Trouble autoguiding (ST-4) - Forums

Topic starter

Aug 5, 2022 · Edited: Aug 5, 2022

I am trying to autoguide with my EQM-35 mount. The camera is a ZWO asi178MC and the scope is a SVbony 60mm f4.
The image camera is an Altair astro 294c and the scope is a Skywatcher 130 PDS.

I'm not sure if I'm missing a step but I think I'm doing everything right. I balance, level, polar align etc exactly as I would have before and can get lovely long subs > 1min so I'm happy everything is good there. I then attach the ST-4 cable between the mount and the guide camera. The mount has two ports, one on the controller (I'm not connecting the mount to my pc, no pulse guiding or ascom etc) and one on the mount itself. I tried both of these ports.

I run PHD2 and setup the camera and scope. It gets the pixel pitch right from the camera autodetect and I enter 240 mm as the focal length. I select on-camera for the mount and connect both. I built a dark library and started looping, autostar detect. I let it choose a star and begin calibration but it just counts west step up and up until it fails with "star did not move enough" error.

I can't see what's going wrong? It's focussed, I'm using the default settings, no messing around. The only thing I can think of is that when I'm slewing the mount with the controller, I have to press the down arrow a few times before the mount responds in that direction. Other three directions, no problem. I wonder if the camera is trying to send this same signal to the mount and it's taking more tries than it should because of this? It's not backlash btw, even on high speed when movement is audible, the button press doesn't work unless I try multiple times. Holding it doesn't 'eventually work' either. Has to be discrete presses.

Any advice on this would be great because there's a load of clear nights coming up in the UK and would like to get the autoguiding working.

Cheers!

Helpful Engaging

andrea tasselli

Frequent contributor

Aug 5, 2022 · Edited: Aug 5, 2022

If the mount is under warranty just return it asap. There might be a setting in phd2 that does the trick but it might not be of help as the lag time might just be too great for your image scale. Failing that I'm not sure what else can you do. You can try using pulse guiding if the mount supports ASCOM.

matt113d

Topic starter

Aug 5, 2022

Thanks Andrea,

I have a second controller from another mount I have just tested and works without this fault. I'll try it with that tonight and see if it resolves the problem!

Cheers,

Matt

Well Written Respectful

matt113d

Topic starter

Aug 5, 2022 · Edited: Aug 5, 2022

Sadly the controller was not the problem. I'm standing next to the scope and no evidence that the camera is sending any info to the mount whatsoever…

Also just to mention, I tried guiding with my imaging camera and same problem.

EDIT: not sure if anyone other than me is following this but if future internetologists are interested, I've combed the forums and web pages dating back 10 years and tried everything suggested (except ascom, not geared for that right now). All the settings suggested to be changed, tightening the clutches, aiming at specific targets. Nothing. I think there must be a problem with the cable. The mount has two ports so unlikely it's both of them and my other camera didn't work so unlikely to be both camera ports. So must be the cable. If not, who knows…

andrea tasselli

Frequent contributor

Aug 7, 2022

I've had a issue once with a st4 cable which was inverted wrt the standard wiring. As a last resort I'd try getting a new one and cross fingers. The only other option is to move to OnStep and ditch the current controller. This would be the right move to do anyways as it is so much better.

Tommy Blomqvist

Aug 7, 2022

I've never liked the ST4-interface and have helped with numerous of incidents with connection problems.

I suspect that you want to be able to use the handcontroller and if it isn't version 5 or newer there is no USB connection available.
(And the HC with USB is a plain integrated USB to serial converter).

When I analyzed ST4 problem i've often started with measuring the signal output at the connection going into the mount.
There is no real signal (voltage) output from the camera thru this interface. Pin 2 is the common level and Pin 3 thru 6 are the four directions. I think most guide cameras are using opto couplers for this.
Not active directions are normally "floating" and the mount are using pull up (or down) resistor circuits.

You may also test the mount the same way by simulating logical levels on pin 3 - 6.

BUT I really recommend you to skip the HC and switch to EQmod. This solution tends to work much better in most cases.
There is also normally no need for star alignment if you just are close to polar aligned and implement plate solve instead.

Helpful

kuechlew

Aug 7, 2022

While it doesn't address your issue just one comment to your list of activities. I attach all cables before polar alignment. After polar alignment I no longer touch anything of my rig - and in case I have to do it I'll double check polar alignment afterwards. Very easy to mess up polar alignment on lightweight rigs. Maybe I'm too touchy …

Clear skies
Wolfgang

matt113d

Topic starter

Aug 8, 2022

Thanks everyone. I think having these solutions available for others struggling is great. I can happily tell you I'm currently guiding beautifully at 10 minute exposures 650 mm focal length! Suffice to say I'm chuffed.

Turns out the cable that came with my second hand zwo camera on had 4 wires between rj12 connectors. Not sure what possible use there is for that or why is was with it in the first place but Amazon and a day later and worked first try effortlessly exactly as it should.

Thanks again for the support everyone!

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Lynn K

Aug 11, 2022 · Edited: Aug 11, 2022

Glade to hear it.

Lynn K.