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Locked Re: GM811G dec backlash

 

On Mon, Jul 18, 2022 at 08:59 PM, Brian Valente wrote:
>>While Losmandy recommends to not change the factory settings, my experience is that you need to know how to change it when it is needed.? The Losmandy is made for DIY so I take advantage of it.? It is nice to have full control.? If it were me, I would try running without the SLW (by taking them off) and with the SLW, and see what works best.

Henk I appreciate your helpfulness, but we make that recommendation for a reason. A number of your suggestions (such as different settings at different ota positions) are not accurate for the SLW and we definitely do not recommend this. It may be the case for your custom DIY, but more often than not adjustments make things worse rather than better.?
To be clear, my DIY SLW fixed my problems because it is always fully meshed (no slack) and eliminates binding.? The Losmandy SLW apparently does not fix the OP's problem.? I suspect it has to do with a safety margin for the backoff to ensure smooth running in all OTA positions.? This is not to say that my solution is better, looser springs may have problems that are not immediately obvious.

>>>The Losmandy SLW has a backoff screw that basically disables the SLW so long as the gear is below the worm setting as determined by the backoff screw.??

this is not correct. The backoff screw acts as a limiter as to how closely the worm will mesh. If adjusted correctly, the spring never is 'disabled'. The reason this was added is because in the original spring version we tested before release, there was no backoff screw. The result was significant stiction. The backoff screw was added as a safety measure against that. If it is not adjusted correctly, it's possible the gears can bind (too tight) or result in a lot of slop (too loose).?
I believe I said the same thing, at least Intended to.? The word disabled was not the best choice perhaps, I meant "not fully meshed".? Thanks for explaining it so clearly!

If for some reason you feel the spring is too strong, you can adjust that as well. The only time i've seen this be of value is for visual observers who may not benefit from spring-loaded worm. In that case, you can just tighten the spring down all the way and adjust the backoff screw until it acts just like a non SLW axis.?

At that point visual observers can use TVC to adjust to taste
Re: How Much Space is needed?

 

nice setup John

What is the pier??

On Mon, Jul 18, 2022 at 9:45 PM John Kmetz <jjkmetz54@...> wrote:
aughtago,

Here are some pics from inside my roll off shed. I pained over how high to make the pier considering I had 6 foot or 72 inch walls, and a 6 x 8 foot shed. But one of the most important measurements is making sure the RA axis hole, seen here with a Polmaster inserted, points up and over the wall so you can do polar alignment. How high this point is will be affected by your altitude setting for your latitude. In the end the top of my pier with leveling head was 39 inches, but I probably could have gone lower. I must flop the scope to the side and have Dec axis horizontal and scope almost horizontal to get the roof to clear, but I still can park at CWD with the roof closed.

The scope shown here is a C925EdgeHD, which is about the largest SCT I could fit inside a shed this size. With guide scope I am just clearing the walls in some scope orientations. For your 1100, you may want to consider an 8x10 foot shed or larger. I also found that having opposed inside corners at an east-west orientation gives the most room for the scope to slew back and forth and do meridian flips.?

So you would need to do some measurements on how high the top of your scope is off the ground at CWD and when folded over, and then how high the RA axis hole is. The rest is trigonometry. But the bigger the shed, the bigger the roof, and the more weight you need to move when rolling it off. All things in consideration. The shed was built with plans I bought from ShyShed, which saved me much time during the build process and materials planning phases.?

Good luck!

John?


--
_____________________________________________________________________________________________________________________________________________________________________________

Losmandy G11G2 on pier; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user



--
Brian?



Brian Valente
astro portfolio?
portfolio
astrobin?
Re: How Much Space is needed?

 

aughtago,

Here are some pics from inside my roll off shed. I pained over how high to make the pier considering I had 6 foot or 72 inch walls, and a 6 x 8 foot shed. But one of the most important measurements is making sure the RA axis hole, seen here with a Polmaster inserted, points up and over the wall so you can do polar alignment. How high this point is will be affected by your altitude setting for your latitude. In the end the top of my pier with leveling head was 39 inches, but I probably could have gone lower. I must flop the scope to the side and have Dec axis horizontal and scope almost horizontal to get the roof to clear, but I still can park at CWD with the roof closed.

