So I have two scopes in the signature. One has - f/4.8, 72mm aperture, pixel scale 2.25 arcsec/px, the other has f/11, 127mm aperture, 0.56 arcsec/px,
I already took an image of the Crescent nebula with the first one.
Now I'd like to zoom in with the second one, so please confirm my calculations.
So if I understand this correctly, to achieve the same brightness of the nebula in a sub, I would need to expose longer by a factor of 11/4.8 = 2.3.
And to get the same SNR, I would need 2.3^2 = 5.3 longer integration time.
Does that sound right?
If so, here's the second problem. My guiding has an average RMS error of about 0.6". My first image subs were 4 min long. That is going to be a problem with the second scope. I would prefer shorter subs.
What if I bin 2x2?
ZWO website states "Something you will notice when you bin 2×2 is your camera resolution is quartered as you effectively have 4 times less pixels. This also doubles the signal-to-noise ratio."
So then, in principle, I can cut down the subs to 2 min and achieve about the same brightness and SNR in a single sub. And the total integration time would not need be longer.
Does this sound right?
So, overall I should be able to increase the resolution of the nebula by a factor of 2 with about the same integration time and SNR - the width of the nebula is about 400 pixels in the first image, and it would be about 800 pixels in the second image.
What do you think?