|
Hi! Lately, I'm experiencing bad guiding in DEC on mu G11. It's OK in RA and at times also in DEC, but unpredictable (so far). Good means a RMA of about 0.7 arc secs. Bad means RMS over 1.5. I use PHD2, and when measuring backlash there, I get values ranging from 16.6 to over 70. So there is a lot of questions here - how can it vary so much, and where does it stem from? I've got the blocks into which the worm gear goes pressed together, to there is no identifiable slack there that, no wiggle back and forth. I've adjusted the worm gear in relation to the gear wheel, so it is close as I dare have it. What else can cause these variations and backlash? The DEC gearbox sounds a lot - far louder than the RA. Could that be a source of backlash and instability? All suggestions very welcome. Magnus
|
HI Magnus
you should probably post this to the PHD group since it sounds like a guiding issue
couple thoughts:
1. make sure you are on the latest phd2 if you aren't already doing that, not the original PHD (not sure which you are using)?
2. set the PVC in you G11 to 0
3. once you calibrate in PHD, use the guiding assistant, do at least 5 minutes on the assistant, and follow all the recommendations for changing settings
4. use backlash compensation and try starting with 500ms, it should adjust on its own to find the right amount
B
|
I¡¯m not sure that agree that it¡¯s a PHD problem. He¡¯s talking about severe DEC backlash. This sounds like a mount issue.
Rob
Get
toggle quoted message
Show quoted text
From: Losmandy_users@... on behalf of bvalente@... [Losmandy_users]
Sent: Friday, November 24, 2017 3:20:58 PM
To: Losmandy_users@...
Subject: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
?
?
HI Magnus
you should probably post this to the PHD group since it sounds like a guiding issue
couple thoughts:
1. make sure you are on the latest phd2 if you aren't already doing that, not the original PHD (not sure which you are using)?
2. set the PVC in you G11 to 0
3. once you calibrate in PHD, use the guiding assistant, do at least 5 minutes on the assistant, and follow all the recommendations for changing settings
4. use backlash compensation and try starting with 500ms, it should adjust on its own to find the right amount
B
|
That's definitely a possibility too
My experience is pretty much all Losmandy mounts have a certain amount of DEC backlash so my thought is it's easier to first make sure the guiding is set up properly before deciding it's in the gearing and fiddling with that.
B
|
Hi!
Yes, I'm interested in working on the mount, finding causes that I can eliminate. I already do as you say, run latest PHD2 and use GA etc. The major problem here, is that it is intermittent... yesterday, I posted this in some frustration - had DEC wildly swinging between +1.5" and -1.5". Then I posted, moved the scope, tested south at the meridian, did meridian flips and tested, moved around, and then, back to same object (NGC2403) and now I had less then 0.5" DEC swings.... calm and nice. Very good guiding quality, given that I don't use PEC yet.
So I'm after the possible mechanical causes. I know of the worm gear slack, that can be fixed or limited with a belville washer (yet have to find one of those). But is there anything else I should look at, in this situation?
Magnus
|
Hi Magnus,
When you moved to another object, or did a meridian flip, the problem went away or got better.??
So I consider 2 possible causes.? One is the DEC of the mount, and the second is the guide scope/guide camera.??
If you are using an OAG, that will solve the 2nd problem and I only guide that way.? Any slight change in the guide camera or guide? scope position will glitch your autoguiding, and due to the weight of the autoguide camera cable, that force changes with RA/time, and with meridian flip.??
Or, as you mentioned, it could be the mount DEC axis too...as you said a possible? cause of the trouble in your last description.?? That is: I think you must have a slight DEC axis physical hysteresis in the worm mounting.??
When you moved to another object, or did a meridian flip, the problem went away or got better.??
If you think about it, in a perfectly polar aligned system, the RA worm is constantly moving toward positive RA, which may keep a force on one worm bearing.? But the DEC worm should not be moving (ignoring refraction of the air, and seeing).? The DEC axis can wiggle.? And PHD will have a time lag or overshoot trying to compensate for that DEC hysteresis.? ?
