Imaging multiple nights

[Calzune]

How do people image the same target multiple nights in a row? How do you target the exact same spot to keep the image the same as the night before? 

[DaveS]

A permanent set up, and plate-solving with a whole sky model.

OK, you can get away without plate solving but having a well aligned mount that stays set up is a great help and Eqmod can also do multiple star alignment. After that it's a matter of picking your target in a suitable planetarium program, I use Cartes du Ciel because it's free and interfaces easily with the telescopes I use (I don't use Eqmod with my main rig BTW).

[PhotoGav]

There are two methods to get back on target for multiple nights of exposures. The first is manual - attempting to match up the position of bright stars by eye until you are pretty much in the same framing. This is time consuming, inaccurate and difficult. The second method is to do that automatically with plate solving. You need to be hooked up to a computer to do this. The sequence is: slew to coordinates of your target, take a picture, software compares the stars in the image with a database of stars until it finds the exact coordinates of where the scope is really pointing. The scope is slewed to point at the target coordinates again. Take a picture, plate solve, move, repeat until the scope is pointing exactly (or near enough) at the target coordinates. This is quick and easy to do once your system is hooked up to a computer. Imaging control software such as APT or SGPro can manage this process for you.

Hope that helps.

[Calzune]

1 minute ago, PhotoGav said:

There are two methods to get back on target for multiple nights of exposures. The first is manual - attempting to match up the position of bright stars by eye until you are pretty much in the same framing. This is time consuming, inaccurate and difficult. The second method is to do that automatically with plate solving. You need to be hooked up to a computer to do this. The sequence is: slew to coordinates of your target, take a picture, software compares the stars in the image with a database of stars until it finds the exact coordinates of where the scope is really pointing. The scope is slewed to point at the target coordinates again. Take a picture, plate solve, move, repeat until the scope is pointing exactly (or near enough) at the target coordinates. This is quick and easy to do once your system is hooked up to a computer. Imaging control software such as APT or SGPro can manage this process for you.

Hope that helps.

Hmm Okey. I use apt and just began platesolving (yesterday) so what you are saying is that is possible for me? 

[PhotoGav]

2 minutes ago, Calzune said:

Hmm Okey. I use apt and just began platesolving (yesterday) so what you are saying is that is possible for me? 

Excellent, sounds like you are already equipped to do this! I am an SGPro user these days, so can’t give you exact instructions on how to use APT to do it, but I’m pretty sure it is possible. 

Have a read through this and you should be able to suss it out:

https://ideiki.com/astro/usersguide/pointcraft_and_plate_solving.htm?ms=AAA%3D&st=MA%3D%3D&sct=MA%3D%3D&mw=MjQw

Good luck, it is definitely worth mastering. One thing, try and avoid moving the camera orientation on the scope between imaging sessions if you can otherwise you need to match rotation as well!

[Calzune]

1 minute ago, PhotoGav said:

Excellent, sounds like you are already equipped to do this! I am an SGPro user these days, so can’t give you exact instructions on how to use APT to do it, but I’m pretty sure it is possible. 

Have a read through this and you should be able to suss it out:

https://ideiki.com/astro/usersguide/pointcraft_and_plate_solving.htm?ms=AAA%3D&st=MA%3D%3D&sct=MA%3D%3D&mw=MjQw

Good luck, it is definitely worth mastering. One thing, try and avoid moving the camera orientation on the scope between imaging sessions if you can otherwise you need to match rotation as well!

Great, thanks! Do I need a guidescope for this? I'm currently doing imaging with no guiding so I do relatively short exposures (around 70 sec) but I'm planning on buying a guidescope kit soon 

[almcl]

You don't need a guide scope to platesolve.  Just the main image from your imaging camera and APT can be asked to drive the scope to position of your first night's image.  It will do this by solving an image, slewing to where it thinks the target is, taking another image and so on until it judges it is close enough. 

The tricky bit (for me) is getting the camera at just the same orientation as it was the night before so that the frames line up and don't require cropping once stacked.  APT does report 'camera angle' but this isn't always reliable, I find.

[david_taurus83]

3 hours ago, almcl said:

You don't need a guide scope to platesolve.  Just the main image from your imaging camera and APT can be asked to drive the scope to position of your first night's image.  It will do this by solving an image, slewing to where it thinks the target is, taking another image and so on until it judges it is close enough. 

The tricky bit (for me) is getting the camera at just the same orientation as it was the night before so that the frames line up and don't require cropping once stacked.  APT does report 'camera angle' but this isn't always reliable, I find.

Have you tried the framing mask? You can take your reference image and create some circles over some bright stars and save the mask. Then if you want to revisit another night, you use Goto++ back to the centre of the reference image and load up the mask. It will overlay the circles back where you had created them. Then you rotate the camera whilst taking images until the stars line up in the mask again. Or so I believe..

Not tried it myself yet as I tend to stick to one target until its finished. If there is such a thing as "finished" in AP!