--- In Losmandy_users@..., "Neal Barry" <nbarry@b...> wrote:

Does anyone know of a source for undersized needle bearings to fix a
weakness in my Losmandy G11 mount? Specifically, 1.247" ID / 1.500

nominal

OD. For the benefit of those who may encounter the same problem, I

have

described it below:

I wrapped some .0015"
stainless steel shim stock around the undersized shafts as a

temporary fix

to remove the bearing slop.

Well, it was like night and day. That simple change eliminated the
'shifting' on each axis, improved tracking and GOTO pointing

accuracy

dramatically, there was no more slop in either axis, and best of

all, the

backlash can be adjusted to virtually zero through a full 360

degrees of

rotation.

Anyone else have a similar experience?

Neal

I have the same problem with my G11 but only in the lower dec bearing
set (the upper set appear to be OK) The shaft is 1.250, but the ID of
the bearing set is oversized. The symptom is that I can slightly rock
the field of view by putting pressure on the OTA. This is
particularly
annoying at high power. The RA axis appears to be OK. It seems to be
an
ongoing variability in out of tolerance bearings. How old is your
mount?? And why isn't this caught by Losmandy??

I think QA may be an issue under backorder pressures to get the units
out. When I received my mount, the RA setting circle wouldn't rotate.
To make a long story short, disassembly of the RA axis revealed that
the nylon clutch washer was missing. This caused the setting circle
ring to be bound up. It seems to me that this should have been caught
by the most cursory of final inspections. Things like this don't
inspire confidence in an otherwise first rate product.

Bill

Is anyone else using the JMI version? If so, what did you find as the
most convenient place to put the Velcro tab to hang the illuminator
control

Hi,

I have no experience with the JMI version but my battery and cord is velcro'ed in
place inside the semi-pier. I just let the cord hang down through the bottom of the
pier then up behind the drive electronics. I just plug it in when needed. At some
point I want to mount an on-off/dimmer switch but it will have to wait for a cloudy
winter night.

Cheers,
Bill

--- In Losmandy_users@..., havriliak@a... wrote:

Eventually, I received my polar alignment scope for the G-11

from

Pocono Mts. Alas, there were no instructions so I tried to figure

it

out. I thought I did but some evidence indicates that I didn't.

Can

someone send me to a post that decribes the procedure. Thanks in
advance. S. Havriliak

Go to the files section of this group and download polar1.pdf. It
helped me understand what to look at. I also remade the polar scope
LED with a dimmer so it was easier to see the second star.

From my experience and discussions with Scott L..the o ring is only there to help hold everything on the shaft ntil you screw the clutches on.
It will work with the o ring or without the o ring but it will bind up if broken.I've removed both.

The delrin gear covers seem to be to thick.There is a proceedure for using some shims when assembling so everything fits up toght and the cover is supposed to fit.I did this but could't get the clutches tight after.
My solution was to remove the cover and file or grind about 1/8 inch from the back(flat side)
eveything in this respect now works fine.

good luck....jimmy

From: "Jay Stanley" <jstanley@...>
Reply-To: Losmandy_users@...
To: <Losmandy_users@...>
Subject: Re: [Losmandy_users] Losmandy G-11 DSC delran covers
Date: Mon, 14 Aug 2000 19:58:58 -0500

So that's what the "O" rings were for...I never installed mine and have not
had a problem, should I install them? As far as your problem I would check
again and make sure all the components are on in the correct order and
tight. I had to send back one of the large gears as it was about .002
undersized and would not fit the shaft.
CS
Jay
PS..I had one small problem with the large gear on the Dec shaft which came
loose that could have 'bound' the shaft, but after a little alignment and a
quick turn of an allen wrench everything was fine.





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The o-rings are dust seals. Stretching them across the threads to
slide them on seems to give them a rather short lifespan. My first
one to go lasted about 2 months and I removed the other one while I
was in there. The local hardware stoor didn't have a goot
replacement so I left it without the o-rings for now.

This may help with the cover moving...

There is a sliding ring that the five (or is it six?) pressure pins
go through. On my G11 the placement of it was critical to prevent a
loose or binding cover. Also note that the lockdown screw for that
ring needs to match up with the flat area (I missed that the first
time). Good luck.

--- In Losmandy_users@..., "Milton Esquinaldo"
<milton10@u...> wrote:

Hey Guys,

Maybe I missed it, but is there any kind of lubricant that works
better than another when re-lubing the GM-8/G11 mount. Would White
Lithium be best? I also heard that green bicycle stuff is good.

