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Counting stars in PixInsight


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Hi

I have an image, heavily populated with stars. I'm looking for a way to count the number of stars in the image, using PixInsight... is this possible? I thought a DynamicPSF may do it. but I'm not really sure what I'm doing...lol.

Thanks

Joe

 

 

The Crescent Nebula.png

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funnily enough I too am looking for a way to count stars in an image... i suspect based on the process console logs of the mosaic integrations I've applied i'm looking at between 14-20k stars

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With PSF you manually select stars. I think the Star Alignment process may help as it counts the stars (too few and it won't align). You will probably need to experiment with the settings to make sure it's counting stars and not noise, etc.

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16 minutes ago, ChrisLX200 said:

Yes, you need to decide what is a star and where the sensitivty cut-off lies. DSS will also give a star count.

ChrisH

But isn't that on single subs? My guess is that star count would be more reliable on the stacked image which has less noise.

(If you only want a guesstimate, you can take a small square of your image and count the stars in that. Then multiply by the number of those squares that would fill the image.)

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5 minutes ago, wimvb said:

But isn't that on single subs? My guess is that star count would be more reliable on the stacked image which has less noise.

(If you only want a guesstimate, you can take a small square of your image and count the stars in that. Then multiply by the number of those squares that would fill the image.)

You get a count for each sub (they will all be different), you could average the count if you like for the stack. You should not be counting noise otherwise you'll be trying to align images using hot pixels :)

From a recent luminance set of M31 I get:

21714, 21088, 22159, 20355, 21107, 21718, 21089, 20869, 20907, 20856, 20279, 20598

ChrisH

 

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SGPro also provides some info which is useful if you have 'image history' switched on:

Imagehistory_zps40065595.jpg

The above graph shows data for sequential 20min subs taken during a single session (this using an Atik490EX), the HFR (half flux radius - or star size) and the number of stars detected.

ChrisH

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