I violently agree with Chip on this one. To me, high resolution absolute axis encoders are just the latest example of Astro-Bling.
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To reinforce his point on the cost issue here is a concrete example:
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Sky-Watcher makes a mount in the 100-lb class called the EQ8. The base model, without?tripod, is about $5.3K here in the USA today.
Who knows about the future? The same model with absolute axis encoders is $9.475K. The encoders are from Renishaw, as very
well respected industrial supplier. Good, so they advertise, to 0.1 arc seconds.
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That's a price difference of $4.175K for the encoder feature, to what end?
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Plus, to this old man absolute encoders, USB hubs, or GPS modules integrated into a mount are just something else that can break.
As the sage said "Someday everything will need to be maintained".
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If I want to know the coordinates of an object precisely I'll use?the Blind Astronomy Solver.
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Mark Christensen
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Re: Gemini/NINA spreadsheet
Franco,
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I do not have a Gemini-1 nor experience in southern hemisphere so I cannot confirm. I would be glad to add notes to spreadsheet based on experimental findings of the group.
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Have others used the spreadsheet as-is in southern hemisphere on Gemini-2? I would have expected the East and West limits to work the same, only physical direction of rotation of RA axis to change.?
?
--
Edward
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Re: Gemini/NINA spreadsheet
Hi Neil, well the update is that I tried using the info on this spreadsheet and I think I finally solved the issues with the flip. The ONLY thing I changed from what's suggested on this spreadsheet is that I switched OFF the "use side of pier" option in NINA, because flips were not reliable when I had this on. Once I switched it off I spent an entire afternoon making flips with my observatory roof closed and they all worked perfectly. However, right after that I started having a new issue which is that when I'm trying to do an imaging session the mount won't slew to a lot of objects, especially around the SCP. So I believe my settings might need some additional tweaking. Here's a couple of screenshots of my settings which seemed to work.
?
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What issues are you dealing with exactly??
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Re: Gemini/NINA spreadsheet
I feel your?pain, Franco. I am also in the southern hemisphere, using Gemini-1 and N.I.N.A.
I'm having EXACTLY the same problem :( So I am watching?this thread with great interest !! -- Thanks and Best Regards Neil
On Sun, Mar 16, 2025 at 6:05?AM Franco Meconi via <francomeconi= [email protected]> wrote: Hi Edward, this is just what I've been looking for, I've been having a really hard time trying to config my G11 to do automated flips with NINA. I have 2 questions though, do you know if this works well with Gemini 1 as well? And also, I'm in the southern hemisphere, are there any considerations I should take into account? I read in the manual that eastern and western limits should be swapped when using the mount in the southern hemisphere, and actually due to the RA motor positioning my western limit is the "shorter" one before the setup will crash into the pier. Gemini also seems to report reversed sides of pier always, at least that's what I see in NINA: NINA will say the telescope is WEST of the pier but my telescope will be on the east. This I believe is because of me being in the southern hemisphere, because if I were to turn my mount 180 degrees in azimuth to face north, the reported side of pier would actually be correct. One would think that it would be an easy thing for Gemini to report the inverted side when your latitude is set south of the equator but this does not seem to be the case, so I wonder if there's anything I should take into account due to this. My issue with flips is that NINA will actually initiate the flip command with the legacy sequencer, but it will get stuck in an endless loop of requesting flips, once the flip is complete. Gemini will not perform another flip, but NINA will keep requesting them.
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Very nice Moon!?
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There are those in the OnStep group who are fascinated with very high resolution encoders.? They want to have a feed back loop that will deal with any inaccuracies that that creep into the step motor drive systems. Step motors are usually spec'ed at +/-0.05-0.09°. But these errors occur randomly and when your microstep rate is 13,653 a second they tend to cancel each other out. Nevertheless, they persist, and have found a PC mouse encoder that is fairly cheap that they are playing with. IF anyone wants to play along the thread is here:
Ultra high DPI mouse as RA sensor:
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Currently, I believe they are using a 32bit ESP32S running at 2.4mHz to process their signals, but I stopped following the discussion a while ago.? Those of us with one foot in the grave don't have time for this. I've got too many graves to piss on.
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Re: Help interpret my unguided log
Hi Paul,
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Thanks for your thoughts and observations!!!
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No idea what could cause or did cause the RA drift to reverse on 3/14.
?
