Focuser Bit Help

[TopHouse]

OK, I don't know what the bits are called but you'll know what I mean.

I want a slight amount of extra 'wind in' on my focuser which is one of the Crayfords on an explorer 200.

Now on the focuser itself, the actual metal tube that moves in and out when you focus, on top of that is a thread and a black ring screws onto that which has what is in effect a female dovetail, another piece of tube which is the 2" eyepiece holder bit has a male dovetail and it fixes to the 'ring' and tightens with thumbscrews.

The bit that is the 2" eyepiece holder with male dovetail, is one available that's just a little shorter, say 10mm or so?

[John]

Is it the bit thats marked 2" Eyepiece Adapter in this photo that needs to be shorter ?:

http://apmamerica.com/images/Skywatcher%202%20inch%20crayford%20focuser.jpg

[TopHouse]

It is indeedy John, by only a small bit too, as i said, 10mm would be enough.

[Mick UK]

Not sure im missing the point here, but cant you just remove the adaptor and wind the focuser "out"a little, to achieve focus?

[TopHouse]

no, it's not an adapter as such, it's the actual 2" eyepiece holder, even though they call it an adapter, it's the fitting that holds the eyepiece fitted to the focuser, ie if you remove it you just have a metal tube with a thread on it

[Mick UK]

looking at the pic in the link, the adaptor can be removed leaving the black fitting connected to the focuser tube, this has 2 grub screws that would secure the eyepiece/camera to the focuser shaft...thats what i have to do on my skywatcher 250pds with its 2" crayford focuser.

[TopHouse]

it might work but it's not a straight tube inside the black fitting, it's like a female dovetail around the perimeter of the inside.

[Mick UK]

Heres some pics ive just took of mine for you, which i think your should be the same?

[TopHouse]

Could work, would have to try, could really use only the 10mm off though as i have just one eyepiece that literally is 'just' out and needs the tiniest bit of inward travel, knowing my luck, if i did the above, all the others would need extra outward! ;(

[Mick UK]

with that 2" "adaptor" fitted when using my Canon350d, i too also needed that extra 10mm inward travel, once i took the 2" adaptor off and put the camera with its bayonet fiiting and small camera T piece, i have about 15mm of inward travel "spare" once i reach focus.

[TopHouse]

I take it they don't make shorter ones of the 'adapter' then? beats me why they make the black ring and adapter as 2 parts, why not just make a 2" and a 1.25 inch that screws straight to the focuser tube instead of the collar in between.

[John]

I take it they don't make shorter ones of the 'adapter' then? beats me why they make the black ring and adapter as 2 parts, why not just make a 2" and a 1.25 inch that screws straight to the focuser tube instead of the collar in between.

Thats a good point. For some reason Skywatcher newtonians always go for this approach wheras their refractors just have a 2" adaptor straight on the end of the draw tube. Really don't know why this is

[TopHouse]

to me it just introduces another possible offset in focuser center accuracy, I'd much rather see adapters available in different lengths with a thread on one end that simply screws onto the focus tube where the ring/collar is screwed on.