Quote:
Originally Posted by pberrett
Hi wonderful people
This question is for those more technically inclined.
I have been reading up on exposure, resolution and aperture. As I understand it in astrophotography aperture is king because a bigger telescope = more light = more saturated and detailed imaged (i.e > resolution).
This can be compensated for however. As an example take a 12" aperture telescope which takes an image with an exposure time of 10 seconds (all other things being equal and assuming one is tracking the object). If one only had a 6" telescope one could compensate by increasing the exposure time (I assume by a factor of 4 = (6^2/3^2) = relative difference in areas of telescope.
My question is whether in doing so one can achieve the same resolution image with the 6" telescope as was achieved with the 12" telescope or whether the use of a smaller telescope restricts the resolution in a way that can't be compensated by longer exposures.
Hoping someone can help.
Thanks Peter
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Hi Peter,
Your question about resolution or the ability to resolve (and capture) detail in an object is governed by controlled / limited by a number of factors:
1. the atmosphere,
2. the optics,
3. the imaging system & settings,
4. the mount tracking precision and
5. processing skills and experience
There are many provisos one could put on an answer to
your question, which is focused primarily on the OPTICS, but
generally speaking as far as OPTICAL resolution is concerned the larger the aperture the better the resolution, all else being equal. This is in accordance with the Rayleigh Limit / Dawes Limit criteria, essentially diffraction limitations on light passing through an aperture, which is also a function of the wavelength of the light. The only other governing parameter optically is the extent to which optical aberrations and/or contrast might reduce the performance further.
If I had to draw a logical line in the sand I'd say that for 2 instruments of equal focal length, equal image circle size and "optical quality", as hard to define as that is, the larger aperture instrument will provide higher resolution. The ability to use or record an image at that higher resolution depends on all the aforementioned factors 1, 2, 3, 4 and 5. Any shortcomings in these factors will only serve to limit this resolution further.
On the issue of exposure duration: Of course exposure duration and/or stacking images for greater overall exposure duration will help produce a cleaner (less noisy) image as the signal to noise ratio is increased, but it will not resolve what the optics cannot see due to aperture limitations.
I will link something further later...
EDIT >Now added....
http://hyperphysics.phy-astr.gsu.edu...pt/Raylei.html
https://en.wikipedia.org/wiki/Angular_resolution
https://courses.lumenlearning.com/au...20the%20other.
Best
JA
