Re: alignment

[Michael Gutzwiller <deepsky@fuse.net>]

> Now that is an interesting suggestion - thanks, Tom!  However, 
> when looking at Tom's raw images that were posted to Storm, I
> never saw what I considered to be 'flare' (I did see flare in the
> early I images posted by Michael R). The psf changed in
> declination, but I attributed that to the VCO rate, since it is
> only correct for one declination zone, and therefore the images
> should be elongated in RA at the extremum and to some extent in
> declination as well (for drift scan, those images not at the 
> proper tracking rate will look like bannanas).  Mike G. has 
> certainly looked at more images than I have.

The flare is minor and is visible only for bright stars.  Also you won't
really notice it's flare until you look for the peak of a bright star
and notice it's not in the center of the white blob.

The edge to edge error induced by the tracking difference between 0
degrees and 3 degrees is only 0.1 percent or half a pixel and would be
mostly in the RA direction.

> You wrote:
> > A misalignment would also explain why the PSF's are asymetric. 
> > That is they flare to one side.
> To which side do they flare?
> Arne

The do flare in declination.  I'll try to get some definitive info
tonight.

Mike G.