ChrisWhite

Nice! Is the elongation in the same orientation as declination? If so, you could be right that it bobbles a bit. Try balancing Declination to be camera heavy just a little bit. You can also try to snug up your backlash a little bit. Before tinkering with the mount worth trying to see if you can fix it with balance.

Yep. If you rotated one of the post-flip images, it would line up fine.

Also, you can view your logs on a PHD log viewer and take a look at the time during your exposure to see if anything jumps out. One more question: Are you guiding with an OAG or with a guidescope? If you are using a guidescope, it's possible you are seeing some sort of differential flex. Make sure all connections are rock solid and the guidescope is orthogonal to the imaging OTA.

I doubt it's optical. What you are seeing is a streak from the star moving during the exposure. What is your capture software? Are you dithering between frames? Are you only dithering in one axis by any chance?

Something is definitely moving during the exposure. Essentially most of the time stars stay put, hence the bright central star spots, however at some point during the exposure the mount moves in either RA or DEC and causes this. It would be helpful to see the guide graph/log to see if it corresponds to a movement. A cause could be cable drag. How is your cable management? Are they dangling off the scope/camera, or are they bundled neatly and supported? Could also be something sticking in the mount. I see that your mount is modded. Did you do this yourself? It's possible that your backlash is adjusted a little too tightly causing some binding. Could also be that your exposure is starting before the mount has fully settled (i.e. after a dither). Tough to tell the cause of this from a single screen grab, but something is definitely moving during the exposure.

Very nice. You did a nice job capturing the Oiii envelope. Nicely processed to bring out the details without overcooking the data.

I suspect that there are also user variables (load, moment, balance, software settings, etc) that exacerbate the problem (or mitigate it). I think this makes it very difficult for ioptron to identify, reproduce and correct the issues for the wide variety of setups out there. I do hope that they solve it. Otherwise it's a great mount. I really like my CEM60 non-EC. Thanks for the encouragement!

Thanks Dragon! Hubble blend is: R=.4*Ha + .6*Sii G=.4*Oiii + .3*Ha + .3*Sii B=Oiii With a little SCNR green removal.

Thanks! Actually, I returned it. While iOptron was trying to sort out the encoder/guiding issue they extended my return window indefinitely (very gracious of them), but after 6 weeks of no progress a second hand Mach 1 came up and I decided to go that route instead. So glad I did. The AP has been a joy to use, and regarding the CEM60EC... still no progress. ☹️

Well, I've been stopping by SGL on and off for a couple of months, and decided to post something here. Over the last couple of weeks had some nice clear nights and imaged the Eastern Veil with my Newt. 8in ONTC + Paracorr + QSI 6120 + Mach1 I've got two versions with this data. The first is a hubble blend and the second is a straight SHO. What I love about this target is that there is such a strong signal in all three narrowband channels. Almost gives it a 3D glasses look. I find that there is an electric feel to it and had a lot of fun processing this one. C&C Welcome. Also, which do you like better?

Thanks for the welcome. Tomorrow night will be a good test. Seeing what cotak and Rainer have posted looks in line with my thoughts. I'm surprised by 15 second exposure, but it makes sense perhaps. I think you want a long enough exposure to eliminate chasing seeing and periodic error, as the EC mount *should* have negligible PE. Really, all you want to do is correct for drift from PA error or atmospheric refraction over time. It seems that people are having problems with guiding and encoder when guide corrections are too frequent. It might be due to how the guide corrections are issued in the firmware. I have tried running a PEC model with the CEM60 and it didn't work. I didn't try long guide exposures though. I wonder if that would make a difference.

@Jkulin: If you switch to arc seconds on your graph it won't look quite as good. .7" total RMS is not bad guiding by any means, but I would expect to see better if things were running optimally. With my CEM60 NON-EC I generally guide below .6" total RMS and often around .5" or below with an 8in Newt OAG at 920mm FL. That said, these numbers are not everything. If your stars are tight and round, then it doesnt matter. Has anyone given PPEC a go? It takes a couple of worm cycles to refine, but with the Non-EC it is brilliant. For the first couple of cycles it behaves like a hystersis algorithm, but then things settle down. I think you would want a pretty high min/mo and long-ish exposures like 3-5 seconds. I hope to test this out Thursday when my mount arrives...

Very interesting. Thanks for the writeup. I've got a CEM60 NON-EC, and also a CEM60-EC on the way. I have found that for the standard CEM60 the PPEC algorithm works very well. I generally use 1.5 second exposures and adjust min/mo based on seeing. I'm curious to see if I can get PPEC to play well with the encoder, but if not I'll use your hystersis logic as a starting point.