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Picking the right Barlow/reducer to couple telescope to camera for Nyquist sampling


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Hello,

 

I recently purchased my first telescope and camera, and now I want to make sure I have the correct Barlow or reducer to couple them together to achieve Nyquist sampling on the camera (or slight over-sampling). In case it’s important, I’m interested in planetary imaging—in theory that shouldn’t matter for this sampling question, but maybe there are other considerations to take into account.

 

I used this calculator (https://astronomy.tools/calculators/ccd_suitability) and plugged in my info:

Telescope: Celestron 8 SE

Camera: ZWO ASI462MC

Seeing: experimented with this one, but would like to get optics that allow for poor or very poor

Binning: prefer 1x1 to preserve spatial resolution, but could consider higher if SNR is a problem

 

I’ve seen on several forum posts that people often use a 2x Barlow to couple the two. However, according to this calculator, that will always lead to over-sampling. If anything, it says I should use no intermediate optics or even a reducer.

 

So my questions are:

 

Binning: Will I be able to see anything with 1x1 binning, or should I expect to need to bin to collect enough light?

 

Is there some other consideration that’s more important here than achieving correct sampling? It seems like most others are over-sampling, and perhaps there’s a good reason for this. If so, is there another formula that would let me determine the appropriate optics to buy?

 

Thanks in advance for any help!

Edited by Rchurt
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Hi and welcome to SGL!

If it were my choice I'd probably go for a 1.5x barlow, and failing that no barlow at all.  But don't get too hung up on perfect sampling...  It wont be the biggest factor affecting your planetary images, not by a long shot. 

Scope collimation, cooling and above all else, seeing, is what will affect your images the most.  Oh and if you don't have one, a motorised focuser is highly recommended. 1x1 binning will be fine, the planets are very bright!

Edited by CraigT82
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