The RA drift on 3/13 was about 200a/s in 40' with a PA error of 9.1. On 3/14 Drift was 140a/c in 40' with a PA error of 0.1. Better PA reduced the drift.
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I'm currently researching RA drift discussions on CN and so far have read thoughts on the cause being atmospheric refraction and the effect of tracking rate, (Sidereal vs King) on drift. Nothing yet on reversal. Still digging...
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And still trying to imagine how drift reverses. I've checked the guide scope/camera and I can't find anything not snugged down.
?
--
Thanks,
Topher
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Re: Help interpret my unguided log
Hi Topher,
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A few things I see from your PHD2 log:
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1. There's a significant drift in RA. May be a large mirror flop, focuser sag, or just polar misalignment. It seems to reverse direction towards the end, which may mean it's more than just polar alignment error. Any thoughts as to what happened around 21:41 mark in RA when the drift changed direction?
?
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2. Even without the reversal at 21:41, the drift is significant, something like 150 arcseconds in 40 minutes, or nearly 4 arcsecs/minute. That's a large drift that will cause the autoguider to work hard to try to correct for it.
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3. With the drift removed, your data appears to show periodic error of about 14 arcsecs peak-to-peak, most of it at 1x the worm frequency @ 13 arcsecs and around 3 arcsecs at 2x the worm frequency. These should be easy to remove with PEC, once you fix the drift.
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Before you try programming PEC, I'd definitely recommend that you figure out what's causing such a large drift and fix it. If you don't know the reason for the drift reversal in your data, I'd investigate that, as well.
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Regards,
?
? ?-Paul
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On Fri, Mar 14, 2025 at 03:30 PM, Topher wrote:
I do believe this is my first post!
?
The attached unguided guidelog is from my CG-11 with several upgrades including brass worm gear on RA, new OPW blocks both axis, Gemini-II w/HT motors, somewhat recent new factory RA and DEC bearings, recent clean & lube with factory grease, I hope still cleaned/dry clutch pads, clutches minimally tight, 200mmFL guidescope. About 45 minutes of unguided time under below average seeing. The PE is rather high and looks to me jaggy, (and I wonder if that's indicative of mechanical, seeing or what.)
?
On a good night I see about 0.75-1.0" rms in PHD2 and am currently imaging at 1.13" and 0.75", so I'd like to see if there's anything I can do to improve performance before I buy PEMpro and create a PEC curve.
?
Yesterday I removed and checked gearboxes/motors, also re-tightened oldham coupler set screws. Adjusted worm mesh but with the OPW this was just by feel - I simply push the worm into the wheel lightly and tighten everything down and if there is no stall I figure it's good - any advice appreciated!?
?
Tonights experiment: if the clouds cooperate, playing with the RA worm mesh after sundown and mount cooldown as previously I'm adjusting at room temp which I know is not smart.?
--
Thanks,
Topher
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?
Here is my eclipse setup, not the heaviest payload in the G11G ever but close.? I had to rebalance by adding an additional 11 lb counterweight, 81 lbs total after adding the 2" AP Maxbright and TeleVue 35mm Panoptic to the M10 f/6.3 SCT.? I almost had to add the 21 lb instead of the 11 lb counterweight to get it to balance, note the 7 lb counterweight on the outside is almost out of counterweight shaft travel.? ?
?
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
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Re: Gemini/NINA spreadsheet
Hi Edward, this is just what I've been looking for, I've been having a really hard time trying to config my G11 to do automated flips with NINA. I have 2 questions though, do you know if this works well with Gemini 1 as well? And also, I'm in the southern hemisphere, are there any considerations I should take into account? I read in the manual that eastern and western limits should be swapped when using the mount in the southern hemisphere, and actually due to the RA motor positioning my western limit is the "shorter" one before the setup will crash into the pier. Gemini also seems to report reversed sides of pier always, at least that's what I see in NINA: NINA will say the telescope is WEST of the pier but my telescope will be on the east. This I believe is because of me being in the southern hemisphere, because if I were to turn my mount 180 degrees in azimuth to face north, the reported side of pier would actually be correct. One would think that it would be an easy thing for Gemini to report the inverted side when your latitude is set south of the equator but this does not seem to be the case, so I wonder if there's anything I should take into account due to this. My issue with flips is that NINA will actually initiate the flip command with the legacy sequencer, but it will get stuck in an endless loop of requesting flips, once the flip is complete. Gemini will not perform another flip, but NINA will keep requesting them.
