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Posts Made By: John Holt

September 3, 2011 08:01 AM Forum: Telescope Making

titled component design for reflector

I missed the Astronomy article, but here are some others on tilted designs.
Beyond my patience to do, but fun reading.

http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/stressedglass/index.html

http://www.wro.org/jones.html

March 4, 2012 06:12 AM Forum: Eyepieces

6mm Radian or 5mm Radian

Posted By John Holt

Bob MacArthur said:

Ok so I have a Televue Pronto (70mm) f/6.8 and a 8" dobsonian f/5.9. I am currently using a 13mm Nagler and need more magnification for planets. I want to get a good view with out going overboard in magnification while keeping the cost down. I am looking at a 5mm or 6mm Radian. Any suggestions on which one I should go with?

Thanks,

Bob

It's the difference between about 197x vs 236x. I usually cruise about 200x in my 8" newt when visiting planets. But if the seeing is cooperative, then I step it up a bit higher, towards 250x.

For hand tracking, the bit lower magnification of the 6mm will yield that the target remains in the field of view a bit longer.
On the other hand, a 13mm Nagler in a 2x barlow put things at right near 6mm, with an even larger field of view.
And the 5mm will give the 70mm a somewhat higher boost in magnification than the 6mm.

So..... If I had a 2x balow, to work with the 13mm.... then perhaps the 5mm.

...

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Posts Made By: John Holt

titled component design for reflector

6mm Radian or 5mm Radian

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