When do you consider you don't need more lights? [Deep Sky] Processing techniques · duardito · ... · 16 · 1351 · 3

duardito 0.00
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Hi to all,
I started this great hobbie few months ago and I am learning always reading in some places, but there is one topic that it is not clear to me, when do you believe you don't need to shot more lights? does it exist a number or it is based on experience.
thanks
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bennyc 8.42
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More lights equals more signal meaning better SNR. So when is your SNR enough?
The better the SNR, the deeper you can stretch the data without the noise becoming too much to handle. 
So, you have enough lights when you can stretch down to reveal the details you want to show without the noise getting too much to deal with. 

Stack your data, look at it and evaluate what you have. This part is a bit experience and a bit taste. 

To be honest "enough lights" is a bit of a luxury question for many of us. With the local climate here not giving me many clear nights per year and buildings obstructing a lot of the sky, for me it's usually "work with what you have". So the pragmatic answer is perhaps: you have enough lights when the weather gods decide you have had enough.
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Rafal_Szwejkowski 7.14
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Some rules of thumb for me:

Clusters: 90-120mins, more is nice, not required.
Narrowband: reasonable image is 10 hours per project, including RGB for stars.  I put in more time for objects I really like.
Galaxies: 5h minimum LRGB.

The improvement rate is not linear so at some point diminishing returns make additional effort not worthwhile.  For most popular objects going past 10 hours gives marginal improvement and past 20h not even noticeable.

Some exotic fare requires 50h or more, some enjoy that type of commitment.
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whwang 11.57
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I never feel I have enough exposure.  Over my 30 years of astrophotography life, NEVER.

I stop integrating because:
1. weather does not allow me to continue, or
2. I have better or more urgent projects, or
3. I can't afford to put more time into one particular project.

I never stop simply because I feel I have enough light.  There is never enough light.
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stevendevet 6.77
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never.. or.. well.. there are always fainter details that are more visible with more integration. and there is always a better signal to noise to be found somewhere. But, obviously, you are limited to the amount of detail you will ever get depending on seeing conditions, pixel size, scope, camera, etc.

I tend to go for quite long projects. And I aim for 20-30 hours on most narrowband projects. - Mainly as my 183MM, while being a great camera, takes a long time to get enough light into those tiny pixels. - Usually I do a quick stack after 10 hours, just to see where I'm at and where I think I could improve and what data would be best to get more of.. 

Obviously fainter targets need a lot more data. And I'll focus on that data to try and get more to pull those fainter details out.


But, I mainly determine a project to be "done" depending on outside conditions
- when the weather turns and when it doesn't look like I'll be able to ad something to the project for another week or 2.
- the moon is out, so getting Oiii data is a bit of a pain.
- position of the target isn't great anymore depending on the season.
- maybe a different target is coming into a better position, so I want to start shooting that.


Either way, there is no magical number. 
You just have to figure out what works for you, what works for your gear and what you want to achieve. 
Some people want to finish a target in 1 night. Others spend months on a 100 hour long mosaic.
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shootnmskies20 3.71
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As you've read above, it is all a matter of taste, plus light pollution conditions, type of camera, etc. The best way to asses is to simply experiment to get your satisfaction. For example, I like detail, especially in galaxies. Here in New Mexico, the skies at my location are fairly dark, so I'll typically shoot 4 hours of luminance data at 5 minutes each, plus 3 hours each of RGB in 10 minutes subs. For H-alpha alone, I'll typically shoot 6+ hours of 15 minute subs (with an 11" SCT and a QSI CCD camera)

As I said, I like detail, but given weather conditions, the Moon, life's schedules, etc., it can take months sometimes to acquire all the data. Since I'm older, I don't typically spend too much time on one subject. Now, on the other hand, it all depends on what level of detail and color you want to get. For example, I suggest you check out Astrobin member Vitali. He sometimes acquires great amounts of data, typically with a OSC ZWO camera. One of his finest images contains 70+ hours of data in 3 minute subs - astounding work!

