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I just started doing longer projects over multible nights and realized that I kind of don't know when to call a project really finished. How much data is enough data, I mean you can just keep going. And also, do you start a project from new if you go back to a Object you've already photographed or do you add to the already existing data so it gets better and better over time. |
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Jens: Great question and would like to see answers of more experienced masters of the craft  I am usually going 'with the flow'. Its really hard for me to calculate how much (which filter) light I need, but with each project is a little bit easier to guess. I have general idea what I would like to see from other images and then day by day when I process latest acquisitions try to 'see' if I am there yet (or if I am satisfied with it yet). Last project I wanted slightly more details but at the same time forecast was bad and I wanted to go to another project ASAP as I got fed up of that one :-D On one another (Ring nebula) started as quick testing RGB acquisitions but when I saw hints of fainter details I continue with adding Ha for those fainter regions until I was somehow happy again. So there is a pattern for my approach I guess :-D There is also another example (Cocoon nebula) where I was obviously not prepared what I wanted to shoot and when I didnt see any signal I just wrap it up ASAP |
1.20
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| Never, you always end up deciding to add to projects the following year. This is why it's important that you find an exposure time that works well for many years to come. Last year's 40 hour projects will turn into 60 hour projects for me this year. |
1.20
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| When your result starts looking like an Astrobin IOTD! For me, that's never. |
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I usually do small process attempts on my datasets nightly, just to see where I'm at. I use that to judge the noise levels, and the amount of signal I need to produce results I'm happy with. Really what it comes down to for me, is can I one-up the best image on Astrobin? No? Probably needs more time then. I have alot of projects sitting in queue with ~50 hours integration so far that I still haven't finished. Not happy with the results yet... but due to moon conditions, sky, etc, I've been unable to spend much time on them to finish. Usually most my time gets spent on Luminance, and Sii data. Ha signal comes in fast, RGB data can be fulfilled with minimal time. Luminance and Sii is where all the details really come in for my images. I try not to short that. For example, here's a current work in progress. (Ignore the flat isssues please) I'm 40 hours deep and probably wont stop until I hit another 50 hours of luminance. I need more signal in the background galaxies as well as the tidal stream so I can drizzle this image. Don't stop until you're happy with it.  |
1.51
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| I'm a pixel peeper. I've never finished a project. Drizzle is a dangerous drug. |
16.26
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A great question. Over the 4 years I have being doing this hobby, I have found that new software tools, and more experience, rather than extra integration, invariably make the biggest difference. The WBPP script in PI and the RC Astro tools have been game-changers for me, so much so that I have slowly going back over all my previously "finished" images and breathing new life into them. In some respects therefore an image is never finished because you will always gain more experience and there will also be new software tools. But that is too glib an answer. For me an image is finished when, to gain a factor of 2 in SNR, it would take the remainder of the clear observing season just for that DSO [around 3 months depending on its Dec]. Since I probably average bout 6 clear nights per month [outside of bright moon], this limits my exposures to 1- 2nghts. And gives me around 3-4 DSOs per month - enough to keep my interest levels high. If I really think I need more, I can push it - like I did with the Helix Nebula recently (out to 40 hours) when there aren'tr eally that many interesting DSOs in the South at these RAs. However, in that case he results weren't really any better than 20 hours. Dominated by systematic errors and not statistical errors. This way I can also come back next year and take new data to add to the odd [keep a good archive!] and with the greater experience and better tools, I can make a much better job. And the DSO appears fresh again as well! CS Brian |
1.51
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For me it's more a matter of what I am imaging vs Bortle skies I'm under as well, 5 typically for me. For brighter nebulae like Carina for example which are relatively bright and have great emissions across all three NB filters, 12 hours is usually enough to get a fairly good result with plenty of detail. For things like the Dolphin which are faint, 20+ hours for me is what I would need for a decent result and this is where I usually add data to a previous year if Melbourne weather doesn't permit, which more often than not it doesn't!! As Brian has mentioned above, 20+ hours is where I'd like to target and that might mean over a few months and even a couple of years. Ultimately it's a cross section of clear nights vs output, and for me, 1 target a month at 18-20 hours would be perfect! |
