SubframeSelector - Part 1

Christopher Baker

I am trying to learn more about the SubframeSelector so I can visually compare the technical difference between my subframes. I know I can blink them but I really like to understand the technical difference and to apply a mathematical selection, especially in those that are not clear outlyers.  You mention in that video that you should set "Subframe Scale" and "Camera Gain (e-/ADU)".   

I believe NINA sets in the FITS Header the "Camera Gain" as "EGAIN".  Is that correct?

Subframe Scale is a bit more confusing.  How can I calculate that?  Is that similar to http://astronomy.tools FOV Calculator's value of "Resolution"?  Is there a better tool or way?

BlockHead

Yes, I think EGAIN is what you want. But why not calculate it yourself withy our own sensor? There is variation from camera to camera- the manufacture will only give you an average/typical. (sensors can change)

I have enough videos it is hard to remember where everything is...but I do explain how to calculate readnoise and Gain. You can use the MUREDenoise detector settings script to do it. You will just need two flats and two biases.

The "subframe scale" is the PLATE SCALE of an image. The link you provided sure looks complicated for want you want.

I explain in one of my videos how to calculate the plate scale. It is a simple formula.

PlateScale = 206265 / (Focal Length of your telescope in mm) 

You can then find the number of arcseconds per pixel. 

As an example...I am using the Takahashi Epilson 180mm (f/2.8)

This means the focal length is 504mm . (180 * 2.8)

The camera I am using has 12 micron pixels (0.012mm)

So I take 206265/504  = 409.25 arcsecond / mm

but I want arcseconds per pixel so I take 409.25 * .0012 = 4.91 arcseconds per pixel

To calculate the field of view... just multiply this number times the number of pixels of your sensor.

You don't need any fancy tool. 

-the Blockhead