Re: [APML] Horsehead and Pleiades testshots with 6x9 camera/OAG and BRC

["Bobby Middleton" <bobm@koyote.com>]

Thanks for posting Loke. The 6x9 frame sure is big! I see a strip across the
top of the HH image that is a different tone. I don't think that is from the
pick-off prism but do you know what caused it? Star sizes and resolution is
good. Focus looks good. Did you attempt to focus the BRC or was it already
at critical focus? I see no sign of mis-alignment in the high-res image.
Was the OAG "user-friendly" with thoughtful design? Did you use vacumn on
the 6x9 camera?
Did you use the 6x9 camera and OAG with your AP 155 for the M45 shot? What
did stars look like with it at high resolution?
The long stars you mention at lower left are hardly noticable, but my
mis-alignment isn't very noticable with PPF. TP may show this worse. It does
on my TP negatives. Your long stars are probably a very slight
mis-alignment. I'd leave it alone unless it's much worse on TP.
Bobby M

----- Original Message -----

From: <tan@home.com>
>
> Just got the chance to try out the Mitsuboshi 6x9 camera with OAG on a
> Tak BRC250. Here are shots of the Horsehead and Pleiades Nebulas which
> are cropped from a full 6x9 frame:
>
> Horsehead:
> http://www.starryscapes.com/nebula/horsehead.html
>
> Pleiades:
> http://www.starryscapes.com/clusters/pleiades.html
>
> These were processed rather hastily and should be considered work in
> progress.
>
> A single full frame of the Horsehead (1 hour exposure) can be seen here
> for those interested. The large version is really large so beware of
> long downloads. The small version suffices if you want to check out
> illumination. The larger version is better for seeing stellar spot sizes.
>
> Small 178kB version:
> http://www.starryscapes.com/tmp/hh2_small.jpg
>
> Large 903kB version:
> http://www.starryscapes.com/tmp/hh2.jpg
>
> As can be seen, there is vignetting at the very edge of the corners.
> This could be attributable to some form of obstruction, but this is only
> a guess. Since it is rather small, I do not think this to be critical.
> Also noticeable is some gradual light dropoff.
>
> I have not empirically measured the stellar spot sizes of this
> combination but I can tell they are small. Please judge for yourself.
> Also noticeable is the fact that there is somewhat of a degradation of
> spot sizes towards the edge of the 6x9 field.
>
> Anyway, I thought this information might be of interest to someone.
>
> Loke
>
>
>
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