Astrophotography help for beginner

[padiggle]

I was hoping a few of you could help us out. I have had a digital SLR Camera for a few years and a Skywatcher 130M Reflector Telescope.

I managed to take a photo by pointing the camera into the eyepiece
An example is:


I bought a Canon T adapter to connect my camera to the telescope but cannot figure out what else I need. I also have the following bits:

T Adapter:


2x Barlow Lens:


10mm Wide angle eye piece:


Using the telescope without the camera I slot the eye piece onto the telescope and focus the telescope. The barlow lens magnifies the image.
I can connect the barlow lens to the telescope and the camera can slot into it, but I cannot focus an image.
Do I need a 10mm lens that the T adapter can slot into, if so where could I buy one of these?

Hopefully someone can advise me, otherwise the telescope will end up back in the cupboard gathering dust

Thanks

Paul

[Joe929]

Hello Paul,
I am a newbie as well and still getting my feet wet as they say. With the T adapter and T ring together(2nd photo), you attach these to your camera the same as you would any lens. You then insert this combination into the diagonal or eyepiece holder the same as you would any eyepiece. You are not actually using the eye piece itself, in this fashion, your scope acts as the lens. You will have to adjust your focus as it is different than using an eyepiece. Try to achieve focus without the barlow first as you will have to adjust focus again with the barlow installed. If you are still having difficulty with focus, try removing the diagonal to get the setup a little closer to the scope. I use an SCT, however, I have tried a Newtonian and had difficulty with focus as well. Good luck.

[padiggle]

Thanks for the quick reply Joe.

So what your saying is I dont need another lens in between the camera and the telescope. I assumed I would because you cant see anything without an eyepiece.

Where does the magnification of the image come from?

cheers

Paul

[SteveInNZ]

Joes description is good. Using the T-adapter is called prime focus photography and uses the telescope in just the same way as a camera lens. So in your case, you have a 900mm f/6.9 'lens' on your camera. Without an eyepiece you see the same as if you look into the end of a camera lens.

The problem is that in order to reach focus with your camera, you need to wind the focus in further than the telescope focuser usually allows. If you focus so that it's sharp looking through an eyepiece, it will need to be about 40-50mm further in when you put the camera at prime focus. It's a very common issue with Newtonian telescopes and people will often modify them by moving the mirror up in the tube.
Using the Barlow may or may not help. Focus the telescope looking through an eyepiece and then put the Barlow in and note whether you have to move the focuser in or out to get focus again. If you have to move it out, then the Barlow will help in getting prime focus. Maybe it will be enough. Maybe not.

[padiggle]

Thanks Steve,

That probably explains why I couldnt get focus. I will have to wait for a clear night when the moon is out to try it.
I dont like the idea of moving the mirror. I imagine it would be difficult to line back up again.
I have noticed that if I disassemble the T adapter, I can connect the ring directly to the telescope screw and gain about 3cm.

Love your signature by the way.

[Nighthound]

If you do not have enough focuser travel to focus with your DSLR you've encountered a VERY common issue when using a factory Newtonian for imaging. If your telescope was larger in diameter I would only choose to move the primary mirror forward in the optical tube as a last ditch effort. An alternative is to purchase a low profile focuser but the problem with that is twofold. First a new focuser can cost more than the telescope itself. Secondly the diameter of your telescope tube will make it difficult if not impossible to find a low profile focuser that will work. So if you can't achieve focus with your current set up then moving the mirror may be your only option. There are adapters out there that are designed for afocal imaging (use of an eyepiece or barlow for additional magnification). Whether or not they will solve your issue is hard to say. Meade makes this one:
http://www.bhphotovideo.com/c/produc...nder_f_LX.html

I've tried this unit and didn't have great success with it but I was at a turning point in the hobby and was moving to deep sky work at the time so I didn't put much effort into it. Tim Kerr here on the forum can likely shed more light on this type of hardware, I seem to recall that he helped someone with a questions about this type of imaging.

A word of advice, if you plan to stay with this hobby. Be cautious about buying numerous hardware/accessory solutions. This can result in a lot of money spent in places that only fill your accessory cases and collect dust. If this hobby is a keeper then I'd suggest you think about apply funds to savings for a telescope and mount that will open the world of astrophotography up to you and bring years of enjoyment. These are words of experience, I have some hardware sitting around that I'm not even sure what it is.

Good luck, and clear skies.

[padiggle]

Thanks Steve (Knighthound), some good advice.

I managed to get out last night and found I couldn't get focus on the moon. By moving as much as I could from the camera adapter and the focuser, I was still about 1 or 2cm out. I also took the mirror out to see whether it would be possible to move it closer.Im thinking of attaching a block of wood as a temporary (and undoable) measure. I will keep the forum posted if I have any success.