After market focuser for refractors

[Moonshane]

I am visual only and really like the ones I have had. That said, for visual I doubt you'd go far wrong with Baader/Moonlite/Feathertouch 

that said to get what most consider the best (FT R&P) £600 is less than some people pay for an eyepiece and it gives pleasure when in use with all your eyepieces so not that OTT really. just save a bit longer if it matters to you! 

[ollypenrice]

9 hours ago, FLO said:

It is okay for someone to own and like one  

Steve

Putting words in my mouth by implication? I wouldn't dream of denying anyone the right to own and like them. I own one and would  like it for visual use. I'd like it even more with a strip of grippier material for the spindle to drive and I wouldn't be in the least surprised to see this introduced. Note that Baader are now on their second generation of 'grippy strips' which suggests that there are engineers out there (and Baader are certainly engineers) who see it as a key issue.

BTW, as I said at the outset I think that the Moonlite design has it over the competition in terms of the effectively self-orientating drawtube/spindle. Many of the solutions to this problem are vastly over-complicated and difficult to adjust.

Olly

Edited July 11, 2017 by ollypenrice
BTW

[Paul73]

Errrrr. Am I allowed to say that I think that my black Moonlite is great.....

Possibly, a tad over complicated, but for visual observing it does the job nicely. It is most certainly a good step up from stock focusers. The Bresser stock r&p is so poor that I'm tempted to shoehorn a stock SW Crayford effort onto the tube.

Part of my work is in Value Management of design solutions. Which looks at how to best meet the real requirements of a customer. ie. Most Value / £. A lot of us won't admit that, for us, small constituents of value are items such as aesthetics  / feel / exclusivity....... This is fine if we admit that this is part of our definition of value. But, when we ignore this and obsessively defend brands from a point of pure functionality, we get overly excitable postings and conflict.

I might have to try a Steeltrack (with a bag over it ?). It'll save me from the Feather Touch money pit for a while.

Paul

Edited July 11, 2017 by Paul73

[ollypenrice]

24 minutes ago, Paul73 said:

Errrrr. Am I allowed to say that I think that my black Moonlite is great.....

Paul

Of course you are! I for one have never said otherwise, nor would I.

[Dave In Vermont]

Oh no!! <wild shreiks in background!> I have 4 Crayfords! Oh - yes - and one to sell - Olly must DESPISE me!    

There! Got that outta my system!

I hope your Moonlites' last their owners well for 100 more years and/or telescopes - which ever comes later.

It's all about fun -

Dave

 

[ollypenrice]

2 hours ago, Dave In Vermont said:

Oh no!! <wild shreiks in background!> I have 4 Crayfords! Oh - yes - and one to sell - Olly must DESPISE me!    

There! Got that outta my system!

I hope your Moonlites' last their owners well for 100 more years and/or telescopes - which ever comes later.

It's all about fun -

Dave

 

I also have four...

Olly

[spaceboy]

I have to say I'm sad to see how this thread has developed. I value everyone's opinion but it seems to be turning in to tit for tat. If Olly isn't happy with his moonlite for imaging then fair enough. I think it is better to have a broad opinion rather than a singular one. I never thought a focuser thread would end up like negative opinions on televue threads tend to do 

I have to admit I agree with Olly's principle argument. I have no experience with moonlite other than ones I have seen on trade stands but I do have experience with refractor crayfords and gloss finished draw tubes. Look very posh but feel a compromise is definitely there regards overall performance. This is why I am probably more in favour of Baaders steeltrack although saying that I do like the look of the Revelation R&P focusers https://www.telescopehouse.com/accessories/focusers/revelation-rack-n-pinion-focusers/revelation-superfocus-2-inch-rack-n-pinion-refractor-focuser.html I have a revelation Crayford on my Newt and it has always performed well for it's price point so I feel confident that the quality of the gravity friendly R&P focusers could closely match.

I know I had originally on planned for the top two higher end contenders of moonlite and Baader for discussion but it looks like I may have underestimated the value of the "budget brands" . Any comments welcomed on these also

[ollypenrice]

To take the conversation in a different direction, I often wonder why focus locks are designed as they usually are - which is to use a screw pressing on the draw tube. To avoid their damaging the drawtube they usually have nylon tips which are, of course, not very effective at holding the drawtube in place. They also push the drawtube from one side which is not good for the friction in a Crayford design or the mesh in an R and P. Nor is it good for the drawtube bearings since it enourages play over time.

An alternative method would be to have a flat strip of low-expansion material attached to the rear of the drawtube and passing through a small clamp at the rear of the main tube. Either the entire focuser including clamp could rotate (the 'Captain's wheel' design) or a rotator could be added at the rear of the draw tube. No pressure would be applied to the draw tube and the strip-and-clamp would be doing what they were designed to do, which is be clamped. The conventional system has a drawtube being asked to do the opposite of what it was designed to do, which is move freely. A scribble:

 

So what we're trying to do here is uncouple the holding still of the drawtube from the quite different problem of driving it smoothly while retaining sufficient tension for it not to slip until fixed.