If you have a slight I mis-balance in DEC, its ring gear will be pulled against its worm gear, pressing the worm either left or right against one of the worm bearings...the other worm bearing is more loose.? Over the night, or pointing to other objects, that misbalance changes net force on the DEC worm.? The net force will be a function of the RA angle and DEC axis angles.? (The force on the RA worm is a function of the RA angle and the polar axis angle, but not the DEC angle.)??
Bottom line, in the Losmandy original design, the DEC worm is not kept in a condition of constant constraint during the night of imaging...even if you had a hanging weight wrapped on it.?
Note that the highly rated Ovision worm system designed in a Belleville washer for this purpose...Losmandy did not.??
As the night temperatures change, the brass or stainless steel worm is going to expand or contract differently than the aluminum holding the worm blocks, and the aluminum worm blocks themselves. So if the system compressing the worm bearings was "tight" at one time/ temperature, it can become loose at another time/ temperature.??
Hysteresis might be curable in PHD2, and it might be tolerable with a wide angle, short FL scope image.? But if you are using a long FL scope like an SCT, it probably is worth trying to fix the hysteresis mechanically.
You mention the possible benefit of a Belleville washer and that you have not found these.? I have a stock of them for the Losmandy worm bearings (and the Orion Synta Atlas too...same problem).??
Since they are flat, they easily mail from US to international destinations in a letter.? For?$5,?I can send you 3 of them, and you have 1 for RA, one for DEC, and one spare (though they never should break).??
You will find installation instructions in our Files section under my name.??
Some simple hand polishing is required with very fine sandpaper or emery cloth to polish down the perimeter of the far worm bearing, so it can slide in its worm block cylinder.? Pulling out the rear bearing can be a challenge but I show how to form a simple puller to do that.??
You lube that cylinder and assemble the washer behind the bearing, pressing the blocks together so the spring constantly pushes the bearing on the worm. That keeps the worm in place, and keeps the Oldham coupler pieces together (which you must do or that alone will cause glitches!), and also keeps both worm bearings "compressed" so they keep lowest rumble preformance.
To get the lowest RA PE about 1 arcsec native PE (no PEC), I found a benefit from replacing my worm bearings too.? I used ABEC7 rated ones, under $20?in the US.? David Partridge in the UK found great results with ABEC5 rated ones he got in Europe.? ?We both used the brass Losmandy worm, but David used original 2 worm blocks and I used an OPW.??
Wow...a lot of writing at 5AM!
Hope you solve your issues...we all await your images!?
Michael?
?
Hi!
Yes, I'm interested in working on the mount, finding causes that I can eliminate. I already do as you say, run latest PHD2 and use GA etc. The major problem here, is that it is intermittent... yesterday, I posted this in some frustration - had DEC wildly swinging between +1.5" and -1.5". Then I posted, moved the scope, tested south at the meridian, did meridian flips and tested, moved around, and then, back to same object (NGC2403) and now I had less then 0.5" DEC swings.... calm and nice. Very good guiding quality, given that I don't use PEC yet.
So I'm after the possible mechanical causes. I know of the worm gear slack, that can be fixed or limited with a belville washer (yet have to find one of those). But is there anything else I should look at, in this situation?
Magnus
|
Hi!
Thanks a lot! Yes, I'd be very happy to buy a bunch (3 might be enough :)) belville washers from you, and see what difference that makes!! Can you email me off the list? magnus @ vista . se.
I've been experimenting with it tonight as well (it's just past midnight here now) and I'm not getting wiser. I'm thinking of taking the mount apart and clean and regrease it too. There might be some stiction playing into it too.... maybe.
Magnus
|
I have the same issues with both axes of my new-design G-11G. I am still going through the trouble shooting process but expect I eventually will have to do the bearing/washer mod. How much does this modification improve performance?
Glenn?
|
Unknown on the new G11G system...? but you have to understand the contributors to noise in the PE and PE error itself.
It was thought that only the worm mattered, and that of course rotates in ~239.4 sec on the G11 (double that time on the GM8).? The idea of PEC is that the rotational speed can be "corrected" by speeding up or slowing down the worm to make it "perfect".??
But there are other factors that come in... some of them do not spin at the same period as the worm so are not correctable by PEC, (But we hope are correctable mechanically).??
