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In my quest to keep improving my images, I’d like to ask the AB community for examples of deep-sky images you find have some of the best-looking stars. Next step will be about understanding the gear / acquisition & processing techniques that can produce such results, but my first objective is to actually find some images that display top-notch stars according to you. Of course highly subjective, but that’s what makes it fun ! CS Emmanuel |
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With newts, these are my favorite type of stars https://www.astrobin.com/dosgf6/J/ And I think these are my favorite, for refractors https://www.astrobin.com/t4ymfz/ |
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With newts, these are my favorite type of stars https://www.astrobin.com/dosgf6/J/ That Newt, my friend. Is a CDK. |
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V.M Legary:With newts, these are my favorite type of stars https://www.astrobin.com/dosgf6/J/ Oooooh  I guess I meant that's how I like stars that have diffraction spikes. |
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V.M Legary:With newts, these are my favorite type of stars https://www.astrobin.com/dosgf6/J/ I don't mind em, or like em. |
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I really love these stars here: https://www.astrobin.com/ahxx7q/?q=Charles%20Hagen I am actually looking for tips on how to process stars to have nice colors. All of these pictures with amazing stars have extremely long exposure times and i wonder how they manage to not totally destroy the star colors with that. Are you aware of good tutorials for amazing star colors!? Cheers, Robert |
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AstRobert: They aren't necessarily all that long, considering apertures and pixel sizes. Under dark skies, with small pixels and narrow band filters it is not unusual to need and benefit from longer exposures. At 300 seconds, just 5 minutes, that is not really all that long. If you had huge pixels, then yes, you might saturate, but with small pixels the stellar signals should be getting distributed over many pixels. I have used 10 minute exposures with an f/4 camera lens with a 150mm aperture using narrow band filters, and 2.4 micron pixels. I would usually clip half a dozen to a dozen of the brightest stars, just a smidge. Based on my analyses at the time, the next brightest stars would have allowed another 180-300 seconds of exposure before clipping. |
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Jon Rista:AstRobert: Well I was looking at the RGB exposure times without NB Filters (cause thats a whole other topic regarding star colors ;-) and I get saturated star cores at 120sec with an F7.5 Scope so that is why I wondered, how these great stars colors with 600s at f4 or whatever come to be. |
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AstRobert:Jon Rista:AstRobert: FWIW, 600s @ f/4 is with 3nm narrow band filters, not broadband filters. I definitely couldn't get 600s exposures with RGB. Some of the images had 1200s exposures with narrow band filters. The RGB filters were 300s, which is only about double and change what your 120s. To that... It will also depend on your gain. People usually use very high gain settings these days. Sometimes, if the camera has a high conversion gain (HCG) mode, then you might only lose a fraction of a decibel of dynamic range, which won't matter. Yes, you'll need to use shorter exposures, but with read noise as little as 1.2e-, then you truly don't NEED long exposures. A lot of cameras that have HCG modes, have identical (or slightly higher) dynamic range at minimum gain, which means you should be able to use even longer exposures at gain 0, integrate fewer subs, but end up with the same results in the end...if you really wanted longer exposures/fewer subs/good star color. On the other hand, a lot of cameras don't have an HCG mode, and higher gain settings are going to diminish your dynamic range by stops. THAT could be part of the problem. If you want the maximize your star quality, then technically speaking you should be using the camera at the gain setting that just gets you to the maximum dynamic range. In some cases, that is the lowest gain setting, other times it might be higher than minimum gain, but lower than other commonly used settings like unity gain or "lowest read noise." Another thing to ask yourself is, how many stars ARE saturating? Ten, twenty? If so, then that is a tiny fraction of the overall star count in most images, and it is really not going to matter if the cores of some stars clip like that. In fact, the way stellar saturation distributes in most images...if you saturate 10 stars at say 120s, you are probably only going to saturate about 15-20 or so at 240s. Depends a lot on the field, but the brightest stars are often SIGNIFICANTLY brighter than the vast majority. So you don't necessarily go from clipping 10 stars at a couple of minutes, to clipping all of them at five minutes...if you choose to increase your exposure length. A lot of the time, you can more than double, or even triple, your exposure and the number of stars that clip will only increase by a small amount. Alternatively, if you are saturating MOST stars in just 120 seconds, I would really want to figure out why, as that generally shouldn't be the case... One possibility could be a gain well above the optimal gain for maximum DR. It may also just be that you are using an HCG mode on your camera, and you simply shouldn't be aiming for long exposures (generally speaking, the HCG mode IS optimal, but it will require acquiring lots and lots of shorter subs and stacking a ton of them, to maximize the benefit...which, really, IS the benefit: very high efficiency! ;)) I guess if you have ridiculously high light pollution, then that might add a significant background offset that could push more stars to clipping. If that is the case, then sadly, your problems with star color are probably not just a matter of saturation, but also pollution. I could never get good star color under light polluted skies, no matter what I tried (LP filters, gapped RGB filters+mono, OSC, etc. etc.) A lot of the time, I think people just think of light POLLUTION as just "the gradient" and that it can be removed without issue, however its a signal pollutant, and is often not just a simple gradient, and it contains a lot of color information as well...and that can certainly muck with star color. IF you then throw LP filters into the mix, then you might as well just forget about quality star color. |
