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Old 20-03-2020, 10:27 PM
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lazjen (Chris)
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Focus/Collimation issue

Well, I think it's a collimation issue.

Setup is GSO RC10 at native FL, so around 2000 mm. No reducers or flatteners. Camera is ASI1600.

See the images below. I think my collimation is whacked, but I'm not sure what needs adjusting as it looked lined up in the tak scope. I've got a rotator on the system (nitecrawler), so if I rotate the image using it, the "defect" rotates as expected.

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Any pointers appreciated.
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  #2  
Old 21-03-2020, 11:03 AM
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multiweb (Marc)
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That trefoil looks like a pinch somewhere. Maybe secondary bonding.
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Old 21-03-2020, 12:33 PM
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I see a similar effect with my newt when it's not in harmony with ambient...
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Old 21-03-2020, 01:45 PM
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lazjen (Chris)
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I'm fairly certain it's not going to be ambient temperature related - this was probably 1 - 2 hr after starting that I took those images.

I had thoughts it might be something pinched from some searches, but I was hoping it wasn't. I guess I will need to pull the scope apart. Hopefully just the secondary will sort it out.
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Old 21-03-2020, 01:59 PM
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Atmos (Colin)
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The out of focus image still looks like the collimation might be off a bit. In focus certainly looks like trefoil but out of focus doesn't look quite collimated yet either.
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Old 21-03-2020, 02:28 PM
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lazjen (Chris)
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At this point, it's probably: "why not both?"

Have to wait until it cools down a bit to pull the scope apart - too hot in the dome.
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Old 21-03-2020, 04:23 PM
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multiweb (Marc)
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You can get a pinch at low temperature if the mirror or lens cell contracts around the glass.
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