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I just received a brand new GM811G and took it outside for first light yesterday.? After successfully polar aligning the mount with a polemaster, I tried to goto several bright stars and each time the mount slewed in a direction that was nearly opposite of where it needed to point.? For example, starting from the CWT down position, I tried to goto Altair (high in the southeast) and the mount tried to slew so the scope would point at the ground in the west.? I eventually had to stop the goto to prevent the scope from crashing.? I've never seen this occur on any other equatorial mount I have owned.
This happened multiple times from the CWT down position trying to go to different stars.? I restarted the mount several times and made sure that everything obvious (I think) was set correctly.? The RA and Dec cables are plugged in correctly, mount type, lat and longitude, date and time are all correct, polar alignment is good, etc.??
Eventually, I disengaged the clutches and manually moved the scope to the star I had directed the mount to goto, Arcturus.? With the mount thinking it was at Arcturus, I retightened the clutches and tried to goto Mizar.? In this instance, the mount reached the correct R.A. for Mizar (I think), but went much too far to the east in Declination.??
I spent two hours trying to get these problems fixed at a dark sky site and ultimately gave up and headed home.? I am out of ideas on this.? What should I check next?? Could this be something that updating the firmware in the controller would fix?
Ryan
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?With the mount thinking it was at Arcturus, I retightened the clutches and tried to goto Mizar.? In this instance, the mount reached the correct R.A. for Mizar (I think), but went much too far to the east in Declination.?
With new users it is hard to know whether the errors are conceptual or due to faulty implementation of issues that are understood.? And then there are errors that occur in the writing of the post which are really editing issues and unrelated to what's going on with the user or the mount but which are confusing to the readers.? On top of that there are some genuinely bizarre outcomes. This post has written has some head scratchers in it.? A mount cannot go too far east or west in declination. Declination is north south and only north south.? It cannot be anything else. I am emphasizing this because if you have conceptually confused right ascension and declination, then you will have connected your wires incorrectly.? That is you will have right ascension inputs in the dec and dec inputs in the right ascension. On top of that it is possible to understand completely and fully right ascension and dec and connect the wires opposite to what they should be in any case. This is called a brain fart. Or maybe you just wrote up your post wrong. So those are things to check. Now in the usual case when the mount seems to be working but doesn't seem to be going to where it needs to go there is confusion in the mount as to which hemisphere it is in. So it needs to be configured for northern hemisphere.? The other thing you need to do is make sure that you always make your first alignment star in the east and have time and date and location correct.? It certainly used to be the case, and I don't know if it's still true, that most equatorial pointing systems assumed an initial alignment on a star on the east side of the meridian.? ?Some systems use GPS to try to remove that issue from the user. But take a star like Vega for example in the first part of the spring and summer it is an star in the eastern part of the sky but as the summer progresses you find it in the west. If you align on the west first the pointing computer may try to make everything workwith time and date settings that are not consistent with Vega being in the West. The result is that the pointing gets turned around.? ?and if the north south hemisphere settings are not correct that is a similar problem. It will assume you are in the southern hemisphere and can see Vega in the northern part of your sky but all the pointing decisions that result from that will be ass backwards. Incidentally I had this problem with analog setting circles I had purchased a mount with southern setting circles I didn't know it. Everything came out ass backwards no computer involved. Telescopes in general and telescopes with robotic pointing systems are beautiful but complex machines with all kinds of rules many of which become second nature to the user but are difficult to master.? ?I always tell people to keep their expectations low for the first month of ownership of devices like this. Take it a step at a time. You've gotten to the point where you can put the scope on them out and get them out pointed in the right direction and you have a power supply which is making the motors work. So you have made huge progress in what I consider to be the one month break-in time for user and machine. So now the next step is to get it pointing at Bright Stars consistently.? ? The backlash adjustment is another potential source of pointing error but it would be very unusual to have it be errors as large as you are describing.? Inertia of the mount and scope may try to keep the telescope pointed still while the motors are trying to move it. The pointing system counts the movement in the servos in order to keep track of where it is.? if the servos are moving and the mount is not that is going to introduce error of varying degrees of severity. To sum up make sure your RA and dec wires are going to the right motors. Make sure you are 100% clear on which axis is declination and which is right ascension. Because even now after doing this stuff for 20 years I occasionally plug my wires into the wrong motor.Make sure your paddle control is set for northern hemisphere, assuming you are in the northern hemisphere.? Make sure time date and location are correctly set. And then make sure that your first alignment star is east of the meridian and preferably by more than a little bit.
