Skywatcher vs. TS monorail SCT focusers

[JamesF]

I've been thinking for some time that I should perhaps get an external focuser for my C9.25.  I'm happy with the Skywatcher/Revelation/GSO (I think they're probably all made in the same place) model that I modded for my PST, but with the SCT it's entirely possible I'll be wanting to hang a filter wheel on the back, either with a mono planetary imaging camera or perhaps something like the 314L+ with a focal reducer.  I'm wondering therefore if I shouldn't perhaps go for the TS monorail instead, particularly as the Steeltrak models appear to be made of unobtainium now.

Anyone have thoughts on the options here that they'd care to share?

James

[JamesF]

No-one?  Someone must have the TS monorail, surely?

James

[JamesF]

Following up to my own post...

I've found very few references to the monorail focusers online, but one review of such an item fitted to the GSO RC suggests that the drawtube clamping screw can cause the section of the focuser in which it is mounted to snap if tightened too much (for a heavy camera/filter wheel etc., say) because that part is only made of plastic.  That makes me rather less keen on it than the cheaper models, though I guess generally I would not be using it for a heavy camera.

James

[Macavity]

I have two. (To both I have added the motor drive and use a RigelSys USB controller).

One came on a TS F4 Newt. The other bought for a MAK150 - Used via SCT adapter.

No major plastic parts IIRC? Except the 5/16" locking screw which does indeed have a plastic tip.

It bears down on draw-tube metal. If you "crush" anything, you'd be doing it ALL very wrong(ly)? 

A minor caveat: Both focussers developed significant lateral slop after a short while. This was rapidly traced to the fact that some internal screws had never(?) been tightened properly. Like many precision "mechanical things" you need to tighten screws in sequence and "jiggle a bit" between operations! I guess the manufacturers don't have time? Once done, the focussers do everything claimed...

[earth titan]

Have you considered the feathertouch focuser option? I struggled for ages with an additional focuser on the rear of my C9.25 before going down the integrated focuser route.

I then fitted a Baader quick lock.

Really is now a thing if beauty!

[JamesF]

No major plastic parts IIRC? Except the 5/16" locking screw which does indeed have a plastic tip.

It bears down on draw-tube metal. If you "crush" anything, you'd be doing it ALL very wrong(ly)? 

Thanks for the information, Chris.

This is the review I found: http://www.progressiveastroimaging.com/viewtopic.php?f=22&t=4843

It's the three last images that made me feel a little uncomfortable.

James

[JamesF]

Have you considered the feathertouch focuser option? I struggled for ages with an additional focuser on the rear of my C9.25 before going down the integrated focuser route.

I then fitted a Baader quick lock.

Really is now a thing if beauty!

You mean the microfocuser unit?

James

[JamesF]

Thanks for the information, Chris.

This is the review I found: http://www.progressiveastroimaging.com/viewtopic.php?f=22&t=4843

It's the three last images that made me feel a little uncomfortable.

James

Actually, looking at the design, even if it were plastic if I fitted an aluminium plate on the flat section underneath the cracked part and used some longer fitting screws the plastic would then be reinforced by the metal and there'd be no risk of breakage.

James

[Macavity]

Thanks for the information, Chris.

This is the review I found: http://www.progressiveastroimaging.com/viewtopic.php?f=22&t=4843

It's the three last images that made me feel a little uncomfortable.

James

Hi James,

Ah, I see now. That's what I call the "tensioning"(?) screw - Bringing the rotating shaft into contact with the bar (Crayford Style). I can see how one might crack the housing - But only with *significant* screw tightening! Just gave mine a quick test. The focusser can certainly lift 4lb weight vertically, with what I would call modest / reasonable tightening. Aware of the construction, I never felt I was likely to break anything! As a later posts notes, to actually *lock* the focusser, there is the aforesaid big (nylon tipped) screw on the other side.

I think it fair comment the micro-focusser might be a bit disappointing. But in the normal way of things (focus roughly achieved) it engages sufficiently well to perform the fine-focus function over the requisite short travel. Maybe these can be "tweaked" too? Visually, I used the SCT version with a 2" diagonal and 500g (Baader Hyperion) eyepiece happily enough. You do have to adjust the tensioner screw in a fairly critical way to get it all to work optimally though? I suppose begging the question: How heavy is the gear you envisage?

Happy to do tests! As a newbie to the (Crayford) principle, with no comparison examples, it's hard to say definitively? These days circumvented by use of the companion electric motors. Loosen all the screws and the gears hold everything! I do like the ability of the focusser to automatically "slip" at the end of travel. The sound of a Skywatcher (stepper) focusser motor "spitting teeth", when a rack and pinion focusser reached the end stop was memorable? 

[earth titan]

You mean the microfocuser unit?

James

That's the one.

[StevieDvd]

How about on of these

Bit heavy but seems well built, not used mine in clear skies yet.

[JamesF]

How about on of these

Bit heavy but seems well built, not used mine in clear skies yet.

Oooh, now, that does look rather nice.  I've not seen that one before.  I'd probably prefer a decent R&P over Crayford given the choice.  The only advantage that the TS model has is the greater travel, but the downside of that is moving the focal plane further from the back of the OTA and I'm not keen to do that any more than is necessary.  Besides, who needs that much travel when it's really only used for fine focusing?

James

[Earl]

Id go for a 2" feathertouch with the sct adapter,

Not cheap, but the best choice for that style of focuser.

[JamesF]

Id go for a 2" feathertouch with the sct adapter,

Not cheap, but the best choice for that style of focuser.

I have been slightly tempted on the grounds that even though it's expensive I'd probably never sell it unless for some strange reason I decided I didn't want an SCT or Mak ever again.  Unless of course it isn't possible to swap the mounting plate should I upgrade to a C11 or C14 at some point.

James

[Earl]

I have been slightly tempted on the grounds that even though it's expensive I'd probably never sell it unless for some strange reason I decided I didn't want an SCT or Mak ever again.  Unless of course it isn't possible to swap the mounting plate should I upgrade to a C11 or C14 at some point.

James

That is the beauty, you can change the adapter to an ed80..... 200p newt.... anything you want.

A Focuser for every scope you will ever own

[astrogardener]

I have the TS Monorail on my Helios 6 inch refractor, it carries a SBIG ST7 and 100mm of extension tubes with no problems.