RA Divisor on Gemini 2 G811 mount.
Folks,
I am trying to understand what the RA divisor should be in my mount. ?Background: ?In troubleshooting some issues between my G811 mount and and ASIAIR i have stumbled across the RA Divisor in the track submenu on the HC. ?There is a number of 448771 in the RA box. ?When I searched web found a reference to this number in a "Level 4" manual dated 2006. ?In this reference pdf on page 31 it gives description and indicates the correct number is 56096 so a factor of 8x different. ?Yet I have never adjusted this (at least not intentionally) since owning this mount. ?My rig was new in summer of 2019 and Has HC firmware 1.2 and Mainboard V 5.21 both dated March of 2017. What is the correct value?
thanks
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Anybody here use RegiStar software? Is there a group for that? I'm having A bit of a problem with it.
Stu
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Hi Bill
The built-in levels are good for that, and I'm not sure using an external level is going to make much of an improvement
The value of an accurate "bubble level" CWD is to improve the accuracy of your first goto . Once you align and start building a model, it's not going to have much impact?past that.??
On Sat, Jan 23, 2021 at 10:21 AM Bill Tschumy < bill@...> wrote: Guys and Gals,
I believe some folks have said they use a level to achieve an accurate CWD position.? On my G811 there doesn¡¯t seem to be a great place to put a level.? I end up setting it on the worn cover? of the Dec axis worm.? That is not ideal because:
1. It assumes you have accurately rotated the Dec axis to 90?
2. It assumes the worm cover is actually at 90? to the counterweight shaft.
I realize that small errors in CWD are probably not that significant, but I was just wondering is there is a better way to accurately find CWD.
--
Bill Tschumy
Otherwise -- Longmont, CO
-- Brian?
Brian Valente portfolio
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I would love to have a way for the scope to actually that it is parked where it thinks it is.? I saw in the Gemini 2 user group that the unit can support homing switches.? Do we know if Losmandy plans to make this available as an accessory?
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Re: Understanding a GM8 for Possible Purchase
Thanks. ?Could you help me understand a bit more what sorts of trouble chasing problems I¡¯d typically encounter with an old mount? ?And even more important, do you prefer to addressed as Chip or Louie?
Best,
Jeff
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Bill,
Get a short "torpedo" level.? The one pictured is 9 inches long.? ?You then use the level and the hour markings on the RA and DEC axes.??
Start with the RA axis.? You rotate the counterweight rod to be about horizontal, then use the torpedo level to get that exactly horizontal.
Now use the marked RA dial and set it to be something convenient, like 12 o'clock.
Then rotate the RA axis back to CWD and use the RA marked indicator to show 6 o'clock (you get the idea...assure you are 90 degrees from horizontal).
For the DEC axis you can put the level on the dovetail, (with no scope in place) when the dovetail is horizontal.? Again note the indicator dial marking.? Then use the marked dial to rotate back to CWD position.
Have fun,
Michael
On Sat, Jan 23, 2021, 10:21 AM Bill Tschumy < bill@...> wrote: Guys and Gals,
I believe some folks have said they use a level to achieve an accurate CWD position.? On my G811 there doesn¡¯t seem to be a great place to put a level.? I end up setting it on the worn cover? of the Dec axis worm.? That is not ideal because:
1. It assumes you have accurately rotated the Dec axis to 90?
2. It assumes the worm cover is actually at 90? to the counterweight shaft.
I realize that small errors in CWD are probably not that significant, but I was just wondering is there is a better way to accurately find CWD.
--
Bill Tschumy
Otherwise -- Longmont, CO
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Guys and Gals,
I believe some folks have said they use a level to achieve an accurate CWD position. On my G811 there doesn¡¯t seem to be a great place to put a level. I end up setting it on the worn cover of the Dec axis worm. That is not ideal because:
1. It assumes you have accurately rotated the Dec axis to 90?
2. It assumes the worm cover is actually at 90? to the counterweight shaft.
I realize that small errors in CWD are probably not that significant, but I was just wondering is there is a better way to accurately find CWD.
