GSO 10:1 Crayford on a Skywatcher 8" DOB

[Tandum]

Rang Andrews yesterday arvo and the focuser arrived today. I was expecting it towards the end of the week, cheers to Andrews.

I have already pulled it apart and greesed it up as described here :-http://www.backyardvoyager.com/gsofocuser1.html (http://http://www.backyardvoyager.com/gsofocuser1.html)

I removed the old focuser and noticed I'll need to enlarge the old mounting screw holes a little as the GSO mounting bracket holes don't line up exactly with the existing ones in the tube and either get longer screws or counter sink the GSO holes a bit to get it installed as the existing screws are too short.

But the old focuser has a flange that fits snugly into the draw tube hole while this one has no such flange and can be moved around a bit in the mounting position. So there is a chance it won't end up in exactly the same position as the old one.

Will I need to colliminate the scope once I finally swap the focuser or does collimiation purely deal with mirror alignment :shrug:

[danielsun]

What I did was put the cheshire collimation tool in the old focuser ,check that it is spot on then remove the old focuser and yes I had to drill bigger holes for the new 10;1 focuser because the new focuser diagonal hole spacings where slightly smaller. Then fit the new focuser with the collimation tool inside and slide it around until it is aligned then tighten up the bolts. and yes I had to fit new screws but I also used flat washers and spring washers to mount the 10;1 because the new drilled holes had to be large enough for me to be able to slide the focuser around to reach the collimation point.

Hope this helps.

Cheers Daniel.

[Tandum]

Thanks Daniel,
But of course I don't own a collimation tool, looks like I need one :P

[danielsun]

Yes, you definitely need a collimation tool.
Also make sure that before you drill your new holes in your tube that you mark the position of your new focuser along the sides or the holes with a pen in the collimated position.

[Tandum]

I should have ordered one with the focuser and the other stuff they sent up here. At least it arrives fast ;)