Initial installation/position of EAF on SCT

danplouf

Quick question for the ZWO team, after reading the user manual it's still not clear to me before installing the motor focuser itself on the focuser shaft what the position of the focuser should be, prior to installing the EAF? Should I set to ( half way in or half way out) or ( or focused on a star). In other words, if my focuser allows a total of 2000 steps from "all the way in"to "all the way out" in what position should the nub be ideally set before the EAF installation?

Tech@ZWO

if my focuser allows a total of 2000 steps from "all the way in"to "all the way out"
=> hello，the max position and zero position can be defined arbitrarily
take example of the “2000 steps”

you can set 2000 to zero or max step
If the focus position was at about 1500，you can set the MAX or Zero position very close to it（Convenient for the autofocus）

danplouf

Thank you Zwo team, my 2000 figures was a simple exemple!! At the moment I don't know the total number of steps of my focuser allow ( in both direction)?? I just want to avoid a situation where the EAF would move right to the end and would force/damage something caused be the torque of the EAF.

Merci encore

w7ay

danplouf At the moment I don't know the total number of steps of my focuser allow ( in both direction)??

The ZWO EAF allows steps from 0 to 65535, if memory serves. If you hit one of those limits, you will hear a double beep I think, if the sound had been turned on.

However, it is not an absolute range. For example, at any time, you can tell the EAF that it is set to 31000 units. This way, you will get at least 30000 steps up and 30000 steps down from that location. If you need to go below 0, you just move the EAF to 1000 or something, and tell it to re-set that location as 60000. That lets you move 60000 steps below what was zero earlier. Rinse and repeat and you can move practically anywhere. Many people use the settable reference to make sure their focuser does not bottom-out (not healthy for rack and pinion focusers as you can imagine).

The EAF does save this "reference zero" in its non-volatile memory, so that when you power it up next it will remember the most recent setting.

With my various EAF and focusers (I have some 7 or 8 of them, lost count), I see somewhere around 1 µm of draw-tube travel per EAF step (belt driven lenses) to 4 µm per EAF step on my FSQ-85. So, 65536 steps would give a draw-tube travel of more than 60mm -- which should in most cases let you focus from 30 ft away to infinity (more range than you practically need).

Chen