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Rotating/tuning objectives?

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#1 roscoe

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Posted 02 January 2013 - 04:06 PM

I have a couple of 60mm scopes that, I suspect, could present better images if the crown and flint were better adjusted.....
how do folks rotate objectives for testing without taking them completely out of the cell each time? My thought was to stick a tab of tape on and with the retaining ring loosened, use it as a handle, but something 1/2" square would, it would seem, degrade the image...... any better ideas? :question:
Thanks,
Russ

#2 dan_h

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Posted 02 January 2013 - 05:09 PM

With the assembly pointed vertical, loosen the retaining ring and use a simple suction device to lift the crown element and rotate it. A section of rubber hose smooth cut and a line you can suck from should do the job.

dan

#3 punk35

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Posted 02 January 2013 - 06:16 PM

I used a small suction cup from a window thermometer

#4 roscoe

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Posted 03 January 2013 - 12:08 AM

Thanks, guys!
I'm going to try Dan's method first - I like that it is instantly removable from the lens face...... and if I don't have luck with that system, I think my son might still have some toy 'bullets' that have suction cups about 1/2" dia on them, and I'll try one of them.
Russ

#5 DAVIDG

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Posted 03 January 2013 - 09:27 AM

If you want to do job right, get yourself an optical flat. Since your working with 60mm objectives a 2-1/2 to 3" diameter one will work perfectly and it doesn't need to be coated. You can borrow the secondary from a large newtonian. Then set the lens up in double pass mode using a ronchi screen. The line should be dead straight, if not you can rotate one element against the other to find the exact position were they are the straightest. No guessing and no waiting for clear weather to do star testing.

- Dave






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