Focus Control Current Position -- is this normal?

[Lee_P]

Hi SGL Wizards,

I'm using an ED-80 with HitecAstro DC Focus, and am controlling it via SGP Pro. I've got autofocus working well (hooray!) but notice that each night the Focus Control's Current Position number gets larger and larger. For example, a month or so ago it was around 9000 for focussed stars with a H-a filter. Tonight it's 12884. Is this normal? I'd expect the number to be absolute, i.e. always around the same number but with some slight variations given temperature and the like.

Thanks in advance,

 - Lee

[RayD]

9 minutes ago, Lee_P said:

Hi SGL Wizards,

I'm using an ED-80 with HitecAstro DC Focus, and am controlling it via SGP Pro. I've got autofocus working well (hooray!) but notice that each night the Focus Control's Current Position number gets larger and larger. For example, a month or so ago it was around 9000 for focussed stars with a H-a filter. Tonight it's 12884. Is this normal? I'd expect the number to be absolute, i.e. always around the same number but with some slight variations given temperature and the like.

Thanks in advance,

 - Lee

This is a Hitec issue not SG Pro.  As the controller doesn't report its last position to SGP on start up, it just takes the last known position.  If your focuser moves when the power is off, this position doesn't change so it will be out, and if this is only a little bit, over time it will be cumulative.

If you use a Laskeside the calibration is within the unit, so it reports its actual position to SGP and doesn't have this issue, but the Hitec driver I think is a little more basic.

It doesn't really matter too much.  All you need to do is every now and then just do a re-zero on SGP so it knows what is fully in.

[Lee_P]

Ok, thanks for clearing that up.

[RayD]

8 minutes ago, Lee_P said:

Ok, thanks for clearing that up.

One thing just to have a little check of Lee is if you are using a Crayford type focuser this could be indicating slip, so you may need to look at this and perhaps asjust the focuser (mechanically) to reduce slip.  Main thing is it isn't absolute, so SGP will just work from the start reading.

[LightBucket]

The Hitecastro DC focus, is for a 12v DC motor and not a stepper, so it wont be very accurate, as DC motors dont have repeatable position, or am i missing something...

[RayD]

4 minutes ago, LightBucket said:

The Hitecastro DC focus, is for a 12v DC motor and not a stepper, so it wont be very accurate, as DC motors dont have repeatable position, or am i missing something...

Could be, but SGP still needs to know or assume the starting position, and if the focuser moves whilst the power is off then this doesn't change relative to the focuser.  I have the same issue with my Mount Hub Pro running on my Lakeside motor, which is a stepper.

[LightBucket]

Yes, been looking into the mount hub pro, but the stepper controller leaves a lot to be desired, as it only works with full steps, and with some motors such as the feathertouch micro motors, this only equated to approx 750 steps per rev, and not enough for me... am supprised they haven’t upgraded the controller, i have also a pegasus motor and controller and that gives 8500 steps per rev which is superb...

sorry OP a little off topic..

[RayD]

11 minutes ago, LightBucket said:

Yes, been looking into the mount hub pro, but the stepper controller leaves a lot to be desired, as it only works with full steps, and with some motors such as the feathertouch micro motors, this only equated to approx 750 steps per rev, and not enough for me... am supprised they haven’t upgraded the controller, i have also a pegasus motor and controller and that gives 8500 steps per rev which is superb...

sorry OP a little off topic..

Yes agreed, I have the Pegasus on my TS80 and it works absolutely fine.  I also have the Pegasus Hub Ultimate and the focus controller in that works really well.

[LightBucket]

27 minutes ago, RayD said:

Yes agreed, I have the Pegasus on my TS80 and it works absolutely fine.  I also have the Pegasus Hub Ultimate and the focus controller in that works really well.

Have you tried the pegasus motor on the mount hub pro, if so how many steps per rev does that give, that info would be useful to me..

[RayD]

Just now, LightBucket said:

Have you tried the pegasus motor on the mount hub pro, if so how many steps per rev does that give, that info would be useful to me..

I've not but I will be as I've just got an adaptor I've been waiting for for the TS so I'll let you know.