Ok, please bear with me as this is may be a bit long and highly illustrated. I've tried to record my struggles as detailed as I could in the hopes of getting some help from you guys, so I beg you to read this carefully if you have experience with guiding issues and/or with the EQ3 Pro (SynScan) mount - I only got this mount about a week ago and I'm still wondering whether these issues is something that can be solved or to be expected, or whether I'm dealing with damaged goods.
So here we go. Bottom line, what is your judgement: is this correctable, is there something very wrong with the mount, or is this to be expected of this specific mount? I have until Friday to return this (14 day return policy), and if this is a lost cause, I'd like to know about it.
Two days ago I initially tried out this mount quickly, I managed to set it up and align it as a practise and fired up KStars/Ekos and PHD2 to see how this baby worked. Weather happened and I didn't quite get to the bottom of it - I did image for a few frames and quickly noticed that while initial calibration went ok, guiding was all over the place. Stars were very oblong on a 3 minute exposure. This didn't worry me much since the sky was getting cloudy and I therefore was a bit bad for testing, but I wanted to get a quick taste of it anyway.
Fast forward to yesterday. Skies were clear, and it was time for more testing. First of all I wanted to see how the EQMod driver worked (instead of using the SynScan driver), i.e. turning on the Direct PC Mode from the controller and going all computerized. No big issues there, except for the horizon limits which suddenly stopped tracking several times. Once I figured this out and disabled the limiting, no issues (except KStars/Ekos did not seem to save this setting). In any case, fast forward to guiding: again the PHD2 graphs were all over the place. A six hour of battle of calibrations/alignments/mount balancing ensued. It was not a pretty sight... in the end I decided to surrender to fight another day and swore that this time I'd properly document these issues. And that's where we are now.
So tonight I tried again. Let's start.
The mount was aligned quite closely to celestial pole from previous sessions. I re-balanced the mount, RA first, then DEC. I powered on the mount, set up date/time/location and engaged Direct PC Mode and fired up KStars/Ekos.
My balcony has no direct sight of Polaris, so I had to veer a bit off to the East to perform polar alignment with the Ekos. I ran the alignment procedure twice, and got pretty close. Finished the alignment using PHD2 Polar drift alignment tool, with PA Err 3 min after letting it stabilize for 3 minutes. Spent a good hour on the entire polar alignment procedure to make sure that a poor polar alignment wasn't going to be an issue.
At this point I was happy so I decided to navigate to a few stars and ran Ekos alignment.
After slewing to a target the captured camera alignment image looked like this:
I have a settle time of 15 seconds on my alignment/solver - even then that's how it looks. The drift after running GOTO appears to be quite a lot. The backlash must be huge or something.
Alright, trying PHD2 guiding then:
Using ST4 guiding, since the mount supports it.
Calibration done pointing East. East-West movement looks good. 21 steps of clearing backlash. I make a note that the mount makes a click sound when moving north on every step.
Another note with South steps: virtually no movement whatsoever. Dist stays at ~29.
Result: Calibration completed but RA and Dec rates vary by an unexpected amount (often caused by large Dec backlash)
Calibration results as below.
Guiding starts. The graph makes me want to cry. Dec is somewhat workable I think, but RA is bouncing all over the place.
Running the Guiding Assistant next to get some insight.
Oh boy, no amount of polar alignment is going to fix this:
Guiding assistant results below:
Ok, so something's majorly screwed up here. I'm really hoping someone with knowledge can pitch in!
So let's try a star-cross test then. Might as well do everything while we're at it. In fact, let's do it a second time, and a third time in another part of the sky.
Again, noticing from viewing live picture from PHD2 that the drift after slew is very noticeable and long.
Now again, for science, let's ditch ST4 guiding and go with mount only. After all there are probably differences!
Calibration East-West: the West direction appears to be flipped. West steps with ST4 went to the other direction! This just got interesting.
North-South direction is identical to ST4 however. Little south movement again.
RA is still flipping all over the place.
Continued on second post due to image limitations per post...
Edited by jusasi, 30 March 2020 - 05:02 PM.