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

[Alan Voetsch <alanv12952@yahoo.com>]

Hey John,

--- John Mirtle <spampit@shaw.ca> wrote:
> 	Sorry about jumping in late, I was out of town this weekend.
> Something isn't right here. Both of your images are badly clipped at
> the
> dark end which I find very odd. This would imply that your scanner
> can't get deeply into the black part of the negative

What I've noticed about the E200 scans is that there is a very narrow,
steep hill on the left side of the histogram that is maybe 1/4-3/8 inch
wide and then there's a then there is a straight line all the way over
to the right side. This is even before I destroy anything with my
attempts at processing. I posted about this a weekago but got no
response. I wondered if I should use another setting on the scanner.
There is an option for "under-exposed color sides" while I used "color
slides". They can be worked with, eventually, but I wanted to know if
my scanning needed adjustment, or maybe I needed to increase exposure
times. I did notice that most of the exposure times on the roll of E200
were in the 60-90 minute range because I did not know what to expect
from that film. I also wondered if it would have been better to ask for
push processing, or increase exposure time, or do they accomplish the
same thing? I do think I will try another roll of E200 and try to
expose the way I normally expose; 120-160 minutes.


 but what is odd here is
> that with
> your gargantuan exposure times, the background shouldn't be very
> dark! To
> see what I mean, look back a week or so for a posting from Jon Kolb.
> He
> posted a set of exquisite images which were also taken on E200. The
> optics
> were an f7.9 refractor - only marginally faster than yours at f8.1.
> Jon's
> shots were in the 70 minute range and yet they went plenty deep. For
> sky fog
> and nebula, f-ratio matters - not diameter! Your shots should be
> recording
> much more. Much, much more!

I've noticed that many times. And wondered why. Chris Cook uses a
FS-102 and said he was going to have some shots soon.

> 	By using the same exposure times as Jon and pushing 1 stop, the
> results should be the same except for a smaller image scale and fewer
> stars.
> The fact that you are exposing much longer and getting less would
> imply that
> you have a problem somewhere. Are you sure that the shutter is
> remaining open the entire time?

There is a strong click when I release the cable, so yes. I wonder if
it's possible that it (shutter) doesn't open all the way. 

Does a roll of "normal" daytime shots from your
> photofinisher look normal?

I don't take daytime pictures, I live for the dark.

> Are there spiders living in your optical
> tube? It
> looks like something is stealing your photons. I recently heard
> something
> about Tak refractors with 2.7" focusers that was a bit disturbing
> that might
> explain some of this. Apparently, at the objective end of the focuser
> drawtube, the drawtube is bottlenecked to 48mm aperture. The 4"
> versions and the FSQ do not have this problem, 

The FSQ is well known for that hot-spot though. If there is that
bottleneck, then how do folks use medium format cameras on the 102
without severe vignetting? I know somw use 645 cameras, Phil Jones may
be one.

All this is food for thought. You know I'm really worried about those
spiders, I'm going to go look, stranger things have happened. 8-)

Thanks for your insights John,
Alan



=====
SCT Astrophotography: http://www.pbase.com/avoetsch/astrophotography
FS-102 G-11/Gemini: http://www.pbase.com/avoetsch12952/tak_fs102
& http://www.pbase.com/avoetsch12952/fs102

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