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can a i use a cheshire to collimate my c8 edge during the day?

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#1 iwols

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Posted 04 August 2021 - 05:05 AM

can a i use a cheshire to collimate my c8 edge



#2 DLuders

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Posted 04 August 2021 - 05:40 AM

Yes, you can collimate during the daytime.  Get a shiny Christmas ornament or other ball that will reflect the Sun's light, and place the ball inside a Garbage Can, tipped on its side, far away from you in the yard.  The shade of the can's interior will make a nice, dark background for the ball's pinpoint reflection of the sunlight.  Point your telescope at the ball, and collimate like it was Polaris or some other star.  


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#3 KerryR

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Posted 04 August 2021 - 08:36 AM

Cheshires don't work with SCT's. I read, somewhere, that adding a small note-book style ring to the center of the secondary allows for some degree of collimation to be accomplished; in the earliest days of Celestron SCT's, the secondary center was marked, apparently. But, my understanding was that things still needed to be finalized by star test, which ends up being the fastest and easiest way to collimate anyway.

I generally haven't had good luck with artificial stars. I can get perfect collimation, but it's off again by the time I get the scope under the stars. I suspect this may be due to the artificial stars' low altitude and mirror flop, combined, perhaps, with the primary mirror's very different location on the baffle when close focusing. It's worth checking out, though, if you must collimate in daylight. Otherwise, it's worth practicing on an artificial star so that you get good and fast at it for use under the real stars. (I rarely need to collimate again, once it's done, if I ensure the secondary screws are nice and tight...)


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#4 DLuders

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Posted 04 August 2021 - 10:06 AM

There is this previous Cloudy Nights Forum topic about using a Cheshire for collimating an SCT.


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#5 Don W

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Posted 04 August 2021 - 04:12 PM

There is this previous Cloudy Nights Forum topic about using a Cheshire for collimating an SCT.

Yeah, the consensus there was it does not work.
 


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