should this reach focus?

[toc (Tim)]

Hi all - been a while

I have a question regarding my Meade 12 inch ACF scope - Im using a Bintel crawford focuser:

http://www.bintel.com.au/Accessories...oductview.aspx

With a mirror diagonal in place, I cannot reach focus with my DSLR. Is that normal? i would have thought that there would have been more than enough focus throw to get there...

Oh, Ive made sure that the mirror lock is not engaged

btw, it works without the diagonal installed, but it's a pain in the butt to use.

[gasman1 (Gary A Sitton)]

This is probably normal for a DSLR in prime focus because of the added ~20mm mirror box depth. The diagonal is typically removed for a DSLR, but a 2X Barlow will probably make this work for you. Another solution is using a MIL camera like my Sony which adds ~20mm of back focus for you.

[tlgerdes (Trevor)]

Remove the diagonal.

[gasman1 (Gary A Sitton)]

Another advantage to the low profile MIL cameras over the SLR cameras is their substantially reduced weight. Also you can focus them without a viewfinder using the LCD screen and a magnifying loop or nothing if you eyes are that good. A DSLR on a CST without a diagonal could be really awkward to focus.

[tlgerdes (Trevor)]

As Gary says the camera focal plane is about 50mm further away than an eyepiece one you add a the 2" nose piece and Canon adapter, hence you need the camera 50mm closer to the scope. That is why you cant use the diagonal. You shouldnt need a barlow.

[toc (Tim)]

Thanks guys - the reason I ask is that the guys from Bintel seemed to think that my Meade SCT should have more than enough focus travel to make it work, even with the diagonal. I was concerned that something might be wrong with the focusing mechanism, which appears a bit dodgy anyway.