Guiding for 10 micron mount

[Ana Ta]

Hello,

I have not guided for 2 years using 10-micron mount. However, I have scope with long FL now, and long unguided exposures (>10 min) do not work anymore. 

Long time ago, I have asked how to set up guiding for mounts with absolute encoders (specifically for 10-micron). I would like to ask this question again. 

What are specific settings for PhD guider, including advance setting? Are there specific settings for 10-micron mount driver (it has specific setting during building a model)? Any particular advice for guiding during focusing and meridian flip? 

Thanks a lot!

Clear Skies!

Armen

[Brian Valente]

Hi Armen

This video describes setting up PHD2 for encoder mounts (it's an AP video, but it equally applies to 10 micron or any other mount with absolute encoders)

https://youtu.be/wCu8PKjDZ20

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Brian Valente

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[Ana Ta]

Thank you Mr. Valente!

I will watch it and try it out.

Clear Skies!

Armen

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[Bruce Waddington]

You haven't really said much about how your setup is changing.  Brian's video is excellent for explaining best practices for guiding high-resolution encoder mounts.  But those practices assume you're using an off-axis-guider for long focal length setups.  If that's not what you're doing, you are likely to run into limitations imposed by differential flexure, something that guiding can't do anything about.

Regards,

Bruce

[Ana Ta]

Hi Bruce,

My set up has OAG.

When I asked the same question 2.5 years ago. You have recommended OAG. Then, I tried it and it worked very well - 0.2-0.3” RMS. 

Now, I asked the same question to refresh my memory, and see whether there are some advances. 

I am waiting clear night to try recommendations from video that I have already watched. 

Thanks a lot!

Armen 

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[Bruce Waddington]

Ok, Armen, I just wanted to make sure you're using an OAG.  When dealing with very accurate, high-res encoder mounts, the goal is to guide very conservatively and not interfere with the encoder or model-based corrections.  The reason for guiding at all is to correct for very low-frequency tracking errors, things like mechanical flexure in the payload that really can't be modeled effectively.  And of course, guiding deals with the inevitable "stuff happens" events. The variable exposure delay feature was introduced to accomplish this without slowing down the operations that don't benefit from small encoder or model corrections - things like dithering and calibrating for example.

Have fun,

Bruce

[Ana Ta]

Thanks, Bruce!

Yes, I would like try a help of guiding, because weight plus long FL could negatively influence unguided tracking. My mount’s capacity is 55Lb. Scope+other gizmos is about 45Lb now, and FL=2000mm. So, I just cannot get FWHM <2.3”. This is good, but not good enough. 

Clear Skies!

Armen 

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[Brian Valente]

Armen

>>>>My mount’s capacity is 55Lb. Scope+other gizmos is about 45Lb now, and FL=2000mm. So, I just cannot get FWHM <2.3”. This is good, but not good enough.

Total FWHM is not a great measure of mount tracking because so much goes into that number. I would look at your star eccentricity, measuring the center 50% of your frame.  imo twould better tell you the tracking performance.

A cautionary note: guiding may not resolve this problem. An absolute encoder mount, the encoder is doing most of the work, with guiding gently and very occasionally bumping things back if needed (hence the name "bump guiding"). This whole approach assumes the mount encoders and any sky modeling is already been optimized, and you just need a little extra help. 

 

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[Ana Ta]

Hi Mr. Valente, 

I will try whether guiding gives this extra help. Half data will be collected with guiding, another half no guiding, on the same target and the same day. Like placebo-controlled clinical trial 😀.

Star eccentricity without guiding is on average 0.35-0.45

Thanks a lot!

Clear Skies!

Armen 

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[Brian Valente]

Armen

those eccentricity numbers (also assuming you are using the whole frame) are quite good. It's possible your higher-than-desired fwhm may just be seeing conditions or other factors. when you set up guiding you should post the guidelogs and note not only the total RMS but the rms of dec and ra separately. You should do an unguided run of 15-30 minutes after calibration to see what the unguided rms is

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[Ana Ta]

Hi Mr. Valente,

I tried once 15 min long unguided. It was mess! Stars were like short line. In comparison, I have the same mount with Epsilon 130. It doesn’t have problems to go 20 min unguided. I have not tried longer.

I will try to record log. 

