Thread: Collimation
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Old 06-08-2018, 10:08 AM
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mental4astro (Alexander)
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mental4astro is offline
 
Join Date: Jun 2008
Location: sydney, australia
Posts: 4,979
I too am long sighted... Getting worse too for my sketching <sigh>

There's a few Cheshire options.

1, the worst is the short Cheshire eyepiece. Puts the cross hairs too close to your eye to properly see. The cross hairs don't need to be sharply focused in your vision, but not a hopeless blob. Also the short Cheshire doesn't reach into the OTA to help with the centering of the secondary mirror as it leaves too much space between the outline of the secondary and the inside rim of the Cheshire. Yes they work, but they are the least reliable.

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2, Long Cheshire - easier to see the cross-hairs in it. I use one of these, and while the cross-hairs are not sharply focused, they are sharp enough so I can see past them for the process. It's longer reach also helps better frame the outline of the secondary mirror inside the Cheshire.

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3, "Auto-collimator" style Cheshire. A slightly different take on the cross-hair Cheshire, and in some ways a bit easier to use for overall collimation. Once your secondary's position in the focuser has been optimized (once determined you won't need to muck around with this again), these auto-collimators are pee easy to use. You might find one of these easier to use if you are having trouble with the cross-hairs.

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I have a 1.25" and a 2" long-tube Cheshires (some focusers are 2", others 1.25"), a couple of 2" auto-collimators and a 2"/1.25" laser. If I can't figure out the collimation with my various Newts, then I'm giving up!

Alex.
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