Re: [APML] Laggon & Triffid

[Stuart Heggie <stuart.j.heggie@sympatico.ca>]

Don, I still think the pic is a success. I'm impressed by the 
performance of the fast achromat. What do you think the MV filter is 
costing you in exposure time? Maybe nothing at all?

Herm, your explanation makes me feel better as I had the same effect Don 
is getting and had no clue what caused it - I was panicking that my 
camera was bent as one side of my photo was in perfect focus and the 
other blurred. Didn't happen again so I was mystified.

Stuart

Herm wrote:

>I bet you are getting humidity induced warping of the film.. film expands
>as it absorbs moisture.. it buckles, shifts etc and the result looks just
>like your picture. If it was field rotation issues it would be consistent
>across the frame. It even appears as if the stars are defocused at the
>center of the frame (but sharp at the corners). Try an experiment, leave a
>lens off your camera and expose film to night air for 30 minutes or so..
>then look at it, it will probably be buckled up from the pressure plate at
>the center of the frame. It does not take much to get the effect you saw.
>
>The solution?, do a dry air purge system.. 
>
>"Don Spencer" <ecdon@cox.net>  wrote:
>
>  
>
>>The results? I still have alot to learn! *L* Like
>>why do I have apparent field rotation even though I had 15 minutes solid
>>drift in both axis(Jim Janusz and I discussed this today and came to the
>>conclusion that we are not sure what is causing this). Flexure? Guiding
>>through the 12" @f7.5? Who knows...
>>    
>>
>
>Herm
>Astropics http://home.att.net/~hermperez
>
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>  
>


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