I hope that soon clear nights will come and I will try different settings: long frames, short frames, unguided, guided, etc. I will definitely post outcome of trials.

Thank a lot!

Clear Skies!

Armen 

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[Brian Valente]

>>> I tried once 15 min long unguided. It was mess! Stars were like short line. 

Then that isn't an eccentricity of 0.35-0.45

Like I said, get it set up and do an unguided session first, followed by some guiding according to the video i sent, you should be good

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[Ana Ta]

That eccentricity is for 3-5 min unguided.

I will do all this. 

Thanks. 

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[Ana Ta]

Dear Mr. Valente,

I set up a PhD guiding for 10 micron mount following your advice and instructions.

It works very well. Guiding accuracy 0.28-0.35" RMS.

Here is what I got.

3 min no guiding and with guiding produced similar results: FWHM 2.3-2.7"; Eccentricity 0.35-0.45

5 min no guiding gave a little bit worse Eccentricity (0.4-0.5), but almost the same FWHM

10 min no guiding was visibly worse: Eccentricity (0.45-0.6) and FWHM 2.6-3.3". No guiding gave stars which were visibly like eggs. 

Guiding produces the same results (FWHM 2.3-2.7"; Eccentricity 0.35-0.45) disregarding length of exposure. 

Why I cannot get FWHM below 2"? Does FWHM depend only on seeing?

Thanks

Clear Skies!

Armen

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[Brian Valente]

Armen

please upload the logs for the sessions you mentioned.

I'm not sure why you included the unguided results, since you asked about how to guide an encoder mount. It sounds like the bump-guiding approach is working for you and producing good results and statistics. 

If you are getting eccentricity of 0.35-0.45 and guiding of around 0.3-4" you are likely seeing constrained.

What does your seeing monitor (assuming you have one) report as the conditions?

Brian

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[Ana Ta]

Hi Brian,

I wanted to compare whether guiding will improve FWHM depending on exposure length. I will try to learn how to upload logs for sessions and will do it. I have done it several years ago. 

I have no seeing monitor. Location of the rig is in Texas; StarFront observatory. 

Clear Skies!

Armen 

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[Brian Valente]

Armen

what is the telescope you are using?

Have you asked Starfront about a seeing monitor? for a facility that supports that many telescopes, I would be surprised if they didn't have that

Just to recap, your guided results suggest you are seeing limited. Unguided results show other tracking issues and may show star elongation, but I think you are seeing limited at this point

When evaluating remote observatories, it's good to know their average seeing conditions as well as the sky darkness (bortle)

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[Ana Ta]

Hi Brian,

My scope is CFF 10"RC. I will ask StarFront bosses about a seeing monitor. Yes, it is the largest observatory for amateurs, but a majority of customers have small scopes. I have been evaluating remote observatories for the last two years. I can measure darkness, but no way I can know about seeing and number of clear nights. The Observatories definitely exaggerate these numbers. Thus, I have already left two observatories in NM. Their numbers for seeing and a number of clear nights were well off. Starfront reported these numbers correctly. But I have not seen any info about seeing. What do you think about the location near Pie Town in NM?

I uploaded the guiding log for one of the imaging nights (frames are 6 min long). It is 7-9h of guiding. One small minus in guiding that I noted is that guiding is 0.4-0.5" during 10-20 seconds after dithering. 

Please let me know your opinions.

Thanks a lot!

Clear Skies!

https://openphdguiding.org/logs/dl/PHD2_logs_a7pD.zip

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[Dale Ghent]

> On Sep 17, 2025, at 18:40, Ana Ta <aaak...@gmail.com> wrote:
>
> Hi Brian,
>

> My scope is CFF 10"RC. I will ask StarFront bosses about a seeing monitor. Yes, it is the largest observatory for amateurs, but a majority of customers have small scopes. I have been evaluating remote observatories for the last two years. I can measure darkness, but no way I can know about seeing and number of clear nights. The Observatories definitely exaggerate these numbers. Thus, I have already left two observatories in NM. Their numbers for seeing and a number of clear nights were well off. Starfront reported these numbers correctly. But I have not seen any info about seeing. What do you think about the location near Pie Town in NM?
> I uploaded the guiding log for one of the imaging nights (frames are 6 min long). It is 7-9h of guiding. One small minus in guiding that I noted is that guiding is 0.4-0.5" during 10-20 seconds after dithering.