Interestingly, as of now, I'm starting to work with a ZWO OSC CMOS camera on the 11". CMOS technology has increased dramatically in just the past few years, which is wonderful for me because I can get results that I'm happy with in a shorter amount of time (theoretically!)

Again, it's all a matter of preference. Take as many images as you need to get the results that satisfy you - there really is no set amount of time because we're all different as far as what pleases us in an image.

 - - Steve
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Rafal_Szwejkowski 7.14
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My perspective is that having 70 hours of data on a target is not, by itself, a measure of quality.  It's not an accomplishment to shoot something for 70 hours, anyone can do it.  Just point the telescope at something, for 70 hours.
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HegAstro 11.75
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For me, 70 hours would be an accomplishment. Where I live, I can only dream of 70 hours for an entire season, let alone 70 hours to devote to a single object. I don't know about anyone else, but I wouldn't be able to do it. My integration times are heavily dictated by an evil weather god.
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SemiPro 7.38
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It's hard to put a concrete number on it since a lot depends on the sky conditions, telescope, filters (if applicable), camera, and of course your target.

When I have access to dark skies or I am shooting narrowband I find that enough lights equals barely having to de-noise, if at all.

How realistic is that? Well I will put it like this - To date I only have one picture where I managed that (although the Orion one got close...)
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Alan_Brunelle
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Not sure I understand all the quotes here of specific times people are shooting without a statement of the telescope or lens f-ratio being mentioned by those doing the quoting.  Maybe all telescopes are f7?

Before I state my situation let me say that it is clearly subjective and personal to the person doing the imaging.  To be determined empirically as suggested by some above.  If you know what you are doing in capture, post processing, etc., then if you don't like what you are getting, by all means collect more subs.  But understand that if someone who uses an f10 telescope and states they have to collect 20 hrs of subs, that will be unnecessary if you use an f2 lens.

I often see those who started with an f8 or 10 switch to an f2 RASA yet still use the same integration times.  Yes, this may be pure luxury.  Or mistrust in the f2's capability.  Or ignorance.  But given the quite real issue of diminishing returns, it would be wise to adjust your times.  

I guess if you are intending to make money with astrophotography, then by all means, collect 100 hrs.  Maybe that can add to the marketing!

Like others here, I live in an area that is very sky limited.  Because of that, I chose an f2.2 RASA and also prefer natural color, so use a OSC camera.  For most deep sky objects, I use 3 to 6 hrs total (edit: for a single frame exposure).  Seems short, but its actually more than what most shoot using an f6 lens.  If I shot with mono R, G, B, L.  Each channel would be shorter, because of the increased efficiency, but my guess is the total time would be similar to what I use with my OSC.  For me, the times I use are because of SNR.  If I am forced to go too short, the work to reduce noise to within "my" comfort level becomes high.  And sometimes I cannot meet "my" standards.  Regarding detail, I find I almost always achieve roughly the same detail as compared to others reporting the same images with the same aperature lens, even with differing f-ratios.  And that means I am more aperature limited than integration limited.  My 11 inch will never match or exceed a well done image from a 24 inch anything.  Unless I do a lot of of "ceative" processing.  But that is another topic...
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Starman609 6.45
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You can put as much time on a target as you want. More is better if conditions dictate. This is my second year and I'm finding that more integration time equals better images.

In my first year, I was into quantity (more targets and less integration). Now I'm moving in the direction of quality (less targets and more integration). As you gain experience with your equipment and processing you will want to improve the quality of your images. I think it's a natural progression in this hobby.
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kuechlew 7.75
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You may like to watch this interesting video by Nico Carver (Nebula Photos): I Took 1,024 Photos Of ORION NEBULA! - YouTube
I would claim you have enough lights when you no longer need to work hard to fight noise and you're happy with the resulting image.
I believe there are just too many variables - sky conditions, equipment, personal taste and ambition, ... - to provide even a rule of thumb.