Please advise.

Milton

Hi Milton.

I ended up using marine bearing grease from the local K-mart. It's
been about a year and so far I have no complaints. Since you're
using it in the FL heat get something that will not run.

Here's what may be a silly question. I recently received my G11 and
bought the JMI version of the polar alignment scope for it since it
was available now.

Is anyone else using the JMI version? If so, what did you find as the
most convenient place to put the Velcro tab to hang the illuminator
control? Apparently the battery holder/controller can't be
disconnected from the polar scope without voiding the warranty, if I
read the paper that came with it correctly.

Thanks!
Doug Culbertson
Midway, FL

Welcome, Girolamo!

I suspect the play in your DEC shaft, and its inconsistency, is caused by
two things:

1) A small amount of play between the worm and the worm wheel (gear); and

2) A small amount of play between the DEC shaft and the shaft bearings.

#2 permits the shaft to be slightly off-center with regards to the axis.
Therefore, #1 can come and go as the worm wheel pushes more or less against
the worm itself.

This is speculation, but there's been a lot of discussion recently on the
list regarding #2.

An alternative possibility, and one that I read about on the
Astrophotography Mail List (APML) about three years ago, is that the hold
in the center of the worm wheel itself is slightly larger than the shaft,
and therefore the worm wheel can be "locked" (via the clutch knob) in a
slightly eccentric position relative to the shaft.

I hope this helps.

Paul Sterngold

--- Girolamo Gallo <ggallo@...> wrote:

I am an Italian amateur astronomer. I have a problem with my brand new
G11.
Since the day one, I noticed a play in the declination axis. It becomes
very evident when the saddle plate is rotated at a particular angle with
respect to the mount. In this condition, if I grab the saddle plate I
clearly feel the play (about 1/3 of degree) that starts decreasing as
soon as the saddle plate is manually rotated by about 60 degrees. It
disappears once the DEC axis is rotated by 120 degrees and starts
increasing again at about 300 degrees.
Some Losmandy users suggested that the play is related to the mechanical
fixation of the declination axis to the saddle plate assembly. They also
said that their mounts have a set screw that locks the saddle assembly to
the declination axis, but I could not find that screw in my mount. Maybe
Losmandy changed the G11 shaft DEC assembly (can anybody confirm that?).
I would really appreciate if someone you could help me to solve this
problem.
Thanks in advance.

Clear skies!

Girolamo Gallo
Avezzano, Italy

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So that's what the "O" rings were for...I never installed mine and have not
had a problem, should I install them? As far as your problem I would check
again and make sure all the components are on in the correct order and
tight. I had to send back one of the large gears as it was about .002
undersized and would not fit the shaft.
CS
Jay
PS..I had one small problem with the large gear on the Dec shaft which came
loose that could have 'bound' the shaft, but after a little alignment and a
quick turn of an allen wrench everything was fine.

I need help with two problems that I encountered with the
Losmandy Delran covers for their DSC. First, let me describe the
anomolus behavior. When manually centering on a star using a Telrad
finder, the centered star drifted about 2 deg. after I removed my
grip from the SCT. Also, when shifting a star from one end of the eye
piece field to the other using the dec drive, the star stoped
moving. The scope is accurately balanced.
1. I followed the installation of the DSC and covers with great
care using the eploded view in Losmandy instruction sheet. After the
incidence described above, I took the Losmandy covers off and found
that the rubber O-rings were torn in half.
2. After re-assembling the DSC with covers, I noticed that the
covers moved with rotation (about a degree) about the Dec. axis. The
net result is that the covers moved against the gears and
significantly increased drag. This drag is probably sufficient to
stall the motor drive. The net result is that movement about the Dec
axis is similar to serious back-lash. Close inspection showed that
there was no back-lash in the gears, it just felt that way.
3. Removal of the cover and rotation about the Dec. axis showed
that there is no apparent back lash. Further more there is no
apparent increase in drag.
Any suggestion is greatly appreciated.

Does anyone know of a source for undersized needle bearings to fix a
weakness in my Losmandy G11 mount? Specifically, 1.247" ID / 1.500 nominal
OD. For the benefit of those who may encounter the same problem, I have
described it below:

With a nominal vertical load, the RA and/or DEC shafts on my G11 mount tend
to 'hang' about .002"-.003" below the axis centerline when the clutches are
relaxed. When the clutches are tighten, the shaft end plate initially
'locks' to the nylon clutch surface slightly below center. When the axis is
rotated far enough that the weight overcomes the grip of the nylon surface,
the axis 'shifts' into a 'more' aligned position. This is normal behavior on
four different mounts that I have examined. Besides introducing tracking
errors, this misalignment distorts the worm/wheel spacing by a small amount,
and causes the backlash to vary as the axis is rotated through 360 degrees.
Changing the load on the mount, or loosening and retightening the clutches
can completely upset prior backlash adjustments. If you are not adjusting
your worm/wheel spacing for absolute minimum backlash, you may never
encounter this aspect of the problem.

