CEM40 and iPolar

[PaulE54]

Has anyone ever had a problem where the iPolar software appears to calibrate successfully, but actually sets the red cross somewhere randomly (and quite significantly) different from where the optical centre actually is?

After 3 failed attempts I've given up and entered the default X and Y values manually, which is marginally better than anything the software did, but still not what the kit is clearly capable of. 

This is driving me nuts! It may well be user error but I've read the manuals loads of times and can't figure out what (if anything) I'm doing wrong. 

Thanks

Paul  

[Michael Hogan]

Your not doing it right read the manual again turn mount 90 degrees on side position 1 then position 2 then position 3

[PaulE54]

MIchael, thanks for reply - sadly, I think that is exactly what I am doing. Repeatedly. And it doesn't work for me. I'm using the latest software and latest manual and it only gives you the option to enter 2 positions not 3. It's page 6 of manual

I start by moving the mount from home to scope east / counterweight west, Ipolar confirm position 1. Then I put the mount back in home position, ipolar confirm position 2. Actually I've had a thought. When you move mount to position 1 from home, then back to position 2 (home) - do you slew using buttons on iOptron commander / handset, or do you unlock RA axis and move the mount by hand? Can't see why it would make a difference, rotating mount around RA axis in both cases. 

Thanks

Paul

 

 

[PaulE54]

May help other iPolar owners. 

OK there may be progress - further analysis needed. If I'm on the right track, the manual needs an update! V2.04 page 6 shows the mount rotated in RA during calibration, and states that 2 positions are needed. It also says "The start and end positions can be arbitrary." I'm starting to think this may not be true. On all the previous failed attempts, I started with counterweight bar horizontal, weight west / scope east for "position 1". Then I moved to weight down / home position for "position 2".

The manual v2.04 only shows "position 1 and 2" being needed for calibration, and the software stated calibration successful on all the previous failed attempts.

Last night for a change I started with counterweight bar horizontal, weight east / scope west. Software took that as position 1, asked for position 2. Moved to weight down / home position. Software took that as position 2. THEN asked me for position 3. Never done that before - and NOT in manual. Moved to bar horizontal weight west. Software accepted that as position 3, and quoted me an optical centre that looked vaguely sane - unlike previous attempts.

Polar aligned using latest calibration and started imaging.

At the end of night, PHD2 log analysis shows 0.9 arcmins PA error. And the cross was not EXACTLY over the dot. in the iPolar app. 

I want to do some another calibration run, to check the answer is the same, and obviously some more polar aligns and guiding, to make sure this is repeatable. But I may be getting somewhere. 

Paul

[Juicy6]

I have a pdf from v 1.3 and it is describing it the way you do (ver should be 2.04):

 

Christer, Sweden

[PaulE54]

Yes, very curious. Although the current manual only describes two position calibration, the software still supports (and seems from my limited experience to work much better with) 3 position calibration. 

Ah well - looks like it is going to be well into next week before I get a chance to do any more imaging. Astrophotography in NW England is not for the impatient!

Paul

[Chris49]

My GEM45 has similar problems with setting up the iPolar - I've started by moving the counterweight bar to horizontal and it doesn't wait for you to press the Confirm Position 1 - it has already pressed it and moved on to Position 2.  You start slewing the RA back so that the counterweight bar is pointing down and before you've got there it says "All position confirmed".  It seems to give sensible values for the Center of Camera X=461.8 and Y=664.2.

I then centered the cross on the dot successfully, but when I checked the polar alignment error in PHD2 it said 37.7 arc-min!

I think I have been starting with scope east/ counterweight west, but if we get to see some stars soon, I will try it the other way round - thanks for the suggestion.

Chris

[PaulE54]

Interesting. I hope to be imaging again tonight so I'll see how the previous calibration holds up when I re-use it. Did hear back from iOptron support, who advised always moving mount by motors not by hand when calibrating - sounds like you're doing this though - and said they would investigate whether the software had a bug. I spent most of my career working with software and it does feel like an "undocumented feature" to me..:-) 

Paul

[PaulE54]

Got a couple of hours in last night. Re-used the same iPolar calibration as last time (centre reported as X=488.7, Y=613.7) and again polar alignment was super easy and PHD2 log viewer reports PA error of 0.9 arcmins. So far so good. The guiding was not great, but I think that's more down to suburban rubbish seeing than anything the mount is doing. 

Paul

[Chris49]

Just got the chance to try the calibration again.  This time, I moved the counterweight bar to horizontal, then clicked on Confirm position 1.  It said to slew the RA more than 45 degrees from previous positions, which I did and it then said it had auto-confirmed position 2 and that all positions were confirmed.  This gave X=462.1 and Y=665.2 so very close to what I had before.

It seems they have made the software even more automatic than in the manual and it knows when it has moved enough to make the calculation.

Unfortunately the clouds rolled in again and I wasn't able to check the polar alignment accuracy in PHD2, but I think the calibration has done the right thing now - so a small step forward!

Chris