Have fun and clear skies
Wolfgang
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BradleyWatson 7.33
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Hi, unfortunately I'll think you will find the theme here is that there is no right answer, every individual APer has imaging configurations and environmental factors that are just too different to the next person to have a single answer to this question. If you want to answer the question you ask yourself a few questions

1. How hast is my current system? F Ratio Do I need 20 times more data than someone with a faster system.
2. What level is the noise I am in? Am I shooting into a light dome where I have say Bortle 8 skys so have to overcome light pollution.
3. Am I shooting with OSC or a mono camera. You will collect more light in each of the channels for mono reducing time
4. How dark or bright is my object, am I chasing faint detail if so I probably need more integration time to capture this (this is affected by all of the above)
5. Personal Taste. Am I happy with noise in my image, am I chasing very sepcific details, do I want an easier ride when it comes to post processing (do I have the tools to manage shorter integration to get my desired image). This point is really "what am I looking to acheive".

So your question is very very subjective as you can see from the points above, BUT do remember if you look at Hubble images and use those as a benchmark you will be very disapponted if you are looking for similar levels of detail with 100hrs of integration, just will not happen so take into account your seeing as this will determine what detail you can get. You can fill in details but if you do not have the resolution and seeing, no amount of integration time is going to get you there.

Does not answer your question but they are some basic pointers.

Below is a test I did looking at integration time Integration Time Comparison - M81 ( Bradley Watson ) - AstroBin

image.png
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ManuelCP 2.39
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Hi duardito,

I have had the same question and came across a couple of sites that helped me with this question:

a. Exposure, Gain, and Cooling oh My | joeytroy.com
b. http://www.gibastrosoc.org/sections/astrophotography/optimum-exposures-calculator
c. https://forums.sharpcap.co.uk/viewtopic.php?t=456

You can also run a response curve with your setup to determine the number of lights you need to take to gain a visible benefit. I did so a few times to get a feel for the performance of my setup on a number of targets, here is an example:

image.png
Hope this helps.

CS
Manuel
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kuechlew 7.75
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Manuel Peitsch:
Hi duardito,

I have had the same question and came across a couple of sites that helped me with this question:

a. Exposure, Gain, and Cooling oh My | joeytroy.com
b. http://www.gibastrosoc.org/sections/astrophotography/optimum-exposures-calculator
c. https://forums.sharpcap.co.uk/viewtopic.php?t=456

You can also run a response curve with your setup to determine the number of lights you need to take to gain a visible benefit. I did so a few times to get a feel for the performance of my setup on a number of targets, here is an example:

image.png
Hope this helps.

CS
Manuel

"Abandon all hope, ye who enter here" (Dante Alighieri)

Alternatively: If you ask a question, don't complain about the answer ...

Please don't get me wrong. As a person with a phd I'm the last one to object against a scientific approach. Therefore thank you for the interesting links and food for thought. However given all the variables you can't control in AP - after all both the weather conditions as well as a complex AP rig are nonlinear systems and therefore subject to deterministic chaos - I have some doubts. While these formulas are certainly helpful to get you in the proper ballpark I'm not sure whether the whole effort of calibrating your gear under "typical conditions" (whatever that may be ...) in order to be able to apply a calculator is time well spent.

I had to smile a little bit about the article whether gain 111 or gain 120 is the best for the ASI 183. I have severe doubts that in a double blind study anyone would be able to figure out the difference between the resulting images. I believe AP is as much a craft as a science and while the scientific aspect is useful and interesting we should not obsess about it. These links are pushing it a bit too far for my taste but everyone as he/she pleases.

We fellow beginner APs may return to these formulas once we overcame all the other obstacles towards a consistent imaging process - and there are way too many ...

Have fun and clear skies
Wolfgang
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duardito 0.00
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thanks to all of you.
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AliAlhawas 1.20
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As others said,, More lights --> better image.. now ask yourself  : When do you stop getting better image ?!
For myself .. I plan one imaging session ( about 5-6 hours) for one target each time.. never accumulate data from many session..
the reason maybe a personal taste of this hobby to get a new target each time.
good luck !
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