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Hi!
FIrst thing to check, always, in situations like this, is time
and location. Is the time correctly set, and is it really the
correct geographical location? You set this with the handcontrol,
if not connected to a computer.
Best,
Magnus
Den 2020-08-12 kl. 14:38, skrev Ryan
Weiss:
toggle quoted message
Show quoted text
I just received a brand new GM811G and took it outside for first
light yesterday.? After successfully polar aligning the mount with
a polemaster, I tried to goto several bright stars and each time
the mount slewed in a direction that was nearly opposite of where
it needed to point.? For example, starting from the CWT down
position, I tried to goto Altair (high in the southeast) and the
mount tried to slew so the scope would point at the ground in the
west.? I eventually had to stop the goto to prevent the scope from
crashing.? I've never seen this occur on any other equatorial
mount I have owned.
This happened multiple times from the CWT down position trying to
go to different stars.? I restarted the mount several times and
made sure that everything obvious (I think) was set correctly.?
The RA and Dec cables are plugged in correctly, mount type, lat
and longitude, date and time are all correct, polar alignment is
good, etc.??
Eventually, I disengaged the clutches and manually moved the scope
to the star I had directed the mount to goto, Arcturus.? With the
mount thinking it was at Arcturus, I retightened the clutches and
tried to goto Mizar.? In this instance, the mount reached the
correct R.A. for Mizar (I think), but went much too far to the
east in Declination.??
I spent two hours trying to get these problems fixed at a dark sky
site and ultimately gave up and headed home.? I am out of ideas on
this.? What should I check next?? Could this be something that
updating the firmware in the controller would fix?
Ryan
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And also check that the RA motor is connected to the RA outlet on the controller and similarly for the DEC. ? David ?
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Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Magnus Larsson
Sent: 12 August 2020 14:26
To: [email protected]
Subject: Re: [Losmandy_users_io] Issues With Initial GoTos on new GM811G? Hi! ? FIrst thing to check, always, in situations like this, is time and location. Is the time correctly set, and is it really the correct geographical location? You set this with the handcontrol, if not connected to a computer. Best, Magnus ? Den 2020-08-12 kl. 14:38, skrev Ryan Weiss: I just received a brand new GM811G and took it outside for first light yesterday.? After successfully polar aligning the mount with a polemaster, I tried to goto several bright stars and each time the mount slewed in a direction that was nearly opposite of where it needed to point.? For example, starting from the CWT down position, I tried to goto Altair (high in the southeast) and the mount tried to slew so the scope would point at the ground in the west.? I eventually had to stop the goto to prevent the scope from crashing.? I've never seen this occur on any other equatorial mount I have owned.
This happened multiple times from the CWT down position trying to go to different stars.? I restarted the mount several times and made sure that everything obvious (I think) was set correctly.? The RA and Dec cables are plugged in correctly, mount type, lat and longitude, date and time are all correct, polar alignment is good, etc.??
Eventually, I disengaged the clutches and manually moved the scope to the star I had directed the mount to goto, Arcturus.? With the mount thinking it was at Arcturus, I retightened the clutches and tried to goto Mizar.? In this instance, the mount reached the correct R.A. for Mizar (I think), but went much too far to the east in Declination.??
I spent two hours trying to get these problems fixed at a dark sky site and ultimately gave up and headed home.? I am out of ideas on this.? What should I check next?? Could this be something that updating the firmware in the controller would fix?
Ryan
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What David and GN said. When I first started out, I did exactly this and was wondering why things were not moving the way they should. It is easy to accidentally interchange RA and DEC when connecting the cables and the Gemini 2 unit won't complain.I was just as convinced as you are that I had done it correctly.