--
Bill Tschumy
Otherwise -- Longmont, CO
www.otherwise.com
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Re: Permanent Pier Parking
Russ,
A pier and a roll off shed is what I have also. Normally the mount sits in the CWD position until I go to start up. I then use Park at Home in the menu to get the counterweight bar to be horizontal, and the scope axis is horizontal too in this position. Then I can roll off the roof without collision. To set this orientation, I used the buttons on the Hand Controller (with speed set at Slew) to move into position, then used Set Home in the Hand Controller Park menu. From this Home position, I usually just go straight to a bright star, and Sync after confirming it's centered in the eyepiece, guide cam, or main cam. Then again to close up, I hit Park at Home to fold over, close the roof, then hit Park at CWD as the stationary position. I usually put a cover over the scope if I won't be returning for at lest several days.
But with Home and CWD already set, I usually don't need the Hand Controller for a new session. After powering on the mount, I start the Gemini app and hit connect. It will give me a pop up on the computer screen which says Cold Start, Warm Start (from CWD), and Warm Restart. I choose Warm Start and I'm good to go. For this pop up, you must go the the app's Set Up Menu, and under Configure Telescope, select Prompt if Not Started in the Boot Mode box. You can also select Cold Start, Warm Start, or Warm Restart as the preferred start mode, but if prefer to select how I am starting in the pop up. With Warm Start my last model will be used and I can usually go directly to the bright star. I may have to slew a bit if I released the clutches, or if I bumped the scope a bit, and then hit Sync again. The model can last quite a few sessions unless I sync on the wrong star, or Sequence Generator Pro slews to the wrong part of the sky, which can happen when clouds mess up a platesolve.
But with CWD and Home set as above, I can just flop over whenever I need to move the roof. That's about it.
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Re: Permanent Pier Parking
Great Questions!!!? Looking forward to replies!!!!? :-)
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Re: Permanent Pier Parking
Super!? Thanks guys for opening this topic!? Like all good riddles, every answer brings up more questions.??
On the Gemini-1, there are 2 options:??
Cold Start (erase all model {error} factors to zero and boot up assuming scope is in CWD position),?
or Warm Start...resume operation from last parked position, and re-use the stored model factors.
That is, the Gemini-1 records where it was parked and resumes from there on its Warm Start.
Now I just got a Gemini-2 and could not fathom the difference between "Warm Start" and the new option "Warm Restart."??
From Brian's writing just now, I have a new understanding: these function slightly differently from the Gemini-1 operation.??
But then comes a design related and usage question:
Why do you need to have a G-2 Warm Start (from CWD only) when a Warm Restart (from where you last parked) could do it all, as Warm Start does on a Gemini-1?? ? Under what circumstances would you need to use the Warm Start on a Gemini-2?? Wouldn't using G-2 "Warm Restart" cover all the bases??
I do know of G-1 owners with roll-off roof observatories who do park at horizontal (to use a lower roof!).? That's a great feature to park anywhere you like!
I wonder how Gemini-net handles this.? Can Gemini.net tell a G-2 from a G-1? ...I'm sure it can ask for the firmware number or the unit type which G-1 displays on its boot up.? Does Gemini.net then know the difference in Warm Start behavior between the G-1 and the G-2?? Paul K will know this detail...!
All the best, Michael
On Sat, Jan 23, 2021, 8:35 AM Brian Valente < bvalente@...> wrote: Hi Russ
sounds like a great project - i hope you keep us all in the loop!
For more permanent pier-based setups, I usually see one of two approaches:
1. Park the mount at CWD and warm start. Warm start = "warm start at CWD position" or 2. Define a Home position (such as 90 degrees) and just park it there and warm restart. Warm restart = "warm start but not at cwd position"
?
Starting new thread regarding parking of mount in observatory/permanent pier since a search of the archives are showing this topic to be over 10 years old without an update.
So, in my case, with mount in an observatory on a permanent pier, I always park at night at CWD (all bubble leveled) and have been doing a Warm Restart on next night.? Should I only be doing a Warm Start instead of Warm Restart??
Additionally, I am thinking of creating a "Park" position at 90 degrees from CWD (telescope pointing to eastern horizon) so I can close the roof (avoiding getting dust into scope) and after roof closed, select park at CWD for its home/storage position.? Is this also do-able?? ?Thanks!!!
--
Brian?
Brian Valente portfolio
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Re: Permanent Pier Parking
Hi Russ
sounds like a great project - i hope you keep us all in the loop!
