Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

joecoyle

Counting stars in PixInsight

Recommended Posts

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

The image solver will count stars. But with any image you should ask where stars end and noise begins.

Dynamic PSF only calculates the star profiles; it doesn't count them.

HTH

  • Like 1

Share this post


Link to post
Share on other sites

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

ChrisH

Share this post


Link to post
Share on other sites
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.)

Share this post


Link to post
Share on other sites
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

 

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

The SubFrameSelecter script also calls StarDetector which will give you a count in the Process Console window.

Andrew

Share this post


Link to post
Share on other sites

Also the FWHMEccentricity script will count the stars for you. It will also give you insight into how well your optical train is aligned.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.