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Re: Help interpret my unguided log
Frequency tab 3/13:
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Frequency tab 3/14:
--
Thanks,
Christopher
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On Sat, Mar 15, 2025 at 10:46 AM, Paul Kanevsky wrote:
I used the Askar 151 (1052mm) quad element refractor with an ASI2600MC camera.? The supporting G11G works portably well with this assembly (~32 pounds on the saddle).
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The lighting during the full eclipse does have a different quality!??
?
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Re: Help interpret my unguided log
Log and screenshots from the following night without adjustments to the entire rig:
?
--
Thanks,
Christopher
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Re: Help interpret my unguided log
Screenshots from the 3/13 log using Auto Filter:
?   --
Thanks,
Topher
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On Fri, Mar 14, 2025 at 01:27 PM, WayBack wrote:
?
On topic, without encoders the Moon in eclipse from last night.? (I'm sure there exists better, this shot is mine.)
?
?
Doug,
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Looks very realistic, the same as I would expect to see in the eyepiece of a good telescope. What optics/camera did you use to take the shot?
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Wayback,
Never underestimate the challenges in getting a good image of a Lunar Eclipse.
toggle quoted message
Show quoted text
On 15 Mar 2025, at 4:27?am, WayBack <corey_d@...> wrote:
?
On topic, without encoders the Moon in eclipse from last night.? (I'm sure there exists better, this shot is mine.)
?
?
?
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Help interpret my unguided log
I do believe this is my first post!
?
The attached unguided guidelog is from my CG-11 with several upgrades including brass worm gear on RA, new OPW blocks both axis, Gemini-II w/HT motors, somewhat recent new factory RA and DEC bearings, recent clean & lube with factory grease, I hope still cleaned/dry clutch pads, clutches minimally tight, 200mmFL guidescope. About 45 minutes of unguided time under below average seeing. The PE is rather high and looks to me jaggy, (and I wonder if that's indicative of mechanical, seeing or what.)
?
On a good night I see about 0.75-1.0" rms in PHD2 and am currently imaging at 1.13" and 0.75", so I'd like to see if there's anything I can do to improve performance before I buy PEMpro and create a PEC curve.
?
Yesterday I removed and checked gearboxes/motors, also re-tightened oldham coupler set screws. Adjusted worm mesh but with the OPW this was just by feel - I simply push the worm into the wheel lightly and tighten everything down and if there is no stall I figure it's good - any advice appreciated!?
?
Tonights experiment: if the clouds cooperate, playing with the RA worm mesh after sundown and mount cooldown as previously I'm adjusting at room temp which I know is not smart.?
--
Thanks,
Topher
|
?
On topic, without encoders the Moon in eclipse from last night.? (I'm sure there exists better, this shot is mine.)
?
?
?
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I tend to agree with you agree with you Chip - the cost of the encoders is pretty darn steep and the number of takers would likely be low. ? If folks do insist on having high res axis encoders then I guess they are probably going to look at 10-Micron or AP at costs north of about 10k or more. ? Given that a G11 and Gemini combo can deliver approx. 1 arc-seconds RMS tracking error … ? PS Ganymede subtends about 1.5 arc-seconds as seen from here. ? ? D. ? ? ? ? ?
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Show quoted text
From: [email protected] <[email protected]> On Behalf Of Chip Louie via groups.io
Sent: 13 March 2025 20:56
To: [email protected]
Subject: Re: [Losmandy_users_io] Encoders, yes or no?? On Thu, Mar 13, 2025 at 03:48 AM, David C. Partridge wrote: As would some other folks, but you have to convince Scott Losmandy to do that.? Ideally this would require a new generation of Gemini (Gemini-3?) with the necessary additional hardware and firmware to talk to the absolute encoders.?? I think it would also be possible to create a smallish additional box that would allow them to be used with the Gemini-2.??? He’d also need to supply the hardware to me as it is likely that I’d end up developing the firmware to support the encoders. ? Adding absolute encoders to an existing mount would be a major exercise involving disassembly of the mount and quite a bit of precision machining. ? So, if it were ever offered, I suspect it would have to be with a new version of the mount, as for most people the cost of shipping the mount back to Losmandy, paying for the work and dealing with the complication of international customs such that you only pay tax/duty on the upgrade charges when it is shipped back to you.?? In the current “trade war” those charges could be huge. ? Please don’t discuss the politics here. ? David?