Also wanted to share how good the pointing accuracy of the GM811G is; I use mine for imaging mostly, but used it for visual last week and for the first time used the GOTO functionality and model. I expected to have to synchronize with multiple stars, but no. Accurate polar alignment and synchronizing with a single star? put every other object I pointed to in the center of at least a low power eyepiece. Made things easy. This is the kind of performance you should expect. The nice thing is that Gemini modeling will only allow you to sync to a star that's sufficiently far from the meridian.
Would suggest doing a dry run in a well lit area or even indoors. You don't need it to be exact, but can assure yourself that the mount is at least moving in the direction it is supposed to.?
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Ryan a few tricks
longitude setup is ¡°-Also south is ¡°-ve¡±!
incl any DST offset ?. Time zone offset is from UTC. if you enter your locality time as ¡°correct UTC¡± time instead of local and set the offset to zero ?then you never have to worry about DST changes ?
Ensure you press ¡° ?
?
?Everyone does that at sometime ?
s some rotate ?opposite due to gearing nature ?
All are already said. Many new users have pointing issues like this usually it¡¯s an issue with time input offset and location.?
--
Brendan
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Since your mount is brand new, you should call the factory in California and discuss the problems.? They should be at:
(747) 283-1075
(The serial number of your mount head is printed on the bottom of the base, but the mount head mechanical parts have nothing to do with this problem: it is a Gemini problem, or a settings problem.? )
However, I'll mention a few key things about the Gemini system:
1. Whenever you enter some new primary value (Latitude, Longitude, Date, Time) you must then turn the Gemini off and "Cold Boot" restart. ? That is because the Gemini still uses the values it read from memory on boot up, and not the new values you entered.? ?Most other programs use the new entries immediately....not this one.
2. You have a GM811.? It has the RA section of a G11 (360 teeth on the RA ring gear) and the DEC section of a GM8 (180 teeth on that ring gear).? Both sections have the same worm.? So if your mount is set to, say, a G11, not a GM811, ?the Gemini would drive the mount to correct RA but move DEC twice as far as the correct position. ? I think from your DEC movement clue, you may have entered the mount model wrongly...since G11 and GM811 sound like they have the same settings.? Double check this. ?
3. Date and time entry are ... A special code.? Here it is from the Gemini-1 manual, that I will attach for reference as the Gemini-2 is largely the same.
It says: The display of date and time from left to right reads as follows: "yymm.dd hh:mm:ss"
(yy = year, mm = month, dd = day, hh = hour, mm = minutes, ss = seconds).
I get this info from:
So for 2020, Aug 11th at 6:15AM you'd take the 20 as the last 2 digits from 2020, the 08 is August, ...:
2008.11 06:15:25
For time after noon like 14:00 = 2pm enter like
2008.11 14:15:25
Also: ONLY enter the UTC time, not the local time.? This avoids the crazy Daylight Savings Time changing dates problem.? Do not enter local time.
4. Latitude (and Longitude) has a special? code entry too,? ? ? ? ?xDEG.MIN Note that the dot . is interpreted as a comma (European style), not US style...it is Seconds, not fractions of a degree!?? There is a? (+/-) sign in front of the DEGrees for the Latitude.? That "x" will be a minus? if you were South of the Equator.? Otherwise it should be a + sign if Northern hemisphere.? For longitude I think it shows a W for West in the US meaning west of the prime meridian, or E for East of Prime Meridian.??
5. If you connect the Gemini to a PC there is a very useful free PC app called Gemini.net. It is on the ASCOM telescope drivers website.? You'll need to install ASCOM first the the Gemini.net driver.? When you run Gemini.net on your PC, look at the Telescope panel and you must download the values from Gemini to the PC and see them.? Use that to confirm the Location. ? Likewise use the Advanced panel to see other values like the Mount type.? Look at the Model values.? After a Cold Boot those should all be zero.? After you enter some Align stars they will change. You must always download the values from Gemini to the PC to see them...the PC values stay in the PC unless you then Upload the values back to the Gemini.? Again after you change values, Park at CWD and then Cold Boot.?
