Re: [ATM] Box Beam Mirror Blank

[Dominic-Luc Webb <dlwebb@canit.se>]

On Thu, 13 Jul 2006, Michael Wheatley wrote:

> interest in a light bucket for occultation.  No fine images would be
> expected.  I would just want as much light as possible from one star
> on the CCD of a video camera mounted at prime focus.  Size
> limitations would be what fits in the back of an old Volvo wagon and
> what I can lift.


Sheee eeesh! Does it really have to be a Volvo wagen? Seriously....

First, from my view, there is a bit of an oxymoron here. You want to
measure occultation. This requires rather exact timing, and good
sensitivity. I know people use CCDs for this, and will not attempt to
undermine their value here. However, a video camera would not likely be
my first choice. Historically, this was done with photomultipliers that
have speeds and sensivity at lower wavelengths that video cameras lack,
rather severely in the case of cheap cameras. PMTs also have excellent
dynamic range, which could prove superior for occultation timing because
you can easily capture the entire curve of very large transitions between
dark and very bright. I have had no problem with starlight falling above
or below the saturation or detection limit, respectively. A video camera
will be essentially useless for photometric data, but maybe you only
want timing (not sure what you're up to).

Before commenting much on this project, I would be interested to know
what wavelengths, signal intensities (e.g., flux) and fluctuations
you expect. Knowing the timing requirements would be helpful as well.

It sounds like you have already decided on a pretty fast system (F2
to F/3), but considerably faster systems exist, especially if you
are not worried too much about image quality, especially off axis.
I must say, I am a little curious what you are up to.

Dominic-Luc Webb


_______________________________________________
ATM mailing list http://www.atmlist.net/