The scope shown here is a C925EdgeHD, which is about the largest SCT I could fit inside a shed this size. With guide scope I am just clearing the walls in some scope orientations. For your 1100, you may want to consider an 8x10 foot shed or larger. I also found that having opposed inside corners at an east-west orientation gives the most room for the scope to slew back and forth and do meridian flips.?

So you would need to do some measurements on how high the top of your scope is off the ground at CWD and when folded over, and then how high the RA axis hole is. The rest is trigonometry. But the bigger the shed, the bigger the roof, and the more weight you need to move when rolling it off. All things in consideration. The shed was built with plans I bought from ShyShed, which saved me much time during the build process and materials planning phases.?

Good luck!

John?


--
_____________________________________________________________________________________________________________________________________________________________________________

Losmandy G11G2 on pier; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user
Re: Understanding a titan

 

Thanks Brian - I'll try that calibration on the next clear night (though the weather forecast for the next week isn't looking the best).
Re: Backspace

 

Thanks Brian.? Supposed to have clear skies on Wed night so I am going to do some experimenting then.
Re: Understanding a titan

 

Your calibration run shows clear problems with the settings. The measured rate is 1/3 of what it should be (2.3as/s vs expected 7.5as/s which is 0.5x tracking rate). As a result you really should have about 12 steps per axis, but instead it's 40 or 50.?

part of it may be you are calibration at dec -84? sounds like it's at the pole. You should be calibrating at dec 0

I'm not sure what else you are doing re: calibration but it would be extremely helpful to follow the baseline guiding setup just to make sure you aren't using any strange settings anywhere:






On Mon, Jul 18, 2022 at 6:00 PM <fulhair@...> wrote:

Thanks all for the responses.
From the research I think the mount is a Losmandy Titan 50 () but happy to be corrected.
The controller is a Gemini 2 with LCD display (). The mount was having uncommanded goto issues so the Gemini Controller, cables and motors were sent last year to Bren Smith in Australia who replace the mount CPU and tested it and replaced the battery. I'm running it off a PSU @ 16v with 4 Amps.
I also had to replace the DEC gearbox casing as it had split and the motor would not screw in firm.

I was connecting to the mount via NINA and it set the time GPS? - which looked accurate to me - (I'm in Wellington New Zealand)and rate tracking as sideral. I aligned the mount using SharpCap on the guide scope so I have confidence that was good (no polaris here to point to).
Via NINA and PHD2 I set up the guiding via the setup wizard which failed with the following result:

I could not get it to guide at all using PHD2 and it would immediately start pinging errors at me.
I took the mount indoors and now get an error on the handset of "DEC : Heavy Duty Tr." - Though I did swap that motor with the RA one during my diagnosing.

The mount does move at slew speeds on both axes and can return to a Home with CWD reliably so I think the motors are working to some degree and when tracking with sidereal rate I can hear ticking from them.? The mount hasn't had much TLC for a while and I have noticed areas of corrosion around some of the bearings and it does seem to swing as freely as I would expect when not loaded up. It's also really difficult to slacked the DEC clutch wheel.



--
Brian?



Brian Valente
astro portfolio?
portfolio
astrobin?
Re: Understanding a titan

 

Thanks all for the responses.
From the research I think the mount is a Losmandy Titan 50 (https://photos.app.goo.gl/wm5h8p7zY4fAcGGj8) but happy to be corrected.
The controller is a Gemini 2 with LCD display (https://photos.app.goo.gl/XhW4PSkSzmyATzNK8). The mount was having uncommanded goto issues so the Gemini Controller, cables and motors were sent last year to Bren Smith in Australia who replace the mount CPU and tested it and replaced the battery. I'm running it off a PSU @ 16v with 4 Amps.
I also had to replace the DEC gearbox casing as it had split and the motor would not screw in firm.

I was connecting to the mount via NINA and it set the time GPS? - which looked accurate to me - (I'm in Wellington New Zealand)and rate tracking as sideral. I aligned the mount using SharpCap on the guide scope so I have confidence that was good (no polaris here to point to).
Via NINA and PHD2 I set up the guiding via the setup wizard which failed with the following result:

I could not get it to guide at all using PHD2 and it would immediately start pinging errors at me.
I took the mount indoors and now get an error on the handset of "DEC : Heavy Duty Tr." - Though I did swap that motor with the RA one during my diagnosing.

