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6" F/5 Primary Questions:

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Posted by Mark Windham on October 8, 2002 16:37:59 UTC

Hi! I have a 6" f/5 primary mirror and am just about to start buying the rest of my scope components and would like to avoid any major mistakes... From what I can gather, a 6" f/5 would normally be paired with something in the range of a 1.6" secondary... however, I know that there are MANY variables in the equation and your advice would be greatly appreciated. I've heard that 17% light blockage from the secondary mirror is optimal (not sure where I heard that), is there a method of determining the blocked light percentage?
If possible, I would appreciate some basic recommendations for all of the general components such as 2nd mirror size, focuser size/height and distance from secondary, tube size, recommended eyepieces and so on. This is my first project (a cheapie) and I hope that, upon completion, I'll be ready to build what I really want: A 10" Dob... (Nothing against the 6" f/5, it should be great for wide field views).

Thanks again!
Mark

Here are all the specs I have on my 6":
Coating = al+sio
Clear aperture 6inches = 152mm
Focal length 29.38inches = 746mm
Focal ratio f/5
Mirror thickness 0.625inches = 15.9mm
Thickness/diameter ratio 1:9.6

FYI: I've tried using NEWT but can't seem to figure out the recommended secondary mirror size.

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