Best of luck in solving your Gemini riddles!!!
Michael
[Edited Message Follows]
What David and GN said. When I first started out, I did exactly this and was wondering why things were not moving the way they should. It is easy to accidentally interchange RA and DEC when connecting the cables and the Gemini 2 unit won't complain.I was just as convinced as you are that I had done it correctly.
Also wanted to share how good the pointing accuracy of the GM811G is; I use mine for imaging mostly, but used it for visual last week and for the first time used the GOTO functionality and model. I expected to have to synchronize with multiple stars, but no. Accurate polar alignment and synchronizing with a single star? put every other object I pointed to in the center of at least a low power eyepiece. Made things easy. This is the kind of performance you should expect. The nice thing is that Gemini modeling will only allow you to sync to a star that's sufficiently far from the meridian.
Would suggest doing a dry run in a well lit area or even indoors. You don't need it to be exact, but can assure yourself that the mount is at least moving in the direction it is supposed to.?
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Not all of UK is +ve Longitude ¨C the meridian passes through Greenwich, London. ? D. ?
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Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Brendan Smith
Sent: 12 August 2020 16:53
To: [email protected]
Subject: Re: [Losmandy_users_io] Issues With Initial GoTos on new GM811G ? Ryan a few tricks
longitude setup is ¡°-Also south is ¡°-ve¡±!
incl any DST offset ?. Time zone offset is from UTC. if you enter your locality time as ¡°correct UTC¡± time instead of local and set the offset to zero ?then you never have to worry about DST changes ?
Ensure you press ¡° ? ? ?Everyone does that at sometime ? All are already said. Many new users have pointing issues like this usually it¡¯s an issue with time input offset and location.?
--
Brendan
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Thanks everyone for the help so far.? Lots of good suggestions here that I will try out tonight.??
Whenever you enter some new primary value (Latitude, Longitude, Date, Time) you must then turn the Gemini off and "Cold Boot" restart. ? That is because the Gemini still uses the values it read from memory on boot up, and not the new values you entered.? ?Most other programs use the new entries immediately....not this one.
This is probably part of the issue.? I did not cycle power to the mount immediately after updating the factory values.? After the first erroneous goto, I double checked everything, but did not cycle power immediately.? My guess is that I started trying different settings before restarting the mount.? I also used "Quick Start" instead of "Cold Start."? I'll check this tonight. I also noticed just now that the mount type was set to G11.? I swear I changed this before observing last night, but since I did not do a Cold Start, it must not have updated. I'll also make sure to verify the cables.? I think I checked them 10 times last night as having them backwards was the first thing I thought of.? Can never be too sure though.?? I am going to set up this evening before it is dark and try it out before it is dark.? I will report back and let you know if the problem is solved.
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On Thu, Aug 13, 2020 at 02:18 AM, David C. Partridge wrote:
Not all of UK is +ve Longitude ¨C the meridian passes through Greenwich, London.
?
Yes, of course you¡¯re totally right!? -- Brendan
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So I just did a couple of trials to see if switching the settings to G811 would fix the issue.? It does not, but working on this in the light gives me a better idea of what is going on.? My post this morning was incorrect about what axis was having the issue, it was not declination, but RA? (I will fully admit to getting them confused sometimes).? It looks like what is happening, at least in part, is that the RA axis is moving in the wrong direction of rotation.? To put it another way, the RA axis rotated clockwise around the RA axis if viewed from the position of looking through the polar scope.? If the RA axis would have moved counterclockwise the same amount from the CWD position, I think the mount would be pointing very close to the location of the star I selected (Mizar).??
I've checked all of the location and time settings and they appear to be correct.? What could be happening to make the RA axis move in the wrong direction?? I have not changed anything in the Mount\Gearing menu, which has the following values:
RA Worm Gear: -270
DEC Worm Gear: 360
RA Spur Gear 50
DEC Spur Gear: 25
RA Motor Encoder: 256
DEC Motor Encoder: 256
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Hi...