The mount does move at slew speeds on both axes and can return to a Home with CWD reliably so I think the motors are working to some degree and when tracking with sidereal rate I can hear ticking from them.? The mount hasn't had much TLC for a while and I have noticed areas of corrosion around some of the bearings and it does seem to swing as freely as I would expect when not loaded up. It's also really difficult to slacked the DEC clutch wheel.
Locked Re: GM811G dec backlash

 

>>While Losmandy recommends to not change the factory settings, my experience is that you need to know how to change it when it is needed.? The Losmandy is made for DIY so I take advantage of it.? It is nice to have full control.? If it were me, I would try running without the SLW (by taking them off) and with the SLW, and see what works best.

Henk I appreciate your helpfulness, but we make that recommendation for a reason. A number of your suggestions (such as different settings at different ota positions) are not accurate for the SLW and we definitely do not recommend this. It may be the case for your custom DIY, but more often than not adjustments make things worse rather than better.?

>>>The Losmandy SLW has a backoff screw that basically disables the SLW so long as the gear is below the worm setting as determined by the backoff screw.??

this is not correct. The backoff screw acts as a limiter as to how closely the worm will mesh. If adjusted correctly, the spring never is 'disabled'. The reason this was added is because in the original spring version we tested before release, there was no backoff screw. The result was significant stiction. The backoff screw was added as a safety measure against that. If it is not adjusted correctly, it's possible the gears can bind (too tight) or result in a lot of slop (too loose).?

If for some reason you feel the spring is too strong, you can adjust that as well. The only time i've seen this be of value is for visual observers who may not benefit from spring-loaded worm. In that case, you can just tighten the spring down all the way and adjust the backoff screw until it acts just like a non SLW axis.?

At that point visual observers can use TVC to adjust to taste
Locked Re: GM811G dec backlash

 

>>> I see a lot of people making observations like mine, but (thankfully)
nobody complaining that the G11 is unusable for astrophotography because
of it.???

It's worth?some discussion here. Michael as you've seen, the actual results when guiding are good, and under normal circumstances Dec is rarely the constraining factor in guided performance.

The main thing we are all seeing is the initial backlash report from PHD2 is crazy high, but actual performance as measured by PHD2 is much? much lower. As I mentioned previously, with new spring loaded mounts there is an initial stiction that could be the cause of this and tends to dissipate with time. But we're talking about how PHD2 measures things, not the actual performance of the axis.?

You can pull up the guidelog in PHD Log Viewer and it will show you the actual measured backlash during a guiding session. (keep in mind backlash is not a fixed value, but changes with altitude, equipment shifts, etc. which is part of the brilliance of the backlash compensation algorithm in PHD2). I think that is where attention is rightly focused when evaluating performance.

The G11 has been around for a long time, so at first glance it may appear all the comments are equal, but there are a lot of versions and these can also be from earlier hardware. Henk's situation i'm pretty sure is from earlier hardware. At a minimum Henk doesn't have the standard spring-loaded worm (i don't know exactly what else you have there Henk) but in his case, the worm meshing mechanism is completely different

As I always say, the actual performance of the axis is what matters most.

Brian




On Sun, Jul 17, 2022 at 5:57 PM Michael A. Covington <astro@...> wrote:
I am reluctant to do anything more than routine adjustments on a
brand-new mount; I'm hesitant to even do that.? So far, I have gotten
good tracking.? The mount is sturdy enough that if I simply get a good
polar alignment, there are hardly any dec corrections, ever.

At the same time, I want to see how this develops.? Ultimately, if the
current technology doesn't satisfy people, Losmandy will come up with
some modification.

I see a lot of people making observations like mine, but (thankfully)
nobody complaining that the G11 is unusable for astrophotography because
of it.? If I start having serious problems with guiding, that will be a
different situation than the one I'm in now.










--
Brian?



