10:1 focuser for 130mm Newtonian??

[Screwdriverone]

Hi All,

Does anyone know of a supplier of 10:1 microfocusers for 130mm Newts?

The only ones I can find are for 8" or bigger newts/dobs and therefore would need to be packed up in a new drilled out hole in my tube to make it fit. Not something I really want to do.

Is there any easier way to get finer focus control on my scope than the tractor steering I have now?? without using a laptop?

I hope someone has an answer for this one.:help:

Chris

[omnivorr]

don't hold much hope Chris.. when I ordered my scopes they didnt have the 6" with 10:1 in stock.. so I asked could I get it later.."err dunno" (incredulity in voice)
"well.." I asked, "can I fit the aftermarket one you sell for 8"ers?" .."er I spose so, ??" altho the curves under the base differ, fitting to a smaller scope than intended for it ,ie an 8" onto a 6" scope might be possible with a spacer/gasket?? we're in a similar boat :P Russ

[JethroB76]

Is your current focuser a crayford or R&P?

You could use an electric motor focuser, I think Bintel sell a Skywatcher one - IIRC Ken came up with a mod using part of an old in-line fuel filter as an adaptor for use on crayfords - there are several old thread about this. These units just use a small hand controller box.

If you want the 10:1 bizo, someone on here recently posted that bintel will sell you the actual 10:1 mechanism which you can just fit to your existing GSO style focuser.

[Screwdriverone]

Hi Guys,

Yes its a Rack and Pinion one at the moment. I may have to look at the electric kit. its only $95 and is for a Skywatcher as you said Jethro! I do want the 10:1 biso as the feel of that is much better than the big chunky R&P wheel.

Time to go searching through the archives.

Thanks

[gbeal]

Get the Bintel one, complete with the base designed for the 8" or so tube.
Make a thin adapter up, to fill the gap in the two radii (is that a word?).
There are a few ways to do this, so if you get stuck, ask.
Gary

[Kokatha man]

Hi Chris - the 10:1 crayford style would be the logical way to go if procurable; but with the rack & pinion on an SW 150mm achro not giving me that option, I purchased an electric focusser for it at just under $100.

This makes a profound difference to the focussing operation of the scope - certainly superior imho to the manual 10:1 crayford on my dob; though you can of course convert those to electric too!

At "finest" rate of adjustment the ability to focus to an absolutely razor-like degree is great; with the added bonus of it being hands-off, avoiding scope vibrations.

If interested in going this direction, just check first to ascertain if the SW r&p's are the same for reflectors as refractors.

Cheers, Darryl.

[Screwdriverone]

Hi Jethro & Darryl,

Great MINDS! Thanks for the suggestion of the Electric Focuser!

I bought (well, sort of, the missus and the mother in law bought me these for my birthday later in the month) the Skywatcher Electric Focuser today for $95 and fitted it this afternoon. You were right, the degree of focus adjustment and the fact that its hands off the scope is FANTASTIC. I wasnt sure if the electric motor could adjust finely enough compared to a 10:1, but its really very good at what what it does and it costs less than a 10:1 focuser!

Basically I had to unscrew the left focus knob from the shaft after scraping off the locking glue inside the knob and slide the electric one on. Both screw holes didnt line up, but its solid enough with just one holding it down. I also had to mod the mount bar though as the R&P axle on my scope was a little thin so all I did was push on a cut down plastic wall plug for masonry over the axle to beef up its diameter and keep the motor on axis with the shaft.

I also bought a Cheshire collimator while I was at it as I suspected my scope was out (and it was :mad2:). This caused me a few headaches, as well as a chipped secondary mirror on the outside when I turned the allen key screws in too far and "grind, crunch, tinkle" came out of the scope before I could stop! - OUCH. Its not so bad though, only just on the secondary's edge and from what I can see, doesnt affect the visual field. Lesson learnt!

So, I figured out how to do it the correct way and lined it all up in the circles and the scope seems to be much better. I had thought about fine tuning it outside, but after the mirror mishap inside, outside in the dark just didnt seem like a good idea.

I just finished testing the collimation and the electric focuser outside and WOW! :eyepop: what a difference!
The 10mm WA eyepiece no longer looks like its bleeding stars and the 12.5mm ED is beeeeewwwwwdiful!

I know I am a gadget freak but considering I couldn't realistically and painlessly change my R&P focuser to a 10:1 crayford without a lot of stuffing around, a metal shop and some luck, this electric focus motor is going to impress me for a long time yet! I suppose I am going to have to start a separate thread in which to keep all of my bits I keep adding to my signature! :doh:

I can't get over how easy it is now to get really fine focus by setting the speed to slowest and pulsing the button. I was out there for an hour just being amazed at how clear everything is now! Really, really happy with the mod.

Collimation and gadgetry, what a difference it makes!

PS. I have added some pics of the electric focuser and the control box for those people who may be interested in what we are talking about.


Cheers

Chris

[erick]

Hey Chris

You are on a winner there. It looks like the Orion Accufocusser which I put on my std GSO crayford and LOVED IT immediately! No more big fat fingers wobbling the scope around at high mags! It is designed for an Orion rack&pinion focusser, so in your case should have been a more ready installation.

I've since moved the Accufocusser to a 10:1 focusser. It needed a bit more grunt to turn the additional gearing, but supergluing the "fuel filter" sleeve to the focusser shaft seems to have done the trick. No more slippage.

One thing I did was use only one grub screw to tighten it up, then replace that grub screw with a screw with a "top" I could get my fingers around (photo in a thread somewhere). In that way, I could loosen off the screw, thereby disconnecting the motor, and make coarse adjustments via the normal knob when I changed eyepieces that weren't parfocal. Then tighten it back up again and used the electric focusser for fine focus. :thumbsup:

[Screwdriverone]

Hi Erick,

Oh, that's a good idea, a piece of hard plastic tube glued on to the shaft. Oh well, I can fix that up later, its working fine for now.

One thing I should have mentioned is the lack of "freewheeling" on the focuser once the electric motor is fitted. There is no clutch mechanism as far as I can tell, so when it is fitted, the manual knob on the right is VERY stiff and I am reluctant to use it manually so as to avoid damaging anything.

Chris

[erick]

If it is the same motor/gearbox as mine, VERY STIFF means it don't move at all - there is no clutch. Hence my bushies' clutch by making it possible to connect/disconnect the shaft from the flexible drive. The focusser shaft then turns inside the flexible drive as you turn the focusser knob, until you tighten the screw up again.

[Screwdriverone]

Ahh!, great idea, Might give that a try.

Thanks!

[erick]

Here is the thread, Screwie, if you haven't found it yet:-

http://www.iceinspace.com.au/forum/showthread.php?t=10782 :)