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Old 12-10-2020, 12:19 PM
Craig_
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M31 Andromeda

Had a crack at M31 over the weekend. Obviously this doesn't make a great southern hemisphere target and from where I was shooting north of Sydney, it barely gets above 15 degrees altitude - so ridiculously low.

I had very, very poor guiding, much worse than normal - I am usually getting 0.7 to 0.9" RMS but this was 2.3 - 2.9" RMS. Is this because of how low the object was? Can this cause poor guiding? Nonetheless, some usable data was gathered. This is around 90 minutes of integration so not a lot, but have to work with what we get on this object in NSW...

Didn't have time to do a mosiac and unfortunately Andromeda is too big to fit in the frame with my gear (Esprit 80 and 533MC) but still don't mind how it turned out. Could use a lot more integration but I don't think I'll invest too much more time in it given the data is never going to be great anyway from this latitude.
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Old 12-10-2020, 12:42 PM
jahnpahwa (JP)
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Thats a great result! Still quite sharp to me, the dust lane edges really look good.
Poor guiding may have been because you were looking through so much atmosphere so close to the horizon, the seeing in the guide scope was probably not great and the star appeared to be moving even if it wasn't. But the proof is in the image, and this looks nice What proportion of subs do you reckon you got rid of?

Any thoughts on using higher SNR stars when seeing is bad/target is low? Sort of makes sense to me.
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Old 12-10-2020, 01:01 PM
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Well colour me impressed. that's a great result for those conditions. Seeing and atmospheric turbulence is always going to be worse at such low levels so expect that's at least a partial explanation for the poorer tracking.
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Old 12-10-2020, 01:27 PM
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PKay (Peter)
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A very good outcome Craig.

I have done this Lady a few times, with my 85mm EON from the south coast, on top of a small mountain.

And your right, a difficult target through a thick atmosphere.

Your result shows a lot more detail than I could manage.

Well done.
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Old 12-10-2020, 01:50 PM
Craig_
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Quote:
Originally Posted by jahnpahwa View Post
Thats a great result! Still quite sharp to me, the dust lane edges really look good.
Poor guiding may have been because you were looking through so much atmosphere so close to the horizon, the seeing in the guide scope was probably not great and the star appeared to be moving even if it wasn't. But the proof is in the image, and this looks nice What proportion of subs do you reckon you got rid of?

Any thoughts on using higher SNR stars when seeing is bad/target is low? Sort of makes sense to me.
Thanks. Yeah the low level off the horizon causing the heavier atmosphere makes sense with the poor guiding. This is actually 100% of subs in the stack.

I didn't have much choice of guide star - posisbly because of how low the target was, but PHD was only picking up about 4-5 stars!

Quote:
Originally Posted by Robert_T View Post
Well colour me impressed. that's a great result for those conditions. Seeing and atmospheric turbulence is always going to be worse at such low levels so expect that's at least a partial explanation for the poorer tracking.
Cheers, yes, makes sense indeed.

Quote:
Originally Posted by PKay View Post
A very good outcome Craig.

I have done this Lady a few times, with my 85mm EON from the south coast, on top of a small mountain.

And your right, a difficult target through a thick atmosphere.

Your result shows a lot more detail than I could manage.

Well done.
Thanks. I wouldn't mind finding a nice mountain top up north in NSW or even in QLD (when the borders reopen) but not sure it's worth the effort for a target so low in the sky - results will never be optimal. Even for this I had to drive north of Newcastle to ensure all the major LP sources were cleared for a north view.
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