Automatic/motor focusers

[Helen]

I've decided that my luxury for £250 is going to be an electronic focuser. Its just which one that I now have to decide. I've been doing some research and come up with the following options:

1- JMI electronic focuser http://www.rothervalleyoptics.co.uk/detail.php?id=950 - well within budget, will work with fastar, can have a shoestring adapter added to allow computer control, but no encoders so no easy repeatability, and still has potential for mirror slop, once attached no manual focussing

2- JMI cassegrain motorised http://www.rothervalleyoptics.co.uk/detail.php?id=950 - a bit over budget, won't work with fastar, but will work on refractors, again can add shoestring adapter, but no endcoders, no mirror slop, can be used manually or electronically

3- Moonlight Crayford with motor - £299 from Ian King - a bit over budget, but its a moonlight , only electronic (so does it matter its a moonlight :?) and add lots more money for computer control... no mirror slop, but no fastar

Import options:

4 - Robofocus - $457 (plus import costs), so about on budget, works with current focuser, gives computer control and automatic/remote focussing, can use manually if really want too (but need to recalibrate I understand), but not very pretty

5- Starizona Feathertouch with micro autofocus - http://starizona.com/acb/MicroTouch-Autofocuser-Wired-Version-P2715C745.aspx $540 plus shipping, import costs (that is if they'll post) - over budget, but looks great as it does it all

Anybody used any of these and care to comment?

Thanks

Helen

[Milamber]

If I were you Helen, I'd stick with an Artemis Focuser... full PC control over USB or there's a handpad - and it's got temperature compensation too. Scarily cheap... and I'm not biased at all.

http://www.artemisccd.co.uk/focuser.htm

Arthur

[coatesg]

Have the Artemis system myself - works great!

Either way, I would advise a stepper based system which allows for PC control. If you will use software like MaxFocus, it needs this kinds of controllable focuser (the standard JMI doesn't I don't believe), and it's so much quicker and accurate than focusing with a motor but pressing the buttons yourself!

Cheers,

[GingerNut]

If I were you Helen, I'd stick with an Artemis Focuser... full PC control over USB or there's a handpad - and it's got temperature compensation too. Scarily cheap... and I'm not biased at all.

http://www.artemisccd.co.uk/focuser.htm

Arthur

Oooooooooooooooeeeeeeeeeeeeeeeeeeerrrrrrrrrrrrrrrrrrrr...................I think I better egt one of these 8)

Yours Roy

[SteveL]

http://www.artemisccd.co.uk/focuser.htm

Arthur

ooo!

"Ambermile Engineering are able to provide a custom adaptor service for other shaft types.".... Really Really need to measure my focus spindle....

Trying to work out how the stabilising "bar" would fit onto the back of a C8 OTA... any ideas?

[Milamber]

Umm - it's only designed to fit onto focusers Steve, not SCT's ... sorry

Arthur

[SteveL]

mmm.... would it work with the feathertouch attached to the back of the SCT?

Just wondering if it would, and the stablising bar attached to the chrome bar under the VB (mine looks like the one on the left)... or should I give up this idea right now

[Milamber]

I donlt think so Steve - you'd need a completely different sort of bracket up from the three screws around the base of the focus knob.

Arthur

[coatesg]

Plus, you wouldn't need the focuser gearbox attached to the 1:10 reducer - the 1:125 gearbox on the Artemis provides small enough movements on it's own. You'd need to attach it directly to the focuser shaft really - I have my gearbox(es) attached directly to focuser shafts on the Moonlite CR1 (newt) and to the shaft on the refractors.

[Helen]

I have a C8 like Steve - so the Artemis is out..... So of the other options, stepper looks a must.. anyone used Robofocus? the feathertouch unit seems really cool though (and they say they'll ship for $55 )

Helen

[Milamber]

Hmm - looks like I need to work on this a little. I do have an LX200 10" in the workshop waiting to be cleaned... anyone know if the three screw holes are the same on the Meades and Celestrons?

Arthur

PS - in our defense, we assumed that those getting serious about imaging and using SCT's would ad an aftermarket crayford and lock the mirror. No, we really did...

[Helen]

Thanks Arthur. Don't know if the screw holes are the same... The mirror on the Celestron doesn't lock, and my concern on a standard crayford is that of clearance, and the fact it won't work with Fastar where the only focusing mechanism is the mirror and at f1.9 focus is particularly challenging!

Helen

[SteveL]

I`ve been looking at "toys" to buy, maybe holding off until my California trip in Feb/March next year, but I`ve had a few issues..

SCT -> (Optional Focal Reducer -> ) Crayford Type Focuser -> Filter Wheel or Drawer -> T-Thread to CCD.

Imaging distance is getting a bit long, and on the smaller C8 OTA only having 1.8" of internal aperture on the VB, the vignetting on large format CCDs gets worse with distance, especially with the FR attached. Weight/Balance isnt so much of an issue, I just dont want to end up buying something that can focus an image train that has more vignetting than I usually have. Also, being fork mounted means that with the FR and a long imaging distance eliminates anything close to Polaris as the CCD hits the mount.

Yes, Yes, get a GEM...

[GingerNut]

PS - in our defense, we assumed that those getting serious about imaging and using SCT's would ad an aftermarket crayford and lock the mirror. No, we really did...

Hi Arthur,

That's what I did, except on the LX90 you can't lock the mirror, but the crayford is great.............do coarse focus with the SCT, then fine focus with the crayford

BTW, on you recomendation, I've just bought one of the focusers from Steve

Yours Roy