DSLR focus through telescope

[D Wright]

I got the chance albeit very briefly last night to try my new DSLR at prime focus on the scope and as I expected with it being a newtonian there was not enough in focus. It was nearly there but not quite. I also noticed my crosshair EP would not focus either. I know this a common problem when imaging with Newts. Can anyone tell me an easy way to remedy this. I am guessing that with the way the scope is made I will have to cut a piece off the end of the tube and this should move the focal plane away from the tube. Any help with this would be greatly appreciated.

[MarkyD]

Have you tried a Barlow?

[D Wright]

Its a 2" focuser so I bought a 2" T adapter and I only have a 1.25" barlow. Also with the focal length of 1200mm I think it may be to much magnification. I might try a 2" barlow and see what its like. I was just thinking that to quickly cut 20mm or so off the end of the tube would cost nothing. It would leave me with plenty of focus for eyepieces aswell.

[DHEB]

May be the solution is to try a low profile focuser?  I would suggest that before making any modifications in your scope you are absolutely sure that what you are planning to do is going to have the desired impact.

[D Wright]

I already have a Revelation dual speed focuser which is low profile. I think that is why I am so close to focus.

[xtreemchaos]

you could try winding your prime mirror adjustment out a bit to move the mirror nearer the focuser every mm you adjust is x2 just dont go to far and wined the bolts right out. charl.

[D Wright]

I have modified the mirror cell to have spring loaded adjusters and I tried winding them out but I only have a few mm of travel before the springs lose tension.

[xtreemchaos]

a few mm might be all you need, i had the same problem with my f5 200p when using a CC, i only had to move the mirror 3 mm up the tube witch gave 6mm more inwards focus travel, you might need to get longer springs but its a lot easyer than chopping the tube. charl.  ps you could allways put some washers at the base of the spings if theres room.

[D Wright]

I am going to have a play with the mirror cell to see if I can move the mirror forward. If all else fails I will take 10mm off the tube length.

[Jokehoba]

I had the same problems with my SW130P. I opted for shortening the tube as I didn't intend using it for visual in future. I shortened mine by about 20mm, which was fine until I bought a coma corrector, and had to cut a further 10mm off to achieve focus!

John