After market focuser for refractors

[Dave In Vermont]

6 hours ago, Joe G said:

Dave

I  realise the GSO focuser is not one of the original focusers  mentioned by Spaceboy  but  do " track lines" similar to the Moonlite  eventually appear on the  drawtubes after a certain amount of use? Thanks in advance Joe

Joe:

One shop here in the States used to print a notice to this effect in their ads for the GSO focusers. So I guess from this that they can. But I've never seen this phenomena with any of the 4 I have. So I'd surmise that some production-runs do, or have, exhibited this behavior. This appears to be harmless to the efficacy of the focuser to produce the intended results: Super-sharp focusing.

I suppose if I'd shelled out 3 times the price of a GSO for a shiny* gold finish, and a smudge were to appear on the drawtube, I'd be rather upset about this.

This is the first time of heard about this happening with the Moonlite ones. Thanks for the information. Does this happen frequently with these - if you know?

Dave

 

* - The gold-finish is actually Titanium Nitride (TiN), not gold. For further information on this stuff:

      https://en.wikipedia.org/wiki/Titanium_nitride

 

 

 

[Moonshane]

don't forget to check the collimation of the drawtube at most in and most out points.

[John]

9 hours ago, Joe G said:

Dave

I  realise the GSO focuser is not one of the original focusers  mentioned by Spaceboy  but  do " track lines" similar to the Moonlite  eventually appear on the  drawtubes after a certain amount of use? Thanks in advance Joe

I've seen these "track lines" on many brands of crayford focuser including GSO (see 1st photo below of a used but still good GSO refractor crayford). It's caused by the small bearings (usually 4, in 2 pairs) rolling against the drawtube under pressure from the steel bar that pressed against the flattenened section on the underside of the drawtube. These bearings are an important part of the design. Some designs of rack and pinion focuser use such bearings as well and you get these lines on those too. My understanding is that it's part of the normal wear that you get with such a focuser. There are a few designs where steel tracks have been inset into the upper side of the drawtube and the bearings press on those rather than the anodised tube (see 2nd photo below).

Hope that helps.

 

Edited July 8, 2017 by John

[Moonshane]

That's one of best design features of the Steeltrack I think John.

[Moonshane]

wow just looked in white light and you can see why it's so active. the AR is very complex !

[Moonshane]

LOL - rushing and posted in the wrong thread -but it is!

[avtaram]

A Moonlite should be arriving on monday for my 120 ed, hope I'm not disappointed with its performance in light of some negative comments about this focuser.

Avtar

[swag72]

I put a moonlite on my 120ed....... Good luck with it!! 

[Grierson]

41 minutes ago, avtaram said:

A Moonlite should be arriving on monday for my 120 ed, hope I'm not disappointed with its performance in light of some negative comments about this focuser.

Avtar

I have one on my more humble 80ED. No problems at all so far. Certainly holds the ZWO 1600 and filter when vertical.  

[John]

5 hours ago, avtaram said:

A Moonlite should be arriving on monday for my 120 ed, hope I'm not disappointed with its performance in light of some negative comments about this focuser.

Avtar

I have one on my ED120. It's much better than the William Optics crayford that was on the scope previously.

Very "blingy" of course so remember to put your sunglasses on before looking at it

 

[Dave Lloyd]

I stuck a skywatcher  10.1 Crayford on my evo 120 and it works a treat. I couldn't justify the cost of a steeltrack or moonlight on my scope and this focusser supports a dslr without slippage and has a really nice action. 

[Dave In Vermont]

1 hour ago, Dave Lloyd said:

I stuck a skywatcher  10.1 Crayford on my evo 120 and it works a treat. I couldn't justify the cost of a steeltrack or moonlight on my scope and this focusser supports a dslr without slippage and has a really nice action. 

The Crayford 10:1Dual-Focus 'branded' Skywatcher is, in fact, a GSO. Nice isn't it, Dave? Indeed it does support a camera - and more I've found. These also are a breeze to rotate as desired, as well as to bolt in place to prevent rotation or slippage.

What's not to love?! I thought my outfitting my Skywatcher-branded ST80*with a GSO Dual-Focus Crayford was pretty outlandish - cost-wise. But I must admit I never even considered giving it a Moonlite instead!

To use an American closing:

"Let's not - but say we did!"

