ST4 port working?

[misterp]

Hello & help please,

I was trying to get autoguiding working on my eq5pro using phd2 & qhy5 Finder guider connected using the st4 port.

When I start to calibrate the selected guide star moves west as expected of about 16 steps, when phd2 changes to move east the star doesn't move back at all. After this the declination backlash won't clear.

I know the system is balanced and the gotos work fine.

So I then took the scopes off the mount and put them on an Ioptron Smart EqPro and everything works fine.

Is there a way of checking the st4 port on the eq5pro please?

Thanks in advance

Ian

 

[Oddsocks]

There are two versions of the ST4 port cable, one version is pin 1 at one end to pin 1 at the other, the other version is a "changeover" cable where pin 1 at one end becomes pin 6 at the other.

If you use the "wrong" one for your mount then only one direction will work, from memory I think this is DEC- but can't be sure.

[Darren Hill]

In order to test the port, go to "tools" at the top of the menu in PHD, select "manual" guide and you will have four directions to select from. You can do this during the day by increasing the guide pulse duration and listening to the mount while pressing each direction. I assume you used the same cables on the other mount. where they are functioning okay?

I have had an issue like this where the USB connection was damaged on the camera, and because of this communication sent via USB from the software to the camera to pulse on the ST4 cable was intermittent or non functioning on the RA axis. The problem doesn't necessarily have to be the ST4 connection. Your EQ5 Pro is also capable of being guided via USB only with EQMOD/ASCOM sending the commands directly to the mount bypassing the ST4 connection. 

Check the pins on the connections, and the wires behind the plastic plugs. Since you state that the mount travels West, but not East suggests to me that the one of the  + or - connections on an axis is not working, or could be making intermittent contact

Edited May 10, 2017 by Darren Hill
Added point

[misterp]

Thanks for your thoughts.

same cables, same cameras & same scope, even same laptop.

The manual guide option looks like a good bet to see if the port works

Thanks again, I'll try later

Ian

[Oddsocks]

A quick look at the manuals for the Ioptron and the EQ5Pro show both use the same configuration of wiring for the signals so the cable should be ok.

The problem may be too much backlash in the drives.

In the Synscan handset set a faster guide speed when using the ST4 port.

To test there are two possibilities.

In PHD use the Tools and Utilities "Manual Guide", as long as PHD is configured to use ST4 guide signals you can manually press the direction buttons and watch to see if the mount moves in all directions.

When using the ST4 port the guide speed is very slow and is set in the Synscan handset so to "see" any movement go into the Synscan setup and choose a fast guide speed otherwise it is hard to see anything happening.

To test the mount guide port via hardware you need to make up a test lead with a Rj12/6 plug at one end, strip back the other end of the cable and momentarily connect the wire from pin 2 (ground) individually to any of the wires from pins 3 to 6. As long as the wires are connected then the mount will drive at the guide speed set in the Synscan handset according to the wires connected.

Depending on the mount make and version the wire on Pin 1 may carry +Ve and the wire to this pin should be left covered and insulated with tape, if you accidentally connect pin 1 with any other pin then the ST4 port electronics can be damaged.

Pin 2 = Common (ground)

Pin 3 = +RA

Pin 4 = +DEC

Pin 5 = -DEC

Pin 6 = -RA

Following images show the ST4 port pinout for the Smart EQ and EQ5Pro.

Ioptron:

 

EQ5Pro:

 

 

Edited June 29, 2017 by Oddsocks

[misterp]

Thanks again

[Oddsocks]

3 hours ago, misterp said:

When I start to calibrate the selected guide star moves west as expected of about 16 steps, when phd2 changes to move east the star doesn't move back at all. After this the declination backlash won't clear.

I know the system is balanced and the gotos work fine.

Forgot to mention before,

If excessive backlash is the problem you can prove this by deliberately unbalancing the mount a little, this is quite a normal approach to use and helps guiding in mounts that have poor worm-gear contact.

For RA backlash:

When setting up balancing adjust the counterbalance weights to be east side heavy, that is, if the telescope is on the east side of the mount adjust the weights up towards the mount a little so that the telescope wants to move downwards towards the ground, the unbalanced weight should be equal to around 0.5Kg to 1kg.

If the counterbalance weights are on the east side of the mount then adjust the weights further out from the mount so that the weights want to move downwards towards the ground, the same range of unbalanced weight should be used, 0.5kg to 1kg.

For DEC backlash just adjust the OTA in its rings so that it is nose heavy, or if this is not possible, add a weight to the nose end of the OTA, the unbalanced weight should be as before 0.5kg to 1kg.

For backlash in RA and DEC then unbalance both axis.

If this improves PHD operation and allows calibration then consider adjusting the worm-gear mesh for whichever axis is the problem.

