Dome observing slit width:

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The recommended observing slit width is 1/3 the Ø of a dome. 3m / 3 = 1m wide. So I cut two battens to space the slit frame to 1m instead of the former 60cm. [2']

To my mind it is aesthetically displeasing. More like a barn door to let a horse and carriage through. Though it doesn't look quite so bad from inside the dome. I took the image at an angle to show the slit framing ribs more clearly.

Here's the same dome with a 2' spacing across the ribs. I feel this looks more normal. Perhaps a little mean. Dome owners warn against making the slit too narrow. Or the dome needs to be moved to often to follow an object. [Assuming manual dome rotation] A narrow slit hides a lot of sky making it more difficult to find constellation and objects. It also blocks stray light and the wind better.

I think I'll try spacing the slit ribs at 90cm or ~3' apart just to see what that looks like. It doesn't cost anything except a couple of lengths of batten at this stage.

90cm didn't look much different from 1m. So I tried 80cm.  I think this looks nicely balanced against the overall dimensions of the dome.

BTW: None of the slits is supposed to be symmetrical with the dome structure. I just laid the frames over to take some pictures. 

I clamped the upper ends of the gores together to hold the dome up. It seems quite stable just relying on friction alone.

Click on any image for an enlargement.

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