Guide camera cable connections confusion !?!?!?

[Tonk]

I've just acquired a SX Lodestar guide camera for use with my QSI683 camera and a 10 Micron mount controller. I've installed the PHD software and SGP software but before I have my first outing to try this hardware out I've just hit some confusion regarding the physical camera cable connections. There is a USB connection between the guide camera and the computer and there is a phone socket connection for a guide control cable direct to the mount. Which do I need to connect - is it one or the other or both?

 

So the specific questions are:

1) Do I need to connect BOTH the USB and the guide cable??   I suspect there are two alternative configurations going on and its one or the other but am not sure
2) Which of these cables are needed by PHD and which are not?  PHD clearly needs the USB connection to the computer but does it also need the direct to mount cable? If it doesn't I assume PHD controls the mount another way (ASCOM?? - 10 Micron mounts connect to external computers via a LAN)
3) Which of these cables are needed by SGP and which are not?  I think SGP delegates guiding to PHD  - is that right?
4) How does PHD involve itself with the direct camera to mount guide cable? I suspect it doesn't.

5) How does the direct guide camera to mount cable really function - is any other software needed to set it up?

Yeah - I'm confused and likely misunderstanding something!
 

[SkyBound]

Hi,

answers:

1. Yes you need to connect both

2. PHD requires the USB cable and sends commands back and fourth to the guide camera on that, then the camera sends commands to the mount via the ST4 guide cable.

3. USB, and yes it works with PHD and negates the guiding to that.

4. No it doesn't  but in the PHD settings there is an option to check "on camera" which means you are using an ST4 cable and not Ascom pulse guiding, which does not require the ST4 cable and just the USB, so one less cable to worry about.

5. The ST4 guide cable functions by sending either a NSEW signal down one of four cables within it, to tell the mount which way to move, the signals are amount of milliseconds to pulse the mount in any given direction.

hope that helps

[Tonk]

Thanks SkyBound - almost there - just two clarifications needed. In your answers

2. "negates" - was that an auto-correction of "delegates" - makes better sense if "delegates" and if so I get it

4. So just to clarify this one - PHD can be set to send commands back to the camera and the camera forwards those via the guide cable to the mount - in which case you need both cables connected
    OR if you set PHD to not use the "on camera" option and it will instead use the mounts ASCOM driver and then you only need the USB cable

 

[SkyBound]

Sorry yes auto correction, should have been delegates

and yes on the second one too, you can use just the USB cable (that's how I do it) and use the Ascom mount driver and pulse guiding, it is supposed to be more accurate, and uses one less cable.

Using the pulse guide method on my mount which is an fork mounted SCT on a wedge, my handset is connected to my PC via a serial cable, not sure about the Mount you have though..as the PC needs to talk to the mount hand control when guiding, so in my case it works flawlessly.

[cjdawson]

For further information, setups get better results from ST-4 guiding verses using commands sent to the scope via the handbox.

For example my scope when I first got it did not support guiding commands directly, so the guiding was done by issuing normal NSEW commands at the slowest speed. This had a problem as the slowest speed is sidereal time.   On my mount, the ST-4 commands are issues, and the mount corrects at 2/3's of sidereal.  This means that when making RA corrections, the RA motor either speeds up, or slows down - it never comes to a complete stop.

[SkyBound]

1 minute ago, cjdawson said:

For further information, setups get better results from ST-4 guiding verses using commands sent to the scope via the handbox.

For example my scope when I first got it did not support guiding commands directly, so the guiding was done by issuing normal NSEW commands at the slowest speed. This had a problem as the slowest speed is sidereal time.   On my mount, the ST-4 commands are issues, and the mount corrects at 2/3's of sidereal.  This means that when making RA corrections, the RA motor either speeds up, or slows down - it never comes to a complete stop.

Sorry to disagree, but pulse guiding is much better...

[cjdawson]

1 minute ago, SkyBound said:

Sorry to disagree, but pulse guiding is much better...

That ok, you can disagree.  My experience is that the ST-4 works better than having the mount stop completely and introducing a backlash element to the equation.

Of course, with ST-4 guiding, you have to have small corrections.  As a result your polar alignment has to be good, as when things go wrong it can take longer to make a big correction.

[Gina]

Yes, I have always believed that pulse guiding is better - I've never used an ST-4 cable.

[SkyBound]

1 hour ago, cjdawson said:

That ok, you can disagree.  My experience is that the ST-4 works better than having the mount stop completely and introducing a backlash element to the equation.

Of course, with ST-4 guiding, you have to have small corrections.  As a result your polar alignment has to be good, as when things go wrong it can take longer to make a big correction.

Why would your mount stop completely, that does not sound correct...it should slow or speed up, but not stop !

 

[Starlight 1]

I am not going into get what best for guiding, I like to know why you are guiding with a 10 Micron mount.

[cjdawson]

26 minutes ago, SkyBound said:

Why would your mount stop completely, that does not sound correct...it should slow or speed up, but not stop !