The worm bearings have tiny balls in them and these rotate on the inner race and outer race and there can be noise there (called "rumble").? Using higher quality bearings have lower rumble and so expected to have better PE and less noisy PE.? ?(We have no measure of "noise" in the PE... )
The Oldham coupler may also contribute on the original striaght line design.? That coupler has some sliding parts that... if they don't slide easily but have noise could cause glitches.? Also any angle between the gearbox axle and the worm axle will give a periodic error of about period/4 (my calculations... may be wrong?) .? The best bet is to keep all those Oldham parts pressed together and line up the left and right side so the coupler never has to slide/move except to rotate.??
Also the bearings are not "up to spec" unless they are under compressive force, called "preloading".? For that, I found (and Ovision already knew) that at Belleville spriing washer is useful to keep those worm bearings uinder constant force.? Some people wrap a weighted cord around the RA axis for that purpose... I only use a Belleville washer for that but the far worm bearing must be able so slide so the spring can push it into the worm.
Aside from the last item:? getting the worm engaged in the Ring gear teeth.. that you have to adjust by hand, and can monitor the separation with car feeler gauges.? Keep compressing that until the axis "stalls" with the motor drive, then back off slightly ( season to taste, shall we say).
The new system has the motor drive wrapped down so it does not interfere with full rotation of the axis.? I don't know the components of that drive system, gears or belts... lots of ways to kill a cat.? But the ideas above are a guide to what to watch out for.
-------- Off-topic....?
There was an earlier question (if in another thread...sorry!) about a 42 second period (not a integral fraction of a worm period so not amenable to PEC correction).? The nice program PECPrep (from the EQMOD group) has many periods for the G11 mount shown.? But no 42 second contributor shown.? These frequencies can be whacked out if you have a lot of DEC drift, so if the main contributor is not the Worm/1 period of 239.4 sec, you likely have some bad PE data and should retake it.??
That program lists these: Worm 239.4 sec Worm bearing ball spin 109.4 Worm 2nd harmonic 118.7 Worm 3rd harmonic 79.8 Worm bearing ball passes outer race 76.2 Worm 4th harmonic 59.8 Worm bearing ball passes inner race 49.2 Worm 5th harmonic 47.9 Worm 6th harmonic 39.9 Worm 7th harmonic 34.2 Worm spur gear 31.9 Worm 8th harmonic 29.9 Servo spur gear? 9.6 Transfer/worm spur gear mesh 3.2 sec
That's the list of known frequencies for the G11? (for GM8 double those) ---------------------------
All the best,
Michael
On Sun, Nov 26, 2017 at 9:42 AM, steamdiesel@... [Losmandy_users] <Losmandy_users@...> wrote:
?
I have the same issues with both axes of my new-design G-11G. I am still going through the trouble shooting process but expect I eventually will have to do the bearing/washer mod. How much does this modification improve performance?
Glenn?
|
Michael?
I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors introduce new gearing ratios (probably true for G11G as well).
This has also been confirmed by Ray with PemPro
B
|
I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the EQMOD group who made up PECprep to add to their G11 list.??
How does that 42 sec peak compare in size to the Worm peak at 239.4 sec.? Is it anywhere near as high as that one? (Or better for me: send me [ mherman346@...] your raw PHD2 log file and I can run it in my PECprep.exe program to see its FFT.)
That 239.4/42 = 5.7.? That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds to me like a design problem...? ?
Best,? Michael
On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users] <Losmandy_users@...> wrote:
?
Michael?
I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors introduce new gearing ratios (probably true for G11G as well).
This has also been confirmed by Ray with PemPro
B
|
That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated
mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds Sorry Michael Herman, but I'm afraid you are using the wrong worm period. The worm period is about 319.1 seconds, over which a 42.55-second frequency repeats 7.5 times. This is not correctable using PEC over a single worm cycle, but it is correctable over two worm cycles as the frequency repeats 15.0 times. The worm gear contributes about 3.7 arc-seconds peak-peak, and the 15x fundamental contributes about 2.8 arc-seconds peak-peak. Best regards, -Ray Gralak Author of APCC (Astro-Physics Command Center): Author of PEMPro: Author of Astro-Physics V2 ASCOM Driver: Author of PulseGuide: Author of Sigma: -----Original Message-----
From: Losmandy_users@... [mailto:Losmandy_users@...]