Glad you wrote that detailed report!
Your RA worm gear is set incorrectly to negative, but should be positive.
That will change its rotation direction to be correct.
Note for the future:? If your mount had McLennan metal gearbox (not a stock item but an aftermarket change some people (like me) make), then ? you would need to have the negative RA Worm Gear value.? For the stock plastic gearbox, you would NOT need a negative value.
The correct values for the G11 RA section of your GM811 mount should be the same as for a stock G11 mount: ? ? ?RA Worm Gear:(G11size)? +360. (plastic stock gearbox. Negative for McLennan metal gearbox) ? ?? ? ? ?DEC Worm Gear: (GM8 size) +180. (+ for plastic stock gearbox.? Negative for McLennan metal gearbox)
? ? ?For both axes...same values: ? ? ?Spur gear ratio:? 25? ? (that's the entire gearbox that is 25:1) ? ? ?Servo Encoder resolution:? 256 ? ? Steps per Worm Revolution:? 6400
? ? Manual Slew:? 800??
(many people reduce that to about 600 to put less strain on the motor)
? ?GoTo Slew:? 800? ? (many people reduce that to about 600 to put less strain on the motor)
Anyway, maybe someone had set up your Gemini-2 before you received it.? If you got it direct from the factory...it should be reported.? It should have been tested by whomever sold it to you.
Best regards, Michael
On Wed, Aug 12, 2020 at 11:33 AM Ryan Weiss < rrweiss14@...> wrote: So I just did a couple of trials to see if switching the settings to G811 would fix the issue.? It does not, but working on this in the light gives me a better idea of what is going on.? My post this morning was incorrect about what axis was having the issue, it was not declination, but RA? (I will fully admit to getting them confused sometimes).? It looks like what is happening, at least in part, is that the RA axis is moving in the wrong direction of rotation.? To put it another way, the RA axis rotated clockwise around the RA axis if viewed from the position of looking through the polar scope.? If the RA axis would have moved counterclockwise the same amount from the CWD position, I think the mount would be pointing very close to the location of the star I selected (Mizar).??
I've checked all of the location and time settings and they appear to be correct.? What could be happening to make the RA axis move in the wrong direction?? I have not changed anything in the Mount\Gearing menu, which has the following values:
RA Worm Gear: -270
DEC Worm Gear: 360
RA Spur Gear 50
DEC Spur Gear: 25
RA Motor Encoder: 256
DEC Motor Encoder: 256
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Hi Ryan, I had a similar?issue recently. I purchased a used G11 and I had a minor pointing issue, which caused me to replace the battery and do a firmware update. After that my pointing was much more problematic. I tried a bunch of different things, but what I kept seeing was my site and time information was not being stored, even after I just input the information. I could see the information was correct but the pointing was way off. What I found was that if you do not hit the store button on both the time screen, and the site screen, before returning to the go to screen, the information is lost.?
I did not read all the responses, so my suggestion may not apply in your case, but it is worth checking.?
James
On Wed, Aug 12, 2020 at 12:44 PM Michael Herman < mherman346@...> wrote: Hi...
Glad you wrote that detailed report!
Your RA worm gear is set incorrectly to negative, but should be positive.
That will change its rotation direction to be correct.
Note for the future:? If your mount had McLennan metal gearbox (not a stock item but an aftermarket change some people (like me) make), then ? you would need to have the negative RA Worm Gear value.? For the stock plastic gearbox, you would NOT need a negative value.
The correct values for the G11 RA section of your GM811 mount should be the same as for a stock G11 mount: ? ? ?RA Worm Gear:(G11size)? +360. (plastic stock gearbox. Negative for McLennan metal gearbox) ? ?? ? ? ?DEC Worm Gear: (GM8 size) +180. (+ for plastic stock gearbox.? Negative for McLennan metal gearbox)
? ? ?For both axes...same values: ? ? ?Spur gear ratio:? 25? ? (that's the entire gearbox that is 25:1) ? ? ?Servo Encoder resolution:? 256 ? ? Steps per Worm Revolution:? 6400
? ? Manual Slew:? 800??
