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Old 10-10-2012, 04:55 AM
TanjaC (Tanja)
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Is there a problem with my optics?

Hi Guys - I've re-collimated my C11 since removing the secondary mirror for my Hyperstar. I don't know if it was like this prior to using the Hyperstar, as I used it 'new out the box' - but spotted this collimating.

Although there might be a few dust donuts etc this looks different to me, and subsequently I always feel like I'm not collimated perfectly. In some images I feel the stars are still flared or "pac-man" like - but that might be me being over critical now, as I'm not using a field flattener on the C11 SCT.

A very out of focus star seems okay, but as it approaches focus there seems to be something bottom left.

Is it normal - should I be worried? I can't spot any obstruction in my OTA.

Thanks
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Old 10-10-2012, 07:23 AM
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multiweb (Marc)
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If the scope wasn't cool it could be a tube current. Otherwise did you shim the secondary cell in the corrector in anyway? Sometime using shims other than cork or paper or too tight can slightly stress the glass when it gets cold and the central hole contracts around the secondary. Nothing major to worry about though. Finally make sure the three collimation screws at the back of the secondary are not too tight.
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Old 10-10-2012, 07:24 PM
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Paul Haese
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That is 100% tube currents. Cool the scope for 4 hours outside and then test the scope. You will find it to have a different result.

Feel free to look at my site on cooling an SCT in the how to section.
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Old 10-10-2012, 07:38 PM
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asimov (John)
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Tube currents
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Old 11-10-2012, 04:41 AM
TanjaC (Tanja)
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Quote:
Originally Posted by Paul Haese View Post
That is 100% tube currents.
Great - I'll try again. I cooled it in a separate room as it was actually too hot outside during that day and temp drops at night.

Yip - made sure the screws are not too tight, Thanks Marc. They were very tight when I first did collimation.

Awesome - great to know it's not something wrong with it - thanks guys.
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