Planetary Camera for Skywatcher 190MN - Forums

Topic starter

Nov 15, 2023

Hi All.

I’m dipping my toe in the water with planetary and lunar imaging using my Skywatcher 190MN Mak Newt. I currently have a ZWO ASI533MC Pro and A Canon 5D Mk IV, neither of which are ideal for planetary or lunar imaging. I also have a 3x Celestron Barlow.

A lot of the info I’m reading online about which camera to buy is a little conflicting so my question is how do I figure out which planetary camera is best suited to my current setup? I’d prefer a ZWO camera as I use ASIAir and I think OSC would be best for me.

Thanks in Advance.

Well Written Engaging

tjm8874

Nov 15, 2023 · Edited: Nov 15, 2023

Televue PowerMate x5 : you get 5000mm f/26. In general 2.9um planetary camera will work, ASI662MC (2K) or ASI585MC (4K) but I think you try 533MC first, not so much difference.
Televue PowerMate x2.5 : you get 2500mm f/13, so you need smaller pixel. ASI678MC 2um 4K.

Celestron x3 Barlow: 3000mm f/15, same as x2.5, ASI678MC 2um 4K.

Helpful

Craig Dixon

Topic starter

Nov 15, 2023

How do you get to those numbers please? I’d prefer to stick with the 3x Barlow I currently have if possible. Am I right in thinking that would mean:

3000 / 190 = f15.8

so I need to find a camera that has a pixel size roughy 1/5 of 15.8?

tjm8874

Nov 15, 2023

Those numbers are derived from these two parameters.
Telescope Spatial cutoff frequency = 1 / (wavelength, ex: 500nm * f value). f/30 = 66.67 (1/mm), f/15 = 133(1/mm)
Camera Nyquist frequency = 1 / (2 * sensor pitch * OSC, 2). 3.76um = 66.5(1/mm), 2.9um = 86(1/mm), 2um = 100(1/mm)

Camera Nyquist frequency desired to be more than Telescope Spatial cutoff frequency.
-> f/30 : 3.76um can match, many people use 2.9um, 2um is oversampled.
-> f/15 : 2um is still undersampled but will work.

Markus A. R. Langlotz

Nov 15, 2023

I also have the MN190, and strongly recommend the ASI585MC.

Deep sky cameras have different photon transfer curves and are not optimzed for short frame exposure times.
Consider buying a dedicated planetary camera. Which 3x Barlow do you have? Televue?

CS

Markus

andrea tasselli

Frequent contributor

Nov 15, 2023

ASI662MC and don't use asair. Don't skimp on the barlow quality.

Craig Dixon

Topic starter

Nov 15, 2023

I have a Celestron x-cel Barlow:

https://www.firstlightoptics.com/barlow-eyepieces/celestron-x-cel-barlow.html

Should I be going for a camera with 2.9 um pixels?

andrea tasselli

Frequent contributor

Nov 15, 2023

Craig Dixon:
I have a Celestron x-cel Barlow:

https://www.firstlightoptics.com/barlow-eyepieces/celestron-x-cel-barlow.html

Should I be going for a camera with 2.9 um pixels?

Yeah. You'd be at around the right sampling for your best expected resolution and if you need a bit of oversampling (say + 20%) you just extract the camera further out. Think also to an ADC for the future (not now, nor the next 2 years for Jupiter but you'll need it badly for Saturn) as you shoot from the UK, right?

Craig Dixon

Topic starter

Nov 15, 2023

Yeah, I’m in the UK.

I like the look of the ASI662MC as it’s at a reasonable price.

I tried shooting Jupiter with my 533MC Pro but I could only get 4 fps out of it. My focus has been on DSO thus far though so I’m a complete novice at planetary.

so if my focal ratio is 3000mm / 190mm = f15.789

and a camera with 2.9um pixels x 5 = 14.5

Does that mean I’d be slightly under or over sampled? My understanding is that it’s better to be slightly over sampled.

andrea tasselli

Frequent contributor

Nov 15, 2023

Your sampling is at around 0.2"/px and you are aiming at around 0.62" resolution so you are right there. If you feel the seeing allows it you can always increase the magnification factor by moving the camera away from the flange of the barlow, virtually without any upper limit.

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tjm8874

Nov 16, 2023

New camera from ZWO, ASI715MC 1.45um 4K $199!
Nyquist frequency = 170/mm so it can match f/15 telescope (133/mm).