RE: V image fainter than I

[droege@snapmail.us]

Richard,

This does not work.  A star that is saturated in I is not saturated in V
and so is lost.  There are lots of I stars for which there is no V star
detected, like a factor of 3.

The scheme would be to stop down the I camera and take longer exposures so
that at the faint level there was a rough match of detection.

Tom Droege

> Speaking as a lurker, I'd change the V vs I parameters in the data
> reduction
> process to accept the difference.  Don't throw out (or block) good data.
>
> Richard
>
> -----Original Message-----
> From: owner-tass@listserv.wwa.com [mailto:owner-tass@listserv.wwa.com]On
> Behalf Of droege@snapmail.us
> Sent: Friday, 18 March, 2005 13:20
> To: tass
> Subject: V image fainter than I
>
>
> As I am setting up the camera for the coming run I notice the V camera is
> even fainter than usual from the I camera. I don't know why and have
> changed out the camera.  We shall see if it is a camera problem when I get
> some clear sky.  I have done all the obvious things like look through the
> lens for dead bugs and hanging chad.
>
> There has always been a bad match.  Many stars are lost because they are
> too bright in the I images and others are too faint in the V.
>
> Rob tells me that different exposure lengths are a pain.  The alternative
> is to stop down the I camera.
>
> The I filter has about twice the bandwidth of the V filter, further the
> CCD is more sensitive in I.
>
> At the moment, the I camera has a great focus.  I really hate to throw
> away all those photons now that they pass through the optics so well.
>
> Should I stop down the I lens?
>
> Any comments?
>
>
>
>