Sent: Sunday, November 26, 2017 10:43 AM
To: Losmandy_users@...
Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the EQMOD
group who made up PECprep to add to their G11 list.
How does that 42 sec peak compare in size to the Worm peak at 239.4 sec. Is it anywhere near as high as
that one?
(Or better for me: send me [mherman346@...] your raw PHD2 log file and I can run it in my
PECprep.exe program to see its FFT.)
That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated
mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds
to me like a design problem...
Best,
Michael
On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users]
<Losmandy_users@...> wrote:
Michael
I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors
introduce new gearing ratios (probably true for G11G as well).
This has also been confirmed by Ray with PemPro
B
--
Michael Herman
mobile: 408 421-1239
email: mherman346@...
|
Ray,
This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes = 4¡Á60sec =240 sec, right?
Here is the text, from the Losmandy website:
Periodic Error Correction (PEC)Periodic Error Correction, or PEC, is a system that improves the tracking accuracy of the drive. PEC is designed to improve photographic quality by reducing the amplitude of the worm gear errors. Periodic error is a slight oscillation in right ascension caused by imperfections in all drive gears. The cycle of the periodic error is equal to one rotation of the worm gear, which is four minutes for the G-11. No matter how precise, all telescope drives will have?some?periodic error, though it is already extremely low on the Losmandy G-11. Using the PEC function is a two-step process. First, you must guide for at least four minutes, keeping the guide star centered on the cross hairs of your guiding eyepiece, during which time the system records the correction you make. It takes the worm gear four minutes to make one complete revolution, hence the need to guide for four minutes. The second step is to play back the corrections you made during the recording phase. The microcomputer inside the electronic console does this automatically after one revolution of the worm gear. Keep in mind that this feature is for advanced astro-photographers and requires careful guiding. Here?¡¯s how to use the PEC function most effectively.
On Nov 26, 2017 12:35 PM, "'Ray Gralak (Groups)' groups3@... [Losmandy_users]" < Losmandy_users@...> wrote:
?
> That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated
> mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds
Sorry Michael Herman, but I'm afraid you are using the wrong worm period. The worm period is about 319.1 seconds, over which a 42.55-second frequency repeats 7.5 times. This is not correctable using PEC over a single worm cycle, but it is correctable over two worm cycles as the frequency repeats 15.0 times. The worm gear contributes about 3.7 arc-seconds peak-peak, and the 15x fundamental contributes about 2.8 arc-seconds peak-peak.
Best regards,
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro:
Author of Astro-Physics V2 ASCOM Driver:
Author of PulseGuide:
Author of Sigma:
> -----Original Message-----
> From: Losmandy_users@... [mailto: Losmandy_users@yahoogroups.com]
> Sent: Sunday, November 26, 2017 10:43 AM
> To: Losmandy_users@...
> Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
>
>
>
> I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the EQMOD
> group who made up PECprep to add to their G11 list.
>
> How does that 42 sec peak compare in size to the Worm peak at 239.4 sec. Is it anywhere near as high as
> that one?
> (Or better for me: send me [ mherman346@...] your raw PHD2 log file and I can run it in my
> PECprep.exe program to see its FFT.)
>
>
> That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be eliminated
> mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that sounds
> to me like a design problem...
>
> Best,
> Michael
>
>
>
> On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users]
> < Losmandy_users@yahoogroups.com> wrote:
>
>
>
>
>
> Michael
>
>
> I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors
> introduce new gearing ratios (probably true for G11G as well).
>
> This has also been confirmed by Ray with PemPro
>
>
> B
>
>
>
>
>
>
>
> --
>
> Michael Herman
> mobile: 408 421-1239
> email: mherman346@...
>
>
>
|
Michael,?
Brian has a G11GT mount, which has a Titan-based RA and a G11-based DEC assembly. RA has a 270 tooth wheel, which translates into just under 320 seconds worm cycle.