When the mount is unbalanced in this way it ensures one side of the worm is firmly pressed against one side of the teeth of the axis gear and prevents or reduces backlash. As long as the unbalanced weight is kept within the range suggested then no harm will come to the mount. If relying on unbalance to improve guiding then as the object being imaged crosses the meridian the effect of the unbalanced weight crosses sides and guiding will usually not be able to compensate. When imaging with unbalanced weights stop guiding as the meridian crossing is approached, flip the mount to the opposite side of the meridian and adjust the RA counterweights again to keep the east side heavy and start guiding, no new calibration is required.

HTH.

[misterp]

Hi,

So using phd2 and selecting manual guide there is definitely longer motor noise/movement when nudging west that any other direction, this is with no scope or weight attached and the guide cam on the table. Think new motherboard is the solution.

Once again thanks

Ian

[Davey-T]

Have you tried pulse guiding so avoiding the ST4 plug ?

Dave

[Oddsocks]

1 hour ago, misterp said:

 

Hi,

So using phd2 and selecting manual guide there is definitely longer motor noise/movement when nudging west that any other direction, this is with no scope or weight attached and the guide cam on the table. Think new motherboard is the solution.

 

Ian,

What guide speed is set in the Synscan handset?

Don't forget, when driving east with guide speed set to x1 sidereal via the ST4 port the RA motor does not turn, the easterly motion at 1x sidereal is actually provided by the earths rotation. When guiding west at 1x sidereal then the RA motor turns at 2x sidereal so you would notice it more.

The maximum guide rate you can set via the ST4 port autoguiding in a Synscan / EQ5 is x1 sideral so it will never move physically eastwards and if x1 is selected under Synscan Setup menu, item Autoguide rate, then the motor stops completely. At guide rates lower than x1 then the RA motor will continue to turn westwards  but slower than normal tracking speed.

Perhaps a simple test of the ST4 port would be to carry out a false one star alignment indoors, select an object and slew to it, read the current RA and DEC angles displayed on the Synscan handset, with a guide rate of 1x sidereal set for autoguiding use the PHD move mount buttons for up/down right/left, the position angles for RA and DEC shown on the Synscan handset will change if the ST4 port is functional and the guide commands are reaching the mount over the ST4 port.

Direct guide or pulse guide via eqmod/ascom allows much higher guide rates but ST4 port guiding on the Skywatcher EQ5 is limited to 1x sidereal or lower only, this is the same speed as normal tracking, don't be too hasty in condeming the mount board, there may be nothing wrong with it....

Edited May 11, 2017 by Oddsocks

[misterp]

9 hours ago, Davey-T said:

Have you tried pulse guiding so avoiding the ST4 plug ?

Dave

Hi Dave,

I tried connecting via the hand set. Connect & worked fine in Cartes Du Ceil but in phd2 I got the error message something like 'mount doesn't support pulse guiding'

Thanks Anyway

Ian

[misterp]

Hi,

Once again thanks for your thoughts.

I decided to get a new motor control box, took a while as Optical Vision were out of stock but it has arrived.

Had a play last night and it worked first time.

Kind regards

Ian

[Sacrofts]

Hi, new to this forum.  Searched for a topic like this online, and reading through I just had to sign up and share my experience so far.

I`ve also been having this very issue.  I use a NEQ6 mount being guided by a QHY5 camera through the ST4 port with PHD2.  My polar alignment is pretty good, and balancing is not so bad. The mount is about 1 year old, so I`d be surprised if there were problems at this stage, it’s been running very well visually.

For imaging, I`ve noticed the same thing.  Will calibrate West, tries to do East but nothing moves, it eventually pretends it’s done something and continues to calibrate north and south.  When it gets to guiding, I get a lovely Periodic Error graph leaning towards the west.  Polar alignment is ok: Dec guiding stays within 0.5s of arc, but the RA creeps up to 12s west and back again in a roughly cyclic pattern.  Guide pulses are sent by PHD2 to correct the drift, but nothing happens and it eventually returns all by itself before starting the next cycle of drift.  I`ve been wracking my head over this one for months, and to find a recent post on exactly this subject, makes me think it isn’t a mechanical fault.  I`m beginning to suspect the wires in the ST4 are as oddsocks has suggested.  I`ve managed to hook up my mount late last night to a serial-WiFi bridge to try pulse guiding to see if that works any better.  Alas, dawn came before I could try it out.  If I get a chance to confirm the results I’ll post it here.

On a plus note, the NEQ6 drifting just 12s arc in RA effectively unguided is one of the small positives to be had out of this.  But I`m determined to squash it smaller!  All my exposures, no matter the exposure time have the same amount of drift appearing in the stars.  I`m betting its that wiring issue.  At least a new cable is the cheapest remedy to try.

[Sacrofts]

Misterp, `mount doesn’t support guiding` error message comes up when the hand controller is using an older firmware than PHD2 wants.  Update the firmware from the Skywatcher website.  I had to force mine into Low data mode to get a connection to update.  After the update PHD2 didn`t complain at all.  I`ve yet to test the Ascom connection under the stars though.  Basic NSWE movements were working for me.  Just need to check the pulse guiding.