Re: [ccd-newastro] Re: WTG Don
- Thanks for all the information, I just need to use them for a while and see
I also really need to get a robofocus to help me with the focus issues.
Hope your shots turned out good. I passed out at my computer at about 0230
a 1.5hr nap.
----- Original Message -----
From: Don Goldman <donclearview@...>
Sent: Saturday, May 31, 2003 9:46 AM
Subject: [ccd-newastro] Re: WTG Don
> Hi, Mike,
> The image is not going to move off the chip with the H-a filter on
> the FSQ. It will likely have to be refocused due to the greater
> thickness of the H-a filter compare to your LRGBs. The transmission
> window ("bandpass") of the H-a filter will move to slightly shorter
> wavelengths at f/5 compared to f/10. So, at f/10, the "window" may
> be designed to be centered at 656.7 nm and transmitting 80% of the H-
> a photons passing through. At f/5, the window may now be centered at
> 655 nm and may only be transmitting 50% of the H-a photons that are
> still at 656.7 nm. Take this to extremes and the "window" will move
> far enough away that only a small % of the H-a photons will come
> through. That may be the case for a FASTAR or HYPERSTAR system at
> f/1.9. In all of the above, you should still see very little
> difference in your stars since they emit broadband light that won't
> be much different over these changes. I'm not quite sure what test
> you did, but you may consider trying to shoot a bright H-a target
> like the fringes around the Ring or Dumbbell so you can be sure the
> object is there, and centered on the small TC237 CCD. If you are in
> the middle of the Pelican or North American with no obvious feature
> on that small chip, and out of focus, for example, you may not know
> it????? I may have missed the point, but hey, I groggy (and happy)
> from an all-night imaging session for the first time in months.
> Let's see. Do I do the househould bills or process the images???? <g>
> --- In firstname.lastname@example.org, "msandquist" <msandquist@j...>
> > Hi Don,
> > I remember the light show well...now by the time I reach Marysville
> > night, I can see your dome already 25 deg. or
> > so above the southern horizon. I am however impressed with the
> images you
> > have managed to capture under such
> > bright conditions!
> > What I was wondering about the FSQ/Ha was the incident angles at
> wich the
> > image reaches the chip (PixCell 237) and
> > given the chips physical size, weather there are angles involved
> that are
> > accute enough to cause drift from the Ha line?
> > I don't have any way to know if there is loss on a purely visual
> > If I expose an evenly illuminated target using the 4.5nm filt.would
> I just
> > be generating a Ha Flat Field or would I be able to measure some
> fall off
> > and calculate drift drift from the 4.5nm line. I think some measure
> > wavelength shift would
> > be a better way.
> > I just got the filters and haven't had time to do much in the way of
> > imaging.
> > Thanks for your input Don.
> > Mike
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