(many people reduce that to about 600 to put less strain on the motor)
? ?GoTo Slew:? 800? ? (many people reduce that to about 600 to put less strain on the motor)
Anyway, maybe someone had set up your Gemini-2 before you received it.? If you got it direct from the factory...it should be reported.? It should have been tested by whomever sold it to you.
Best regards, Michael
On Wed, Aug 12, 2020 at 11:33 AM Ryan Weiss < rrweiss14@...> wrote: So I just did a couple of trials to see if switching the settings to G811 would fix the issue.? It does not, but working on this in the light gives me a better idea of what is going on.? My post this morning was incorrect about what axis was having the issue, it was not declination, but RA? (I will fully admit to getting them confused sometimes).? It looks like what is happening, at least in part, is that the RA axis is moving in the wrong direction of rotation.? To put it another way, the RA axis rotated clockwise around the RA axis if viewed from the position of looking through the polar scope.? If the RA axis would have moved counterclockwise the same amount from the CWD position, I think the mount would be pointing very close to the location of the star I selected (Mizar).??
I've checked all of the location and time settings and they appear to be correct.? What could be happening to make the RA axis move in the wrong direction?? I have not changed anything in the Mount\Gearing menu, which has the following values:
RA Worm Gear: -270
DEC Worm Gear: 360
RA Spur Gear 50
DEC Spur Gear: 25
RA Motor Encoder: 256
DEC Motor Encoder: 256
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Thanks Michael for this response.? I changed the values to the ones you stated in your post and this solved the issue.? First goto from CWD was almost in the field of view of my lowest powered eyepiece.? Once I aligned on it, i went to a number of objects in the same half of the sky without any issues at all.??
Ryan
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You are very welcome, Ryan.
I only got familiar with these "hidden" gear settings when I changed my gearboxes to McLennan metal ones, from the stock plastic version. The stock plastic ones were fine for many years, but one or two cases eventually cracked apart after a decade or so.? On the older systems I have, the motor hangs out the end of the gearbox and that weight might cause gearbox breakage.??
The metal gearbox version output shaft rotates opposite to that of the plastic type.? So in the Gemini system, you must select Custom mount, and then change the Worm setting from positive to negative.? That's why I got more deeply into those gear settings. Strangely, the gear settings are not documented in the Gemini manual.... I should write up a document for that.? I got them out of the Gemini itself using the Gemini.net Advanced panel display.?
Anyway, I'm quite happy as you are that you solved your riddle.??
The bigger riddle is: why was your new system not set up properly from the factory (if you bought it directly) or from your retail vendor?? Someone along the line should have tested it out before you received it.??Anyway, it is worth a phone call to your vendor, to help...the next person... (If you bought it from a place like Adorama ... call the factory who put the kit together.? Did it come with instructions on setting up the Gemini settings?)
Another puzzle to me is: that RA Worm setting should not have been negative.? I believe the MI (Mountain Instruments) -250 RA and Titan RA motor revolves in the opposite direction to the G11.? ? Gemini-1 mount settings default to Titan...hmmm maybe your Gemini-2 was still set to Titan not GM811???
?As I said when you change a major setting, park at CWD then reboot into a cold boot to get the settings into use.??
Have fun with your new GM811.!
Michael
Thanks Michael for this response.? I changed the values to the ones you stated in your post and this solved the issue.? First goto from CWD was almost in the field of view of my lowest powered eyepiece.? Once I aligned on it, i went to a number of objects in the same half of the sky without any issues at all.??
Ryan
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I, too, run a GM811G HD.
On occasion mine would go haywire and do a 180¡ã slew.
fixed the odd behavior. Which also requires you do your initial set up settings over again.
I will usually do my start up via menu just to make sure my previous settings are still sound.
That leaves me at a cold start anyway. But with the assurance everything is sound.
--
SonnyE
(I suggest viewed in full screen)
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David C. Partridge
Michael Herman
James B