Can I Polar Align with a DSLR(and PC) for long exposure astrophotography?

[evilgeenius]

Hi

Is it ok to use a DSLR to polar align my CPC scope on a wedge so it can be accurate enough for long exposure astrophotography? or do I have to do it in the eyepiece so the alignment stars can be properly centered?

My concern is that It will be impossible to center the star in a DSLR because the sensor of my Canon 1000D is not exactly in the center of the light path. So although on my laptop it may seem like the star is centered, it won't actually be. Is this a valid concern?

Cheers

Chris

[steppenwolf]

This is a little confusing! Polar alignment and star alignment are two very different processes.

Can you confirm if you are using your Canon 1000D piggy backed on top of the telescope (or even in place of the telescope) with a camera lens of are you using it at prime focus - i.e. attached to the telescope in place of an eyepiece?

[evilgeenius]

Sorry for the confusion! I'm using my 1000D at prime focus. I just want to know if I can do the two different processes, star alignment and polar alignment, with it.

Cheers

Chris

[ronin]

You polar align the mount, with or without scope and or camera.

Hopefully you align the scope+- camera to the mount but it is a seperate thing.

You probably cannot polar align the scope, as Polaris is not on the rotational axis of the earth. So even if you did centre Polaris it would mean that you are not aligned sufficently to do astrophotography

Polaris is NOT on the rotational axis of the earth, it is close but close is not enough for astrophotography.

[evilgeenius]

Currently I am using the All Star polar align routine of the CPC which allows me to use any star to polar align with and it's really easy to do. Im just wondering if I could use my DSLR instead of looking through the eyepiece.

[brantuk]

I think you'll find you need to get your polar alignment as close as you can then do a drift alignment. You'll also require guiding for long exposure photography using a wedge configuration. Once all this is done to a satisfactory degree you can then attach the camera.

[steppenwolf]

You can do both polar alignment and star alignment with it, I do this routinely and if you have it attached at prime focus, then the sensor should be centred in the light path.

You will need to do a drift alignment using the DSLR to capture regular images and check for drift - here is a link to one method but a Google search will find others too.

Star alignment using a DSLR is simply a matter of slewing to the chosen alignment star, taking a series of quick images (6 to 10 seconds should do it) and centring it in your sensor's FOV. Once centred you can 'SYNC' or 'accept' the alignment.