Regards,
? ? -Paul
|
Michael we're talking a G11GT - the 'T' is for the titan RA portion which is the 319 worm
also I don't know about the regular G11 with tucked in gears, but i wouldn't be surprised if those added some periodic error somewhere as well
B
On Sun, Nov 26, 2017 at 1:18 PM, Michael Herman mherman346@... [Losmandy_users] <Losmandy_users@...> wrote:
?
Ray,
This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes = 4¡Á60sec =240 sec, right?
Here is the text, from the Losmandy website:
Periodic Error Correction (PEC)Periodic Error Correction, or PEC, is a system that improves the tracking accuracy of the drive. PEC is designed to improve photographic quality by reducing the amplitude of the worm gear errors. Periodic error is a slight oscillation in right ascension caused by imperfections in all drive gears. The cycle of the periodic error is equal to one rotation of the worm gear, which is four minutes for the G-11. No matter how precise, all telescope drives will have?some?periodic error, though it is already extremely low on the Losmandy G-11. Using the PEC function is a two-step process. First, you must guide for at least four minutes, keeping the guide star centered on the cross hairs of your guiding eyepiece, during which time the system records the correction you make. It takes the worm gear four minutes to make one complete revolution, hence the need to guide for four minutes. The second step is to play back the corrections you made during the recording phase. The microcomputer inside the electronic console does this automatically after one revolution of the worm gear. Keep in mind that this feature is for advanced astro-photographers and requires careful guiding. Here?¡¯s how to use the PEC function most effectively.
-- Brian?
Brian Valente portfolio
|
Michael, This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes =
4¡Á60sec =240 sec, right? I know you are just trying to help, but Brian's mount is not a G11. It is a G11GT, as both Brian and Paul have already confirmed in their recent posts. Best regards, -Ray Gralak Author of APCC (Astro-Physics Command Center): Author of PEMPro: Author of Astro-Physics V2 ASCOM Driver: Author of PulseGuide: Author of Sigma: -----Original Message-----
From: Losmandy_users@... [mailto:Losmandy_users@...]
Sent: Sunday, November 26, 2017 1:18 PM
To: Losmandy_users@...
Subject: RE: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
Ray,
This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes =
4¡Á60sec =240 sec, right?
Here is the text, from the Losmandy website:
Periodic Error Correction (PEC)
Periodic Error Correction, or PEC, is a system that improves the tracking accuracy of the drive. PEC is
designed to improve photographic quality by reducing the amplitude of the worm gear errors. Periodic error is a
slight oscillation in right ascension caused by imperfections in all drive gears. The cycle of the periodic error is
equal to one rotation of the worm gear, which is four minutes for the G-11. No matter how precise, all telescope
drives will have some periodic error, though it is already extremely low on the Losmandy G-11. Using the PEC
function is a two-step process. First, you must guide for at least four minutes, keeping the guide star centered
on the cross hairs of your guiding eyepiece, during which time the system records the correction you make. It
takes the worm gear four minutes to make one complete revolution, hence the need to guide for four minutes.
The second step is to play back the corrections you made during the recording phase. The microcomputer
inside the electronic console does this automatically after one revolution of the worm gear. Keep in mind that
this feature is for advanced astro-photographers and requires careful guiding. Here?¡¯s how to use the PEC
function most effectively.
On Nov 26, 2017 12:35 PM, "'Ray Gralak (Groups)' groups3@... [Losmandy_users]"
<Losmandy_users@...> wrote:
> That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be
eliminated
> mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that
sounds
Sorry Michael Herman, but I'm afraid you are using the wrong worm period. The worm period is about
319.1 seconds, over which a 42.55-second frequency repeats 7.5 times. This is not correctable using PEC over
a single worm cycle, but it is correctable over two worm cycles as the frequency repeats 15.0 times. The worm
gear contributes about 3.7 arc-seconds peak-peak, and the 15x fundamental contributes about 2.8 arc-seconds
peak-peak.
Best regards,
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
physics.com/index.htm?products/accessories/software/apcc/apcc <
physics.com/index.htm?products/accessories/software/apcc/apcc>
Author of PEMPro:
Author of Astro-Physics V2 ASCOM Driver:
Author of PulseGuide:
Author of Sigma:
> -----Original Message-----
> From: Losmandy_users@... [mailto:Losmandy_users@...
