Narrow slit

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Peter Carson

Hello Grant,
Until fairly recently I used a 315mm f/8 Dall Kirkham astrograph in my 2.1m dome. It was a bit snug!

Jeremy is right to draw your attention to the Pulsar narrow slit and viewing obliquely through it. This is a major concern if you have a German Equatorial mount with a large dec axis offset from the RA axis as it exaggerates the obliquity. 

My dome is over 30 years old and didn’t owe me anything so I took a saw to it and enlarged the slit to one metre wide. I fibreglassed some new slit aperture perimeter upstands and made a new aluminum shutter and it works a treat.

I don’t suggest you try this on a new Pulsar dome though.