Re: [APML] The Veil...

[Philip Perkins <philip@astrocruise.com>]

Don:  This would be a fine shot if it weren't for the misfocusing in the 
centre. This one has me a little foxed because my initial thought is field 
curvature.  However field curvature usually results in slightly elongated 
stars (radially away from centre). So what about film buckling?  I used a 
Pentax Spotmatic for several years and never saw any real film buckling, 
whereas in this case the buckling would have to very severe.  So I'm back 
to field curvature - perhaps there is a little elongation in the edge stars 
but it's just not visible at this image scale, and perhaps you 
inadvertently misfocused and just by chance you had the edge of field in 
focus.  The Spotmatic is not an easy camera to focus - the screen is rather 
dark and it's not interchangeable.

Chuck:  The Pentax Spotmatic was one of the real classic SLR cameras of the 
1960's.  Pentax, as well as inventing the pentaprism (I believe - hence the 
name Pentax), also invented this method of TTL spot metering (I believe - 
hence the name Spotmatic).  My Spotmatic is still working superbly after 37 
years - a really lovely camera.  I have never got rid of it because it's 
such a classic.  I used it for a lot of my early astro photos before I got 
the Nikon.

--Philip

At 07:11 30/05/03 -0700, you wrote:
>Don,
>
>It looks to me that the photo is just out of focus. Since you're using an 
>SCT with no field flattener (I assume), it's not possible to get the whole 
>frame in focus at the same time. Normally the image will be in focus in 
>the center and out of focus as you move toward the corners due to field 
>curvature. You have the opposite. I'd look carefully at your focusing 
>method before film buckling unless your camera body is poor at holding the 
>film flat. I've never heard of a Pentax Spotmatic but I assume it's 35mm. 
>Film buckling of this severity with a 35mm camera would be unusual.
>
>Chuck <aa6g@aa6g.org>
>
>--------------------
>
>>Hi All,
>>           I just finished processing my first attempt at shooting the Veil.
>>http://members.cox.net/ecdon/veil.html
>>You'll notice in this shot that the center seems a bit out of focus, the
>>edges focused real well, but somewhat rotated. This is the second shot from
>>that night that has this appearance, which leads me to believe that dew was
>>the culprit(it formed earlier and stayed longer the 2nd night I was out). By
>>comparison, my M8/M20 photo shows slight curving at the edges and dew was
>>just starting to pick up at the time the photo was shot. I also learned a
>>valuable lesson...it is better to take multiple shots of one area, stack
>>them, and get a quality photo, than it is to spend 2 nights shooting 1 shot
>>of anything in site! I am battling noise in both my Antares region and
>>IC4592 shots.
>>Thanks,
>>Don Spencer
>
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Philip Perkins - philip@astrocruise.com
Wiltshire UK & Luberon France
Astrocruise - http://www.astrocruise.com

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