focuser

[ving]

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]

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]

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]

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]

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! :bashcomp: :D

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.. :prey:

[ving]

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]

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]

Did it get there today Mike?

[ving]

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

[iceman]

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.. :prey:

[Vermin]

Yep, lunchtime Tuesday.

[iceman]

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]

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]

Bugger, should definitely be there Monday.

[iceman]

It arrived this morning V!

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

w00t!

[Starkler]

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]

Glad to hear it finally arrived Mike!

V.

[iceman]

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]

Found some very interesting "myths" on this page (http://web.telia.com/~u41105032/myths/myths.htm).

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]

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.

[iceman]

I'm sure that won't be necessary - it feels great on the fine focus side. I think the course is just stiff, as you said.

[iceman]

Installed and re-collimated last night..

Here's the first pic, more in a few days when i've done the writeup :P

First impressions, it's GREAT! Used it for a quick peek at Saturn last night (around 10:45pm) and it was great using the fine-focus to get the sharpness had been lacking with the old focuser.. it was really easy just to go a bit each way until it was spot on.. with the old focuser I was always going too far one way or the other and the scope was shaking about while I was focusing.

On an unrelated note though, I think I need to flock and/or paint flat black on parts of the inside of my tube.. I noticed quite a glare glowing from around Saturn last night, was really lacking in contrast. It didn't help that the 75% full moon was nearby, but I really think flocking will help, especially now I have 4 shiny metal screws sticking inside the tube :)

I'll start a new thread about flocking on another day and Geoff + others can help me with that :)

Anyway here's the pic. I'm really happy with it, installation was quite straightforward and there were no dramas :D

[iceman]

Oh and I used the 1.25" adapter from my old GSO focuser, rather than the one that came with the moonlite, simply because it's better. The moonlite has just 1 rough screw, no compression rings.. the GSO adapter has a nice easy to move screw with compression rings inside to protect the eyepieces and hold them in place better.

[Starkler]

The focuser looks very pretty Mike :)

Things you can do to reduce the glare include flocking and also fitting a focuser baffle and/or a tube extension.

They will help to reduce unwanted off-axis light arriving at the focal plane.

For flocking material have a look in Bunnings in the wallpaper section. I used adhesive black velvet and I think it cost $10 a metre when I got it.

[beren]

That looks great Ice , i know when i replaced my focuser with a better cryford type life was a lot easier . Is that a angle gauge resting on the back , looks interesting.

[iceman]

Thanks guys, yeh it's heaps smoother, I love it.

Sure is, I bought it last weekend when I did my bunch of other mods (finder, handles, knobs). It's called an "angle finder" or something, bought it for $10 from Mitre 10, and it simply magnets onto the OTA.

The magnet in the bottom is quite strong, snaps onto the OTA and stays on even when past vertical. It tells me the altitude i'm tilted at, which will be handy for the MSC's when I get around to doing the azimuth ones.

[beren]

Cool , i had similar knobs on my reflector to very handy indeed, nice work . Ill have to have a look for one as well [gauge]

[ving]

whats attached to you finder there Mr Ice?

[wavelandscott]

That sure is pretty!

[Vermin]

Glad you're happy with it Mike, you did a top job of the installation, it looks like great.

[iceman]

Vingmeister, check here (http://www.iceinspace.com/?finder) and ye shall find.

Thanks guys

[ving]

Why thankyou kind sir. that was most enlightening.


hehe

get it? enlightening! :P

[astrodave]

Friday night I'm out there playing with the moon and Saturn and having a wonderful time when one of the focuser knobs comes off in my hand!! ... Not happy. Had to pack up and sneek into bed.

Now my scope's second hand and the previous owner had fitted one of the cheap electric motor focuser kits. It was great to sit at the laptop screen and focus, but it wasn't truely central and so the torque wasn't consistent.

So I'm lying in bed thinking how can I improve this thing... and my mind turns to stepper motors..

Then on Sat I read this thread for the first time. Now I've got to agree that a nice new crayford focuser would be lovely (I spent some time wishing at the DBA and JMI websites) , but if you cannot afford it (particular motor drive) then ... I'm with Ving. I'm also lucky in that my R&P focuser tube is quite sturdy and could be worth saving.

I built a "barn door" about two years back and I drove it with a stepper motor ratted out of an old 5.25" floppy drive. I build the circuit to crystal drive the stepper and it would be easy enough to do something similiar with a focuser project. I've got another of those floppy drives and so I'm thinking along the lines of three switches : up, down push switchs and a fast-slow toggle. The gearing is such that a direct drive would give me a 1 inch per rev on the stepper. The stepper is 100 steps per rev so not withstanding the slop of the R&P I'd have accuracy down to 1/100th of an inch. Should be good enough don't you think? Two speeds: say 4 steps per second and 16 times that at 64 steps a second. Now it wouldn't be too much trouble to add a counter display to add and subtract these steps and that gives a digital readout of the focuser position - that would be nice!

My electronics isn't wonderful, but I should be able to come up with a circuit to do this. Off the top of my head it looks like 6 ICs(time base, divider, invertor, gates, flip-flips, darlington drivers) for the Stepper driver, plus a bunch for the counter and 7-segment display. How's your electronics Ving could you come up with a more optimal way of doing this?

[iceman]

Sounds like a nice idea.. though I think Ving was more along the lines of a mouse running around on a ferris wheel to drive it :D

[ving]

hey, the mouse would work!! :P

I am not electronically minded at all Dave. but my brother is. I havent had a chance to run the idea past him yet. this might take a while

[astrodave]

Another project to add to the list for me. I don't usually get around to these very quickly - (especially not now with the wife in a "we've got to redecorate mood") - but I do want the scope back in action...

[Dave47tuc]

Like the focuser Mike:D
Hope it gives you many observing nights with snap focus images
(seeing on your side:P )

Best.


:astron:

[Vermin]

No point re-inventing the wheel, there's a cheap stepper driver kit here:

http://oatleyelectronics.com/kits/k022.html

[Starkler]

Did you see my new focuser (http://www.iceinspace.com/forum/showthread.php?s=&postid=4156#post4156) Ving ?

$125US shipped and its a beaut.

[ving]

still cheaper to build my stepper powered focusing machine thingy :p

thnx anyhow :)

[astrodave]

Thanks Ving. The kit's only $18 and is based around a UCN5804 stepper driver. Such a driver would simplefy my circuit by 2 ICs. Now Farnell sell the 5804 for $24 - so it would be cheaper to buy the kit and use it for parts. The kit won't provide dual speed, but it does have variable speed so it maybe it will do. Food for thought - thanks

[ving]

hey this has been done before... try these links

http://www.apex.net.au/~twalker/focus.html
and
http://www.pk3.org/Astro/index.htm?astrophoto_ef.htm

looks easy :)

[astrodave]

Yeah those projects are all very well and good for what they are doing. I already had such an electric motor based focuser - when the wheels fell off... What fires me up about a stepper motor based solution is the digital readout. I can get to know at what number each of my eyepieces are in focus and then only have to fine tune for the (small) slop that exists in my rack and pinion. I have hopes that the foscusing would be good enough for visual observing...

In your searching Ving have you come across any stepper motor based solutions?

[ving]

not yet....

i'll keep looking tho

[ving]

you are aware of this arent you?
http://www.homedome.com/robofoc1.htm

[ving]

and check out motofocus at this site:
http://www.jimsmobile.com/

[astrodave]

I hadn't done any R&D on it so thanks for the links ving. I was aware of jims mobile (it's where I bought the mounting hardware for the rotary encoders for my DSC). robo focus ($us395) is again out of my immediate price range though.