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RE: [APML] Another tech pan Q: (developing, etc.)



Brian;
    My 180mm f2.8 has a bit of a 'hot spot' in the center of the frame as well, when shot at f2.8. I try to hide it by strategically placing a nebula where the hot spot is. :^)
My biggest concern last night was tracking...I was deathly afraid that my Skyview deluxe mount wouldnt handle the H-a test, but it did very well for 30 mins and I had no apparent flexture.
Good! If you have flexure, tech pan will find it for you.  
Ok... in the darkroom is where my probs begin once again...I got the photoflo right this time and had absolutely no problems with smearing or spots..good..thats over with.
What did happen was the negs were too dark...especially in the middle of the frame.
When you say that your negatives are too dark, do you mean the whole neg (around the frame numbers and sprocket holes) or just the exposed area?  Are you shooting under a street light or somewhere dark? 30 minutes @ f2.5 isn't long at all. Ha filters will reject a lot of light pollution, but they have their limits. I agree with Robert - if the hot spot is really bad, try stopping down to f4. Your focus is less critical at f4, your stars will still be extremely sharp. Ha filters do wonders for chromatic problems, but they can't help you with vignetting.
    If your negs are too dense over the entire negative, sprocket holes and leader then you might have to look at cutting back on development time. (sorry Chuck!) When I was using Lumicon film, I found that some batches were hypered to a higher background fog level than others.
 
Why do women have to bother you at the worst possible of times?  Because they can? 
 
One more thing...WoW...That filter is amazing..the stars are soo small...incredible!
Thanks for posting that page John once again.
 
You're welcome! You are going to love it when you start shooting some shots in the Milky Way.
 
John Mirtle
Calgary, Ab. Canada