Best Feathertouch focuser for C11?

[casstony]

There appears to be two options for the C11: a 0.8" travel focuser with a short adapter, or a 1.5" travel focuser with a longer adapter.

I'd prefer to keep the setup as short as possible, but is 0.8" travel enough? Just wondering what others have found in actual use.

[gbeal]

While I don't have any actual hands-on with the setup you are asking about, I would follow the recommendations of what the manufacturers suggest.
Bear in mind the guy that made these and will have made this suggestions is a good and dear friend, whose suggestions I trust implicitly, LOL.
One thing though, the longer travel unit may not be able to extend in far enough, if it contacts the rear cell or mounting area (within the SCT - F/T adaptor).
As well, out travel could be an issue for "swing-through" where the forks dictate how much hands off the rear of the cell.
Assuming you use the in-built primary focus, then the F/T will just fine-tune this, either manually or via the digital motor.
Either way, in my mind there is no better out there.
Gary

[multiweb]

I use this one (http://starizona.com/acb/Feathertouch-SCT-MicroFocuser---Celestron-Edge-HD-11CPC-1100CGEM-1100-P2518C654.aspx)from Starizona. Works very well and you can motorize it later on (cable or wireless).

[casstony]

It's the crayford in particular that I'm interested in, not the replacement for the existing knob. I really like the precise and quick action of the crayford.

Shortly I'll be comparing views through a 6.3 reducer/22 Nagler versus a Titan ED 35mm without the reducer(same magnification 80x) and if the 35mm looks better I'll be getting a feathertouch. In smaller SCT's I've generally preferred the view without the reducer.

I don't have a fork to worry about, so it's purely a matter of whether 0.8" travel is enough.

[multiweb]

Are you looking at imaging or observing?

[casstony]

just visual.

[multiweb]

Cool - you're right then. Go for the crayford on the backcell. Much more practical.

[mithrandir]

I might have a simplistic view of this, but whatever drawtube length you have in the crayford, it is not going to be your only focusing device. You'll still need the C11's focuser to get you in the ball park. On that basis the 0.8" would probably be adequate.

[marki]

You are dead right Andrew. Shorter drawtube = less possibility of flex etc. Tony you still have to move the primary to get it in the ball park then fine focus with the crayford. I have found the 10:1 feather touch replacement focuser for the primary knob is also a useful addition.

Mark

[casstony]

Thanks guys, I'll go with 0.8". I won't be getting the primary focus replacement though since I'm already pushing the budget with the crayford.

[casstony]

I ended up grabbing a 1.5" travel model because it came up on Astromart for a good price. It's a lot less chunky looking than the Moonlite and doesn't weigh too much - very nice to use and doesn't create balance issues.

After comparing views at the same magnification with/without a focal reducer, I still prefer the view without the reducer - the outer field is better with the reducer but on axis seems better without it - hard to define exactly what the difference is though. In any case, I'd have to dump the feathertouch to use the reducer and that's not going to happen :)

[asimov]

Good choice:thumbsup:

[gbeal]

Nice to see. What is the issue with the reducer, can you not "install" it within the focuser, or the adaptor that allows the F/T to attach?
There was discussion a while back that they were going to thread the drawtube to allow this, maybe see if you c an?
Gary

[casstony]

Gary, the focuser tube is threaded but it's not a SCT thread or a standard 2" filter thread(48mm) - it's a 52mm thread.

[gbeal]

Hi Tony,
yep, realise that, but if you were to fit the reducer inside there somehow, would this work, that is would the reduce fit far enough in to not impinge on the rear cell? If it did, then a simple 50 (SCT) to 52mm adaptor is what is required.
Gary

[casstony]

There is enough room to fit the reducer and adaptor inside the focuser assembly, though I'd only be left with about 0.5" travel (still enough to do the job). Can you give me a link to the SCT to 52mm adaptor?

The best solution would be a flattener that threads into the diagonal (focal ratio reduction isn't important) but the only one I've seen (TSSCKorr2)requires a precise distance to the eyepiece focal plane which is shorter than the light path length through a 2" diagonal.

[gbeal]

Tony, no, I c an't, it was a hair-brain idea I had while writing, but any machinist could whip one up I am sure.
Another alternative is to get a reducer which will fit within the draw-tube, like the 2" Optec versions.
Gary