Re: Everything is Hotsy-Totsy Now

[Stupendous Man <richmond@a188-l009.rit.edu>]

  Michael S. wrote:

> Apparently, from looking at the next few images I didn't skip, we are
> able to process these images even with some clouds. Would we want to
> (does it affect the photometry)? 

  One way to find out: reduce a night, skipping the images which 
show any evidence for clouds.  Then re-reduce the night, this time
including the images which have clouds.  Then examine

      - scatter among measurements in first case (skip all clouds)
      - scatter among measurements in second case, using
                 clear images only
      - scatter among measurements in second case, using
                 cloudy images only

  These numbers will tell you empirically how much the clouds
increase scatter.

> should/could the system
> be automated to skip those pairs of images that crash the pipeline?

  Find a reliable, robust indicator of clouds (hint: sky level,
sky sigma), provide limits on acceptable values, and I can build it
into the pipeline.

> With regard to flats, I noticed that Michael added a parameter in
> make_flat.param to differentiate between observation flats and
> twilight/light box/etc. flats. How would the clouds affect the flats?

  I'm not sure.  Clouds are generally no big deal for flats, but 
we have a much larger field of view than most telescopes, so we might
see residual features even with 1-minute exposures.  Using "dome flats"
would be safer, I think.

> Now back to the pipeline. Disks 7 & 8 await.

  Don't be afraid to go back and re-reduce disks 4 and 5, testing
some of the ways to answer the questions you've been asking (as I
describe above).  You don't _have_ to keep looking at new data :-)


                                    Michael