The problem is not actually building a Losmandy mount with absolute encoders, I have no doubt that Losmandy could design and produce such a mount.? The problem is getting enough people to buy the resulting mount as the cost would be quite high.? Even if you simply added an RA axis encoder ring and the double read heads needed to get the required resolution your talking about doubling the cost of a G11G just for the all new mount hardware design BEFORE you get to the all new controller hardware and new version firmware you will need to run the G11G+Absolute Encoder mount.? So would you pay nearly $8,000 for a 65 pound payload mount with absolute encoder RA?? Would you pay $10,000 for a dual axis absolute encoder mount that did not need guiding for the commonly used short subframe imaging we use today?? I don't think so because in reasonably skilled hands, modern autoguiding on current model G11G mounts is already good enough to produce excellent images for most sub 2,000mm focal length optics.? Not to mention that with all the money you saved you could buy an entire second imaging rig.? ? ??
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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On Wed, Mar 12, 2025 at 03:32 PM, DaleN wrote:
Better! A bit of follow-up to my GM811G with poor Dec guiding for SVX140T:
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I followed a few of the great suggestions, namely reducing the CW moment arm and Dec guiding aggressiveness.
i ordered a 21 lb CW, and installed it at the top of the shaft, with an 11 lb up against it. A 7 lb midshaft for balancing. So now at 39 lbs CW rather than 29, but much higher on shaft, so moment arm is greatly reduced.
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dialed back the Dec Aggression to 60, and stretched the guide imaging to 3 sec from 1.5. Got down to ~.45” both RA and Dec for a while, but more generally .7” ish for each for several hours, with low eccentricity. Much better. I’ll see if I can’t dial that in better now.
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many thanks for the suggestions!
CS, Dale
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There are differing schools of thought on this based on what I have observed others doing and when asked why I got a lot of different answers.? IME ideally you want to use enough counterweight so you can position the counter weight mass up as high as reasonably possible (mechanical interference is the obvious limit and varies based on where you are) and still achieve good balance.? I use the small 7lb. counterweight on the end to make fine adjustments easier.? Using this method requires having the most counterweight available.??Of course the heavier the payload the more counterweights end up on the shaft and they also tend to naturally move up the shaft which is ideal.
?
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
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On Thu, Mar 13, 2025 at 03:48 AM, David C. Partridge wrote:
As would some other folks, but you have to convince Scott Losmandy to do that.? Ideally this would require a new generation of Gemini (Gemini-3?) with the necessary additional hardware and firmware to talk to the absolute encoders.?? I think it would also be possible to create a smallish additional box that would allow them to be used with the Gemini-2.??? He’d also need to supply the hardware to me as it is likely that I’d end up developing the firmware to support the encoders.
?
Adding absolute encoders to an existing mount would be a major exercise involving disassembly of the mount and quite a bit of precision machining.
?
So, if it were ever offered, I suspect it would have to be with a new version of the mount, as for most people the cost of shipping the mount back to Losmandy, paying for the work and dealing with the complication of international customs such that you only pay tax/duty on the upgrade charges when it is shipped back to you.?? In the current “trade war” those charges could be huge.
?
Please don’t discuss the politics here.
?
David?
?
The problem is not actually building a Losmandy mount with absolute encoders, I have no doubt that Losmandy could design and produce such a mount.? The problem is getting enough people to buy the resulting mount as the cost would be quite high.? Even if you simply added an RA axis encoder ring and the double read heads needed to get the required resolution your talking about doubling the cost of a G11G just for the all new mount hardware design BEFORE you get to the all new controller hardware and new version firmware you will need to run the G11G+Absolute Encoder mount.?
?
So would you pay nearly $8,000 for a 65 pound payload mount with absolute encoder RA?? Would you pay $10,000 for a dual axis absolute encoder mount that did not need guiding for the commonly used short subframe imaging we use today?? I don't think so because in reasonably skilled hands, modern autoguiding on current model G11G mounts is already good enough to produce excellent images for most sub 2,000mm focal length optics.? Not to mention that with all the money you saved you could buy an entire second imaging rig.? ? ??
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
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Edward Plumer
Paul Kanevsky
Chip Louie
David C. Partridge