Re: hints and tips for DS 20

[Michael Sallman <msallman@pro-ns.net>]

Michael,

Thanks for the tips. I will attempt to put them to good use.

>       - the I-band flats show faint circular arcs
>             (probably the arcs mentioned by Michael S.).
>             These are common in CCD chips at long wavelengths:
>             I believe they are caused by small variations
>             in the thickness of the silicon or coatings.
>             The circular shape is a result of the manufacturing
>             process.
>

I just finished re-running make_dark & make_flat, and the artifacts that I
originally saw are no longer there (though I do see the arcs you mention
above).
I think I've figured out what I did wrong. Here is what I did:
I copied all the images from disks 1,2,9,10 to the input directory.
As make_flat looks for images of type "object" (which I just noticed this
last run), it didn't use the flat images from disks 1,2 (which are labeled
"flat"). Thus, it must have used the actual images from disk 9,10 to create
the master_flat(s).

>       - the images drift by about 1.5 pix E/W and 0.5 pix N/S between
>             exposures on disks 7,8

Not that it matters (if my above assumption is correct), but could this
drift explain the arcs I saw? They were just a multitude of short diagonal
arcs of 5 "dots/stars", distributed over the entire image.

As a side note, is there an easy (as in you not having to rewrite all your
software) way in TCL to get the output to a log vs. stdout?

Thanks,

Mike