Max exposure time and stacking

[Wael Hassan]

Hello, I just started astrophotography and i have two questions... Is there a max exposure time after which there will be no added data to the image? i.e If i take a 7 hours exposure to orion nebula , then if i take 10 hours there will be more data and details in picture... so at what exposure time there will be no data added more and will be useless to take more exposure for the image? The second question: i took last night several images for Ic 4606 but i needed to change the battery so i lost some time and i stop the guiding then the orientation of the stars changed a little and i could not return to first orientation.... so how could i solve this problem during stacking ? Or the stacking app has a feature to aligh the images to one orientation ?

[JSeaman]

Exposure time varies depending on your target and equipment. If you are running a 'dumb' mount just tracking then you may be limited to something like 1-2 minutes. If you are guiding then you will likely to be able to get longer exposures (typically something between 5 and 30 minutes). 

People don't tend to do more than 10 minutes most of the time for a number of reasons such as aeroplanes / mount issues / clouds etc. spoiling a lot of data and the fact that this will normally give you all the detail you need

If you are shooting something really bright like M42, you may only want 1-5 minutes and you will also likely want some much shorter (between 3 and 60s) exposures on the core

The stacking software should deal with field rotation no problem

[AstroAndy]

Hi Wael

Generally speaking, yes, after  lot (can;t tell you how many) of sub exposures (roughly between 1-30 minutes, the law of diminishing returns will kick in.

Practically speaking, it also matters how you go about it. While a total 10 hour exposure (10hrs of integration time in, eg, 60x10min) is still 10 hrs., you have to factor in equipment (eg. guiding capability), & sky conditions (eg. shorter sub exposures for brighter sky, and, as was said up there, things like planes and satellite trails).

 

I don't know what you use for stacking, but in DSS (Deepskystacker), if you choose, after registering, the image with the highest value, and set it as the reference frame, all the images will stack to it. If you use a reference frame from a mono camera, shooting in LRGB (say, a luminance one), you can still stack the color ones precisely to it, just uncheck it, keep it as the reference frame and leave it in the stack.

If you wish, you can have a look at this, while this is about CMOS cameras, it's still pretty informative.
https://www.youtube.com/watch?v=3RH93UvP358

Andy

 

[Wael Hassan]

On 01/04/2021 at 08:55, JSeaman said:

Exposure time varies depending on your target and equipment. If you are running a 'dumb' mount just tracking then you may be limited to something like 1-2 minutes. If you are guiding then you will likely to be able to get longer exposures (typically something between 5 and 30 minutes). 

People don't tend to do more than 10 minutes most of the time for a number of reasons such as aeroplanes / mount issues / clouds etc. spoiling a lot of data and the fact that this will normally give you all the detail you need

If you are shooting something really bright like M42, you may only want 1-5 minutes and you will also likely want some much shorter (between 3 and 60s) exposures on the core

The stacking software should deal with field rotation no problem

Thank you....i found star alignment in pixinsight and it helps me 😊

[Wael Hassan]

On 03/04/2021 at 20:34, AstroAndy said:

Hi Wael

Generally speaking, yes, after  lot (can;t tell you how many) of sub exposures (roughly between 1-30 minutes, the law of diminishing returns will kick in.

Practically speaking, it also matters how you go about it. While a total 10 hour exposure (10hrs of integration time in, eg, 60x10min) is still 10 hrs., you have to factor in equipment (eg. guiding capability), & sky conditions (eg. shorter sub exposures for brighter sky, and, as was said up there, things like planes and satellite trails).

 

I don't know what you use for stacking, but in DSS (Deepskystacker), if you choose, after registering, the image with the highest value, and set it as the reference frame, all the images will stack to it. If you use a reference frame from a mono camera, shooting in LRGB (say, a luminance one), you can still stack the color ones precisely to it, just uncheck it, keep it as the reference frame and leave it in the stack.

If you wish, you can have a look at this, while this is about CMOS cameras, it's still pretty informative.
https://www.youtube.com/watch?v=3RH93UvP358

Andy

 

Hi Astroandy....thanks alot for the link....it was really helpful....Last night i begin my imaging session for IC 4606 and RHO OPHICHUI region.. i made around 40 ×3 minutes exposure slots....i used canon 200 D with optolong l pro filter and Redcat 51 scope....i am using skywatcher eq 35 mount... I am doing strectching now for the stacked photo....But the colors still not appeared now for the nebulas .