 

And that was the problem with guiding using the serial cable on a Meade LX-90, it did not include the commands to slow the drive, just stop it.  The ST-4 interface however does slow the drive.   Hence why my experience is that it is better than using the serial cable.

[SkyBound]

1 hour ago, cjdawson said:

And that was the problem with guiding using the serial cable on a Meade LX-90, it did not include the commands to slow the drive, just stop it.  The ST-4 interface however does slow the drive.   Hence why my experience is that it is better than using the serial cable.

I have autoguided an LX90 fork mounted scope on a wedge, with no issues at all, and have had subs longer than 10 mins with nice round stars...? So it can work, I also had the APM port on it which included a guide port, so I did once try an ST4 cable, and the guiding was certainly no better, in fact maybe a little worse, hence what I always used the serial port on the handset and pulse guided.

[Tonk]

"I am not going into get what best for guiding, I like to know why you are guiding with a 10 Micron mount. "

 

You eventually have to albeit at a very low correction rate - 10 Micron themselves only rate unguided tracking remaining below 1'' error in 15 minutes. This is my experience with a ASA N10 Newtonian on a 1000HPS - you cant go much longer than 10 - 15 minutes without paying very careful attention to ensuring correct refraction data especially if conditions are changing. Also my Newtonian astrograph doesn't model as well as my refactors - much larger RMS pointing error (x10 worse) - but this can only be expected. Also I've deliberately miss set refraction data to determine how critical it this for tracking at mid sky altitudes - and it is.  

I also have a 2000HPS that so far tracks well for at least 20 minutes - I haven't tried longer yet. 

[Davey-T]

1 hour ago, SkyBound said:

Why would your mount stop completely, that does not sound correct...it should slow or speed up, but not stop !

 

I thought I'd read that PHD didn't reverse the RA drive but simply stopped it and waited for it to catch up.

Dave

[kens]

It's not a function of PHD but the motor control. Essentially all mounts are driven in pulses and any movement east is achieved by withholding motor pulses. This applies equally to ST4 as it happens inside the motor control unit. Some mounts may reverse the RA motor for guide speeds greater than sidereal but as it causes backlash the highest guiding speed eastwards is usually 1x sidereal and motor reversal is used only for slewing. Withholding pulses should not cause backlash unless you are out of balance.

Whether you use ST4 or pulse guiding with PHD it is beneficial to connect the mount via USB (use Aux Mount if you mount setting is On Camera for ST4) as you can then calibrate once and use the same settings at any declination. It also helps with troubleshooting to have the mount tell PHD it's settings

[Tonk]

I'm now confused again - is the guide socket on a 10 Micron an ST-4 one or something else? I've not seen a USB connection on the controller either so I'm not sure how this latest advise is helping me.

[RayD]

I believe the GM100 HPS does have an ST4 port:

http://www.10micron.eu/en/product/gm1000-hps/

You can choose whichever guiding you want, but I do believe from watching Chris Shillito on EQMOD videos, that pulse guiding does have some benefits.  I don't have an ST4 cable plugged in and mine is fine, but using ST4 is not going to hurt.

[Davey-T]

This from manual.

Dave

 

[Tonk]

Thanks Davey-T. OK I understand the st4 now. The "you can" bit in the manual about RS232 is of not much use to me as it neglects to say how!!

 

What about guide  control via the 1000HPS LAN port. This is how it's connected to my computer and how the virtual keypad app controls the mount and how ASCOM programs also control the mount (e.g. SGP). I would have thought guiding could be done this way through the LAN port?

[Davey-T]

I've got mine running over wireless LAN but not guiding.

The common connection for pulse guiding is an RS232 serial port connection traditionally following the LX200 protocol, either via RS232 socket or via a serial to USB converter, presumably this can be done on the 10Micron using the RS232 socket.

There was someone on here who used guiding on their 10Micron when they first got it, Barry Wilson possibly ?

Have you had a browse of the 10Micron forum ? there may be some posts on there about guiding.

Dave

[Tonk]

OK dumb question I know - what do you connect the 10 Micron  rs232 to?my Intel NUC computer doesn't have rs232

 

 

[Tiny Small]

29 minutes ago, Tonk said:

OK dumb question I know - what do you connect the 10 Micron  rs232 to?my Intel NUC computer doesn't have rs232

 

 

You use an RS232 to USB cable and stick it in a free USB port. They cost in the region of £20 to £30 quid. Startech ones are pretty good but there are many others out there.

However... if you can control the mount through the LAN connection, I think you may be able to guide through it too. The computer is still sending movement commands through the LAN cable if you are controlling it so there should be no reason why you can't guide from it. Whether or not the software you use supports that or not, I don't know.

[Davey-T]

3 hours ago, Tonk said:

OK dumb question I know - what do you connect the 10 Micron  rs232 to?my Intel NUC computer doesn't have rs232
 

 

5 hours ago, Davey-T said:

The common connection for pulse guiding is an RS232 serial port connection traditionally following the LX200 protocol, either via RS232 socket or using a  serial to USB converter in the 10Micron using the RS232 socket.

Dave