Re: A Comment on the Lenses (part 2)

[Tom Droege <tdroege2@earthlink.net>]

Those not familiar with the design should know that the filter is used as 
the camera window.  Part of the camera body, the camera window, and the 
shutter are all one unit.  Changing the filter means building a new 
camera.  You all should remember that I give these things away, so I have 
tried to keep the cost down in every way possible.

Is it possible to just add something to just cut off the tail of the IR 
response?  Is this even desirable?

Having learned a little, my present interest (for the systems that I run) 
is to just take specific fields night after night attempting to cover the 
whole sky.  I can now see that this has absolute photometry problems.  At 
my location I could probably not solve these even if I tried.  It does 
appear that I can do field specific relative photometry with considerably 
better precision.  This will detect variable stars in two simultaneous 
filter.  We may never be able to get good calibration on the either the V 
or the V-I photometry.  Sigh!  That may be life in Batavia.  I am hoping 
that a large catalog of such measurements will still be useful.

Tom Droege

At 09:07 AM 11/5/02 -0700, you wrote:
>One option would be to order an interference Ic from Custom
>Scientific, and try that on your I-band camera.  This has the
>proper bandpass and would not have any out-of-band transmission.
>I am not sure how well such a filter will work in an f/4 beam,
>but you can ask David Marcus (owner).
>   This test would perhaps be simpler than experimenting with
>internal aperture/pupil stops.
>Arne
>
>Tom Droege wrote:
>>The filters are "Bessell I" from Omega Optical.  I assume they are 
>>"stock" since there were no special instructions on the order.  This is 
>>something that Michael Richmond selected after talking with the expert at 
>>Omega Optical.
>>Tom Droege