ZWO Electronic Automatic Focuser

[Saturn488]

Has anyone got one of these? Highly anticipated for a long time and wanted to see if anyone had any thoughts about it?

[The_bluester]

I do, I was going to do a quick review for Sidereal Trading who I got it through but I have not gotten a lot of use out of it just yet due to clouds. From the little use I have got out of mine it seems consistent position wise and without noticeable backlash, on my little ED72 it can rack the focuser through the full travel range quickly enough not to be a bother when you rack it fully in in to pack up or back out again setting up next time. Setup was a 5 minute job once it was mounted.


One thing to note, you don't need to buy a temperature probe with it (I did) unless you want to use temperature as an input from a specific area rather than at the focus motor. The early documentation at least, did not mention it but it has an internal temperature sensor which is disconnected if you plug in the one on the flying lead.

[Saturn488]

Fantastic.

I currently use a Skywatcher Focus motor with the HiteCastro focus controller box on my refractor.

Thinking of replacing it with the ZWO.

[The_bluester]

I just finished remaking my cabling and did a bit more testing on mine, it equates to abour 2.2 microns per step, with a roughly 60 micron critical focus zone on the ED72 it should be pretty forgiving.

[cyberblitz]

The biggest issue i have with this focuser, is that once it is fitted you can't manual focus; there is no way to easily disengage it without undoing the grub screws!!! For me this is a real pain, becasue i don't have a permanent setup. It takes me an hour to setup usually and focusing my scope is part of it and i have to connect it to a PC just to be able to focus it now!!

[beren]

Hand control is nice....and more adapters

[LewisM]

You sure that's not the hand control from a hospital bed Stuart? :lol:

[beren]

:P was trying to think why it looked so familiar

[The_bluester]

That I would assume would resolve cyberblitz's issue, if you can effectively use it manually.

Mine is an imaging rig only so manual focus does not matter. I know I just need to fire it up, send it to about 3800 steps from fully racked in and it will be close enough to get started. I have used it for another night since posting with no issues.

[cyberblitz]

I am expecting the hand controller but ZWO are very, very slow shipping these out. Actually, i purchased my focuser using BINTEL, they are expecting a delivery from ZWO next week but not necessary the hand controllers.. I'm pretty desperate for this hand controller now

[The_bluester]

I do understand though why they don’t provide for it. If you move the focuser manually then the calibration is gone position wise.

For something like the Moonlite units on their own crayford type focusers it is not an issue as from what I have seen the motor runs a calibration routine to ensure that it is fully racked in at zero steps, but given these could be put on anything at all they can’t really do that.

The Moonlites as an example can just rack the focuser in on connection by enough steps to be sure it is all the way in and if it was already there then the crayford style focuser will just slip, but do it to my SCT and you are looking at a damaged focuser assembly.