Mark wrote:

Message: 2
Date: Thu, 3 Aug 2000 17:36:59 -0500 (CDT)
From: markdambrosio@...
Subject: RE: HGM-200 Stiction

Hi Gil, To get at the dual Roller Bearings inside the Dec. Assembly,
you must first remove the Saddle Plate, which is held on by 4 Allen Cap
Screws.
(You may have to tap the allen wrench with a hammer to break the bolts
loose, Mine were tight.)
Then you will need a large set of Snap Ring Pliers to remove the Snap
ring that is present under the Saddle Plate (I found a pair at Sears,
Small snap ring pliers will not do the job adequately, it is a large
ring)
There are a couple of washers then I believe to come out. (Don't lose
thier orientation0,
Then the Large Dec.Clutch Wheel will unscrew from the shaft.
You will then be able to lift the Sub-Saddle Assembly (What the Top
Saddle Plate bolts to) completely off the Dec Shaft.
Clean the two Rollers Bearings very well with a solvent like
Turpentine/Naptha/Gasoline (Don't smoke!), and then repack the bearings
with your finger with a high quality grease.
Reverse this order for reassembly.
The difference will be dramatic! (Two finger movement at the scope once
it's balanced) If you have any questions feel free to e-mail me, Mark

Thanks for replying. Glad to see there's at least one other
HGM owner out there. I had not considered performing the operation
so soon since the mount is new, but I guess it wouldn't hurt.

I suppose the Permatex grease suggested earlier would be appropriate?

The stiction problem is a real bear, since I end up pushing the
scope back and forth over the same DSS reading, then have a tough
time composing in the eyepiece. In particular, once I've gotten
set up, and have PEC going, I don't like to give up that 8 minutes
to PEC training in order to have the slew speeds available for
finding and composing objects prior to photographing.

D'ya suppose that Scott might ever make a change in the
electronics so that PEC is permanent, or at least allows you to
use slew speeds without disabling it and having to start again?
This is a frustrating part of the operation of the mount.

Thanks again,

-- Gil

There are a couple of things you should know about the GM8 mounts in
general, and the G9 in particular. My G9 shared a "stiction"

problem with

the GM8s, particularly in DEC. A replacement teflon bushing from

Scott

Losmandy resolved this problem, although it introduced a minor

issue: the

DEC clutch must be tightened more to achieve the same amount of

resistance.

IMO, that's a minor irritation, compared to the stiction problem,

which was

a HUGE pain-in-the-***!

Gee, this sounds familiar....so Scott has already had this fix in
his bag of tricks for the G9. When I emailed him about replacing the
nylon clutch washer with teflon on my G11, I got the impression from
his response that it was a new idea. Nothing was said about the fact
that he already did this on the G9. Hmmmm...curiouser and curiouser.

Bill

--- Jack Metcalfe <jlmetcalfe@...> wrote:

A couple of questions and hopefully some recommendations from the
group. It's been quite a while since I've had a scope for
observing, but the bug has bitten again. Years ago, I had a Cave
Astrola on a GEM and a few years after that, a C-8 on a fork mount.
Currently, I'm most interested in a Celestron 9.25, but I don't
like Celestron's mount.

Question 1. Would the Losmandy GM-8 be adequate with the 9.25 or is
this overkill for visual use only?

Hi Jack. Congrats on getting back into the hobby! I recently acquired an
older CG9 (the C9.25 on a Losmandy G9 mount) and really like it. The C9.25
seems to be slightly superior to other commercial SCTs that I've looked
through. I have to admit that the focus micrometer that is built into mine
(it's the older model) is a wonderful, wonderful thing. Too bad that don't
still include that feature. If I bought one now, I'd probably add the JMI
aftermarket DRO.

The mount is a good match for this instrument for visual use only. No, it's
not overkill. IMO, it's not enough mount for this scope for prime focus
photography.

There are a couple of things you should know about the GM8 mounts in
general, and the G9 in particular. My G9 shared a "stiction" problem with
the GM8s, particularly in DEC. A replacement teflon bushing from Scott
Losmandy resolved this problem, although it introduced a minor issue: the
DEC clutch must be tightened more to achieve the same amount of resistance.
IMO, that's a minor irritation, compared to the stiction problem, which was
a HUGE pain-in-the-***!

There are two downsides to the G9 mount compared to the GM8, and one
upside. First, it came on the infamous extruded aluminum tripod that
Celestron and others use on many of their mounts. Calling it a tripod does
serious offense to all legitimate tripods in the world! <g> I knew about
this problem in advance, so it wasn't a surprise. Fortunately, I had an
older Celestron SP mount with the nice hardwood legs. I swapped tripods,
and the improvement is dramatic. Still, I lust after the GM8 tripod and
will probably invest in one someday soon.

The second issue was a complete surprise, and quite a disappointment. I
have seen people state over and over that the G9 head is the same as the
GM8, but when I disassembled it to clean and relube it, I discovered that
IT HAS NO NEEDLE BEARINGS ON EITHER AXIS! There are simply polished
aluminum bearing surfaces. There are washer-type roller bearings at the
clutch-end of each shaft.

I asked Scott if needle bearings could be press-fitted into the shaft
housings, and he said that it would be difficult and expensive. Bummer.