For more permanent pier-based setups, I usually see one of two approaches:
1. Park the mount at CWD and warm start. Warm start = "warm start at CWD position" or 2. Define a Home position (such as 90 degrees) and just park it there and warm restart. Warm restart = "warm start but not at cwd position"
?
Starting new thread regarding parking of mount in observatory/permanent pier since a search of the archives are showing this topic to be over 10 years old without an update.
So, in my case, with mount in an observatory on a permanent pier, I always park at night at CWD (all bubble leveled) and have been doing a Warm Restart on next night.? Should I only be doing a Warm Start instead of Warm Restart??
Additionally, I am thinking of creating a "Park" position at 90 degrees from CWD (telescope pointing to eastern horizon) so I can close the roof (avoiding getting dust into scope) and after roof closed, select park at CWD for its home/storage position.? Is this also do-able?? ?Thanks!!!
-- Brian?
Brian Valente portfolio
|
Starting new thread regarding parking of mount in observatory/permanent pier since a search of the archives are showing this topic to be over 10 years old without an update.
So, in my case, with mount in an observatory on a permanent pier, I always park at night at CWD (all bubble leveled) and have been doing a Warm Restart on next night.? Should I only be doing a Warm Start instead of Warm Restart??
Additionally, I am thinking of creating a "Park" position at 90 degrees from CWD (telescope pointing to eastern horizon) so I can close the roof (avoiding getting dust into scope) and after roof closed, select park at CWD for its home/storage position.? Is this also do-able?? ?Thanks!!!
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Re: Understanding a GM8 for Possible Purchase
>>>
?Since it has 4 buttons on its face it does not look like the Gemini-2 hand controller
i'm fairly certain that is the current Gemini-2 hand controller
We don't really offer an option of a hand controller with no touchscreen that is Gemini-2 compatible.
But you can ask the seller for a picture of the other side to confirm
This is great information.? Thanks, all.? I will follow up with the seller on a couple of the points you raise.
Interesting question, Derek, about the hand controller.? Since it has 4 buttons on its face it does not look like the Gemini-2 hand controller Losmandy now offers as part of the Gemini-2 Upgrade package, here:?? Michael, Brian, others¡ªdoes that reduce functionality at all, or otherwise present an issue?
I¡¯m by no means a mechanical wizard but I believe I can handle the sorts of tinkering you describe.?
Do any of you care to hazard a guess as to what it¡¯d cost to ship this from the E Coast to Arizona?
Kind regards,
Jeff
-- Brian?
Brian Valente portfolio
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Re: Understanding a GM8 for Possible Purchase
On Fri, Jan 22, 2021 at 05:47 PM, Jeff Rothstein wrote:
Hi all.?
I¡¯m on the waiting list for a GM-8G, and a used opportunity has come my way. ?The mount was made pre-2011, had Gemini-1 and has been upgraded to Gemini-2. ?It¡¯s also been upgraded to OPWBs but they are not spring-loaded. ?Current owner does not know which motors are on the mount but says it slews as fast as any GOTO he¡¯s used. ?I¡¯ve attached a couple of pictures. ?It appears to have been well-maintained
I have three questions: ?
1. ?Can you tell which motors these are??
2. ?What material function and convenience would I give up choosing this mount over a new one? ?(I see these are not tucked-in motors and appreciate I¡¯ll need to watch for snags and bumps, and be extra careful moving the mount.)
3. ?Beyond the details of its features and what the seller knows about maintenance, what else should I be asking?
Thanks for your advice!
Jeff
Hi Jeff, As a long time Losmandy user who just recently sold a valued old friend in my classic GM8 Gemini and bought a new GM8G mount after upgrading my G11 to a G11G 3 years ago my advice is buy the new mount. It will save you a.lot of trouble chasing the problems of an old mount and trying to update during a time when Losmandy is running full bore and cannot spend the time to do basically custom work while his production falls behind. Buy the new mount, it will save you time getting to where you want to be.? ? -- Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astropheric Weather Forecast - South Pasadena, CA?
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Hmmmm... Thanks Derek.? Will need to check on that.? Since my system is in an observatory and is fixed, I read somewhere to always use Warm Restart.? But since I do park at CWD, I will need to find out whether Warm Start or Warm Restart should be used.
