01:03
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I have a 6" reflector and 12" dob, and I definitely think the sweet spot is 8-10". Unless you have a collapsible dob, the 12" is too heavy and bulky to be easily portable (including the base, mine is ~60lb and 5.5 ft tall) which tends to discourage you from wanting to lug it outside unless it's a really nice night- not something you want in a telescope! The 6", on the other hand, doesn't have enough light gathering power for a lot of faint deep-sky objects unless you're in a fairly dark sky area. It's lighter and easier to carry around, and it's my standard "portable" 'scope, but I'd recommend going for either an 8" or 10" in general.
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May 28, 2015 21:08
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Pukestain Pal posted:I got a private tour of Goddard yesterday and got to see some pretty cool stuff. You should crosspost this to the Spaceflight thread. Also I'm so goddamn jealous holy poo poo. Also extremely excited for JWST.
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Oct 27, 2015 16:56
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You got both M32 and M110 in your Andromeda pic too. Nice shots!
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Jan 7, 2016 06:04
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I went out observing tonight on a whim to see some carbon stars and hit R Leporis and Y CVn (La Superba). Man, they are just spectacularly red. They're gorgeous! R Leporis, being only a couple degrees away from Rigel, is a good target this time of year- definitely worth checking out. I would have also tried S Camelopardalis but I couldn't seem to find it- telescope was fogging up too badly, probably.
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Feb 2, 2016 07:06
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8 or 10 inches is the sweet spot in portability and light-gathering power. 12 inches get you more light, but is at the limit of being easily portable- my Z12 is about 60 lbs and the size of a house hot water heater. If it's too big to move easily, you'll find yourself not observing just because you don't want to put in the effort to haul the scope out- and at that point you've gone too big.
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Feb 3, 2016 03:33
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If you're going 12" or more, a truss tube is basically an absolute must. My 12" is a solid steel tube (hence the quite literal comparison to a hot water heater) and it makes it extremely difficult to haul around, both in dimensions and weight. It's totally worth it to pay the extra for the bonus of portability. Observing with a 12" on La Palma sounds fantastic, though- I'd love to do that someday.
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Feb 3, 2016 23:22
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If it wasn't Albireo, it could have been Gamma Andromedae (Almach). Big yellow star, smaller blue one.
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Feb 7, 2016 23:17
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I've never been able to hold binoculars at all thanks to extremely shaky hands, so I'd recommend a tripod for them if you can. I have a super nice pair I got as a gift that have basically never been used for this reason.
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Feb 13, 2016 18:37
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I've always wanted to go to NEAF, budget and school just hasn't permitted it. Maybe I should look more into going this year.
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Feb 21, 2016 19:04
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