HELP | sbig st-i unsuccessfully sending guid corrections to mount.

[oishiimsg]

Posted this on a few other sub forums here and have yet to receive a response. Hopefully this area might be better. Here's the deal.

Spent hours trying to get my new sbig st-i to play nice with my cgem dx. As it stands I can't get the camera to send guide corrections successfully to the mount. I am using phd2 with options: camera set to sbig, mount set to on-camera. The st-i is connected to the computer via usb and the the mount via the autoguide port. No matter what I've tried so far the move commands don't seem to work. I am using the manual guide tool to test and the mount doesn't seem to respond at all (motor movement is pretty audible in my mount and I don't hear any movement from the mount in response to a command.) I checked all drivers were installed and up to date, tried windows 7 and osx. I even tried on another celestron mount (alt az for the 8se) and still nothing. I'm hoping you guys might be able to help. Thanks!

[PNJ]

Hi

Not familiar with PhD, as I use maxim dl, but I thought the mount should be connected to the computer via USB

In order for it to communicate with software on the computer, also the camera , then from camera a lead to the auto guide port

This how it works in maxim dl

Paul

[Oddsocks]

When using the st4 guider port option, correction signals sent from camera relays to the mount guide port directly, the guide speed is only a fraction of the normal sideral speed so unless you can hear the motors during normal tracking mode then you won't hear anything happening.

To test, go in to the handset "mount setup menu" look for the guide speed option, the number shown for RA and DEC is a percentage of sidereal rate so 50 would be half sidereal or 50% of normal tracking speed, temporarily set 99 for the DEC option (which equates to 99% of normal tracking speed) then use the "test manual guide" tool to try the DEC drive only, keep the software test button pressed and watch the coordinat display on the handset, after a while, depending on the angular resolution of the display, the lowest coordinat numeral will begin to change showing that the signal from the camera guide port is arriving at the mount, as above, the guide rate is so slow you won't here it or observe it happening but the coordinat display on the handset will confirm it.

When tested go back to the set up menu in the handset and change guide speed back from 99 to 50 as a starting point, you can fine tune this setting once you begin actual imaging.

If still no luck check the st4 guide cable you have is the correct pin sequence for your camera and mount, unfortunately there was no internationally agreed standard for this so some camera/mounts used a common on pin 1 and signal on pin 2-5 where others used a common on pin 5 and signal on pin 1-4, so you need either a "straight through" st4 cable or a "change over" st4 cable depending on your camera/mount, it usually does no harm if you have the wrong one but if so only one of the RA or DEC directions will actually work, the other three directions will have no response.

[Oddsocks]

Attached are the pin-outs for the ST4 port of the Sbig St-i from the St-i manual and the ST4 pin-outs from the Nexstar resource site, as these are mirror images you would need an ST4 change-over cable for your camera to send guide commands correctly (pin 1 at the plug of one end of the ST4 cable should be connected to pin 6 at the plug of the other end).

You might find it easier to ditch the ST4 cable altogether and configure your guide software to not use "on camera" or "camera relays" and to use "direct" or "pulse" guiding instead, this will issue move commands for guiding via the laptop-USB-RS232 port connection, many imagers prefer this method as it removes the need for the ST4 cable and possible command delays when using the on-camera relays, it also has the advantage of sending a larger range of guide speeds than are possible using the ST4 port.