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Re: Understanding a GM8 for Possible Purchase
This is great information. ?Thanks, all. ?I will follow up with the seller on a couple of the points you raise.
Interesting question, Derek, about the hand controller. ?Since it has 4 buttons on its face it does not look like the Gemini-2 hand controller Losmandy now offers as part of the Gemini-2 Upgrade package, here:?? Michael, Brian, others¡ªdoes that reduce functionality at all, or otherwise present an issue?
I¡¯m by no means a mechanical wizard but I believe I can handle the sorts of tinkering you describe.?
Do any of you care to hazard a guess as to what it¡¯d cost to ship this from the E Coast to Arizona?
Kind regards,
Jeff
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Re: Understanding a GM8 for Possible Purchase
Hi!
The only motor that is clearly shown from side view is the RA motor, visible from your rear view photo.? That motor shows no "cooling fins" so that is an oldest version servo motor.? The latest HiTorque motor has about 6 cooling fins around the barrel, and I don't see any in that photo.? Photos of the various motor versions are at this website, so you can clearly tell the motor from counting the cooling fins:
But if the old motors work, there is nothing wrong with them.? You can increase motor torque by supplying say 17 to 18 volts to the Gemini DC power input instead of 12 volts to get proportionally higher motor torque.? If a motor does wear out, a replacement motor is about $225.? All the motors are interchangeable.? They all use the same stock gearbox from the company.? ??
Now...as you requested understanding.... here we go:
Autoguiding is essential and the Gemini-2 gives you that, but it is better if the autoguider needs as little corrections to do as possible.? So if you are looking to do deep sky imaging, then low PE is the factor of interest in any mount.? ?
It is pretty easy to tune this earlier style mount to low PE, as the RA drive has only got a few components (motor into gearbox into coupler into worm in worm bearings).? The OPW on the RA generally improves PE by holding the worm bearings in line, getting the best worm bearing behavior, and the OPW makes worm to ring gear space easier to adjust because it helps hold the worm bearings tight on the worm.??
The latest version "tucked" motor has its own OPW, and adds in two large transfer gears and another shaft to hold the inner transfer gear, and these add a few more elements to control for low PE.? ?The "spring loaded" version adds a spring and a back off bolt.??
Owners can improve these mounts by adding a Belleville spring washer to eliminate worm axial shift, and putting in higher quality RA worm bearings.? These are easy to do.? Perhaps this mount already has these elements.??
The GM8 has a 180 tooth ring gear on both RA and DEC, and a 480 second worm period.? The larger heavier G11 has 360 teeth in the ring gears and a 240 second worm period.? The smaller diameter GM8 ring gear would amplify the GM8 PE of the worm by 2X.? But the worm is only a part of the PE contributors.? The lineup of the Oldham coupler, perfection of the RA gearbox and worm bearings are important factors as well.? My own GM8 looks just like this one, and has about 1.6 arcsec RMS PE (about 4 arcsec peak to peak). I imaged with it using 5 inch or 6 inch refractor, and the GM8 was designed for up to 8 inch SCTs.?
The GM8 has 3 inch OD clutch disks, so if you are planning to image, you may want to install high friction disks, but these are inexpensive and easy to install.? The bigger G11 had 4.25 inch OD disks.??
This unit has also got a nice polar scope and latest illuminator.? That will help you get a good polar alignment.? It has a lightweight foldable tripod.? I have only heavier tripods, if you need a more beefy base there are other tripod options if you want one.??
The Gemini-2 is a good go-to controller.? This system shows some nice holders in the legs for the G-2 handset.?
I notice this particular GM8 has what looks like my DEC extension under the dovetail clamp.? That DEC extension allows the dovetail to rotate past the RA motor end, and gives the mount an ability to do a meridian flip.??
( Have I left anything out?! )
Have fun, Michael
On Fri, Jan 22, 2021, 7:59 PM Brian Valente < bvalente@...> wrote: Hi Jeff
these look like the high torque servo motors. your seller should be able to confirm this
other than the tucked in motors, the big missing item is the spring-loaded worms, which are imo probably the most significant mount improvement in the last handful of years.? You won't have to think about east biasing your weight and it does a great job of minimizing backlash as well. Generally you won't need to reset your worm gears either.?
