Re: My first live stacks.
Posted: Sat Mar 23, 2019 10:11 am
Andy cracking images just wish the skies here would clear.
I agree with Robin that amazing images can be achieved with CMOS cameras that will compete with CCD and as Robin points out and explains exceptionally well in the talk at this years conference there are pro's and cons for both setups but one cannot be said to be outright better than the other. This is a similar discussion that would have been had 20 years ago between film camera users and digital cameras users with the debate that they would never be as good but try and find film cameras now and they are a rarity a bit like hens teeth.
I am not saying CCD will go the same way I am just stating that they are two diferent technologies that achieve a similar end result. As for the long exposures the photons are hitting randomly over the course of a period of time and if you use CMOS or CCD over that period of time the same number of photons arrive on the end of the telescope QE efficiency will determine the capture rate of these so different QE will have an effect between different sensors. However if there are a thousand photons and you do 6 x 10minutes exposures on a CCD versus 30 x 2m exposures on a CMOS then I do not see that there will be that much differnce as the read time on a CMOS is dramatically faster than CCD so the potential shutter open time (if we had one) would be very similar between each sensor so you would capture the same number of photons assuming QE was the same.
Then in the stacking stage the CMOS 30 frame stack would potentially have a lower noise level as signal to noise ratio significantly improves based on the number of images in the stack as explained by Robin in his talk.
The other thing when comparing images is you are not solely comparing the sensor as the optics will have a massive effect as well as seeing and other factors so you would never be getting a true comparison unless you had the exact same rig at the exact same time and place with exactly the same quality CCD sensor on one and CMOS sensor on the other and collected the same total exposure time regardless of sub length. With cameras you always aim to buy the most expensive glass as this will be with you the longest as camera / technology improve but the lens not so much.
Just my two cents worth not trying to start yet another CCD vs CMOS debate as I would rather spend my time imaging if the skies ever clear.
Cheers
Nick
I agree with Robin that amazing images can be achieved with CMOS cameras that will compete with CCD and as Robin points out and explains exceptionally well in the talk at this years conference there are pro's and cons for both setups but one cannot be said to be outright better than the other. This is a similar discussion that would have been had 20 years ago between film camera users and digital cameras users with the debate that they would never be as good but try and find film cameras now and they are a rarity a bit like hens teeth.
I am not saying CCD will go the same way I am just stating that they are two diferent technologies that achieve a similar end result. As for the long exposures the photons are hitting randomly over the course of a period of time and if you use CMOS or CCD over that period of time the same number of photons arrive on the end of the telescope QE efficiency will determine the capture rate of these so different QE will have an effect between different sensors. However if there are a thousand photons and you do 6 x 10minutes exposures on a CCD versus 30 x 2m exposures on a CMOS then I do not see that there will be that much differnce as the read time on a CMOS is dramatically faster than CCD so the potential shutter open time (if we had one) would be very similar between each sensor so you would capture the same number of photons assuming QE was the same.
Then in the stacking stage the CMOS 30 frame stack would potentially have a lower noise level as signal to noise ratio significantly improves based on the number of images in the stack as explained by Robin in his talk.
The other thing when comparing images is you are not solely comparing the sensor as the optics will have a massive effect as well as seeing and other factors so you would never be getting a true comparison unless you had the exact same rig at the exact same time and place with exactly the same quality CCD sensor on one and CMOS sensor on the other and collected the same total exposure time regardless of sub length. With cameras you always aim to buy the most expensive glass as this will be with you the longest as camera / technology improve but the lens not so much.
Just my two cents worth not trying to start yet another CCD vs CMOS debate as I would rather spend my time imaging if the skies ever clear.
Cheers
Nick