I have some doubts on how to use those numbers to help me better understand how everything works together.
For the sake of simplicity, let's ignore seeing
Let's consider the following gear:
- guide camera 2.9um pixel, guide scope 205mm FL. Resolution is (2.9/205)*206.3 = 2.918 arcsec/pixel
- imaging camera 4.2um, imaging scope 350mm FL. Imaging resolution is (4.2/350)*206.3 = 2.476 arcsec/pixel
- guide camera 2.9um pixel, imaging scope 2032mm FL. Resolution is (2.9/2032)*206.3 = 0.294 arcsec/pixel
- imaging camera 4.2um, imaging scope 2032mm FL. Resolution is (4.2/2032)*206.3 = 0.426 arcsec/pixel
The guiding/imaging ratio when using the short FL scope with the guide system is (2.9*350)/(4.2*205) = 1.179
The guiding/imaging ratio when using an OAG with a long FL scope is (2.9*2032)/(4.2*2032) = 0.69
Let's say that my mount total RMS is stable at 0.5" every night. Am I correct in saying that:
- when using the short FL system, in order to have round stars (0.5*1.179) <= (imaging resolution [2.476]). All good in such a case.
- when using the long FL system + OAG, in order to have round stars (0.5*0.69) <= (imaging resolution [0.426]). All good also in this case but, due to the seeing, I should bin 2x2 in order to be less oversampled.
Now the question is: is my thinking correct? If not, what's the correct way to obtain the numbers I'm looking for?
TL;DR: how can I calculate what value of "Tot RMS" gives round stars (binning 2x2 allowed) with the setups I wrote at above?
Edited by polslinux, 13 April 2021 - 07:05 AM.