DSLR help

[Crossy2010]

I recently bought a Canon Rebel XS DSLR with intentions of using it for some astrophotography. I have an 8" Dob for now, but I should be able to get decent photos. I also bought a Canon adapter kit to connect the camera to my scope.

So, I set it up over the weekend with little success, and last night I took it back out to give it another go. I got Jupiter in the field of view, but I could still see the dobs primary and secondary mirrors in the image. I tried adjusting the focus several times, but my focuser does not seem to be able to focus. Can I use my camera without a lens or eyepiece? Do I need an extension? What is the setup that I need to connect my camera to the scope and still have the camera lens on?

I still got some decent pics.

[Black Knight]

I had the same problem, in my case, not enough inward travel on the focuser. One possible workaround is to use a Barlow lens. That does work but a Barlow reduces the amount of light reaching the cameras sensor. Another way round it would be a direct camera connection, if your focuser has one.

To keep the lens on the camera you need to take images afocally, i.e. by pointing the camera into the eyepiece. The camera would be held in place using a bracket attached to the scope.

There is also eyepiece projection photography where (I believe) the eyepiece is attached to one end of an adapter, with the camera attached to the other end of the adapter. The eyepiece projection adapter is then inserted into the focuser. Don't know much about this option, I've never tried it.

The other option would be simply to attach the camera with its lens attached to a tripod or a mount and take pictures that way. Or piggyback the camera onto the back of your scope.

The main problem you are likely to get is the length of exposure on a dob will need to be quite low to avoid star trailing caused by field rotation. To get longer exposures, most DSLR users would use a scope on a motorized EQ mount, perhaps utilizing a guidescope as well.

[Crossy2010]

Thanks a lot for your suggestions and assistance Black Knight,

I think I am going to try the tripod approach for now. Currently I have some sort of a kit that I probably should have looked into a little more before buying. I am going to get a scope more apt for AP in the spring, but for now I am having fun messing around with the challenges that AP and dobs create.

The kit I have now holds an eyepiece, but only my smaller 12mm, 9mm, and 6mm plossls. I am going to also try adding the barlow to whole kit to see if that will give me enough of an extension to focus. The worry that I have with that is that there will be a slight bend from the focuser to the camera. Should be interesting.

Thanks,

Shane

[dmahon]

Can I use my camera without a lens or eyepiece? Do I need an extension?

It's likely that your problem is the opposite. Rather than need an extension, you need to cut down the distance between the secondary mirror and the camera chip to get it into focus.

[Revs]

Hi Crossy. Have a look in this thread... http://stargazerslounge.com/imaging-discussion/121040-astro-questions.html

EDIT: You'll need one of these if you haven't got one already... http://firstlightoptics.com/proddetail.php?prod=tadaptor

[simon84]

Have you tried moving your primary mirror as far up the tube as it will go?

You can normally gain a small amount doing that, make sure to re-colimate after doing it though.

[Crossy2010]

Prior to posting this I was hoping to find a previously started thread, but after about two and half seconds of looking I gave up. Well maybe a little more time, but I think I get it now. I tried the tripod last night with no luck, and now I know why.

Thanks for the help everyone,

Shane

[Dave]

Hi Crossy. Have a look in this thread... http://stargazerslounge.com/imaging-discussion/121040-astro-questions.html

EDIT: You'll need one of these if you haven't got one already... Adaptors - T Rings

I'll second that... Don't try and move your mirror.