RE: [APML] IC 410 uploaded and IC 405 adjusted

[John Mirtle <spampit@shaw.ca>]

Alan,
	Sorry if I missed your post about this a week ago, I was not
available to answer. Have a look at
http://www.astrofoto.ca/john/files/curves1.jpg - this is a scan of an
Ektachrome slide with my old Minolta scanner. It sounds like you are only
getting part way into the "hump" on the left side. To get the full hump (and
all the faint image data) you will need to increase your exposure time with
your scanner. Mess around with your settings, see if you can do this. If you
still can't, try pushing 1 stop next time out. It makes it easier to scan
the dark parts of your slide.
	The next time you are out, take a couple of daytime shots too. This
should confirm that your shots aren't dark due to weak chemistry where you
are getting your film done. Looking at other people's work with E200, your
exposure times are just nuts! I would like to see other FS-102 images using
E200 for comparison. Something just doesn't smell right.
	As for the FSQ hot spot - yes, there is one. This is a trade-off of
the Petzval design. As I understand it, you can only have a 100% illuminated
field that is half the size of your rear lens element. The 48mm diameter
stop at the lens end of your drawtube isn't theoretical - rack out your
focuser and measure it. :) This subject came up on a Tak newsgroup recently.
Even with your SCT shots, your exposure times seemed to be longer than
anyone else and still picking up less. Is there something between the camera
and scope that could be reducing your photon flow? I previously thought that
perhaps your Supra was bad but now it is looking like something else may be
causing the problem.

John Mirtle
Calgary, Ab. Canada



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