Upgrading focuser on 'Old Gold' SW 100ED

[kerrylewis]

I am looking to upgrade the focuser on my old gold finish Sky-Watcher 100 refractor - photo attached. 

Has anyone done this either with the SW dual speed or another make?

FLO and their supplier are not sure if the SW version fits the old scope as it is designed to fit the newer black version. On mine there are three screws evenly spaced around - one can be seen just below the label. So, alternatively, can anyone with a modern black version confirm if it is the same? 

Thanks 

Kerry 

[Skyline]

A nice moonlite focuser will work on that scope, something like this.

https://www.firstlightoptics.com/moonlite-focusers/moonlite-cf-crayford-focuser-for-refractors.html

You could use three screws to secure the flange down using the existing screw holes.

Al.

[John]

The stock focuser on the ED100 is the same one that was on my ED120 but with the larger scope there is an additional flange to fit it into the larger diameter tube.

I've a Moonlite on my ED120 at the moment but I've also had a William Optics and the Skywatcher Crayford upgrades on there and I think they would all have fitted the ED100 as well.

It's worth thinking through the finder mounting arrangements when you are considering upgrading because many replacement focusers don't have the integral finder shoe and you need to make alternative arrangements.

 

[kerrylewis]

Thanks Al and John

I like the Moonlite focusers  - I fitted one to my Dob. The current 'rack and pinion' focuser on the ED100 is not good so anything would be an improvement; I just wonder if it's worth the investment in the extra cost of the Moonlite when the SW would itself be a real improvement for less outlay. 

However, if the focuser was improved I think that I would use the scope more. It's so light and easy to set up  - so perhaps the investment would be worth it

 

[F15Rules]

It's not the rack and pinion design that's at fault though...it's the lousy execution (cheap) used by Skywatcher/Celestron to keep the cost down.

I have a super rack and pinion focuser (dual speed) on my Vixen ED and it NEVER slips, unlike every crayford I have ever used (even Moonlight crayfords can slip if not adjusted properly).

If you can find a suitable R&P, then I would use that. Takahashi use R&P focusers for a reason!

That said, I think the Moonlight crayford is very good, and very well built.

Good luck. Your scope is worth the investment, very nice objective.

Dave

[John]

I think the stock focusers on the older ED doublets used to be a single speed crayford but not a particularly well executed one. The main issue used to be that the flat area on the bottom of the drawtube was not actually flat but slightly concave. One "mod" was to file the area flatter to allow the rod that bears against it to have a better purchase.

If it is a rack and pinion please ignore the above - and forgive my confusion !

 

[Skyline]

I have a stock rack and pinion focuser on my Celestron C100ED. It has been tuned with some Teflon strips which has improved any shifting, I have also found it can take some weight as well without slippage.

These scopes have wonderful pin sharp lenses with a high strehl value.

 

[DRT]

Kerry,

i had one of those scopes last year and fitted a new SW dual-speed Crayford to it. The black one that sells for around £125. A Moonlite will also fit, but is obviously much more expensive. 

I like the SW dual-speed. It is excellent value at that price. 

Derek

[kerrylewis]

Thanks for the comments everyone. In my ignorance I am describing it as 'rack and pinion' however it probably isn't,
and could be the type that John describes. See further photo.

Whatever it is, after over 10 years it doesn't work too well especially with the heavier eyepieces. The scope's optics are still good though.

Now that I know that the SW version fits (as confirmed by Derek) I am inclined to go for that one as I have things in mind to spend my 'astro-budget' on 

Kerry

 

[Saganite]

20 hours ago, John said:

I think the stock focusers on the older ED doublets used to be a single speed crayford but not a particularly well executed one. The main issue used to be that the flat area on the bottom of the drawtube was not actually flat but slightly concave. One "mod" was to file the area flatter to allow the rod that bears against it to have a better purchase.

If it is a rack and pinion please ignore the above - and forgive my confusion !

 

Hi Kerry,

I had one exactly the same,and it is a single speed crayford. I took mine apart, filed, flattened, and smoothed the bearing surface, and then fitted a 10:1  Lacerta microfocuser, which cost about £60. The result was a very usable dual speed unit.

I sold it nine months ago when I bought the Refractor in my signature, and regret doing so; a very very fine 4" scope !

[cotterless45]

Cheapest and easiest way to improve focussing on old scopes is one of these,

https://www.firstlightoptics.com/diagonals/william-optics-125-90-degree-erecting-prism.html

not only do you get an erect image (useful on the Moon), but a nice brass compression ring.Saves playing around with flanges and adapters. The focussing is a joy, equivalent to a dual speed. Better still you can transfer it to other old fracs, nice,

Nick.

[kerrylewis]

Saganite  - interesting. I've never taken the focuser apart and I am not very dextrous! However,  I've actually ordered the SW unit now and look forward to giving the old scope a new lease of life. I agree it is a fine scope for what it cost and I would never part with it. Anyway, cosmetically it doesn't look great after a few 'incidents' over the years, so what I would get for it would not be worthwhile, and I still find it very useful particularly as part of a 'grab and go' set up on a Portamount.

