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Scale estimate fail

gregory miller
in PixInsight
Hi Adam:

Local Normalization failed in WBPP for the luminance data set I ran recently. "Unable to compute a valid scale estimate" was the error in the process console. I re-ran the data using the Multiscale Analysis function as opposed to PSF Flux Evaluation and it worked. Being of like mind in the ABS Universe, I wanted to know why so I reviewed WBPP and Local Normalization videos.

I ran the data again following the manual method of LN processing trying different scale factors, still to no avail. Next I checked the "No scale component" box and this was successful, but I'm thinking this is no different than just running the Multiscale Analysis, which if I understand correctly from your video is somewhat of a legacy process.

I'm wondering if the failure of this particular data in the PSF Flux Evaluation method is due to the telescope itself. My usual instrument is an Astro-Physics 130mm refractor which produces images with beautiful pinpoint stars from corner to corner, and data from this scope sails through WBPP with no issue. The Local Normalization failure I'm having with this current data set is from a small 61mm widefield refractor that exhibits star images that look like pointed arrowheads on about 1/3 of the frame. The other 2/3 of the frame shows round stars. This is first light for this scope, and possibly last. 

Could these deformed stars be the reason for the processing failure or am I missing something else entirely?  

Thanks very much for your help.
Gregory B. Miller   

Comments

  • BlockHeadBlockHead
    You got it right. If multiscale analysis works- it means PixInsight does not agree that your PSFs are of good quality.  And so as you note the star shapes are the issue. PSF fitting will fail (as it should) and multiscale methods (basically structure detection instead of PSF fitting) will work.

    So everything makes sense here. Multiscale method is legacy in the sense that PSF fitting is the primary method..but you can revert back to the less precise method if the stars are poorly formed.

    -the Blockhead
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