Dave

 

* I have both a Skywatcher-branded blue-tube ST80, as well as the Orion-branded ST80. Orion-USA got ahold of these a few years ago, but they were originally branded 'Skywatcher' when they first became available in the US.

[Joe G]

I've been following this topic closely for a number of reasons but can't figure out the thinking behind why generally telescopes  with Crawford focusers with theit inherent " track line" issues, paint their drawtubes while telescope manufacturers such as Tak, Vixen, Stellarvule  generally don't with their r&p  focusers. I understand Moonlite  giving  costumer choice  but GSO thinking  makes little sense to mention

[Dave In Vermont]

My GSO 10:1's aren't painted black - they're anodized - anodised in the UK - to create a thicker layer of oxide to prevent wear over time. Try this:

https://en.wikipedia.org/wiki/Anodizing

Anodizing can be done in most any colour, but why black? Likely to cut down on reflections, but this is a guess. You could try writing to Guan Sheng Optics and asking them. It's not a difficult process to anodize a hunk of aluminum. If you wanted to, it wouldn't be terribly costly or difficult to do it yourself. You'd just need some simple equipment like a good battery and a source for a few chemicals like Titanium Nitride if you wanted your GSO to be shiny golden like a Moonlite.

Hope this helps -

Dave

[John]

1 hour ago, Joe G said:

I've been following this topic closely for a number of reasons but can't figure out the thinking behind why generally telescopes  with Crawford focusers with theit inherent " track line" issues, paint their drawtubes while telescope manufacturers such as Tak, Vixen, Stellarvule  generally don't with their r&p  focusers. I understand Moonlite  giving  costumer choice  but GSO thinking  makes little sense to mention

Not all GSO crayford focusers have an anodised drawtube. I've had a couple which had a polished alloy drawtube. The track lines still get there but they are not as apparent.

All the focusers of the scopes that I've owned (around 30 over the years ) have eventually showed some sort of marks on their drawtubes from friction either with bearings or the pads that hold them in place. This includes my Takahashi and Vixen refactors. The one exception is the Feathertouch crayford on my TMB / LZOS 130mm refractor -  it's 11 years old but unmarked

 

 

[spaceboy]

You will have to forgive me chaps but I missing the significance of where the tram line topic is going? I can only assume I am missing something??

Do they have a significant impact on performance or is it purely a cosmetic peeve ?

If anything would it not actually improve the performance as the bearings are no longer running along the shiny (possible soft?) black gloss surface but against a texture and solid metal surface?? Are looks more of a necessity to users than performance?

On a side note I believe I would prefer to go with the Baader offering. I recently passed up on a feather touch for a good used price (I know some may consider this lunacy) as I particularly like rotating focusers. The only thing I am not sure with the Baader over the moonlite though is the ability to fix a finder to the focuser. I would rather have a quality R&P but moonlite seem to have considered everything an astronomer would want an upgrade focuser to offer. Even a selection of bling  colours . As by far the biggest seller of astronomy kit synta refractors often come with focuser shoes on their focusers so this can leave one with a dilemma of drilling in to the ota to fix a shoe. Again this can lead to awkward positions for the finder to be viewed through.

[Dave In Vermont]

This minor 'scuff' is harmless to the performance of the focuser. In other words - cosmetic only. Assuming it only appeared following use, not caused by being run over by a car or beaten with a steel-pipe!

But it does seem this minor (in my opinion) quibble has taken on a life of it's own. Your confusion is well justified.

Hope this helps -

Dave

 

[John]

I agree - it's a minor issue.

 

[spaceboy]

Thanks for clearing up the confusion guys. I admit I had at first thought it a minor cosmetic issue but as it was mentioned several times I began to doubt my own judgment . I suppose if I had a five grand apo the tatty look of a well used draw tube could distract from the beauty of a well made instrument. Personally though I would struggle to notice anything in the dead of night.

[Stu]

5 minutes ago, spaceboy said:

Thanks for clearing up the confusion guys. I admit I had at first thought it a minor cosmetic issue but as it was mentioned several times I began to doubt my own judgment . I suppose if I had a five grand apo the tatty look of a well used draw tube could distract from the beauty of a well made instrument. Personally though I would struggle to notice anything in the dead of night.

