Inward focus

[jambouk]

I bought a second hand old blue skywatcher reflector (fl 1200, apperture 254mm, f/4.7) over 6 months ago, and only used it for the first time last night and was really pleased with it; a friend helped me collimate it.

I tried to attach my dslr to it, but i just didn't have enough inward travel on the focus. It has an old grey stiff focuser on it, but do you think a new low profile focuser would give me a sharp image on the dslr sensor?

Thanks for any replies.

James

[brantuk]

Always a dodgy one with these James. A low profile focuser will help for sure - but you may still end up having to shift the primary a small way up the tube. You'd need some longer mirror bolts if you have to do that. I'm sure Graham could help there.

[jambouk]

Thanks kim. What i might do is measure roughly where rhe sensor needs to be to achieve focus, then calculate if the low profile thing will allow me to achieve that.

Do you remember when i got that scope kim, and stopped off at yours on the way home! And i've only just given it a go. I was blown away at how much light it was gathering, and with a three quarter moon too. Leigh and i both got a bit of retina burn when looking at the moon. I'm really pleased i've got it though and it's going to be a keeper! I'd just like to try and do some simple dalr imaging with it.

Jd

[brantuk]

Yes I do remember and was surprised you'd left it till now to try out. Looking at the moon is better with the tube cap left on and the smaller offset cap removed (if you have one). It reduces the light considerably and though it effectively stops the tube down a bit it make a bright moon more comfy to look at. Or you could slap in an lpr filter for similar effect.

[jambouk]

Looking at my measurements, I think either of these low profile focussers will do the trick. Is there much between them, other than FLO don't have one and the other is £50 more?

http://www.firstlightoptics.com/skywatcher-focusers/skywatcher-dual-speed-low-profile-1252-inch-crayford-focuser.html

http://www.firstlightoptics.com/baader-steeltrack-focusers/baader-steeltrack-nt-newtonians.html

Thanks

James

[knobby]

Is it worth trying a Barlow? I've the same (similar anyway) scope and with a Barlow in place I can just fit the moon in two half and then stitch in Photoshop for a nice high res. Image

[jambouk]

Yes, a Barlow would tease the focus out, but I also want a much smoother (and dual speed) focuser too as this is rough and ready (more rough than ready!).

But good point, I'd forgotten that the Barlow would help. I don't have a 2" Barlow (at present), as my dslr adapters are 2" at present.

I'm just excited to get that scope out again.

James