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Surplus shed mirror+cell, 114mm?

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4 replies to this topic

#1 Jerry-rigged

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Posted 01 February 2013 - 12:15 PM

Anyone have an opinion of these mirrors from Surplus shed? 114mm dia, fl 900mm, F7.8, comes mounted in a plastic cell with spring loaded colmination bolts. They also have a 3 vein spider w/ secondary. $35 for both seem like a deal, if the mirror is decent.

Question - at f7.8, will a spherical mirror be OK? SS says the don't know if they are parabolic or spherical, so I figure assume they are spherical...

They also have a 114mm morror at f4.4, but I am guessing that if it is spherical, that one will be ugly...

#2 furrysocks

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Posted 01 February 2013 - 12:26 PM

You could have fun making a small 4.5" binoscope with these. ;)

#3 dan_h

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Posted 01 February 2013 - 01:17 PM

<< at f7.8, will a spherical mirror be OK?>>

114mm diameter, 900mm focal length, sphere is about 1/5 wave error on the wavefront, so yes, it could be a good little mirror if it is smooth to the edge.

dan

#4 Geo.

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Posted 01 February 2013 - 06:55 PM

These are hard to find on the market today. Most 114mm are being ground to f/3.6 for the Bird-Jones short tubes. I have a few steel tubes that these would work well in. Yours for the postage.

#5 operascope

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Posted 02 February 2013 - 09:25 PM

That didn't take long. It appears that the item is already out of stock.
Price was good while it lasted.


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