:o( Focusing issues using Canon 40D and Skywatcher 130em

[majik_moo]

Hiya,

We tried (finally) to shoot some images of the moon tonight - but was hugely disappointed to find that once the camera was fitted to the t-mount and onto the telescope that there wasn't enough range in the focusing. Absolutely no way could I get the image even remotely sharp.

I bought a T-Mount to fit Canon EOS - it seems to attach to the telescope fine. I'm somewhat confused. I've done a quick search to see if there are any other t-mounts that I could have got, but can't find any.

Is anyone able to advise me please? I feel a bit deflated

[Cornelius Varley]

The problem is that you cannot get enough imwards focus when using a camera and t adapter. There are two methods to get round the problem. The first involves moving the primary mirror up the tube so pushing the focus point outwards sufficiently so that you can focus the camera. Sometimes it can be enough to just screw in the colimation screws, lifting the mirror upwards a little. The other method uses a barlow lens which should move the focus point outwards so that the camera comes into focus. I should try the second method first as this seems to work for most people. There is also an advantage in using a barlow when photographing the moon. A 2x barlow with your telescope will give a moon image of about 12mm diameter on the sensor compared to image of about 6mm without.

Peter

[majik_moo]

Hi Peter - Thanks so much for your reply! Phew - glad it wasn't something I was doing wrong That makes a lot of sense...will check out the barlow lens option and report back

[majik_moo]

Which barlow lens would you recommend?

I've been looking at getting this..

Opticstar Adjustable Eyepiece Projection Kit

To use our existing eye pieces in. This is all getting a bit confuddling for me!!!

[Merlin66]

That equipment requires you to use an eyepiece as a projection lens and generally is only used for extreme magnification, like x5 plus.

I'd recommend a 1.25" x2 barlow to start with.. keep it simple, minimum hassles, maximum chance of success!

Ken

[majik_moo]

Hi Ken, Thanks for your reply. Yeah - want to start off easy. Not sure what I'm looking at with the barlow lenses though - I have one that came with the telescope but that wouldn't fit onto the adapter I have. Is there another adapter I would need to get or would I get a specific barlow made for fitting a camera?

[Merlin66]

Hmmm,

If you only have a T2 adaptor for the camera body, you'll also need a 1.25" to T thread adaptor.

Screw this into the T2 adaptor then slide the camera ( like an eyepiece) into the barlow....

Adaptors

( near the middle of the page)

Ken

[Cornelius Varley]

I am not sure what you mean by "wouldn't fit onto the adapter I have" I assume you mean the t -ring doesn't fit onto the barlow. If that is the case you will need one of these t adapter . Skywatcher also make a barlow with a t thread on the end which attaches directly to a t ring Skywatcher - Skywatcher Deluxe 2x Barlow

Peter

[majik_moo]

Ah-ha!! Suddenly it all makes sense!!

Fantastic - I will get myself one ordered - that you very much for helping me out

[majik_moo]

Hi Peter - Yes, that's what I meant. The T-ring adapter would not fit to the barlow...but I see there is a T-mount that I also need I will get there in the end!!

Thanks again

[majik_moo]

Ordered the adapter this morning - can't wait to get it and get back out

Thanks again for your help!!