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Low Power EP for 127mm Mak

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#1 Eric63

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Posted 15 January 2013 - 10:17 PM

I currently use a 2 inch 32mm 70 degree Titan as a low power eyepiece in my 127Mak. I love the view I get in this eyepiece and I can get approximately 1.5 degree FOV. I'm therfore wondering if a 38mm 70 degree eyepiece would also work, or is it too low for this scope. I have the SW 127Mak, which came with a 2 inch diagonal, however the visual back is less than 2 inches.

Thank you
Eric

#2 Ed Holland

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Posted 16 January 2013 - 01:42 PM

You'll get something, but there will be vignetting. I use a ~60° 35mm (1.25") as my lowest power EP on the 127. This has some vinetting, but you have to look for it - for casual observing it is not intrusive. It's most easily detected when looking at the out of focus diffraction pattern of a star. The rings will appear distorted/cut off as you move the scope to place the star at the edge of the field in the EP.

Can you give the setup a try before purchasing?

Ed

#3 Eric63

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Posted 16 January 2013 - 07:00 PM

Thank you Ed. I'm mostly a visual observer, and with my limited experience I have yet to recognise any vignetting. I think I will take your advice and see if I can try out a 38mm EP first. Right now I like the 1.5 degree FOV that I have with 32mm. I guess I'm just trying to get a bit more sky in my view :grin:

Eric

#4 Ed Holland

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Posted 16 January 2013 - 07:59 PM

I don't blame you for trying. Not until I tried to look at the Pleiades, did I realise what restricted field of view really meant. That said, I purchased the scope as a convenient means of planetary viewing and to satisfy a curiosity about catadioptric instrument designs. For these purposes, it has served very well indeed :)

Ed






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