EQMod through EQDir or handset 'PC Direct'

[Mark_C]

Hi all,

I am currently operating my AZ-EQ6 GT using EQMod through the handset using 'PC Direct' mode, it seems to work fine but was wondering whether I would notice greater responsiveness/performance by investing in an EQDir adapter? Has anyone compared performance with both connection methods?

Thanks,

Mark

[red dwalf]

don`t think thats there any real performance to be had but using the eqdir adapter means that the handset is totally unnecessary and is alot easier to use with a pc, just one small usb cable instead of the handset. i haven`t used my NEQ6 pro handset since buying it. 

[Avocette]

I am curious to read responses to the same question. According to the Synscan handset manual the PC signals are just repeated through the handset so there should be no difference in response. I have the impression from EQMOD that using PC direct mode should only be used for 'testing'. One obvious reason for swapping to EQDIRECT would be to save power being drawn unnecessarily to run the handset, and another reason may be that touching the handset keys still steers the mount but the positional changes are not reported back to the PC.

[chrisshillito]

PC-Direct is a software function of the handset - the PC interface does not physically connect to the mount interface but rather the synscan firmware must itself read data from one port and forward it to the other. This requires message buffering and introduces delays in both sending and receiving mount messages. If that were all PC-Direct were doing then there wouldn't be much of an issue but it is apparent that the synscans own mount control  is still active when in PC-Direct mode in which case in addition to the forwarding of messages between PC and mount the synscan must also somehow route messages to ensure that response to PC originated messages are sent to the PC and those to the handset are not. Again this wouldn't be much of a problem if the protocol used for messaging was designed with a routing layer - but it isn't, it is very basic with no source / destination addressing and no error detection / correction.

Mount Positional changes made by the handset will be picked up by EQMOD - there is no problem there. The problem lies in the fact to command the mount the synscan must interfere with the regular polling activity of EQMOD (which provides limit protection etc) and the communications can become corrupted or the state machines fall out of sync.

EQMOD was developed to be the sole device in control of the mount and has never been written specifically for use with PC-Direct mode. That it appears to work well may be more luck than judgement and could easily be compromised with each new release of EQMOD or synscan firmware. I've no problem with folks using PC-Direct, many do with absolutely no issues. However my own opinion is that it is not advisable for unattended operation and the most robust EQMOD setup will always be via a direct hardware only adapter to the mount. From an EQMOD developer perspective I'm sure you can understand we can't officially recommend PC-Direct as an 'approved' interface given we have absolutely no idea how it operates and, despite its now widespread use, skywatcher still fail to provide any real details of its intended purpose in their own documentation.

Chris.

[Mark_C]

Hi Chris,

Thanks a lot for the very informative and helpful reply. I suspected that there may be latency (even if it may be slight) whilst using PC Direct mode, which is why I was apprehensive about using it to begin with. I use pulse guiding through EQMod and it seems to work fine, however I am curious to know whether the performance of autoguiding is affected, especially for longer periods of time?

Either way, I think I will invest in an EQDir adapter, for the price it seems like it's certainly worth it.

Thanks,

Mark.

[chrisshillito]

Hi Mark,

The handset appears to add in an extra 16ms or so of latency over what you get with a USB or RS232 EQDirect interface - Bluetooth EQdirects add something like an extra 40ms. Guiding corrections by their very nature are always lagging and within the context to the length of guide exposure and time taken to retrieve and process the guide exposure these communications lags are probably insignificant. However, whilst the performance of the EQDirect is very consistent - (Being just hardware) the handcontroller firmware may introduce more variability depending on what else it happens to be doing at the time. To implement a guide pulse EQMOD must send two commands to the mount - one to set and adjusted tracking rate and one to return the rate to sidereal.   If the delays getting data to the mount are not consistent then not only will the guide pulse lag but it will have an error in duration. The affect on guiding is always going to be a difficult one to assess given all the other variables present in a closed loop system where it can prove difficult to separate cause from effect

EQDirects can be very cheap to self build - and even the commercial ones  (3 to 4 time the cost of self buid) represent good value for money for those not wanting to risk take up a soldering iron (I always like to push the diy options because EQMOD is at heart DIY project - though it is fair to say it only took off big time once commecrcial EQDIRs became available)

Chris.

[Merlin66]

I understand Chris's comments re PCDirect and EQMod....

I use an HEQ5pro and NEQ6pro mount (Synscan V3.27) with PCDirect/EQmod and CdC. I use a Lodestar ST-4 direct connect for guiding.

Touch wood, I have never experienced any problems/ issues using the PCDirect and the occasional direction arrows on the handcontroller for positional corrections over the past six years.

[Baffa]

I'm a handset guy but I have been using PCdirect mode with EQmod and I didn't encounter any problems. I also was really bad and used the directional arrows aswell and that didn't break anything either ;-)

[dennis1951]

HELP HELP HELP !!!!

What the heck am I doing wrong ???

Eqmod driver has pulse guiding chosen.  Eqmod driver connects to CdC just fine.    I am trying to use PHD and pulse guide with a cable from Shoestring so no handset is involved.  PHD says mount IS connected but then a second eqmod driver window pops open  with an error message showing in the mount window area saying "Connect Error: Port Not Available."  

Should I just ignore this message and hope PHD works ??? 

The only way I can get the error message for  PHD to disappear  is to close CdC....then a new eqmod driver window opens with all the usual mount coordinates running.    But now I don't have access to CdC.     Something ain't right !!

Thanks and hope this makes sense !!  

Dennis1951

[chrisshillito]

The "heck" you are doing wrong is you're running different applications with different rights. Set everything to run as administrator and only one instance of EQMOD will run. If your planetarium and phd run with different rights then two instances are started but only one can grab the COM port and the second will fail.

Chris

[PNJ]

I used both , and cannot find any issues using pc direct, in fact i use pc direct mode all the time now,  i use the handset to do a 2 or 3 star alignment, think its much quicker this way, then i switch to pc direct to image and guide.

I've never had a problem with guiding.   in fact using eqmod adapter, i have had problems with connections, and volt drop.   i do have a portable setup , and have to set up new each night, thats why i find this method easier for me, however if i was observatory set up, then i would prob have a direct connection.

paul j

[dennis1951]

The "heck" you are doing wrong is you're running different applications with different rights. Set everything to run as administrator and only one instance of EQMOD will run. If your planetarium and phd run with different rights then two instances are started but only one can grab the COM port and the second will fail.

Chris

Chris,

            Thank you VERY much.   Run as Administrator was indeed the problem.......After watching your videos over and over I should have picked up on that somewhere in the process...........its tough getting old...................