IC 2602 Southern Pleiades

[Startrek]

While not as famous as M45 , the Southern Pleiades is still a spectacular open cluster with a prominent and interesting stars pattern
35 x 2 minute subs
20 x darks
ISO 800
PHD2 guiding
Stacked in DSS
Processed in Startools
A bit of coma or field rotation in off axis areas ?

[Anth10]

Hi Martin,
Nice subject well done. I see what you mean though, the stars look a little elongated and I believe it’s a tracking issue over and above coma. Coma wouldn’t be as prominent in the middle of the frame, generally most pronounced around the corners however the stars in this image seem affected across the entire frame. I can’t comment on the guiding precision since I don’t run an autguider but I am aware of coma. I have recently lashed out on a corrector and it has fixed up the issue.
Field rotation, well again not an expert but I would have though DSS would have sorted that out.
In saying that, the overall image is quite a sight, like it.
Cheers
Anth

[Startrek]

Thanks Anthony
It’s a nice cluster to image
Next time I’m out imaging ( cloudy now for 6 days ) I might try a 10 sec, 20sec, 30sec and 60sec sub both guided and unguided and compare the off axis stars in each frame to try and sort out the cause

[raymo]

Hi Martin, Definitely coma; if the image is enlarged to 200% it is obvious,
with the action radiating out from the centre. It is quite pronounced for an f/6
scope, assuming that that was what you were using. Also, definitely a little
tracking error about 11.30 to 5.30. Also double diffraction spikes.
raymo

[Startrek]

Hi Raymo
Good observations
Thanks, yes I’ve checked some old 20 sec images from last year and they appear the same, eggy or flared on the perimeters and round in the central on axis area
Unusual for a 6” f6 newt ?
Also aware of the offset diffraction spikes , given up on trying to align them so many times
Cheers