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It depends of you, your image must satisfy you. At the beginning, the goal is to be in progress. For myself, I need to feel that I could not do better with my present level. I know that my image is not perfect. Hence, I keep, my datas & my DOFs in order to make again the target with new tools & new knowledge. I see a lot of people here that re-work their images. |
11.22
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If depth or area coverage is the concern (anything that can be "bought" with imaging time), I call it finished if I don't foresee any way to improve it with the equipment I have within reasonable amount of time. The real question is what's "reasonable amount of time?" It can be forever if you just want to perfect an object in your entire life and you don't care about anything else. But that's not what most people would do. For me, I would say it's probably 4 years. If I spend the majority of my imaging time on a target whenever it is up for four years, I consider it my limit. For example, it took me three years to finish this project. To make it significantly better, I think it will take another 3 or even 4 years. Adding just one or two years of imaging will not significantly help. So I call it finished. On the other hand, sometimes it's not simply depth. It's how you view the universe. If you get everything you expected, it's finished. The real question here is how do we know what to expect before we spend N hours? Suppose you spent 10 hours on an RGB broadband image of a nebula. In the final processed image, there is rich nebulosity, sharp stars, high S/N everywhere. So is it finished? But how about adding 40 hours of OIII? Something new may show up, right? (Now more and more people are doing this and they do find many new things.). Why not another 40 hours of SII? How about infrared? Questions like these will never end. There will almost always be something new. If that's what you are going after, it will not end. In my opinion, the end point is whether I have obtained an image of that part of the universe that I envisioned or expected. If I reach that, I call it finished. So the limit is really your imagination (and partly your knowledge about that area of sky). My 2 cents. |
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| I generally decide filters, exposure times, and total integration time when I select the target before starting to image. It all goes into the spreadsheet. Experience helps me determine this using object magnitude, size, etc. Galaxies/Clusters I tend to shoot for ~10 hours integration time. Most everything else I target 20hrs. How many nights is determined by the quality of my skies. I'm planning April at the moment. Cheers! |
7.61
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For me it’s a bit more arbitrary….. I really enjoy processing (at least when the data is being cooperative…. ) so I try to balance acquisition such that I always have something in the processing queue. Fortunately, I’m a slow processor, so I can usually get about 20 hours before culling (or 30 including Ha). I don’t spend 20 hours processing a target, but because I’m working at it an hour or two here and there, plus considerable time after ‘finished’ letting it settle and tweaking (another when are you done question…..), the overall time in days is about equal. Many would probably say 20 hours is excessive, especially under bortal 3/2 skies but if my processing line is just going to back up, then I figure why not? And I like being out imaging at least as much as processing. Occasionally, if I’m going after faint detail, then I’ll go longer, or revisit and add data annually. Cheers, Scott |
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You need double the time to reduce the noise by half. So for me, I'm done when I feel that spending 2x the time elapsed is no longer an appealing prospect. I think 'is having half this amount of noise worth doing the whole thing over again for?' For me that's usually around the 40-hour mark, which is around two months in my climate. |
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It's actually 4x the integration time to double SNR..... But I wonder why double is always the goal. If you're trying to bring out some faint signal that's right at the border of the background noise level for a particular integration time, like IFN, or a galaxy's tidal stream, couldn't a relatively small improvement in SNR, 25% say, make enough of a difference where that faint signal can now be worked on? Cheers, Scott |
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11.22
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| Actually, if you try to stack different numbers of subs, you will see that doubling the S/N is a dramatic improvement. It is of course good, but can sometimes be an overkill. On the other hand, if you double the number of subs to increase the S/N by 1.41x, you may find that the improvement is already quite noticeable. Because of this, I would say that for whatever you have achieved, doubling the integration time is the next meaningful milestone. If you don't find the result satisfying and if you have time, doubling the integration again. You don't need to set a goal of quadrupling the integration unless you know exactly what you want and exactly what that will bring you. |
