In focus and low profile focusers

[TheThing]

I have a SW 200p newt which suffers from the usual problem of not having enough in focus when attaching a DSLR to bring the image into focus.

I have managed to reduce the focuser size a little and it currently measures 90mm from the top of the focuser plate to the top of the 1.25" tube, when wound all the way in.

I'm thinking of replacing it with something like the Revelation . I have been told by kindly fellow SGLers that this measures 75mm from the top of the baseplate to the top of the focuser tube.

My question is, will the extra 15mm be enough for me to find focus? Is there some formula for working this out or can someone tell from experience at all please?

[TheThing]

Think this might be better here.

[Sparrow]

Hi The Thing - with a Celestron 8" Newt I had the same problem which I intially solved by a bit of butchering of the T ring and the scopes 2" adaptor plus some strong glue - it work but I was uneasy about how secure it was.

I've now fitted a low profile focuser which gives plenty of focus travel for my DSLR (Canon EOS1000D)

First Light Optics - Skywatcher Dual-Speed Low Profile 1.25/2 inch Crayford Focuser

Dearer than the one you showed but this should definately let you achieve focus and I'm concerned that the one you show would not solve your problem - I did have to do a bit of DIY to fit it as it's a Skywatcher and my scope is a Celestron (new mount holes had to be drilled) but not a difficult job. If in doubt speak to First Light Optics - they'r every helpful.

Regards

John

[Moonshane]

another option others have used is to move the primary up the tube a little. you'd need to do some measurements to ensure you get it right but then you could use your existing focuser and just have to drill three holes?

[AndyH]

If your existing focuser is fine, then I'd seriously think of a mirror move too.

Could be done two ways. Physically moving the mirror cell up the tube or getting a set of longer screws n springs, to push the mirror up inside the cell.

Andy.

[markarian]

Is the problem that you have to use the 2" eyepiece adapter to attach the camera? If so then changing the ring at the top of the focuser may help as that removes the need.

2 options that I know of:

2' adapter with brass compression ring for Skywatcher Newtonians

Skywatcher kurzbauender 2' Adapter für Crayford Auszüge

I did it by having a friend shave the adapter already on the focusser - before I knew about these.

Mark

[TheThing]

I don't really want to move the mirror up as it is fime where it is for visual and webcam imaging.

Just wondered if the replacement focuser being 15mm lower will allow a DSLR to come into focus?

[AndyH]

Only other I can think of then, is get hold of a piece of tube or something cut to the replacement focusers size, take off the existing focuser and try to focus with the dslr held to the tube. Then you'd know for sure that the new focuser would work.

:icon_scratch:Andy