Nick. That's interesting too. I didn't realise that unit had focussing ability. I do have an erecting diagonal which I use on my small WO refractor for occasional territorial use but it does not have a focuser. They also only take 1.25" eyepieces of course, and I do have quite a few 2" ones. 

Kerry 

 

[AstroSylv1]

Another way of having a good focuser is to add the Lacerta fine knob upgrade..

[ollypenrice]

On 20/07/2016 at 14:55, F15Rules said:

It's not the rack and pinion design that's at fault though...it's the lousy execution (cheap) used by Skywatcher/Celestron to keep the cost down.

(even Moonlight crayfords can slip if not adjusted properly).

If you can find a suitable R&P, then I would use that. Takahashi use R&P focusers for a reason!

That said, I think the Moonlight crayford is very good, and very well built.

 

Dave

I have a Moonlite and don't think much of it, but it's very red and pretty. It also has a nice way of keeping the drive roller parallel with the driven surface: the roller's angle simply defines the angle of the drawtube. That's a good idea but the fatal flaw is that the roller drives a smooth slippery surface. How is that supposed to be any good? It's fine for an always-horizontal Dob focuser and probably fine for lifting an EP but is not fine for lifting a heavy CCD. That's why Baader came up with the steeldrive and the diamant. You need the roller to grip the drawtube's driven surface.

Olly

PS A good R and P wipes the floor with a good Crayford in my view. 

PPS I might have said that before... 

 

[kerrylewis]

It's on! Tight fit into the tube but a bit of gentle hairdryer treatment on the end of the tube and it went in OK 

Scope looks good now.

 

[DRT]

Very nice, Kerry.

As you will no doubt have noticed by now it comes with the added benefit of being very heavy compared to the stock focuser, which allows you to get the tube farther up in the rings to achieve balance and allows a more comfortable viewing position

 

[kerrylewis]

Yes Derek, it's quite a bit heavier as a result of being built more solidly. I gave it a quick test last night in a clear spell and am very pleased with it. A worthwhile upgrade.

Thanks for your advice which gave me the confidence to order it 

Kerry 

[Alan White]

Sorry to bring up an old thread,

how did you fit a finder after this upgrade Kerry?

[DRT]

1 hour ago, Alan White said:

Sorry to bring up an old thread,

how did you fit a finder after this upgrade Kerry?

I managed to fit a finder shoe to one of these focusers just a few weeks ago. On the main body of the focuser is a seemingly redundant plastic 4mm grub screw. It does nothing other than fill a tapped hole. I took a standard Synta finder shoe and filed the front of the base so that it fitted the profile of the focuser's cowling. I then attached the shoe with a single 4mm screw to the vacant hole.

@Paul73 now owns the scope so could perhaps post a picture of the mod?  

[John]

Just now, DRT said:

I managed to fit a finder shoe to one of these focusers just a few weeks ago. On the main body of the focuser is a seemingly redundant plastic 4mm grub screw. It does nothing other than fill a tapped hole. I took a standard Synta finder shoe and filed the front of the base so that it fitted the profile of the focuser's cowling. I then attached the shoe with a single 4mm screw to the vacant hole.

@Paul73 now owns the scope so could perhaps post a picture of the mod?  

When I had one of those focusers, thats more or less what I did as well

[Alan White]

Thanks Derek, 

I need to replace my sw focuser as after all the adjustments and fiddles the damn thing still slips.

Money at present will not run to a Moonlite or better, so the black SW unit looks the best option, but the finder was the challenge.

Pictures from anyone will help a lot.

[Paul73]

Here are a few pics of @DRT's handiwork.

Works a treat. It is a significant step up from the standard SW Duel Speed unit. Not in Moonlight territory (sorry Olly, but for non imaging...). I have no urge to upgrade from this.

Hope that this helps.

Paul

[nightfisher]

44 minutes ago, Alan White said:

Thanks Derek, 

I need to replace my sw focuser as after all the adjustments and fiddles the damn thing still slips.

Money at present will not run to a Moonlite or better, so the black SW unit looks the best option, but the finder was the challenge.

Pictures from anyone will help a lot.

Alan, another option is to get a £6 finder bracket and drill a couple of M4 holes in the tube after working out where you want the finder then use supplied bolts to fasten to scope tube a little way in front of the focuser, i have done this a couple of times

[DRT]

I thought about doing that, Jules, but the advantage of putting it on the focuser is that the finder rotates with it if you need it to. 

[Dave In Vermont]

I have now outfitted 4 of my telescopes with the Dual-Focus 10:1 Crayford-Focusers from GSO. These come with a fitting for the 8 X 50mm Finder-Scopes that I like. And these will also rotate to orient the focuser to where you wish it to:

 

 

And the fine-focus on them is as sharp as a scalpel. As well as about 1/3rd the cost of a Moonlite. These Crayford's are made for not just refractors, but also I have them on my SCT and Maksutov. TS in Germany sells them that I know of. Likely others over there as well.

I can't think of how these could be improved - they're excellent. And light-years over the standard R & P - type focusers that came with my beloved ST80's!

Enjoy -

Dave