Earthshine blog

Earthshine blog

"Earthshine blog"

A blog about a system to determine terrestrial albedo by earthshine observations. Feasible thanks to sheer determination.

PSF profiles from the NGC6633 images

Post-Obs scattered-light rem.Posted by Chris Flynn Apr 07, 2013 09:38AM
The PSF of the VE2-band Arcturus data deviated markedly from the other bands (next to previous post). We check on this further by looking at the PSF profiles of the stars in NGC6633, which were used to calibrate the filters (in this post).

We plot the central flux normalised PSFs in B, VE1, VE2 and IRCUT versus V (shown in green in each panel). The PSF is formed from 95 different stars spread over the frame in each case: e.g. this shows the stars in the IRCUT image.

The PSFs look like this:

Same plot as above but in log-linear form:

None of the PSFs are as sharp as the V band one -- they all have more flux at greater distance from the center. Interestingly, the VE2 band profile is not discrepant, so the conclusion is that the IRCUT data for Arcturus may simply have been out of focus.

It would seem the lesson from this is that the PSF can vary quite a bit -- but note well that this is in the core only -- as this is not a test of the extended power-law wings at all, as we are only probing to a radius of about 4 pixel (~30 arcsec) with these data.

  • Comments(2)

Fill in only if you are not real

The following XHTML tags are allowed: <b>, <br/>, <em>, <i>, <strong>, <u>. CSS styles and Javascript are not permitted.
Posted by Chris Flynn Apr 08, 2013 12:52AM

I'm afraid I don't recall which filter was the sharpest -- actually, I don't recall even looking into it...

Posted by Peter Apr 07, 2013 12:44PM

So at the very least we now have a tool to generate psfs for out-of-focus cases? Sage, unless OOF implies 'error in filter selection'. Dont see why B is not the sharpest? Wasn't it, earlier?