Brian Valente
astro portfolio?
portfolio
astrobin?
Re: How Much Space is needed?

aughtago
 

it looks far better than I could have drawn, and looks real nice sitting on my concrete pier next to my garden wall (for orientation) now just to design a shed around it.?
Re: How Much Space is needed?

aughtago
 
Edited

THANKS GREG! ?that is perfect as I am designing my ROR in Sketchup.
Re: Backspace

 

Hi Russ

here's a pic of my setup. The filterwheel is screwed directly to the 2600mc behind it (not shown)

Perhaps the main difference is i have an optec TCF focuser replacing the built-in focuser, but I can see i still have the spacer in there



On Sat, Jul 16, 2022 at 10:03 PM Brian Valente via <bvalente=[email protected]> wrote:
Russ this can be super frustrating, i know from experience

I'll have to look at my setup when I get home

Just a thought looking at your reducer, is there an extension tube on that you can remove? it looks modular


Brian


On Sat, Jul 16, 2022 at 8:42 AM Russ via <njrusty=[email protected]> wrote:
On Sat, Jul 16, 2022 at 06:47 AM, Brian Valente wrote:
I have just the flattener. I can¡¯t recall specifics from memory but immodesty sure nothing was in front of it
?
I can take a pic when I¡¯m back at the scope Monday.?
?
I think the details of backfocus etc are covered in the manual as well
?

On Sat, Jul 16, 2022 at 8:24 PM Russ via <njrusty=[email protected]> wrote:
Thank Brian.? I will do that this morning.? One question I am curious about, with the SW 0.77 FR, did you add spacers between it and your scope, then more behind the scope??

?

?

--
Brian?
?
?
?
Brian Valente
astro portfolio?
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astrobin?
I've tried to see if I could put a spacer in front of the FR toward the scope but I do not have the correct size.? As I stated earlier, when putting 56mm after the FR, I am unable to itain focus because the focus travel is maxed out (see attached, but this is showing my backfocus set at 51mm so there is still room for focus tube movement but now I have coma in all 4 corners).
?



--
Brian?



Brian Valente
astro portfolio?
portfolio
astrobin?



--
Brian?



Brian Valente
astro portfolio?
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astrobin?
Re: M45 The Pleiades to bring awareness about ALS/Lou Gehrig disease

 

Hi Carl

there's no admin policy i'm aware of that would remove?it. I wonder if it's possible due to the attachment size that it aged out??

Updating your post?with an external link to the image would definitely stick

On Mon, Jul 18, 2022 at 10:57 AM Carl Bj?rk <carl.bjork@...> wrote:
Hi,

I dont understand, the image is no longer displayed and has been replaced by "May be an image of sky"

Have I done something wrong here ?

Thanks,

Carl



--
Brian?



Brian Valente
astro portfolio?
portfolio
astrobin?
Re: M45 The Pleiades to bring awareness about ALS/Lou Gehrig disease

 

Hi,

I dont understand, the image is no longer displayed and has been replaced by "May be an image of sky"

Have I done something wrong here ?

Thanks,

Carl
Re: Snow Angel Sh2 -106: Another clear night, another Sharpless Object!

 

Nice work, Peter.? The 12 inch Newt gets a lot of light.? Needed because the Narrowband filters need so much light.? ?
Beautiful work!!!

Michael


On Mon, Jul 4, 2022, 1:57 PM Peter Boreland via <pcboreland=[email protected]> wrote:

[Edited Message Follows]

This one has been on my list for sometime, but I did not think it would work out given how small it is. Actually ridiculously small! Pixel scale is 0.35 arcsec/pixel. Seeing these results, I might just stay in Bin 1 mode with my ASI 294 MM Pro camera for all targets. Seeing conditions where not very good, so I know I lost detail for sure. I've not really found too many examples on Astrobin, so perhaps it is not a popular target.?

Total integration 5.11 Hrs. Nights now getting a bit longer, huray!? 400s frames (18 O3, 14 S2 and 14 Ha). Image taken July 3rd, 2022. 12" F4 Newtonian (FL 1380mm), modified L. G11 running Onstep, ASI 294 MM Pro camera, 3nm Chroma NB filters, OAG with QHY5III178MM guidecam.

Wikipedia says:?

This emission nebula is created by "two jets of matter streaming from its poles heat surrounding matter to a temperature of around 10,000?¡ãC.