In this regard it's probably one-or-the-other choice - sending in a G8 for the upgrade is probably more $ than if you just bought a new mount.?
you would of course want to know the history of the mount upgrades, any issues the seller has had with it, has it been dropped or roughly handled, etc. look for unusual marks or scrapes. It does have the LW?tripod spreaders which are an additional accessory when buying new.?
HTH
Brian
Hi all.?
I¡¯m on the waiting list for a GM-8G, and a used opportunity has come my way.? The mount was made pre-2011, had Gemini-1 and has been upgraded to Gemini-2.? It¡¯s also been upgraded to OPWBs but they are not spring-loaded.? Current owner does not know which motors are on the mount but says it slews as fast as any GOTO he¡¯s used.? I¡¯ve attached a couple of pictures.? It appears to have been well-maintained
I have three questions: ?
1.? Can you tell which motors these are??
2.? What material function and convenience would I give up choosing this mount over a new one? ?(I see these are not tucked-in motors and appreciate I¡¯ll need to watch for snags and bumps, and be extra careful moving the mount.)
3.? Beyond the details of its features and what the seller knows about maintenance, what else should I be asking?
Thanks for your advice!
Jeff
--
Brian?
Brian Valente portfolio
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>>>
in short, Murphy's Law likes?astronomy.? Plenty of things to go wrong ....
i would add to Murphy's Law for Astronomy. Plenty of things to go wrong, and usually you overlook the easiest answer
Last week i updated all my various software packages (ASCOM to 6.5SP1, Sequence Generator pro latest version, focuser driver, etc.) on my remote telescope that is in the Atacama Desert in Chile
Then I started noticing my FWHM getting pretty high, and realized the telescope was no longer autofocusing.?
So every night for the last 5 nights, rather than sleeping i was pushing the focus button every hour or so while i tried to find the problem
Tonight?i finally got up the courage and time to downgrade everything back to where it was, but the problem was still there!
After yelling and screaming I looked through my settings, only to find that my "use autofocus" checkbox was somehow unchecked.?
I re-enabled the function?and now it works perfectly.?
5 solid nights of missed sleep and pouring through debug logs.... smh
On Fri, Jan 22, 2021 at 12:07 PM Michael Herman < mherman346@...> wrote: Hi Russ, and all,
Hopefully not beating a dead horse...
To answer your question, when you are polar aligned, you?are polar aligned when at CWD. You?are also polar aligned at all other RA rotations too.
When you are polar aligned your?mount is aimed at NCP. If your mount were aimed directly at Polaris, you would be about 0.7 degree of arc off of NCP.
The Earth's rotation axis is moving slowly.... and Polaris itself and the Sun are moving relative to each other too.? Polaris is close enough to Earth ...about 330 light years (distance estimates vary too).? From Stellarium program calculations, Polaris appears to be moving closer to the actual NCP North Celestial Pole position.?? The movement of Polaris apparent distance from NCP was why the optical polar alignment scope needs a new glass reticule?produced every 10 years... to put the NCP position on the glass at the newer position of Polaris.
Today, Stellarium reports for Polaris this data: RA of Polaris using J2000:? 89deg 15 min 51.5 sec? ? so it was off by ~44.9 arc minutes in year 2000 RA of Polaris today's date: 89 deg 21 min 14.7 sec? ?so it is off by ~39.75 arc minutes today. ? For reference, the diameter of the full moon is about 30 arc minutes (varies with moon distance from Earth).? ?
(You can have fun with Stellarium... running the clock forward, Polaris gets as close as 89 deg, 31 min, 52.9 sec on Sept 23, 2086. ?That seems to be about the closest Stellarium predicts Polaris will be to NCP...about 28 arc minutes away from NCP, or about 1 full moon diameter away from NCP.?? ?Just wait 45 more years! )
This is also why the PoleMaster software uses many stars around Polaris to identify the correct location of NCP.? You?can't count on Polaris alone!
If you bump your tripod, or have an earthquake (a West Coast specialty), then... your mount might be again off of polar alignment.
