Re: Status Report for March 2003

[Andrew Bennett <andrew.bennett@ns.sympatico.ca>]

On Fri, 04 Apr 2003 20:34:32 +0000,  Tom wrote:

>>On Tue, 01 Apr 2003 18:35:57 +0000, Tom wrote:
>>
>> >Andrew and all,
>> >
>> >Michael allows fitting a 0, 1, or 2nd order surface to the data.  I use
>> >only the first order.  I think this does not bother a nice star field.
>> >
>> >I have looked at lots of fields.  DS9 has a feature that allows taking N-S
>> >or E-W sections through the image.  The way I set up the cuts, this these
>> >sections are either flat within the noise, or I throw the image away.

>At 11:41 PM 4/4/03 +0100, Andrew Bennett wrote:
>>
>>Sorry! I just don't see how 1st or even 2nd order can
>>leave a galactic plane image, replete with blobby star
>>clumps and dust lanes, flat.

>Do you have a better suggestion?
>
>Tom Droege

I currently reject raw images on the basis of (among
other things) mean level. This does a fair job if all
the images are from the same bit of sky but needs some
tuning to deal with an extensive data set. Getting rid
of all the bright images gets rid of all the obviously
cloudy ones and also many that look OK at first
glance but presumably have haze or thin cloud. Bright
aeroplane trails get thrown out too. 

Then I reject images that don't give a good photometric
correction using all the non-varying stars - this is the
iterative process I posted a little while back. With
sufficiently ferocious pruning, I was getting down towards
0.01 mags rms.

Andrew Bennett, Avondale Vineyard