Focuser idea.

[Kaptain Klevtsov]

Today it occured to me that a slow 'scope is easier to focus because of the bigger range of focus travel where the image is in focus (depth of focus), so it seems entirely reasonable to have the focuser on the slow end of the Barlow lens if you are using one. Is there a device out there which adds a focuser between the barlow lens and the EP / camera? This ought to make focusing much easier when trying to zap a planet or whatever, and could help if you are blessed with a notchy R&P focuser.

Captain Chaos

[Astroman]

Hmmm, I haven't heard of one, but it sounds like a great project!

[geppetto]

Sounds like a plan to me..

Wonder if you could stick one of those Borg helical jobbies onto the

eye end of a barlow

[Kaptain Klevtsov]

Do you know if the camera, sorry eyepiece, end rotates as you turn the focuser with the Borg doodah Phil? Or anybody else?

Been scratching my head looking at a slide copier SLR attachment just now. That has a ring which turns to vary the magnification by moving a lens system back and forth in a tube. The tube stays where it is, just the lens bit slides, so that kind of thing would work well. I think that moving the Barlow lens within the barlow assembly would do the job admirably, and the travel needn't be very much at all. It's got to need batteries though, just to make it worth playing with.

Captain Chaos

[geppetto]

rotates as you turn the focuser with the Borg doodah Phil

CC if I remember right, they come in two types.

One rotates (cheaper) and one that doesn't (dearer)

Edit: found the link

http://sciencecenter.net/hutech/borg/focuser.htm

[geppetto]

Seems that these focusers are threaded at the front and they do an adaptor

to screw on the end which then means the whole thing can push in like an eyepice.

Ideal for sticking into the barlow...

Food for thought

[Kaptain Klevtsov]

Good find Phil. Looks like this one might do it, unless its too long. http://sciencecenter.net/hutech/borg/parts/html/7315.htm

A bargain at $90 (£140 at a guess) plus the adapter bit.

Captain Chaos

[GordonCopestake]

Only 10mm of travel though

[Kaptain Klevtsov]

Just found out that SCS Astro don't sell them at £45. They appear to, according to the Google results, but their website is missing. So is the Borg UK one. Might be importing time then.

Captain Chaos

[FLO]

... a slow 'scope is easier to focus because of the bigger range of focus travel where the image is in focus (depth of focus)

Yes, but the fast scope has the effect of 'snapping' into focus in a nice definitive way

[The Warthog]

The thing you are describing, CC is a variable Barlow. If you put your ep further away from the Barlow lens, it increases the magnification.