Thread: New COMA Killer
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Old 14-08-2019, 07:40 AM
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alocky (Andrew lockwood)
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Join Date: Aug 2010
Location: perth australia
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Thanks Greg - itís only a few extra pixels per star, so Iím pretty satisfied with it. There is the new Nikon ĎNochtí 55mm, which is claimed to be coma free at f 0.97, but it sounds like they are only releasing it for their new z mount, and it will be 3-5K... so not really an option for me.
I also did a similar mod to my Polaris. The counterweight definitely increases the payload, but being able to fine tune the polar alignment after setting the camera up makes all the difference.
Cheers
Andrew.

Quote:
Originally Posted by gregbradley View Post
Lovely shot Andrew. A bit of coma but that's about as good as it gets at F1.4.

The only other lens that may do better is the newish Sony 24 1.4 GM. Sony specifically stated that they were able to minimise corner aberrations for astro. But the supply of them seemed to stop for a while as a few quality control issues surfaced on the net. They are making them again now.

F1.4 though is perhaps not the best target for a lens as my Zeiss Loxia is pretty perfect at 21mm f2.8 and with a tracker you simply expose longer or do more subs to compensate for the slower F ratio.

I tarted my Polarie up. I got the counter weight from the Star Adventurer and the upgraded holder from Vixen so the polar scope can always see through the holder plus I put a wedge on it.

Greg.
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