RE: Everett and Howell Paper

["Creager, Robert S" <CreagRS@LOUISVILLE.STORTEK.COM>]

See questions inserted inline...

> -----Original Message-----
> From: Andrew Bennett [mailto:andrew.bennett@ns.sympatico.ca]
> Sent: Tuesday, November 06, 2001 5:17 PM
> To: tass@listserv.wwa.com
> Subject: Re: Everett and Howell Paper
> 
> Actually, it doesn't need to be anything like that good. To
> use the same set of reference stars, one needs to do better
> than 1/10 image width if one puts up with losing 20% round
> the edges. Similarly, with flat field errors of order 0.1
> mags across the field, one should be down at the 0.001 mag level
> if one only has to correct inside 1/10 x 1/10 image: basically 
> the sort of thing Arne has already done in the MK III post 
> processing.

I don't understand your 1/10 references, like 'better than 1/10 image
width'.  Is this tracking?  'correct 1/10 x 1/10 image'?  I'm sure this will
spring out at me if you speak more slowly ;-)

> > 
> Our flat fielding is entirely inadequate. We need some
> sort of dome flat. The last time this was discussed, we 
> turned up (among others) a design that produced circularly 
> symmetrical illumination. IIRC this was good to around 
> 0.1% (a few digits in a 12-bit system) and could be built 
> to fit the MK IV lens. So flat fielding is a solved problem 
> for pixel to pixel calibration (but not across a 4 degree
> image!) We should do it.

I understand the circularly symmetrical illumination, and I get the gist of
the pixel to pixel calibration, but how would this information be used
practically?

Thanks,
Rob