The needle bearings on both the RA and DEC are set back about 2" from the
'business end' on each axis. As an experiment, I pressed an additional
1.250" ID needle bearing into the opening so that the shaft was supported
nearly to the end of the opening. Additionally, the shafts I have seen
measured 1.2470" dia instead of an optimal 1.250". I wrapped some .0015"
stainless steel shim stock around the undersized shafts as a temporary fix
to remove the bearing slop.

Well, it was like night and day. That simple change eliminated the
'shifting' on each axis, improved tracking and GOTO pointing accuracy
dramatically, there was no more slop in either axis, and best of all, the
backlash can be adjusted to virtually zero through a full 360 degrees of
rotation.

Anyone else have a similar experience?

Neal

Hello,

I am hoping someone may be able to help. I have a GM-8 and there seems
to be a problem with RA function. It's axis has shifted some 20 degrees.

If I position everything on the entire mount head as if it came out of
the box, the RA motors, bearing and housing now sit at an angle to
everthing with the motor assembly sitting lower and the right side
(looking at the mount from the side of the alt-adjust) pointing higher
than it used to.

If you look at your mount, imaginge the bolt which holds the worm gear's
bearing housing (the housing closest to the RA moto)r now positioned
over the curved portion of the alt-adjust bracket at the base of the
mount.

I took the mount completely apart last night (easy to do if anyone needs
instructions) all the way down to main housing. The part which has
shifted it's position is the only part that had no apparent way to be
disassembled. As if it were pressed in like bearing on auto axels. It
will not move, and is tight as a rock......as if that is the position it
is meant to be in.

Am I just imagining a problem?? The mount seems to work fine, just does
not look like it used to.

Thanks for any help in advance and take care out there,
Gregory david Stempel
FIREFRAME

Test

James,

The other issues are whether just changing the gears alone will do it<<<

I agree with you, but the way I look at it, any upgrade is better than
no upgrade at all, true??

I could not understand your formula, but it does seem like a formula
worth knowing.

I guess slop is one major issue, so braketing/gear mounts to ensure a
quality fit is important.

Thanks James, take care.
Gregory david Stempel
FIREFRAME

HI Greg,changing gears seems easier than done.
I satrted down that road and am witing for aim controls to determine if the can make a retrokit feasable.The other issues are whether just changing the gears alone will do it.The play in bearings,gear mesh etc all add to error.
Aside from the inheirant error from forming the worm and cutting the gears there is all this potential play in other components.Apparently as little as 31 millionths of an inch play in meshing or gear slack or bearing to shaft play causes 1 arc sec error.So if the engineers of a mount are operating in standard 10,000th of inch measurements,they are way off.

Perhaps the biggest piece of info I have learned recently is the arc error guideetolerance formula.....7200?flocal length= arcsecs error tolerance (as a rule of thumb.)

So a 1200 mm refractor can tolerate 3 times the guide error of a 12"sct.

this is going to mean big things in the industry shortly as we have already seen members of our group using ccd's at multi exposures but short durations.Tou can use smaller scopes.
But,aperture still prevails visually so if you hope to see these objects a larger scope is necessary ergo a better mount in needed and especially if using film.

catch 22.

good luck....jimmy

From: Gregory David Stempel <fyrframe@...>
Reply-To: Losmandy_users@...
To: Losmandy_users@...
Subject: [Losmandy_users] Gearhead
Date: Thu, 10 Aug 2000 21:37:18 -0700

Hello,

I am a new member to the list, glad for the opportunity to talk about
the Losmandy mount.

Has anyone changed the main gears in the losmandy head to something like
Byers or another quality manufacturer?? Would I also have to change the
worms? I am wondering just how difficult of a process it would be.

Thanks and take care out there,
Gregory david Stempel
FIREFRAME



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Losmandy_users-unsubscribe@...

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Hello,

I am a new member to the list, glad for the opportunity to talk about
the Losmandy mount.

Has anyone changed the main gears in the losmandy head to something like
Byers or another quality manufacturer?? Would I also have to change the
worms? I am wondering just how difficult of a process it would be.

