Synscan question

[raymo]

Can somebody tell me, if when I select a slew/ tracking speed on my
HEQ5 hand controller, does the controller directly set the desired speed, or does it simply tell the motor controller board what speed is required, and the board actually sets the speed? I know nothing about stepper motors; assuming that the supply voltage is within the acceptable range,
can the motor run slow, or is it a case of they work, or they don't?
If my problem should turn out to be the motor board, does anyone know whether it is possible to get it looked at, or where to get a replacement?
Thanks in advance
raymo

[AndrewJ]

Gday Raymo
The Hbx sends a std serial command to the motor card to run at a set speed, and the motor card then does all the hard work.
The Hbx has preset speeds, but if you use something like EQMod, you can manually set the speed to just about anything from barely moving to 800x sidereal.

Andrew

[raymo]

Thankyou Andrew. I am being sent an Hbx to try, and see if it fixes my problem, but it seems that as the mount is tracking [albeit not fast
enough], it is more likely that the problem is in the motor card. If it turns
out to be a card problem, it sounds like I should try EQMod as a first cheapest fix.
raymo

[AndrewJ]

Gday Raymo

I have mainly been playing with the low level commands directly for my own purposes, but i know EQMod has a function in it to tweak the tracking speed but i'm not sure on its exact usage.
Do you know ( in absolute terms ) how slow you are tracking????
( Ie have you used PEMPro/PHD/Metaguide etc to see what yr RA drift and tracking is really like on both sides of the meridien? )
That will be more instructive up front than just trying EQMod.

Andrew

[raymo]

I am not very comp literate. I bought BYEOS and have never used it.
All I have measured fairly accurately is my possible sub time without
star elongation. With a f/l of 1000mm at or near 0 declination I have always managed 60-90 secs [depending on my P.A.], and at high
decs such as Crux, 100-120 secs. In both cases the limiting factor
was drift in Dec, not in R.A. Now I get around 9-10secs and 16-18 secs
respectively. During that short space of time there is no Dec drift at all; all of the drift is in R.A. so it is tracking much slower than normal. I have checked everything mechanical, no slipping gears.
As I said in another thread, adding or removing large amounts of weight [7-8kg, not good for the motor I know] made no difference to the tracking rate, so I think the problem is electrical rather than mechanical.
raymo

[AndrewJ]

Gday Raymo

Again, are you sure it is drift and not Periodic error?
PE will show up in different ways in shorter subs, as it depends on where in the PE cycle you did each sub.
ie Some may be good and some bad depending on how much PE there is in the range where you did the subs.

Andrew

[raymo]

Hi Andrew, I am sure periodic error has nothing to do with this problem.
Start tracking, and it will immediately start to fall behind as it were. The drift starts as a straight line, and continues that way for as long as you keep tracking, joined after a couple of minutes by the Dec error drift,[ in
a different direction of course]. You will of course see the effects of P.E.
on that straight line. The line is not really drift at all; it is just that the tracking is not keeping up. I still need to know whether stepper motors can run slow, or whether they either run at the commanded speed, or not at all.
raymo

[AndrewJ]

Gday Raymo

I dont doubt what you are saying, i am just pointing out that something like PEMPro/PHD/Metaguide will give an absolute value to the drift you are seeing and from that, you may deduce something.
Steppers can certainly miss micro steps if overloaded, and hence run slow, but again, unless we know the absolute characteristics of the drift, its hard to tell whats causing it.

Andrew

[raymo]

I don't have a laptop available for a few days, and then am going up to the big smoke for about a week, so it'll be at least ten days before I can try anything. The whole thing is quite odd; I've been using the same rig
for close to two years without any tracking problems.
raymo

[killswitch]

You've probably done most of this already but if not:

-Check RA axis rotates smoothly and not binding

-Try a different power source, preferably 13-15v

-Reset handset to factory settings

-Reflash Synscan firmware to newer or older

[raymo]

R.A. smooth and free.
Power 13.7v via mains adaptor, also car battery.
I've never changed the handset settings, so I assume it is still as it left the factory.
Good idea to go back to 3.27 and try that.
thanks
raymo

[raymo]

I'm beginning to think that the problem is in the handset, as BruceG
suggested it might be. Last night the 2 star alignment error readouts
went crazy. I was down to around a minute on both axes, and the next iteration, after a tiny adjustment, read Mel +33* 22' 11", Mal -33* 09' 05"
which is clearly impossible. The next iteration ,without any adjustment,
yielded Mel +14* 20'and Mal +14* 10'. Gibberish.
raymo

[glend]

Raymo where are the encoders located? I assume there has to be some device that tracks where it is pointing or is it all software based on pulse counting by the controller?

[raymo]

I don't really know Glen, but I think that the latter is probably right.
raymo

[glend]

I am looking through my Synscan manual for V3.35, just trying to find something related to your problem, and to make sense of hiw it uses encoding. In section 8.12 Synchronixing Encoders, the manual mentions needing to re-sync the encoders if the correct position has been lost
Have you tried to re-sync the encoders as per 8.12?

[Eden]

In a typical session it is only necessary to re-sync the encoders if you disengage the clutch and perform a manual movement on either the declination or right ascension axis. For improved pointing accuracy, the secondary encoder should be explicitly disabled in the hand-controller.

Raymo I hope the problem you are experiencing is just something trivial like the hand-controller and that a re-flashing or something similar will resolve it for you.

[raymo]

Thanks for the responses Glen and Eden. I don't disengage the clutch
during a session, so it has never occurred to me to re-synch. Hopefully
I will know more after trying the hand controller that I am being lent.
Re-synching would only affect the go-to accuracy; it wouldn't have any effect on the tracking rate. My go-to is in fact as accurate as it has always been. If the borrowed one fixes my problem I will try re-flashing mine.
If that doesn't fix it, I guess I will have to get a new one. $$$$$$.
raymo