field rotation, live stacking

Discussions of Electronically Assisted Astronomy using the Live Stacking feature.
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just Klaas
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Joined: Sat Oct 14, 2023 10:55 pm

field rotation, live stacking

#1

Post by just Klaas »

Hi all.

When the sky is clear (which unfortunately is extremely rare in the Netherlands the past half year :cry: ) I sometimes try to do some EAA using my dobsonian with motors.

Of course, since it is an ALT-AZ mount, field rotation is a thing. Luckily I have a ZWO294 which has a not so small sensor so I can crop.
I could invest in an automatic rotator, but such a piece of kit is quite expensive. Certainly more than I needed to pay for my old second hand dob with all the bells and whistles.

But this got me thinking: during live stacking, the images are aligned with respect to the earlier ones which requires two translations (X and Y) and a rotation (around the Z axis) of the image.
Wouldn't it be nice if Sharpcap was able to generate a notification, which summons you to rotate your camera a certain amount of degrees clockwise or counter clockwise after which live stacking proceeds? I can imagine a setting in which you can set a specific amount of rotation "interval" in degrees.

Manual rotators are quite affordable and you could stick a simple scale on it: just print something, and glue it onto the rotator. It also does not need to be very precise, since the goal is not to do long exposure photography, but only to limit issues at the corners in the stacked image.

Since I am not an experienced Sharpcap user, I might have missed such an option already exists... If this is the case, sorry for bothering everyone.
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admin
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Re: field rotation, live stacking

#2

Post by admin »

Hi,

there is no automatic option to do the notification for you, but live stacking does have a drift graph tab which shows both the X/Y offsets of each frame on a scatter graph, but also the rotation of each frame. By watching this you could decide when the rotation had reached a suitable amount (say 5 degrees), pause stacking, rotate the camera and then unpause. It would certainly be worth a try!

See https://docs.sharpcap.co.uk/4.1/#Drift%20Graph%20Tab

cheers,

Robin
just Klaas
Posts: 8
Joined: Sat Oct 14, 2023 10:55 pm

Re: field rotation, live stacking

#3

Post by just Klaas »

Wow! I did not know this.
Whenever we have clear skies over here, I will try it out.
Right know I do not have a rotator, but I can just partially unscrew the camera a bit and rotate and play. (and unfortunately put everything back in focus after rotation).

Thanks!
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admin
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Re: field rotation, live stacking

#4

Post by admin »

Hi,

good luck - I did wonder about the effect that moving the camera would have on focus. I guess if the camera has a 1.25 or 2" nosepiece rather than being fixed by a screw thread then you should be able to rotate it without signifiant movements affecting the focus...

cheers,

Robin
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turfpit
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Re: field rotation, live stacking

#5

Post by turfpit »

Are flats being used? If so, there would be an impact?

Dave
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