Replacement focuser for Skywatcher 250 Newtonian

[Alnitak]

I've just received a 20710 Skywatcher low-profile dual-speed crayford focuser, with the intent of replacing the rack and pinion focuser that the scope originally came with.

However the new unit doesn't appear to anything like a drop-in replacement.   Although the mounting holes are in the right place, the base of the new focuser doesn't fit even remotely flush to the body of the telescope, leaving lots of gaps for light to enter through the side of the telescope tube.

Also (and bizarrely) two of the mounting holes in the base are obscured so much by the crayford mechanism that it appears impossible to even fit it without disassembling the focuser itself.

So:

1.  Am I just doing it wrong?

2.  If not, which focuser would work as a direct drop in replacement?

cheers,

Ray

[Tinker1947]

The Moonlite CR2 is a drop in replacement, not low profile though if this is important....

http://www.firstlightoptics.com/moonlite-focusers/moonlite-cr-dual-rate-tri-knob-crayford-focuser-for-newtonians.html

Installation kit, this allow the focuser to fit all Newts in the kit range..

http://www.firstlightoptics.com/moonlite-focusers/moonlite-installation-kit-for-newtonian-focusers.html

Installed in a 250P-DS

[Alnitak]

The Moonlite CR2 is a drop in replacement, not low profile though if this is important....

Yeah, I'm afraid that's somewhat outside my budget...  thanks, anyway!

[lensman57]

I've just received a 20710 Skywatcher low-profile dual-speed crayford focuser, with the intent of replacing the rack and pinion focuser that the scope originally came with.

However the new unit doesn't appear to anything like a drop-in replacement.   Although the mounting holes are in the right place, the base of the new focuser doesn't fit even remotely flush to the body of the telescope, leaving lots of gaps for light to enter through the side of the telescope tube.

Also (and bizarrely) two of the mounting holes in the base are obscured so much by the crayford mechanism that it appears impossible to even fit it without disassembling the focuser itself.

So:

1.  Am I just doing it wrong?

2.  If not, which focuser would work as a direct drop in replacement?

cheers,

Ray

Focusers are all standard items, more or less,  it is the base that you need to source and it has to be a match to the outside diameter of the scope. You may have a look at the TS site to see if they have anything useful but I believe their focusers are mostly designed with Meade/GSO scopes in mind. Also check out the focuser bases on the 365 Astronomy site.

A.G

[Alnitak]

Focusers are all standard items, more or less,  it is the base that you need to source and it has to be a match to the outside diameter of the scope. You may have a look at the TS site to see if they have anything useful but I believe their focusers are mostly designed with Meade/GSO scopes in mind. Also check out the focuser bases on the 365 Astronomy site.

Ironically it's 365 that I sourced the Skywatcher focuser from, and I did briefly discuss this with Zoltan yesterday.    He didn't suggest his bases, and looking at them just now they're not the right size or hole spacing for a Skywatcher 250.

I've figured out how to remove the focuser from the supplied base so that I can actually attach that base to the tube and then reattach the focuser to the base, but I don't like the way the entire assembly would then sit above the tube potentially letting light in.