The southwest US giveth and, during monsoon season, it can certainly taketh. The 4-corners states are among the better areas of all areas of CONUS to host a telescope. But there are environmental aspects that do impact the number of imaging nights and these environmental aspects can vary from year to year, ranging from benign to suffocating.

There's no way around a bad monsoon season, and monsoon season is just what happens over the summer in the southwest. It's just like hurricane season in the gulf and east coasts. Some years it's quiet and pretty calm, and other years it can be weeks of wondering when the nighttime cloud cover will end. It's a regional pattern that is influenced by other global macro pattern. This season, in 2025, seems like a "bad" year. Great if you adore desert greenery, but not so great in terms of racking up imaging time at night.

I've noticed that folks tend to obsess over seeing and sky darkness stats, which is fine and important. But folks do also seem to gloss over one completely unrelated effect that has an outsized effect on guiding - wind. In these open, large bay roll-off-roof observatories, there's little to no wind protection. To get that, you need a dome, but that's not scalable in terms of the number of telescopes you can put under it.

To help realize this, I've been collecting weather stats and telemetry from my own L-350+CDK14 system that's hosted at HCRO, outside of Pie Town, NM. It's situated at 2290m/7513' (measured at my pier). I've been graphing wind speed (measured by the site's weather station) with total guide RMS from PHD2 and see clear effects there. Here is an example from just the other night:

https://daleghent.com/hcro-cdk14/goto/eyOXTJCNR?orgId=1

The flame line is the wind speed and the green line is the guide RMS. It's pretty clear that breezes buffet the telescope and that is reflected in the guide RMS.

I've only just started recording seeing metrics and have a few days' worth. There are two commercial seeing monitors that I'm aware of out there, and neither have out-of-the-box ways to record detailed telemetry. But HCRO has both the SBS SM4 and Alcor Cyclope and, with the Alcor Cyclope, I've been able to work with its vendor to get the seeing stats exported. Here's the past 2 days' worth:

https://daleghent.com/hcro-cdk14/goto/KPXSAJjHR?orgId=1

The green dots are individual measurements and the yellow line is the rolling 15 minute average of them. Seeing can change a lot over the course of the night. Usually it's high and noisy at the start of the night, then settles down towards morning. Weather fronts moving through also affects. But, as the summer transitions into fall, there are some times when seeing drops below < 1". In the winter, that becomes almost a standard feature of the night at this site.

To help tie this info together in another visual way, I'm now creating timelapse videos of my rig with point-in-time weather data overlaid on the frames. It's interesting to see how both seeing and wind correlate to clouds moving through and being under the edges of fronts. You can see those and play with the metrics I record here: https://daleghent.com/hcro-cdk14/

/dale

[Ana Ta]

Hi Dale,

This is very informative! 

In NM near Mexico border, there is no such excellent seeing. Not even close. 

What is HCRO?

Thanks a lot! 

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[Brian Valente]

HCRO is howling coyote remote observatory

I would add Dale's comments support my original comments re: it's likely seeing, but wind is also a commonly overlooked gremlin as well

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[Dale Ghent]

Howling Coyote Remote Observatories, near Pie Town NM. If you contact them, you'll likely talk with the owner, Greg, who is quite affable. I think one of the advantages the site has is its high altitude. It's also at the eastern end of a long high plain that stretches up towards Flagstaff in Arizona, so there is not much in the way of turbulence-generating mountains to the west given the prevailing weather patterns of the area. At least, that's my read of it. I'm anxious to see what the seeing is like once the monsoonal fronts start tapering off as we head into the fall.

/dale

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[Ana Ta]

I see. I read about this observatory. 

This is high end observatory facilities for large scopes. I am not there as yet 😉.

Thanks!

Clear Skies!

Armen 

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[Ana Ta]

I agree. Wind near StarFront is quite strong.

So, overall, it seems I am near optimal possible level. I don’t think I will get FWHM < 2”. 

Thanks a lot!

Armen 

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[Brian Valente]

>>>  I don’t think I will get FWHM < 2”. 

I wouldn't say that. All that this discussion is saying is that your tracking and guiding performance are likely not constraints to your overall results.

seeing changes from day to day and season to season. 

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[Ana Ta]

Ok. Fingers crossed then!

Thanks 

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