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How to measure sharpness in your images | Hyperion Astronomy

How to measure sharpness in your images

It is hard, sometimes, to discern if your images are really as sharp as they might be. While your eyes are great to spot the difference between a blob and a sharp star, it is preferable to have some real data to actually analyze. 

Stellar Sharpness Measurement ( One image )

As soon as you download an image from your camera, you can very easily see if your seeing and/or focus are up to par. Just right click on your images and choose Stellar Sharpness Calculations then the size of the zone to be measured. If you choose 512x512 for a fast turnaround. If not, the entire image will be used.

 Here is how you measure a single image


measure stellar sharpness with one click

 Measure Multiple Images

Another great tool in PRISM is the "Quality Check (Stellar Images)" under the analysis menu. This tool allows to analysis a whole set of images ( same size and pixel type that is ) in order to understand how the imaging session evolved of the course of a night for example. Here is a quick rundown.

1. Load the tool, check an area of 1/8(for faster analysis) the frame and press OK

2.The output is as follows:

Mean sky background

Median sky background

Seeing calculation

Elongation of the stars

And finally, the actual output of the tool with all the data

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Hamza - October 27, 2019

For elongation, you want the smallest number possible, this means you collimation and focus are working well.
For the rest of the numbers, it is a great indication that you tracking and collimation are good as well.

John Monroe - October 19, 2019

Hi Hamza, once I run this tool how do I interpret what the numbers mean?
Thank you, John.

Hamza - October 9, 2019

Thanks Craig. It is a great feature set that will really help you find and only utilize the best data. It is a very quick indicator of how well your system is tuned too. Awaiting images from your new system.

Craig - October 9, 2019

Great tool! I didn’t know about the Stellar Sharpness capability until I saw your post- thanks for highlighting it. I especially like the seeing estimate and it ran plenty fast even though I processed a 4096×4096 image. I have to say that Prism has a really nice set of analysis tools. When I installed my new scope recently I was able to quickly characterize the optical system including collimation and field flatness which saved me a ton of time because I found that no adjustments were needed before going through the whole collimation process. That was especially important for me because the observatory is about 2000 miles from home and my installation window was very tight.

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