Daytime viewing with my 80ED refractor resolves objects upside down.. if I use an erecting prism diagonal will I have enough "in" focus racking distance? thank you, John Meiners
correct view?
Started by Midnight Sun, 04/14/2010 04:24PM
Posted 04/14/2010 04:24PM
Opening Post
Posted 04/14/2010 05:31PM
#1
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Probably.
A regular "astro" diagonal, either a prism or a mirror will put things right side up but leave them reversed left to right. It is easy enough to get accustomed to this view.
A 1.25" erecting prism has somewhat less path length than a 2" mirror diagonal. If you use a 2" diagonal for star gazing, the erecting prism won't cause in travel problems. Also note that for most terrestial viewing, targets are closer than astro targets so typically you need to focus further out.
dan
Probably.
A regular "astro" diagonal, either a prism or a mirror will put things right side up but leave them reversed left to right. It is easy enough to get accustomed to this view.
A 1.25" erecting prism has somewhat less path length than a 2" mirror diagonal. If you use a 2" diagonal for star gazing, the erecting prism won't cause in travel problems. Also note that for most terrestial viewing, targets are closer than astro targets so typically you need to focus further out.
dan
Posted 04/14/2010 07:14PM
#2
John Meiners said:
Daytime viewing with my 80ED refractor resolves objects upside down.. if I use an erecting prism diagonal will I have enough "in" focus racking distance? thank you, John Meiners
A correct image diagonal will both flip the image top to bottom and left to right. If the image is currently upside down then you must not be using a diagonal or you are using a star diagonal horizontally.
Myself, I use a star diagonal for terrestrial viewing, birding and such, the image is correct top-bottom but reversed left to right. The left-right reversal is not confusing and the simpler light path of the star diagonal means for sharper, cleaner images than were I using a Correct Image Diagonal.
I think it's a good compromise, everything looks natural since top is up.
Jon
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