On moonlites it is certainly not an isaue Nick, just cosmetic. I once had a scope, bought used, where the paint on the drawtube was almost flaking off under the bearings. It looked bad, and the movement was a bit rough as a result.

I sanded the paint down, giving probably a worse looking drawer tube but it was down to the metal under the tracks and smoothly feathered back up to the paint surface. After a bit of fettling, it worked much better.

[wookie1965]

On 7/8/2017 at 00:19, John said:

Yes, but you need to do the refractor first and confirm that the optical axis of the focuser is aligned with that of the objective ie: with no diagonal in place, a well collimated laser in the focuser should exit the objective lens pretty much bang in the centre. If you then put the diagonal in, put the laser in the diagonal, and find that the beam now exits the objective lens off centre, that is a diagonal collimation issue.

Once the focuser axis is aligned with the objective lens, you check the tilt of the objective using the cheshire method described by AlisairW.

 

So checked collimation the Tal was spot on the diagonal however was way out, I have adjusted it now so should get better views now.

[ollypenrice]

On 07/07/2017 at 22:51, AlistairW said:

I have a question. If you attach an electronic focuser such as a Lakeside to the Moonlite, shouldn't the Lakeside hold it (the focuser) in position, by the nature of the motor drive. Would this not then eliviate the slippage ? - (if you use Bhatinov only and manual focus - this obviously still would have the potential to slip I guess?)

Sadly not. The electronic focuser holds the focus knob reliably but the Crayfoprd design relies on friction between the focuser shaft and the draw tube to hold the payload. That is why Baader insist on the nature of the driven surfaces in their naming. There's the Steeltrack which has an unpolished steel driven strip and the diamant which has a grippier industrial diamond driven strip.

Having the steel shaft drive a slippery anodized aluminium drawtube is just not good practice. Sure, they often work - but they sometimes don't. Why not just get it right first time? If an imager's robo focus works by counting motor steps it needs to know that a step is a step and not a slip.

Olly

 

[FLO]

4 hours ago, ollypenrice said:

Having the steel shaft drive a slippery anodized aluminium drawtube is just not good practice. Sure, they often work - but they sometimes don't. Why not just get it right first time?

I didn't realise you were still running your anti-Crayford campaign  

We offer all the brands discussed in this thread so are as neutral and objective as any retailer can be. I do understand why, Olly, in your circumstances a Starlight Instruments FeatherTouch R&P focuser is the right choice. It is beautifully engineered and bomb-proof but it's price (around £600) puts it out of reach for most astronomers. Fortunately, for most applications, it isn't necessary. 

I like the Crayford design because it can be made to a high standard at an affordable price (it isn't possible to make a good R&P focuser at the prices most Crayfords sell at). And, when done properly, a Crayford is a delight to use and is more than enough focuser for most astronomers. Even Starlight Instruments acknowledge this - their more affordable focusers (around £400) are Crayfords. 

HTH, 

Steve 

[ollypenrice]

5 hours ago, FLO said:

I didn't realise you were still running your anti-Crayford campaign  

We offer all the brands discussed in this thread so are as neutral and objective as any retailer can be. I do understand why, Olly, in your circumstances a Starlight Instruments FeatherTouch R&P focuser is the right choice. It is beautifully engineered and bomb-proof but it's price (around £600) puts it out of reach for most astronomers. Fortunately, for most applications, it isn't necessary. 

I like the Crayford design because it can be made to a high standard at an affordable price (it isn't possible to make a good R&P focuser at the prices most Crayfords sell at). And, when done properly, a Crayford is a delight to use and is more than enough focuser for most astronomers. Even Starlight Instruments acknowledge this - their more affordable focusers (around £400) are Crayfords. 

HTH, 

Steve 

I thought I was being rather balanced here! I have made a clear distinction between good and bad Crayford practice, 'bad' being driving a smooth anodized drawtube directly with a steel roller. It just is bad, in my book. I think my Moonlite is poor for this very reason. (Poor for imaging. It would make a nice visual focuser on a Dob. Very smooth.)

Olly

[FLO]

17 minutes ago, ollypenrice said:

I thought I was being rather balanced here! 

You have been actively bashing Crayford's since around 2011... 

Moonlite are faithful to the Crayford design and there are a lot of happy Moonlite owners here at SGL. It is okay for someone to own and like one  

Steve