Electronic focuser options

[gregbradley]

I'd like some advice about a good electronic focuser.

I am wanting to fit it on an AP130GT which has a 3.5 inch focuser and feathertouch fine focuser.

I have read there is an Optec unit that is good similar to (or the same as) the Feathertouch HSM unit. I have one of those on another smaller scope and it seems fine.

Suggestions?

Greg.

[beren]

https://m.ja.aliexpress.com/item/1005004944887723.html?gatewayAdapt= Pc2Msite


https://youtu.be/9JujzPyfX9E

[gbeal]

In my case I am sort of tied to the ZWO eco-system, so use their EAF. Even if you are not tied (ASIAIR etc) their EAF with hand controller is an option.

[RugbyRene]

I've found the Pegasus Focus Cube to quite good. They're sold by Sidereal Trading in Melbourne.

[gregbradley]

Thanks Beren.

What do you know. Those are the guys who ripped me off recently.

That title and photo is clear but they had another ad which had a photo of the focuser and it said focuser in the title but it wasn't for the focuser it was for a mounting adapter for various scopes for their focuser.

I told them and they wanted me to initiate a refund (they should have just given me a refund) and the form did not accept when I tried to submit it with some unusual detail they wanted.

It looks the same as a Feathertouch HSM or an Optec Lynx.

It may be OK but don't want to deal with dodgies or people who post misleading ads and don't take responsibility.
Not worth the $50-100 you save.


Greg.

[gregbradley]

Do you have to use a ZWO EAF with ASIAIR? I just got one of those and that was one of my question if it only works with its brand products.

The EAF is a bit of an ugly thing but I can't get past that if it works well.

Greg.

[gregbradley]

Thanks Rene.

Are they compatible with an ASIAIR?

Greg.

[Peter Ward]

Micro-touch by Starizona.

Not cheap but none better.

[DavidTrap]

The Microtouch motor alone is close to $1000 AUD. Then add the controller.

The ZWO EAF looks far more attractive at around $350 all up

DT

Sorry - I was quoting prices for the Feathertouch Posidrive Motor (USD$590) and Focuser Boss Controller (USD$360)

[gbeal]

Sorry, answered this a few hours ago, well thought I did, old age is cruel. I'll do it again.

If you want the "Auto-Focus" side of the EAF, then yes, I believe an ASIAIR is needed, I certainly use it like that, it computes a V Curve, and sets the focaus, at will, or as programmed (temp change or time between checks).
However, one does not have to use the ASIAIR to use the EAF, in my case I have a 90mm refractor with an EAF fitted, and for solar imaging I simply focus with the hand controller.

[Peter Ward]

I must admit to being continually disappointed by many "made in the ROC"
products, due some plain dumb engineering, poor QC and short longevity
(read: gentle puff smoke escaping on power-up)

I have one of these (https://starizona.com/products/microtouch-autofocuser-wired) on my 130GTX. It's been ticking away for 7 years without a glitch. (It's interchangeable with my AP155 focuser)

and it didn't cost $1k....

[g__day]

I always heard Optec have a very solid reputation. Must admit I like my Moonlight Instruments motor focuser - excellent build quality and never any issues after you have set it up correctly...

I am just trialling my ZWO EAF now - seems okay but nowhere near the build quality of the Moonlight unit.

[RugbyRene]

Sorry don't know. I use KStars and it works great.

Maybe someone else on the forum knows the answer to this?

Rene

[DavidTrap]

Made in the USA isn’t always better. Our use case is fairly hostile to electronics.

We’ve got a high end American camera that is toast after 5 years in the observatory with circuit boards corroded beyond repair. Electronics tech who looked at it for us was scathing about the general build quality of the boards. It’s headed for the bin, to be replaced with a QHY or ZWO camera. At about 1/3 to 1/4 the price of the American camera, it’s a no brainer.

We’ve also had to replace the American made focus controller - that was inside a weatherproof steel cabinet.

DT

[Peter Ward]

Sure, made in USA doesn't guarantee quality, but going well beyond a sample of one
as a dealer, I rarely had to send cameras back to say, SBIG (bar one infamous sample that admittedly did not fare well in a marine environment).

My personal STX16803 is now a decade old and still producing excellent data.

Unfortunately the failure rate with our ROC made lines is not so good...that said, their price tags are indeed very competitive.

Getting back to focusers, the Micro-touch at $US500 will not disappoint IMHO.

[gregbradley]

Peter,

Do you use your Starizona for autofocusing?

Greg

[Peter Ward]

Yes. The nice thing about the micro-touch is it couples to the fine focus
knob shaft, hence adjustments are very precise.

I have a Chinese unit that couples to my FSQ...but for reasons beyond understanding couples to the coarse focus shaft. :shrug:

[joshman]

My understanding is that the chinese steppers usually use a stepper that has a reduction gearbox, which give an inordinate number of steps per revolution, when coupled with the focuser, you end up with near sub-micron resolution per step in the focus mechanism. if you're dealing with large critical focus zones, the 10:1 reduction of the fine focus isn't necessary.

[Peter Ward]

Large zones are simply not a hallmark of Astro-Physics optics ;)

[joshman]

my understanding is that the critical focus zone is a function of the physical parameters of the scope, and nothing to do with the manufacturers quality. (the mechanical quality of the focuser in being able to realise the required fidelity is another matter altogether though).

In particular, the wavelength of light, seeing conditions, telescope aperture and effective F-ratio all play a part in the how large the critical focus zone is. ultimately, a stepper motor like the ZWO EAF that hase 5760 steps per revolution is more than accurate enough on the course focus to deliver accurate focus.

[Peter Ward]

Disagree. Dick Suiter's book on star testing 'scope optics ponders this at length. Excellent optics "snap" into focus.

Those with SA or some other fault never really reach focus...they sort of endlessly mush through it.

Thats said, sure, faster optics have tighter zones and are more sensitive to focal plane tilt etc., but it's often the case that a whole lot more needs to be on the money first.

[joshman]

Interesting, I'd be keen to see the quality of AP scopes. I've only ever heard good things about them.

[DavidTrap]

I recall reading something about focus motors attaching to the coarse knob being better because it removed another 10:1 gearbox that introduces slop/backlash. Nonetheless, my focus motor attaches to the fine shaft of my AP scope. Random checks of autofocus with a bahtinov mask have usually been satisfying.

DT

[lazjen]

I got the Posi Drive for the Feathertouch on my scope. I control it via the Pegasus UPB.

It seems to work very well, but I can't really recommend it, because they're basically out of stock and difficult to get.

[gregbradley]

I have a POSI focuser but Starlight sent me the wrong model. I am hoping they will take it back and swap it out for the correct model.

Greg.