Paul, it was you alignment with Polaris that was troubling me – that’s why I asked if the counter-weight was still pointing down – something didn’t feel right about this step in your workflow but I was too dopey to see it. Kinch has hit the nail on the head. When the mount is set on CNP the counter-weight will be straight down and the dome slot should be facing north, the dome encoder (if connected) should read 0 (360) degrees and the mount Az should also read 0 (360) degrees. Depending upon the time of day, if you then centre on Polaris the counter-weight will be anywhere from horizontal East to horizontal west and (I think) there will be two points in time when it will be pointing straight down. I’ve just run up my gear. The first screen-shot of POTH is when the Mount is on Home Position (CNP). Mount Az shows nearly 0 degrees, the counterweight is straight down, and the Dome Az shows 000.0 degrees which is because the Arduino, which counts ‘steps’ (and calculates headings in degrees from the number of steps moved) and not absolute degrees (no encoders), re-sets to 000.0 on boot-up. I check the dome slot is facing north and then engage Slave (which was when the screen-shot was taken.
I then commanded a slew to Polaris (at around 0830 this morning, site is 30 miles NW of London) and you will see from the second screen-shot the Mount Az has hardly moved (less than 1 degree east) but the Dome Az (and hence the dome slot) has shifted 17 degrees West (the counter-weight bar is now about 30 degrees from vertical out to the east). These results look very similar to results you posted, so it looks like your setup is basically functioning.
The things to sort now are:
- establish the point in your workflow that you slave the dome,
- check your dome movement calibration in terms of motor-steps per degree of dome rotation and
- check your dome geometry settings
For 1. I suggest you establish a home or park position on CNP, manually move you dome slot to north, check you dome and mount Az readings are both very close to 0 degrees, and engage Slave.
For 2, the way I did this was to mark the inside of the observatory wall with N, S, E and W (also I have mine marked every 5 degrees) and put an arrow marker on the dome, centred in the middle of the slot and close above your N,S,E W markers. In POTH connect only your Dome, check your Dome Az is reading 0 Degrees and the slot arrow is above the N marker, type 090 in the box (to the right of the GoTo button) and hit GoTo. The dome should slew to E (090 degrees). Repeat for 180, 270 and finally 0 (360) and confirm the dome rests as near to S, W and N markers. Your Arduino will have a formula for translating degrees into motor steps and if the foregoing test misses the marks then you will need to adjust the formula. While you are doing this it is worth also checking that your dome always takes the shortest route when slewing. For example, on a meridian-flip, while your mount does a 360 degree move your dome should only traverse the relatively short distance across the meridian.
For 3 – experimentation with different settings might be required