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I agree

Suddenly trouble with long exposures

Steve_Starman
27 Aug, 2019 07:39
Hello Astrobin community,

during the last few sessions doing Deep Sky Imaging I have had trouble with exposures longer than 4-5 minutes. Two nights ago the stars where egg-shaped during the whole 4 hour session (8 Minute subs). Last night the stars had a different shape. More like the star was doubled from vibration (a bigger and a smaller image of the same star besides). The artefacts pointed into a different direction every night even though the camera was mounted exactly the same way on the telescope.

My technique worked well before with the same equipment and the same approach. I even did 10 Minute subs without trouble before.
There also was no wind at all in these nights.

My Equipment is a 150/750 Newtonian on a EQ6R-Pro, a  Lacterta MGEN 2 mounted on a 8x50 guide scope,  and a Nikon DSLR. I am polar aligning manually but I always make sure that it is as good as it can be.

Any help would be appreciated!

Steffen

By the way: I hope this is the right sub forum for such a question?
khrrugh
27 Aug, 2019 09:31
Hey Steffen,

i am using the same mount and want to share my experiences:
Polar alignment is absolutely essential -> I am having trouble when the alignment is below 30 arcseconds in every direction (measured with SharpCap).
My mount has often issues when pointing to the northeast. In the same night with nothing changed the guiding is really bad when pointing to the northeast and gets better the nearer the target moves to meridian. After the flip the guiding is totally smooth. This may be related to balancing issues.

I am not sure if this helps, maybe you have all these factors under control. Just wanted to share my experiences :-)

Grüße aus dem Norden,
Michael
Edited 27 Aug, 2019 12:05
Steve_Starman
27 Aug, 2019 14:17
Hi Michael,

I indeed went for M52 deep in the northeast. I quickly checked my images and I think the quality improved when the object approached the meridian. Thanks a lot for your helpful comment! I have the same opinion as your have regarding the polar alignment. Thats the reason why I take a lot of time to align as good as it can get because I dont want to waste the images of one of the rare clear nights here in southern Germany. smile

Viele Grüße in den Norden und clear skies!
Steffen
Starminer68
27 Aug, 2019 14:35
I would recommend Iphone app PS Align, you can choose your mount polar scope, I own EQ5-Pro- no problem with 5, 10, 20 min exposures. But to be fare - close to meridian flip stars get deformed.
 
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