Camera Orientation

[MattJenko]

I have seen some mention in various threads of always orienting the camera the same way for every imaging run. To date, I have always simply aligned the camera to get the best framing for the object intended, but now having done this imaging lark for a few months, I can see the advantages of having a known framing as you can easily revisit targets, which is something this weather pretty much mandates.

My question therefore is thus:

How do people align their cameras consistently? I also picked up that if you align with RA/Dec you get the bonus of being able to trouble shoot aligning issues and trailing problems, so I am keen to do this for this reason as well, but I am not 100% sure on the mechanics of doing it.

As always,   to you all who help out others.

[Leveye]

I use Stellarium to do a basic composition of the objects i'm imaging that night and then later rotate and crop with the final image in post.

[MattJenko]

Apologies Leveye, not quite with you - so you have the camera at a fixed orientation all the time and then rotate in post-processing, or base the orientation for the imaging itself on what looks a best fit in stellarium and do a final rotate of that in post-processing for aesthetics?

[PorkyB]

I have never been able to work out the orientation of my camera, turning the scope in its rings confuses the issue..

If I really want the finished picture to have a particular orientation, for instance if I want it to be the same as my star atlas, then I find my target, pick out a bright star in live vew, then wiggle the RA knob on my mount and see which way the star moves.  I can then rotate the camera until the movement is up-down on the camera.  Check the framing and focus one more time and then go.  It's all a bit hit-and-miss, and not at all scientific, but it works for me.

Most of the time, however, I set the orientation to get the best pretty picture and remind myself that there is no 'up' in space.

[r3i]

Must admit I've tended to keep the camera in the same orientation for every imaging run, which has been mostly okay for my needs but could be an issue if the target only fits into the FOV if the camera is rotated to suit.  I typically try to get the camera seated so that the long side of the chip is parallel with the Dec axis, then 'up and down' commands translate pretty much to RA & Dec.

To get the same orientation on multiple nights you could put some kind of witness marks where you fit the camera into the focuser, something like a small dab of Tippex that can be easily removed afterwards?  You probably won't get perfectly matched alignment between sessions but it should be good enough for when you're stacking the images they should mostly overlap okay.

[ollypenrice]

The easy way to know how you're aligned is to take (say) a 5 second sub while slewing on one axis. This will give you a star trail. Repeat after rotating the camera till this star trail is vertical or horizontal.

If I have to take a camera out I set the CW shaft and OTA to horizontal (with a bubble level) and the camera will be either horizontal or vertical (landscape or portrait). I note its orientation and when I put it back I do so with the bubble level again. The orientation will often need a slight tweak using the trails method but it starts off pretty close.

The long term benefits of being consistent in this way really do pay dividends. Also doing mosaics in any other orientation is murder. Since one of our rigs is a tandem the star trails method means the two scopes' images combine almost perfectly.

Olly

[MattJenko]

Thanks all - I imagine it is easier to square off straight edged cameras than round ones then, good job I have a DSLR to put a bubble level on rather than a lovely circular CCD! 

I will add this step to my ever-developing (and expanding) setup routine...