<mailto:Losmandy_users@...> ]
> Sent: Sunday, November 26, 2017 10:43 AM
> To: Losmandy_users@...
> Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
>
>
>
> I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the
EQMOD
> group who made up PECprep to add to their G11 list.
>
> How does that 42 sec peak compare in size to the Worm peak at 239.4 sec. Is it anywhere near as
high as
> that one?
> (Or better for me: send me [mherman346@...] your raw PHD2 log file and I can run it in my
> PECprep.exe program to see its FFT.)
>
>
> That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be
eliminated
> mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that
sounds
> to me like a design problem...
>
> Best,
> Michael
>
>
>
> On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users]
> <Losmandy_users@... <mailto:Losmandy_users@...> > wrote:
>
>
>
>
>
> Michael
>
>
> I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors
> introduce new gearing ratios (probably true for G11G as well).
>
> This has also been confirmed by Ray with PemPro
>
>
> B
>
>
>
>
>
>
>
> --
>
> Michael Herman
> mobile: 408 421-1239 <tel:(408)%20421-1239>
> email: mherman346@...
>
>
>
|
Ray,
A quick question for you. Is there set yet for Pempro 3?
Rob
Get
toggle quoted message
Show quoted text
From: Losmandy_users@... on behalf of 'Ray Gralak (Groups)' groups3@... [Losmandy_users]
Sent: Sunday, November 26, 2017 1:37:59 PM
To: Losmandy_users@...
Subject: RE: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
?
?
Michael,
> This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes =
> 4¡Á60sec =240 sec, right?
I know you are just trying to help, but Brian's mount is not a G11. It is a G11GT, as both Brian and Paul have already confirmed in their recent posts.
Best regards,
-Ray Gralak
Author of APCC (Astro-Physics Command Center): http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma
> -----Original Message-----
> From: Losmandy_users@... [mailto:Losmandy_users@...]
> Sent: Sunday, November 26, 2017 1:18 PM
> To: Losmandy_users@...
> Subject: RE: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
>
>
>
> Ray,
>
> This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes =
> 4¡Á60sec =240 sec, right?
>
> Here is the text, from the Losmandy website:
>
> http://www.losmandy.com/g-11-manual.html
>
>
> Periodic Error Correction (PEC)
>
> Periodic Error Correction, or PEC, is a system that improves the tracking accuracy of the drive. PEC is
> designed to improve photographic quality by reducing the amplitude of the worm gear errors. Periodic error is a
> slight oscillation in right ascension caused by imperfections in all drive gears. The cycle of the periodic error is
> equal to one rotation of the worm gear, which is four minutes for the G-11. No matter how precise, all telescope
> drives will have some periodic error, though it is already extremely low on the Losmandy G-11. Using the PEC
> function is a two-step process. First, you must guide for at least four minutes, keeping the guide star centered
> on the cross hairs of your guiding eyepiece, during which time the system records the correction you make. It
> takes the worm gear four minutes to make one complete revolution, hence the need to guide for four minutes.
> The second step is to play back the corrections you made during the recording phase. The microcomputer
> inside the electronic console does this automatically after one revolution of the worm gear. Keep in mind that
> this feature is for advanced astro-photographers and requires careful guiding. Here?¡¯s how to use the PEC
> function most effectively.
>
>
>
> On Nov 26, 2017 12:35 PM, "'Ray Gralak (Groups)' groups3@... [Losmandy_users]"
> wrote:
>
>
>
>
>
>
> > That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be
> eliminated
> > mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that
> sounds
>
>
> Sorry Michael Herman, but I'm afraid you are using the wrong worm period. The worm period is about
> 319.1 seconds, over which a 42.55-second frequency repeats 7.5 times. This is not correctable using PEC over
> a single worm cycle, but it is correctable over two worm cycles as the frequency repeats 15.0 times. The worm
> gear contributes about 3.7 arc-seconds peak-peak, and the 15x fundamental contributes about 2.8 arc-seconds
> peak-peak.
