Well,

My EQ6-R guides between 1.2 and 1.5" with lots of peaks +-3''. Imaging at 1.85"/pixel I would say that my stars are round. Although, they may be a bit fatter and more bloated than they should be.

So, at least to me, your guiding numbers sound awesome.

At what pixel scale are you imaging?

I too have a CEM120EC. I normally get around 0.75" RMS going down to 0.25" on a really good night and once everything has thermally stabilised. My seeing is rarely better than 1" and my imaging setup is 0.8"/px so I do not worry too much. I have more problems from optical sources (poor collimation, CCD plane etc) than from guiding. I do take care to physically balance my twin rig on the mount, using dummy weights to help me move between configurations. I also have an old HEQ5, used for wide angle work (24mm DSLR lens + SC694) and get about about 1.5" RMS on that for an image scale of 38"/px! On both setups I use the Ekos guiding module, with long exposures and correction periods (typically 10 secs).

Regards

Tim

I also have a CEM120 EC2. I don't usually need to guide when imaging at 0.8" / pixel (C11 f/7 and ASI1600MM) but when I do guide, I run around 0.4". But this varies dependent on seeing.
When seeing is very good, humidity under 25%, and my PA is spot on, I can get down to 0.25" (I live at 7,000ft in NM, so these conditions are not uncommon fortunately).



I would do a lot more unguided work, however I am still struggling to get highly accurate PA. This means that a two minute exposure is fine, but after a few exposures my tracking is off by a few arc seconds. After 60 minutes it's moved enough to need to have the target realigned.

With average seeing, I can be very stable at 0.4".

I'm happy with less than half a pixel, whatever that works out to with a given optical train.

If you had the HST and got 0.1" guiding, you'd send it back for a refund. If you had one of the popular Samyang/Rokinon 135mm f/2 lenses on a canon 10D, 5" is less than half a pixel.

Very cool, yeah I think I am just fighting a non-existent problem. I was thinking I had below average performance, I do typically get .5 - .25 or so, Thanks a lot for the graphics, they do help.

I was messing with the sextractor settings in the guiding section to try and improve, but I do think I am just chasing ghosts.

I do go deep sometimes with planetary work, and sometimes like to go into 2000mm focal range to get some targets inners, but I think I am just thinking I should get better when I actually have it pretty good already.

Yeah PA is a pain, I go between the iOptron iPolar thing, and using EKOS - both give me the same results. I should just do drift align, that would probably help.

Yeah I'm ready to go back and try and old fashioned drift align too.
EKOS will say I nailed it, and then when I go the other direction, it's off again.

Seeing tonight was not great and I was only able to achieve 0.5"/pixel. But then, at 1:30AM, it got real calm and I was able to get such better.
However, I was imaging at 0.8"/pixel so I really didn't see any improvement.

The CEm120 EC2 is a lovely mount, and when you have perfect PA and excellent seeing - there's no need to guide at all.
I am guiding here, but you can see there are no corrections. Here's my settings.





PS: This is a C11 EdgeHD at f/7, Moonlight Litecrawler (rotator/focuser), Celestron OAG, Lodestar X2 guide camera, EFW, and ASI1600Mm Pro.

Nice! Really great performance out of your RIG. I see you are doing OAG, and it looks really great!

The other night I was guiding at .3 - .4 with lots of turbulence in the upper atmosphere. I am thinking of putting in an IR only filter to see if I can get better results. But like I said, I think it's doing great, but I am just wanting less than .4" RMS.

Hi Peter,

I have a CEM120EC2 as well - for about 8 months now. I see that we are shooting with the same OTA at the same focal length. Do you mind sharing your settings in the options tab? While I'm at a lowly 500 feet above sea level, my guiding very consistently issues pulses to the mount and while my guiding can be <.5" it is often greater than that and approaches 1". While my stars are still round, there are frames where the bloat is visible when blinking a nights images. As a result I'm constantly fiddling with the options settings trying to improve performance. One thing I notice is that you have your guide camera set up for 1x1 binning. I've gone back and forth and am currently at 2x2 and getting ok results.

Thanks for any thoughts you care to share - Fred

When seeing is bad, I just let the mount track unguided. It’s better than chasing seeing.