Scope/camera resolution & sampling equation

[dannybgoode]

Quick one this - can someone remind me of the formula for calculating a scope/ camera saving resolution please?

 Someone posted it a while ago on another thread but I just can’t find it. 
 

Thanks all

[vlaiv]

206.3 * pixel size / focal length

(pixel size in um and focal length in mm)

If you want to be exact - that is for mono cameras, for color cameras it is twice that value

[dannybgoode]

Thanks @vlaiv - that’s the chestnut I was looking for. Am I right in thinking that it is pixel size in um (apologies on the phone so can’t get the proper character!). 
 

So if my pixel size is 4.5 um then I just use 4.5?

[vlaiv]

2 minutes ago, dannybgoode said:

Thanks @vlaiv - that’s the chestnut I was looking for. Am I right in thinking that it is pixel size in um (apologies on the phone so can’t get the proper character!). 
 

So if my pixel size is 4.5 um then I just use 4.5?

Yes - if you have 4.5um pixel size and for example 500mm FL - resulting sampling rate is in arc seconds per pixel - 1.86"/px

Btw - check out top of this page - menu on SGL - there is Resources menu, and first item there is astronomy tools - it will give you some basic tools for calculations / fov, etc ... (although I don't agree with some of the things there - like CCD suitability)

[dannybgoode]

Thanks again @vlaiv  

Would I be right in thinking then that binning can be useful to prevent oversampling (or undersampling - I can’t quite get my head around which!) with long focal length scopes?

 So for example using my SX674 mono with my TMB 105/650 gives me a result of 1.43” pp so about right. 
 

However if I wanted to use my Meade 10” SCT with an FL 2500 then binning 2x gives me 0.74 or using my f6.3 flattener/reducer 1.18 so just about spot on?

Edited December 19, 2019 by dannybgoode

[vlaiv]

1 hour ago, dannybgoode said:

Thanks again @vlaiv  

Would I be right in thinking then that binning can be useful to prevent oversampling (or undersampling - I can’t quite get my head around which!) with long focal length scopes?

 So for example using my SX674 mono with my TMB 105/650 gives me a result of 1.43” pp so about right. 
 

However if I wanted to use my Meade 10” SCT with an FL 2500 then binning 2x gives me 0.74 or using my f6.3 flattener/reducer 1.18 so just about spot on?

Yes indeed - one way to look at binning is as increased pixel size, so you are right, it is a way to combat oversampling (low "/px number means high resolution and oversampling - it is inverse in pretty much same way wavelength and frequency are inverse of one another)