Astro CCD Scope comparison

This code tries to show you what a specific Sensor (CCD) and Lense combination will produce.

This is M81, when using an SV555 and an IMX585 based CCD Camera.

You can generate other combinations of Sensors/Lense so you may compare expected results.

This shows ASKAR71 with a IMX533 on the left, compared to an SV555 and a IMX585 on the right. Here you can clearly see the differing sensor formats on the M81.

But this is the same sensor - with very similar lenses.

Redcat51 and SV555 - on M31.

Reason for this code

I am in the market for a new CCD camera - sadly my Nikon decided it had enough and locked up the shutter for good. Faced with a large capital expense I wondered if the time had finally come for a dedicated Astro CCD Camera, with a telescope.

Prior to this - I have either used prime projection, or camer/lense on a star tracker/EQ mount.

There are many many choices and options (which is a good thing), but it can also be quite confusingl If you are trying to work out what would suit your budget/interestes etc.

Alternatives instead of this code

You can simply create a Telescope, and a Sensor in Stellarium or KStars (and I am sure many others) and compare as you click around the sky. I wanted something a little more focused, and when I forgot the results of M31 say were, I did not have to repeat the simulation.

The code

There are essentially 3 sections

• The Camera (Sensor)
• The Scope
• The Targets

I now have split these into seperate files.

• Ccd.py
• Scope.py
• Target.py

These files are VERY SIMPLE data class collections.

Adding the libraries

It should be all over with a

pip install -r requirements.txt 

However... you may need to provide the GDAL objects (used by starplot).

Running

Simple execute this command where the source file is located

python Astro_CCD_Scope.py -c <CAMERA> -s <SCOPE> -t <Target> 

Examples: python Astro_CCD_Scope.py -c imx585 -s -t

It takes under 30s to process 20 objects on my Mac. After this you can look at the png files.

How to Compare ??

Change the command line options

Try a different scope

use

-s or --scope <scope name> 

You can find the list of scope names using

 python Astro_CCD_Scope.py --list-scopes 

Try a different camera/sensor

use

-c or --camera <camera name> 

You can find the list of scope names using

 python Astro_CCD_Scope.py --list-cameras 

Try a different target set

yes you guessed it

-t or --target <target Name> 

You can find the list of scope names using

 python Astro_CCD_Scope.py --list-targets 

Using any image viewing software - you now can compare that the scope/ccd combinations are expected to produce.

But it does not take into consideration....

• The sensor is Cooled, if it has a dew heater.
• I am using mono image capture
• My lense is 4F not F8 at this focal length
• I use a guide scope
• I have a super mount - much better than ....
• My scope has super optics.
• The CCD camera has small/large pixels - and a built in guide camera

None of these things effect the expected image size when using a focal length of X, with a Sensor size of Y.

I do not disagree the items listed previously will generally improve the image quality - but they will not effect the size of the expected data capture area.

What does not work?

Very wide (<300mm) and very large width Cameras cause an internal error if the amount of sky > 9.6 degrees.

You will get an error message of ✖ Sorry. Field of View too large to compute

The Sony IMX455 chip is (currently) the only sensor that causes this issue, if used on something like an SV555.

So this would fail

python Astro_CCD_Scope.py -c imx455 -s SV555 -t Quick 

But this will work

python Astro_CCD_Scope.py -c imx455 -s ASKAR71F -t Quick

Becuase the scope has a longer focal length, which despite a massive sensor, makes the FOV (field of view) within bounds (phew!).

Thanks

StarPlot is a great framework; many thanks to the authors for publish and creating it.