Olly

PS I suspect, but don't know, that such a clamp would have less effect on fine focus than the present methods. As all imagers know, locking the draw tube does affect critical focus.

PPS Oops, no good for remote operation! 

 

Edited July 11, 2017 by ollypenrice

[GavStar]

Olly

I have wondered how the locking screw on my feathertouch focuser work. Is it really as simple as a screw with a nylon tip or does starlight use a different approach?

Gavin

[ollypenrice]

1 minute ago, GavStar said:

Olly

I have wondered how the locking screw on my feathertouch focuser work. Is it really as simple as a screw with a nylon tip or does starlight use a different approach?

Gavin

I don't know but it looks like a soft tipped pressure screw on mine (pressing down from the opposite side to the R and P mechanism.) I tend to give it a slight tweak after each focus iteration before looking at the FWHM since it always affects the value if I focus first and then tighten.

Crayfords seem to have an assortment of ways of making the lock screw press on something - and not always the same thing.

Olly

[gnomus]

I'll add my 2c.  I have 2x Moonlites and 1 x Feathertouch.  First off, my Feathertouch is certainly rotatable, but I don't know the range well enough to say whether or not they all are.  I have found the Feathertouch to be entirely reliable.  The Moonlite has 'slipped' on several occasions when under the load of a camera plus wheel.  I would be happy using the Moonlite with lighter eyepieces, and with my planetary cameras.  I wouldn't use it with a CCD and wheel (I have tried it and it wasn't reliable).  I would feel a bit anxious putting a big (say 1kg), expensive eyepiece in it on my refractor.  I haven't had a problem, but because of the issue holding the CCD, I just wouldn't feel relaxed about it.  My second Moonlite is on my Dob.  Because of the way this works - the weight is all downwards - I am quite happy using the heavy eyepieces with it.

         

[Bukko]

I have replaced most of the original focusers on my scopes; the older 2" OO focuser with a Feathertouch, the 60mm Lunt with another Feathertouch and lastly my SW Equinox 80 with a Moonlite.

I really wanted to fit another FT, but the focuser would cost the same as the scope, so I hesitated. I would have liked the Steeltrack, but at the time, they were not available. FLO offered a Moonlite with the right Equinox adapter, so I bought it.

Firstly, compared to all the others, the Moonllite is heavy. On the Equinox, it has pushed the CofG back so far, I struggle to mount it now, without placing extra weights on the scope. It is certainly well engineered, but lacks the finesse of the FT. (But then it's half the price)

With a 2" diagonal and big EP, it tends to slip a bit. The locking screw is up against the dovetail, where the CofG is so far back... I have considered going back, but the Moonlite is smooth in operation and still a lot better than the original, so a mixed review from me..

If anyone is interested in the Feathertouch, here is a link to the patent. http://www.google.co.uk/patents/US6069754 It is clever, a subtle variation of the steeltrack, but the same principle, you should find out all you need to know about the brake.

Olly, I agree with your opinion of Crayfords for imaging, especially once a significant load is applied (Corrector, OAG, filter wheel and cooled CCD is a LOT of weight). Both my FT's are Crayford's, but as you say, well engineered is the key. And I know you are not anti - Crayford design, as, basically, your favourite mount is just a big version of the same principle !!

Gordon.

[ollypenrice]

10 hours ago, Bukko said:

And I know you are not anti - Crayford design, as, basically, your favourite mount is just a big version of the same principle !!

Gordon.

Steve Richards got me with the same observation a few years ago! 

At the risk of responding too solemnly to a good joke, the essence of the Mesu is the extremely fastidious manner in which the friction drive is engineered. Above all the choice of materiel for the driving and driven surfaces is critical. The Mesu does not use smooth anodized aluminium on either. You could  suggest to Lucas Mesu that he try it but I'd be inclined to stand well back as you do so!

This is why Baader have invested so much time in finding the right material for the driven part of the drawtube and why Moonlite should, in my view, do the same. Their product could easily be modified accordingly. Other aspects of their focuser are excellent but there are more than enough posts in this thread to confirm that it can lack the grip needed for heavy-camera imaging and even, it seems, for supporting heavy eyepieces. I think mine would support heavy EPs but, so far, we've only tried it with a camera in a motorized focus application where it failed due to slippage.

Olly

Edited July 12, 2017 by ollypenrice
Typo

[Dave NZ South Island]

I bought a Moonlite CF 2.5" Focuser for my 120ED back in 2013 and although it is very well made it still slips when I attach a Canon 60D for imaging.

Despite my efforts at adjustment I can not achieve a compromise between smooth action and weight capacity. In fact, when I adjust the two grub screws to increase load to the non-slip point then the fine focus knob becomes redundant and just turns without moving the drawtube; so I can only use the coarse focus knob

I took it up with Moonlite and they offered an upgrade for it for US$100 (required sending it in which is big cost from New Zealand to and fro) so I just gave up as I don't want to be without a focuser and will now resort to tuning my old Crayford that came with the 120ED as it is relatively easy to strip and tune. The main issue seems to be lack of contact surface with the focuser shaft and simply 'honing' the flat section to get it dead flat (it is slightly concave) with an oilstone appears to give much improved grip and responsive tension control.