Dust that is not ionized by the star's jets reflect light from the star. With an estimated surface temperature of 37,000¡ãK, it is classified as a??star. It loses around 10?6??per year in solar winds, ejecting material at around 100?km/s."

Peter
Re: How Much Space is needed?

 

I don't remember where I found it (so I can't verify the accuracy of it), but this is a SketchUp (.skp) model of the G11 which I used for designing an automated slide-off enclosure for my rig.
Re: Understanding a titan

 

There is a Losmandy titan group...but it kinda been not used much these days.
--
Brendan
Locked Re: GM811G dec backlash

 

I am reluctant to do anything more than routine adjustments on a brand-new mount; I'm hesitant to even do that.? So far, I have gotten good tracking.? The mount is sturdy enough that if I simply get a good polar alignment, there are hardly any dec corrections, ever.

At the same time, I want to see how this develops.? Ultimately, if the current technology doesn't satisfy people, Losmandy will come up with some modification.

I see a lot of people making observations like mine, but (thankfully) nobody complaining that the G11 is unusable for astrophotography because of it.? If I start having serious problems with guiding, that will be a different situation than the one I'm in now.
Locked Re: GM811G dec backlash

 

You will find many threads with similar observations.? When I noticed that my G11S (before I added my DIY SLW) had a lot of backlash, I tightened it using the easily accessible adjustment screws.? Turns out, by doing so it then easily binds up when slewing - at least with the 3rd party motor / controller kit that I bought (the G11S has no goto).? The reason for this is that either the ring gear is not round, or that it does not rotate centered due to some other reasons such as play in the axes.? So, without SLW in order to slew there needs to be a good amount of slack.? In my case, as it was delivered from Losmandy, the slack was very noticeable and annoying in the FOV when just moving the scope gently back and forth.

The Losmandy SLW has a backoff screw that basically disables the SLW so long as the gear is below the worm setting as determined by the backoff screw.? Once the gear is engaged in the worm to the max due to whatever non-roundness, the SLW engages and there will be extra pressure from the spring - which seems to be quite strong.? That will cause friction and may have side effects (I don't know - for my DIY SLW I use weak springs that slowly engage but I don't need a backoff screw).?

Being practical, forgetting about the SLW, backlash in RA does not matter much for tracking so long as the gear is pushing (use a counterweight if needed).? For DEC, once you reach your target it won't need to change much.? That means that you can tighten it to reduce the backlash, just for that position.? When you have to slew again, loosen it so it won't bind.? Or you can live with slack in DEC and see if PHD2 can fix it - but it's not ideal.? These types of problems are quite commonly discussed here, and it is also my personal experience.? If you have the SLW, in that case you should engage it fully by turning the backoff screw so the worm is fully engaged without slack.? Or you can take it off and follow the above and see what works better.

While I don't have a Losmandy SLW myself, at the Grand Canyon / Kaibab Lodge star party I have adjusted one from a friend who had just received his G11G with all the trimmings from Losmandy and had horrible backlash.? I don't think this was Losmandy's fault, I think it happened because he did not know to disengage the clutches when transporting the mount.? As a result, huge forces occur that can cause the settings to be dislodged.? Fixing it was easy though.? We had looked at the Losmandy video on this and it's quite easy following Scott's instructions.? However, if your mount is like mine, you may need different settings at different positions of the OTA.

While Losmandy recommends to not change the factory settings, my experience is that you need to know how to change it when it is needed.? The Losmandy is made for DIY so I take advantage of it.? It is nice to have full control.? If it were me, I would try running without the SLW (by taking them off) and with the SLW, and see what works best.
Re: Understanding a titan

 

Titan drives have no Oldham coupler.

The older Titan version had a single worm gear meshed to a single gearbox gear.

The newer G11T Titan tucked motor has 3: a transfer gear between the worm's gear and the Gearbox's gear.? But no Oldham coupler in either Titan system.

Best,
Michael


On Sun, Jul 17, 2022, 12:37 PM Edward Plumer <eplumer@...> wrote:

Assuming Titan motors are coupled the same way as G11 and GM8, another item to add to the checklist is that the Oldham couplers between the gearbox and worm are not slipping.
--
Edward

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