>
> Best regards,
>
> -Ray Gralak
> Author of APCC (Astro-Physics Command Center): http://www.astro-
> physics.com/index.htm?products/accessories/software/apcc/apcc
> physics.com/index.htm?products/accessories/software/apcc/apcc>
> Author of PEMPro: http://www.ccdware.com
> Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
> Author of PulseGuide: http://www.pulseguide.com
> Author of Sigma: http://www.gralak.com/sigma
>
>
> > -----Original Message-----
> > From: Losmandy_users@... [mailto:Losmandy_users@...
> ]
> > Sent: Sunday, November 26, 2017 10:43 AM
> > To: Losmandy_users@...
> > Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
> >
> >
> >
> > I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the
> EQMOD
> > group who made up PECprep to add to their G11 list.
> >
> > How does that 42 sec peak compare in size to the Worm peak at 239.4 sec. Is it anywhere near as
> high as
> > that one?
> > (Or better for me: send me [mherman346@...] your raw PHD2 log file and I can run it in my
> > PECprep.exe program to see its FFT.)
> >
> >
> > That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will have to be
> eliminated
> > mechanically if possible, or different gears used to get it to be an integer fraction of 239.4 sec, but that
> sounds
> > to me like a design problem...
> >
> > Best,
> > Michael
> >
> >
> >
> > On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users]
> > > wrote:
> >
> >
> >
> >
> >
> > Michael
> >
> >
> > I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in motors
> > introduce new gearing ratios (probably true for G11G as well).
> >
> > This has also been confirmed by Ray with PemPro
> >
> >
> > B
> >
> >
> >
> >
> >
> >
> >
>
> > --
> >
> > Michael Herman
> > mobile: 408 421-1239
> > email: mherman346@...
> >
> >
> >
>
>
>
>
>
|
Rob,
I'm hoping to have the initial V3 release available tomorrow. That said, there will be a quick set
of follow-up releases as I have not finished updating the documentation and a couple new features.
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
Author of PEMPro:
Author of Astro-Physics V2 ASCOM Driver:
Author of PulseGuide:
Author of Sigma:
toggle quoted message
Show quoted text
-----Original Message-----
From: Losmandy_users@... [mailto:Losmandy_users@...]
Sent: Sunday, November 26, 2017 1:52 PM
To: losmandy_users@...; losmandy_users@...
Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
Ray,
A quick question for you. Is there set yet for Pempro 3?
Rob
Get Outlook for iOS <>
________________________________
From: Losmandy_users@... <Losmandy_users@...> on behalf of 'Ray Gralak
(Groups)' groups3@... [Losmandy_users] <Losmandy_users@...>
Sent: Sunday, November 26, 2017 1:37:59 PM
To: Losmandy_users@...
Subject: RE: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
Michael,
This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes = 4¡Á60sec =240 sec, right? I know you are just trying to help, but Brian's mount is not a G11. It is a G11GT, as both Brian
and Paul have already confirmed in their recent posts.
Best regards,
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro:
Author of Astro-Physics V2 ASCOM Driver:
Author of PulseGuide:
Author of Sigma:
-----Original Message-----
From: Losmandy_users@... [mailto:Losmandy_users@...]
Sent: Sunday, November 26, 2017 1:18 PM
To: Losmandy_users@...
Subject: RE: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
Ray,
This is a quote directly from the Losmandy G11 mount manual, which says the G11 period is 4 minutes = 4¡Á60sec =240 sec, right?
Here is the text, from the Losmandy website:
Periodic Error Correction (PEC)
Periodic Error Correction, or PEC, is a system that improves the tracking accuracy of the drive.
PEC is designed to improve photographic quality by reducing the amplitude of the worm gear errors.
Periodic error is a
slight oscillation in right ascension caused by imperfections in all drive gears. The cycle of the periodic error is equal to one rotation of the worm gear, which is four minutes for the G-11. No matter how
precise, all telescope
drives will have some periodic error, though it is already extremely low on the Losmandy G-11. Using the PEC function is a two-step process. First, you must guide for at least four minutes, keeping the
guide star centered on the cross hairs of your guiding eyepiece, during which time the system records the correction
you make. It takes the worm gear four minutes to make one complete revolution, hence the need to guide for
four minutes. The second step is to play back the corrections you made during the recording phase. The
microcomputer inside the electronic console does this automatically after one revolution of the worm gear.
