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Old 01-09-2018, 12:39 AM
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Hemi is offline
Join Date: Dec 2010
Location: Darwin
Posts: 237
Originally Posted by Zuts View Post

I have an edge HD 9.25 and had the same issue. I was thinking of getting a hyperstar so attempted to take out the secondary in the normal manner by twisting the large black locking nut.

Horror, the entire secondary assembly just rotated with the locking nut.

I took it to bintel and and they said this shouldn't happen and that basically the secondary assembly was loose. To fix it they removed the corrector so they could tighten the secondary assembly.

Edge HD's are made in the US and all have a mark indicating the correct orientation of the corrector, also they don't use shims anymore. Taking off the corrector tightening the secondary assembly and re-assembling took around 3 minutes courtesy of Don at Bintel, at no charge I should add, and I didn't buy the scope at Bintel.

I had to re-collimate the secondary and now everything is fine.

I can easily remove the secondary mirror now as the secondary assembly is now tight. Putting back the secondary mirror is simple as the Edge HD secondary has a pin and the mirror can only go in in one orientation.

However I am not sure if all the above applies to a regular C9.25.

Hey Zuts,

The vanilla 925 (mine) has shims around the corrector.
Not sure if there is a pin ensuring only 1 conformation/orientation for the secondary as I didn't go that far. But like you am considering a hyperstar.
Have held off as I'm considering upgrading to a c11 edge hd. It's a marginal gain.

I completely agree that Don and the Bintel crew are excellent. He was my first port of call when this happened, but alas he was away. I do feel though that some of this stuff is lore! And stuff of myth and mystery. There's a great you tube video showing an experienced South African astronomer, stripping a c14 to clean it! Dispels a few things. I think taking apart an ota or mount for cleaning, repairs and upgrades should be reasonably achievable. I live in Darwin so popping into Bintel is not an option. And we have no Astro societies/community either. You should look at some corrector plate cleaning videos! Wow! I get the principles, but really only clean the corrector on a full moon in a leap year? And you must hold your breath for the entire process as saliva moisture might get onto the glass and eventually corrode the entire scope in 25yrs time


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