Star Graphing / FWHM Feature

[Simon Hicks]

Hi PI Guys,
                    Suggestion for a useful feature. It would be great to be able to drag a rectangle around a single star, or click on a star, and see a graph of intensity (better still...L,R,G and B) vs radial distribution in pixels. It could show FWHM or any other useful info. I think this might be helpful when analysing the various features in an image...useful to see if stars have saturated in one colour, and also useful for knowing what parameters to put into a deconvolution module.

By the way...I can sort of estimate FWHM at the moment....just zoom right in till I can see individual pixels, then move cursor around till I see half the max intensity (taking background into account) and then just counting pixels to the corresponding position on the other side of the star.  But how does the FWHM relate to the Standard Deviation that is used in the Deconvolution module? Is there a simple multiplier so I can estimate one from the other?

Regards
                Simon

[Juan Conejero]

Hi Simon

We have almost ready a new star statistics tool that works in a similar way to what you have described. It should be ready soon, and of course it will give FWHM measurements, among other values (centroid coordinates, peak value, total flux, etc).

The full width at half maximum (FWHM) of a Gaussian function is given by:

FWHM = 2*Sqrt(2*Ln(2)) * sigma

where sigma is the standard deviation of the Gaussian distribution. A sufficiently approximate formula is:

FWHM = 2.35482 * sigma

Cheers
Juan

[Simon Hicks]

Hi Juan,
               Fantastic...thanks again!  

Cheers
             Simon

[Andres.Pozo]

Juan, this tool would be great if it could also automatically find the stars in the image and show the average FWHM and perhaps other statistics. DeepSkyStacker has a measurement like this, but I don't know if I can trust it.

I think you are developing an automatic registration tool so using it for finding the stars the "star statistics tool" can be made quite easily.

However, in my opinion, PixInsight has other priorities (documentation of the algorithms, documentation of the user interface, saving of sessions, customizable toolbars, better support for dual screen, ...).

[Nocturnal]

I think the DSS FWHM feature works fine. DeepSkyStacker Live is great to monitor the image quality as the images come in.

[Juan Conejero]

Hi Andrés,

I add to Sander's opinion about the quality of DSS's FWHM measurements: you can definitely trust them.

Regarding a tool for star statistics in PixInsight, it is in the TODO list with a high priority level. It will be available, and quite soon, hopefully.

With respect to PixInsight's handling of dual-monitor setups, which are your complaints? I am very interested in knowing them because dual monitor support is an important feature of PI's GUI.

[Andres.Pozo]

With respect to PixInsight's handling of dual-monitor setups, which are your complaints? I am very interested in knowing them because dual monitor support is an important feature of PI's GUI.

I use a couple of monitors of different resolution and one of them is on a portrait orientation. I don't know how to use the full area of both monitors. IMHO it would be better if you could place the property pages of the tools outside the window of PixInsight. In this way I could put them where I like.

[NKV]

We have almost ready a new star statistics tool that works in a similar way to what you have described. It should be ready soon, and of course it will give FWHM measurements, among other values (centroid coordinates, peak value, total flux, etc).

Juan, 

[RobF2]

Wow - had not heard of DSS Live - sounds like a very useful concept - must check out

+1 for these astrometric indicators to become available in PI too.....

[Carlos Milovic]

We are very close. Take a look at the Software Development subforum. I have uploaded beta versions of our PSF reader tool.

[RobF2]

Thanks Carlos - I did start reading about your PSF reader work, but wasn't smart enough to figure out compiling etc.
I think the beta might have been 64bit only too from memory? (I'm running XP 32bit)

[Carlos Milovic]

I'll upload this evening the win 32 compilation.

[RobF2]

I'll upload this evening the win 32 compilation.

Thanks Carlos!      8)