Keep in mind that this feature is for advanced astro-photographers and requires careful guiding. Here?¡¯s how to
use the PEC function most effectively.
On Nov 26, 2017 12:35 PM, "'Ray Gralak (Groups)' groups3@... [Losmandy_users]"
<Losmandy_users@...> wrote:
That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will
have to be eliminated
mechanically if possible, or different gears used to get it to be an integer fraction of 239.4
sec, but that sounds
Sorry Michael Herman, but I'm afraid you are using the wrong worm period. The worm period is
about 319.1 seconds, over which a 42.55-second frequency repeats 7.5 times. This is not correctable
using PEC over
a single worm cycle, but it is correctable over two worm cycles as the frequency repeats 15.0 times. The worm
gear contributes about 3.7 arc-seconds peak-peak, and the 15x fundamental contributes about 2.8 arc- seconds
peak-peak.
Best regards,
-Ray Gralak
Author of APCC (Astro-Physics Command Center):
physics.com/index.htm?products/accessories/software/apcc/apcc <
physics.com/index.htm?products/accessories/software/apcc/apcc>
Author of PEMPro:
Author of Astro-Physics V2 ASCOM Driver:
Author of PulseGuide:
Author of Sigma:
-----Original Message-----
From: Losmandy_users@... [mailto:Losmandy_users@... <mailto:Losmandy_users@...> ]
Sent: Sunday, November 26, 2017 10:43 AM
To: Losmandy_users@...
Subject: Re: [Losmandy_users] Re: Help with DEC backlash/jumpy guiding
I am certain you are right... if you can identify which gear is the culprit, that should be also sent to the EQMOD
group who made up PECprep to add to their G11 list.
How does that 42 sec peak compare in size to the Worm peak at 239.4 sec. Is it anywhere near
as high as
that one?
(Or better for me: send me [mherman346@...] your raw PHD2 log file and I can run it in
my PECprep.exe program to see its FFT.)
That 239.4/42 = 5.7. That's a non-integer ratio and no way for PEC to treat that... it will
have to be eliminated
mechanically if possible, or different gears used to get it to be an integer fraction of 239.4
sec, but that sounds
to me like a design problem...
Best,
Michael
On Sun, Nov 26, 2017 at 10:24 AM, bvalente@... [Losmandy_users]
<Losmandy_users@... <mailto:Losmandy_users@...> > wrote:
Michael
I would be happy to show you the 42 sec interval. i have a G11GT, and I think the tucked in
motors introduce new gearing ratios (probably true for G11G as well).
This has also been confirmed by Ray with PemPro
B
--
Michael Herman
mobile: 408 421-1239 <tel:(408)%20421-1239>
email: mherman346@...
|
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Show quoted text
?
Hi!
Lately, I'm experiencing bad guiding in DEC on mu G11. It's OK in RA and at times also in DEC, but unpredictable (so far). Good means a RMA of about 0.7 arc secs. Bad means RMS over 1.5. I use PHD2, and when measuring backlash there, I get values ranging from 16.6 to over 70. So there is a lot of questions here - how can it vary so much, and where does it stem from?
I've got the blocks into which the worm gear goes pressed together, to there is no identifiable slack there that, no wiggle back and forth. I've adjusted the worm gear in relation to the gear wheel, so it is close as I dare have it. What else can cause these variations and backlash?
The DEC gearbox sounds a lot - far louder than the RA. Could that be a source of backlash and instability?
All suggestions very welcome.
Magnus
|
Magnus,
A little backlash is actually preferred and is often better than no backlash at all. If your RA axis does not have any movement at all, the worm might be too close to the gear causing just a bit too much friction under some conditions and mount position. It's best to leave just a little wiggle room between the worm and the gear, and to then weigh the mount slightly heavier to the East side. This allows the worm to turn freely, with the gear fully engaged,?while the Eastern over-weight helps stop it from wobbling in between worm teeth.
Regards,
? ?-Paul?
|
Michael Herman
Paul Kanevsky