Testing ST4 socket

[Davey-T]

Hi All

If I knock up a cable can I send  "pulses" to the ST4 socket on the mount to see if it's working ? so eliminating PC, guide camera, software etc from the equation.

Anyone know what form ,voltage the pulses need to be ?

Could it just fry the mount ?   

Dave

[Merlin66]

dave,

on the ST-4 connector there's no voltages involved...it just acts like a series of switches. You just need to short the common wire with each of the others in turn to "close" the guide switch for guide corrections in that direction......

Pin 1: Usually not connected, but this may be power pin on some mounts

Pin 2: Common (ground)

Pin 3: RA+

Pin 4: Dec+

Pin 5: Dec-

Pin 6: RA-

See:http://www.store.shoestringastronomy.com/guide_port_cables.pdf

[Davey-T]

Thanks for reply, I'll  give it a go, got the pin out plan for the mount , need to sort it as not responding to PHD at the moment.

Dave

[Davey-T]

Right done that and the mount responds in all directions if I just short out the appropriate pins, Soooo why doesn't it respond in South and East using PHD ?

Any way of testing the output from PHD ?

Dave

[steppenwolf]

What guide camera are you using and have you selected 'On Camera'?

[Davey-T]

Using SSAG , when calibrating in PHD the green square moves up a dozen or so steps then it says it's doing South steps but the green square doesn't move, same happens in East/West then it starts giuding but if the mount is drifting South  PHD sends 

longer and longer pulses 'till it maxes out at 1000ms but none of the guiding corrections make it to the mount and graph shows uncorrected Southerly drift.

Selected on camera and SSAG in drop down list and it connects to camera and loops etc

Dave

[IanL]

Are you sure it isn't responding in just two directions?  It seems odd that calibration/guide commands would work for N and W but not S and E, especially since you have tested the ST4 and it works.

If you had relatively poor polar alignment, you might get enough drift that PHD thinks the calibration steps are working:

- The mount might be failing to respond in any direction, e.g. if you had the wrong settings in PHD; you need to choose 'on camera' to use ST4 guiding otherwise commands will be sent by ASCOM pulse guiding.

- The mount might be responding in all four directions, but the drift is too much for PHD to keep up with.

You can test whether the PHD guide commands are working on a distant daylight target.  Use the PHD 'Tools' -> 'Manual Guide' option, and you'll get four buttons for NSEW.  See if you can get the mount to move in all four directions whilst looking through an eyepiece.  If that works then your set-up is fine and you need to look at other things like polar alignment, backlash (shouldn't affect E-W though), etc.

[Davey-T]

Fitted a laser level in the dovetail aimed at obs'y wall and used the manual commands in PHD and it only seems to move in North and West .

Could it be excessive backlash ?

Attached two 10min pics, one guided one unguided don't look any different. This was after I skewed the PA  a bit to exagerate it so may have confused the issue.

Dave

[IanL]

Sorry should have been a bit clearer when I posted this morning.  As far as East-West goes, you'd only see movement in the West direction.  Assuming the mount is tracking, the East 'motion' is actually to slow or stop the tracking and wait for the sky to catch up, so in a static test you wouldn't see any movement East - depending on the length of the beam you might be able to detect tracking motion over time and perhaps detect it slowing or stopping if you press the manual East button repeatedly.  On my NEQ6 I can definitely hear the change of motor sound when I press go East vs. the normal tracking sound, so that is perhaps another diagnostic.

For North-South, you should be able to see motion in both directions.  If you have backlash then it might take a while to clear if you are going in the opposite direction from the last slew of the mount.  Nonetheless you would expect to see the mount move the opposite way if you keep hitting the appropriate key repeatedly until the backlash clears.

The two pictures look pretty identical to me too, so it seems to suggest the guiding is having no effect on the mount.  Have you checked connectivity on the ST4 cable?  Pretty easy to test for continuity using a multi-meter.  Also check how it is wired.  It should just be a straight through connection on all six pins, no twist in the cable or crossed pairs of wires.

Do you have the option to try Ascom pulse guiding instead of ST4?  Don't know whether your mount supports it or not but might be worth a try.

[Merlin66]

My money is on the cable....As Ian says above check that it is in fact a "straight thru" cable - many telephone extensions look "similar" but are crossed!!

[Davey-T]

Hi Guys

Thanks for the input

Tried two guide cables and bought a new one just in case but no joy.

When I tried it by shorting out the appropriate cables I could see the laser moving in all directions, but not when using the manual controls in PHD.

Am going to try ASCOM next clear night.

Thanks again

Dave

[Davey-T]

So tried tonight using PHD and ASCOM and it works fine, kept Capella in the center of illuminated reticle for twenty minutes.

No idea why it wont work  with ST4 socket.

Dave

[Merlin66]

Hmmmm

If the cable is OK

and the connector on the mount is OK

that only really leaves the connector on the camera - are the pins inside the connector clean and positioned well??

[Davey-T]

Camera (Star Shoot Autoguider) works OK with PHD and ASCOM just refuses to move the mount South or East using the ST4 socket so could be problem with ST4 socket on the camera I guess, will have a look , don't know if it's possible to test it.

Dave

[Merlin66]

Visually, does the socket on the camera look OK?

The only other method is to try the camera on another scope/ set-up and see if pain persists....

[Davey-T]

Hi Merlin ,

Thanks for all your input, socket on camera looks OK, guess I'll give up and stick to ASCOM , have Loadstar  on OAG on obs'y set up but don't really want to disturb it as it takes a lot of fiddling to get right

Dave