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What is considered good guiding?

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I have both an iOptron CEM120EC and CEM60EC.

I may be expecting too much from mounts based on seeing, I typically get guiding RMS down to .5" - .3"

What is considered good guiding? What is your typical guiding that gets you nice round stars?

I would love to hear everyone's opinion on this.
3 months 1 day ago #87686

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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?
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3 months 1 day ago #87688

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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
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3 months 1 day ago #87690

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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.

iOptron CEM120 EC2 and CEM25P
Celestron C11 EdgeHD and William Optics Star71
ASI 1600MM Pro, ASI 462MC
Moonlight Litecrawler (C11) and Motorfocus (WOStar71)
LodeStar X2 and ZWO OAG
Nextdome, AAG Cloudwatcher
MacMini
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3 months 18 hours ago #87695
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With average seeing, I can be very stable at 0.4".


iOptron CEM120 EC2 and CEM25P
Celestron C11 EdgeHD and William Optics Star71
ASI 1600MM Pro, ASI 462MC
Moonlight Litecrawler (C11) and Motorfocus (WOStar71)
LodeStar X2 and ZWO OAG
Nextdome, AAG Cloudwatcher
MacMini
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3 months 18 hours ago #87696
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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.
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3 months 17 hours ago #87701

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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.
Last edit: 3 months 17 hours ago by Sonny Cavazos.
3 months 17 hours ago #87703

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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.

iOptron CEM120 EC2 and CEM25P
Celestron C11 EdgeHD and William Optics Star71
ASI 1600MM Pro, ASI 462MC
Moonlight Litecrawler (C11) and Motorfocus (WOStar71)
LodeStar X2 and ZWO OAG
Nextdome, AAG Cloudwatcher
MacMini
Last edit: 3 months 16 hours ago by Peter Kennett.
3 months 16 hours ago #87704

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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.


iOptron CEM120 EC2 and CEM25P
Celestron C11 EdgeHD and William Optics Star71
ASI 1600MM Pro, ASI 462MC
Moonlight Litecrawler (C11) and Motorfocus (WOStar71)
LodeStar X2 and ZWO OAG
Nextdome, AAG Cloudwatcher
MacMini
3 months 11 hours ago #87705
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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.

iOptron CEM120 EC2 and CEM25P
Celestron C11 EdgeHD and William Optics Star71
ASI 1600MM Pro, ASI 462MC
Moonlight Litecrawler (C11) and Motorfocus (WOStar71)
LodeStar X2 and ZWO OAG
Nextdome, AAG Cloudwatcher
MacMini
3 months 11 hours ago #87706
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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.
3 months 3 hours ago #87716

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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
Fred

Celestron EdgeHD 11/Moonlite LiteCrawler/iOptron CEM120EC2/ASI6200MM Pro
Radian 61/Radian Focuser/iOptron CEM26EC/ASI6200MC Pro
OAG: ZWO OAG-L/ASI174MM or ASI290MM
ZWO EFW (7x2")
PegasusAstro Ultimate Powerbox V2
Raspberry Pi 4, 8GB/StellarmateOS
3 months 2 hours ago #87717

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