Thanks and take care out there,
Gregory david Stempel
FIREFRAME

Regards
Peter Ward.

P.S. Early Losmandy encoder kits did suffer from some encoder

movement

when the either clutch knob was turned. The current kits have

thrust

pins and washers, which fixes the problem...plus they look a whole
lot better than the DSN kit ;)

But they don't have the resolution of the DSN kit. As is often
sadly the case, form wins over function (but not usually with
Americans I find).

--- In Losmandy_users@..., "GC GC" <gcert1@i...> wrote:

Thanks for the information.

I'm particularly interested in the encoder support.

The Gemini Goto system will support up to 32768 counts per revolution.


Regards
Peter Ward.

P.S. Early Losmandy encoder kits did suffer from some encoder movement
when the either clutch knob was turned. The current kits have thrust
pins and washers, which fixes the problem...plus they look a whole
lot better than the DSN kit ;)

Thanks for the information.

I'm particularly interested in the encoder support. If I understand
you correctly, the scope can be moved manually, the GoTo
functionality continues to work as before without needing any extra
calibrations etc. and the only problem is that after such a
manual move, the pointing accuracy drops to a resolution 4196 ticks
per revolution.

I was looking at using these encoders instead of the standard
losmandy encoders:



here's a better picture of them on a G-11 from their old (and nicer
looking site)



These are 8192 encoders using a 4x ratio giving a total of 32768
steps rather than the normal 4096 steps.

I first saw these mentioned at the end of this review of the
SkyCommander which seems to suggest that they will work fine with the
SkyCommander:



SkyCommander's site says if you have their latest software (V4.0)
it'll support 32768 steps.

As I said, I was looking at getting this mounting kit and these
encoders at 4x ratio, and now that the Losmandy GoTo is out I'd like
to make sure the GoTo can handle them.

So my question is that do you know if the Losmandy GoTo will handle
32768 and is the sample rate high enough that even with fast manual
scope movement ticks are not lost?

As a separate question to the group, has anybody had any experience
with these encoders and their Losmandy mounting kit [which uses the
same holes in the mount as Losmandy's own encoder mounting kit],
either with the Deep Space Navigator interface or connected to a
SkyCommander? In e-mails with Brian Kidwell (the designer of Deep
Space Navigator and the Losmandy mounting kit pictured) I have been
told that the method used on the moutning kit is far superior to the
Losmandy encoders as it elimnates completely any clutch problems.
Here's what I was told and would appreciate any comments about this:

"The Losmandy kit has some real problems with locking down the
telescope for heavy loads and this can affect the position of the
gear train. The alignment can be affected when the scope is locked
and released repeatedly. Our mounting kit eliminates this problem
entirely and higher resolution pointing is gained at the same time."
...
"The shaft has been flatted on one side but only where the gear sits.
The gear is bored round with a set screw. Tightening the lock nut
over the gear and releasing will cause some movement of the gear
before the end of the night. In addition, the knurled nut he
provides to lock down the scope makes it very hard to get a real good
lock down for accurate tracking during photographic exposures. My
kit has none of these problems as the lock nut has not contact with
the primary drive pulley."
...
"One of the main points [of Deep Space Navigator's Losmandy mounting
kit] to notice is that the locking nut [the large octagonal shaped
silver thing at the bottom end of the RA axis between the mount and
the large pully gear] ins place on the threaded shaft before the
pulleys are installed. When the locking nut is tightened or
loosened, there is no effect on the pulley. The holes on the flat
sides of the nut are for the tightening tool I provide with the kit.
This allows easy lock down of the nut to the maximum tightness
needed to prevent movement of the mount. This is especially helpful
if you are doing astrophotography."
...

[And with respect to SkyCommander and 8192 step encoders here's what
Kidwell had to say (and I would be interested in experiences of
anyone using 32,768 CPR with the SkyCommander):]

"If you want software that is easy to use with your telescope and you
want the highest resolution available for a reasonable price, then
you should use Deep Space Software and The Deep Space Navigator. I
have many customers who have tried the other systems and have then
purchased our system. They have done this as they were not happy
with the other systems accuracy. If you read the information about
the Sky Commander carefully, I believe that you will not find mention
of using the 8192 CPR encoders with gearing that would increase the
resolution of the encoders beyond the 8192 CPR. While the Sky
Commander may be used at 8192 with very deliberate (slow) motion of
the telescope, you may find the need to recalibrate due to missing a
count or two from time to time."