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RE: V image fainter than I
Is it worth it to implement this feature (differing V/I exposure times)
in the control program from your perspective? I can do it, it was just
the first non 5 minute change Tom asked for (a few days likely, with
some thought required).
Cheers,
Rob
> -----Original Message-----
> From: owner-tass@listserv.wwa.com
> [mailto:owner-tass@listserv.wwa.com] On Behalf Of Arne Henden
> Sent: March 18, 2005 2:22 PM
> To: tass
> Subject: Re: V image fainter than I
>
>
> This is no different than the case of going through a
> reddened region, where you see more Ic stars than V stars.
> Just leave everything alone and have a few more unmatched Ic measures.
> In general, the throughput between V and Ic is about equal
> for most CCD cameras. Stars tend to be brighter at V and the
> QE is higher at V (not Ic, as Tom suggests), so the net
> effect is to compensate for the wider Ic bandpass. My usual
> exposure times are about 1.2x longer at V than Ic. Arne
>
> droege@snapmail.us wrote:
> > 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?
> >
> >
> >
>
>
>