Also be sure to check your tripod leg adjustment bolts.? I found one of my tripod legs slowly creeping shorter over time.? That mount is quite overloaded in weight, but I thought the legs would not slip... And check your AZ lock down bolts.? (There is a central bolt under the center of the mount head, where the mount top rotates around when you adjust AZ. )
in short, Murphy's Law likes?astronomy.? Plenty of things to go wrong at the worst possible time...
Stay well, Michael
Going to do some tests tonight with SharpCap and its Polar Alignment tool.? Just to be clear, when my G11G is at CWD (bubbles leveled) the scope should be polar aligned with the NCP.? Correct??
--
-- Brian?
Brian Valente portfolio
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Re: Understanding a GM8 for Possible Purchase
Hi Jeff
these look like the high torque servo motors. your seller should be able to confirm this
other than the tucked in motors, the big missing item is the spring-loaded worms, which are imo probably the most significant mount improvement in the last handful of years.? You won't have to think about east biasing your weight and it does a great job of minimizing backlash as well. Generally you won't need to reset your worm gears either.?
In this regard it's probably one-or-the-other choice - sending in a G8 for the upgrade is probably more $ than if you just bought a new mount.?
you would of course want to know the history of the mount upgrades, any issues the seller has had with it, has it been dropped or roughly handled, etc. look for unusual marks or scrapes. It does have the LW?tripod spreaders which are an additional accessory when buying new.?
HTH
Brian
Hi all.?
I¡¯m on the waiting list for a GM-8G, and a used opportunity has come my way.? The mount was made pre-2011, had Gemini-1 and has been upgraded to Gemini-2.? It¡¯s also been upgraded to OPWBs but they are not spring-loaded.? Current owner does not know which motors are on the mount but says it slews as fast as any GOTO he¡¯s used.? I¡¯ve attached a couple of pictures.? It appears to have been well-maintained
I have three questions: ?
1.? Can you tell which motors these are??
2.? What material function and convenience would I give up choosing this mount over a new one? ?(I see these are not tucked-in motors and appreciate I¡¯ll need to watch for snags and bumps, and be extra careful moving the mount.)
3.? Beyond the details of its features and what the seller knows about maintenance, what else should I be asking?
Thanks for your advice!
Jeff
-- Brian?
Brian Valente portfolio
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Re: Understanding a GM8 for Possible Purchase
Hi
Jeff..
?
Motors
look like mine.. Hi Torque Servo..
See..
and
scroll down..
?
I
see on the above page the controller in your image is shown as a ¡°492¡±
controller.. And you said ¡°upgraded to Gemini II¡±.. No idea how the
upgrade would work ¨C someone here does ¨C but that is something to
look into.. It doesn¡¯t look like my controller..
?
I
bought my G11 / Gemini II used. I also live close to Michael
Herman (or too close depending on who you ask) and he was
nice enough to both explain the mount and it¡¯s operation, and install his
simple ¨C but very effective! ¨C upgrades.. That¡¯s a priceless
benefit for me, granted..
?
If
the price is right, I¡¯d buy it.. Those OPWs.. I do wish I had those
myself, but even without them, I get excellent tracking.. Again.. G11, but I,
for one, bought used and love it!
?
Derek
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Jeff Rothstein
Sent: Friday, January 22, 2021
5:46 PM
To: [email protected]
Subject: [Losmandy_users_io]
Understanding a GM8 for Possible Purchase
?
Hi all.?
I¡¯m on the waiting list for a GM-8G, and a used opportunity has come my
way. ?The mount was made pre-2011, had Gemini-1 and has been upgraded to
Gemini-2. ?It¡¯s also been upgraded to OPWBs but they are not
spring-loaded. ?Current owner does not know which motors are on the mount
but says it slews as fast as any GOTO he¡¯s used. ?I¡¯ve
attached a couple of pictures. ?It appears to have been well-maintained
I have three questions: ?
1. ?Can you tell which motors these are??
2. ?What material function and convenience would I give up choosing this
mount over a new one? ?(I see these are not tucked-in motors and
appreciate I¡¯ll need to watch for snags and bumps, and be extra careful
moving the mount.)
3. ?Beyond the details of its features and what the seller knows about
maintenance, what else should I be asking?
Thanks for your advice!
Jeff
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Aaron Lovett
Michael Herman
Bill Tschumy
Chip Louie