focuser

ving (David) · #1 13-01-2005, 04:49 PM

when focusing while looking thru the scope it moves the image around, yes? a motor on the focuser stopt you clumsy hands from bumping things sooooo.....

seeing that my gso dob comes with a cheap focuser i have decided to see if i can motorise it.... I am no expert but worst case scenario is that i have to buy a new focuser...

any sugestions are welcome.

wish me luck. i have no idea how long this will take to complete

Starkler (Geoff) · #2 13-01-2005, 06:13 PM

The scope moves and wobbles because of the force you have to exert on the focuser knob just to turn it.

Have you tried stripping the focuser down, cleaning out the gunky glue grease and regreasing with something a bit more viscous? This helps a lot.

You can also adjust the tension with the four screws on the bottom plate under the focuser shaft. The tradeoff here is extra slop.

If all this doesnt produce satisfactory results, consider upgrading the focuser. I reckon motorising the stock gso dob focuser is pretty extreme .

mch62 (Mark) · #3 13-01-2005, 06:48 PM

Totally agree , invest in a descent focuser of the Crayford design.
It's going to cost a bit and a motorised one even more but you will appreciate a good focuser .
Trying to motorise a rack and pinion could be done and most probably has , but they still suffer the rock and roll in the draw tube, and the reduction is coarse as compared to a Crayford design.
I don't think there is much point in going motorised when you still have to be hands on to push the tube.

wavelandscott (Scott) · #4 13-01-2005, 07:24 PM

Sounds like an interesting project...I am interested in how it works but have no helpful suggestions to make...

It does remind me of an old old story I heard about a young man who was looking for advice on what business to start...he was told to look in the phone book at the listings, take the first thing he was interested in and find a way to automate it...

The new version of the same story is do the same phone book search but put a computer chip in it...

Good luck with the motor!

iceman (Mike) · #5 13-01-2005, 08:16 PM

I have to agree with Geoff and Mark, for the cheap GSO focusers it's just not worth it.

I really dislike the GSO focusers, especially when trying to focus with the webcam in the hole. Everytime you try to adjust focus the whole thing wobbles in the FOV (cause of the high power) and you can't even tell if you're bloody in focus.. and by the time i've finished adjusting it, the star has moved off the FOV of the chip!

As Geoff said, the trade off of stiff focussing or sloppiness in the barrel.

I can't wait to get my moonlite, it didn't arrive at my doorstep today - hopefully tomorrow..

ving (David) · #6 14-01-2005, 12:32 PM

dont think i want a sloppy barrel either...

I was thinking of setting up a stepper to do the focusing. jaycar sell them for $15. the whole thing shouldnt cost too much.

gbeal · #7 14-01-2005, 01:58 PM

I agree with the majority here, and suggest the "better focuser" route, BUT................
If the JayCar stepper doesn't pan out try a power screwdriver, I have seen/heard they work.

Vermin (Tom) · #8 14-01-2005, 02:09 PM

Quote:

Originally posted by iceman
...
I can't wait to get my moonlite, it didn't arrive at my doorstep today - hopefully tomorrow..

Did it get there today Mike?

ving (David) · #9 14-01-2005, 02:11 PM

I too agree about the better focuser, and if anyone wants to buy me one I'll be happy to take it

iceman (Mike) · #10 14-01-2005, 02:13 PM

Not sure yet V, my wife hasn't rang to say it's at the door.. hopefully she just hasn't looked yet.

You posted it on Tuesday didn't you? It should definitely be here by today..

Vermin (Tom) · #11 14-01-2005, 08:33 PM

Yep, lunchtime Tuesday.

iceman (Mike) · #12 14-01-2005, 09:50 PM

It didn't arrive

Cross my fingers for monday..

Maybe it went via boat across the bass strait, and then maybe out past the great australian byte, up the west coast, across the top end, and is heading down from cairns as we speak.

It should be here in Sydney on Monday.

ballaratdragons (Ken) · #13 14-01-2005, 09:58 PM

Hey Ice,

I saw it go past my place on the way up there.

If I had've known, I would have grabbed it for you and sent it tonight via this Forum for you.

Vermin (Tom) · #14 14-01-2005, 09:59 PM

Bugger, should definitely be there Monday.

iceman (Mike) · #15 17-01-2005, 09:09 AM

It arrived this morning V!

The spacer + install kit should be arriving from DBA later this week..

w00t!

Starkler (Geoff) · #16 17-01-2005, 12:24 PM

It took me less time to receive my focuser from the USA !
Ordered Friday and received the following wednesday

Mike you'll have to get hold of a small G clamp or similiar to flatten where the existing tube mount holes have been stretched up as the existing focuser has a hollow base. At least I had to.

Its crucial that the new focuser sits exactly square to the tube and of course you'll have to recollimate your scope.

Geoff

Vermin (Tom) · #17 17-01-2005, 06:18 PM

Glad to hear it finally arrived Mike!

V.

iceman (Mike) · #18 21-01-2005, 08:14 AM

Yesterday I received my moonlite install kit from DBA Astronomy. Top bloke, came nice and fast too.

I'll be installing it tonight/over the weekend, Last night I screwed the curved mounting plate and 1/2" spacer to the focuser itself. It looks nice and feels smooth and accurate on the fine focus knob. The course knob feels a little rough, and seems to move in jerks - is this normal?

Also, on both the course and fine knobs, there's a threaded hole on the grip - what is this for? Can you screw in a metal screw for example, to give you extra leverage and more fine and accurate control over focussing?

Geoff, how did you make sure it was exactly square to the OTA?

I knew I'd had to recollimate, and so I finally got myself a collimation tool - I got the cheshire from DBA at the same time as the install kit.

iceman (Mike) · #19 21-01-2005, 08:34 AM

Found some very interesting "myths" on this page.

Including that the focuser need not be exactly square..

Geoff or others, your thoughts on any of these myths?

Also, how far in or out should I rack the cheshire when collimating? All the way in? All the way out?

Thanks

Vermin (Tom) · #20 21-01-2005, 09:06 AM

I didn't find it jerky at all, but the coarse focus adjustment was stiff.

I think the grub screws on the sides of the knobs are to hold them on!

You could try giving the bearing surfaces (including the barrel) a wipe down with isopropyl and water (50/50) to remove any dust or dirt.

There are tension adjusting screws on Crayford type focusers, but have a chat to the guys at Moonlight about this first. I have not made any adjustments

My hassle free money back offer still stands if you are not completely satisfied.