combining stacking sessions for 31

[philip57]

Hi,

I am a relative beginner in astrophotography but I think getting there with lots of help.

I am working on imaging m31 andromeda.

My problem is i need to stack over more than one night to obtain a better image of andromeda. Unfortunately i have to bring in my mount, camera and telescope every night and reset again the next session.

I was wondering what others do to ensure the camera is aligned in the same position and andromeda is in the correct place on the image as it was on the imaging from the previous session.

I use dss for stacking and BYEOS for capturing the images.

Philip

[Spikey]

Hi Philip, As pretty much an AP beginner myself I can't really give you the benefit of much experience.

I have done this on M31 over 2 nights and am in exactly the same position you are in. I have to dismantle and re-assemble every night.

I use APT to control the Canon which has a framing mask feature and used that to get the image as close as I could. Basically, it allows you to pick out prominent stars and saves it as a sort of template. This then overlays as you are framing the image on the subsequent night. Once you have the correct stars fitting the mask you should be the same as the previous night.

[Stephen]

You're never going to line it back up perfectly - you just let the stacking software take care of it

Your end result will have some funny shaped borders which you then crop out a bit.

Close enough is good enough?

[kookoo_gr]

Two tips as i image over several nights a single target.

1. when setting up drift align to remove any field rotation that will appear when you stack images over several nights. Simple polar alignment is not enough

2. in order to avoid any rotation of the image (not field rotation),frame your target and have much easier alignment of the frames i would advise not to remove the camera form the focuser. simply remove the telescope but be careful when storing the ota not to damage the camera.

[philip57]

thx for replies.

I will probably try to keep camera attached when storing away.

As regards field rotation i only get that near the edges of the images. If my object is in the central 50% were there seems to be no field rotation, i would expect that to be ok.

I have been told now that DSS will take care of the alignment as long as you have your imaging object nearish to the previous session.

Philip

[Spikey]

Yes, good idea to keep it attched. I keep mine attached and also don't touch the focusser as I usually take flats on the morning after.

[earth titan]

That was going to be my question. Leave camera attached I thought - saved me asking the question.

I've found that if I do my alignment right and save the location, Synscan pretty much puts me back on the same spot.