The upside of the G9 is that it comes with the G11 saddle plate, instead of
the smaller GM8 one. This helps me immensely because I have an older GM100,
which uses the G11-style dovetail system. All my OTAs, SBS assemblies,
etc., are completely interchangeable.

Question 2. Are there other mount options for this instrument?
Actually, I always thought the fork mount was fine for visual use,
but it's no longer available for the 9.25.

IMO, the current G9 is a pretty good deal. The C9.25 OTA on its own sells
for only $100 less, and I assume (I know, I know...) that you could
probably sell the mount for a lot more than that. Maybe not.

You might consider a Vixen GP-DX mount, if you can purchase one with a
wooden tripod instead of the aluminum one. Other than these two mounts, you
pretty quickly get up into the price range of the G11- hey, that's not a
bad idea! (IMO, if you can afford the price difference, which is about
$500, get the G11.)

Cheers,
Paul Sterngold

__________________________________________________
Do You Yahoo!?
Kick off your party with Yahoo! Invites.

Hi Jack,

From my limited understanding, the GM-8 is a fine mount for the C9.25.
David Silva uses exactly this setup, and is quite happy.

Robert.

A couple of questions and hopefully some recommendations from the
group. It's been quite a while since I've had a scope for
observing, but the bug has bitten again. Years ago, I had a Cave
Astrola on a GEM and a few years after that, a C-8 on a fork mount.
Currently, I'm most interested in a Celestron 9.25, but I don't
like Celestron's mount.

Question 1. Would the Losmandy GM-8 be adequate with the 9.25 or is
this overkill for visual use only?

Question 2. Are there other mount options for this instrument?
Actually, I always thought the fork mount was fine for visual use,
but it's no longer available for the 9.25.

Hi Paul,
I noticed that fuzzy as well and just assumed it was a galaxy. I
checked the Digitized Sky Survey

and it shows the galaxy pretty clearly.
The ability of these commercial CCDs to pull out these dimmer objects
is really amazing. It is one of the things that I really enjoy about
this hobby.

Thanks
Tom C

Paul Sterngold wrote:

Greg,
The delay after correction (usually about .8 seconds) is absolutely
required. Until I did that, my corrections were always in the .5 to 1
pixel range. The mount was still responding to the prior move when the
next guiding exposure was started.
If I use a tracking rate of more than 2 seconds, and there is a change
in RA and DEC (my minimum move times are usually .2 to .25 seconds),
then it can be up to 2+.2+.2+.8+.8 = 4 seconds between corrections.
This now starts to get kind of long. I have noticed that the way my
drive works is that it hums along pretty well, and then has a jump of
.7 or so pixels that is usually guided out on the next correction. If
I wait too long between corrections, it will be too long before the
error is guided out.
I am still working with the drive. Since it is brand new, I have not
yet taken it all apart for a cleaning as recommended by so many other
G-11 motors. For the most part, I am very satisfied. The DSC are just
great and the mount is well built.

Tom C

Greg Crawford wrote:

Tom,

+/- .2 pixels is excellent. Would you have obtained the same level of
guiding accuracy ifyou had exposed the tracking CCD for say, 2 secs, without
any delay?

Greg Crawford

Hi Tom,

Very nice images. In the combo shot with 5905 at the center, there appears
to be another, bright FFO (galaxy?) close to the bright star that is just
to the left and above center of the frame. Is that a deformed star
(unlikely), some kind of reflection in the optical train (unlikely), or a
legitimate FFO?

Cheers,
Paul Sterngold

--- Julie and Tom Carrico <carrico@...> wrote:

Hi all,
We had some okay nights at our observatory in central Oregon this last
weekend. 3 nights were clear with reasonable seeing, but some high
clouds. Two other nights had us chasing holes in the clouds. Still,
any night under the stars is wonderful.

Continuing to work out all the bugs on the G-11. When it is all tuned
up, it works just great. However, it seems to be very sensitive to
balance in RA. During guiding, the mount is kept heavy to the east.
This means that with the RA clutch loose, the scope will move and you
must pay attention when moving from the sky. If it is not that heavy,
the RA tracking suffers.
I have also found that the tracking rate that works best is 1.3 to 1.5
seconds with a delay between corrections (as set in MaxImCCD) of 0.8
seconds. If the delay is not set or is set too low, the mount seems to
chase corrections all over the place.
With the mount balanced and the guiding rate and delay properly set,
and when used with my 4" Tak (820 mm focal length), the tracking error
is usually +/- 0.2 pixels with an occassional flier of .7 or .8 that
gets corrected immediately. The camera is an ST-7E.

My latest images are:






The bubble nebula has been retouched to remove the blooming, as has
the cocoon. Tough images that will get another look next month.
I have learned that imaging at f/8 just requires lots of exposure. The
galaxy images could have used 2x the time I used here. That's also for
next month.

There will be more images posted later this week.

Thanks
Tom Carrico

__________________________________________________
Do You Yahoo!?
Kick off your party with Yahoo! Invites.

Hi all,
We had some okay nights at our observatory in central Oregon this last
weekend. 3 nights were clear with reasonable seeing, but some high
clouds. Two other nights had us chasing holes in the clouds. Still,
any night under the stars is wonderful.

Continuing to work out all the bugs on the G-11. When it is all tuned
up, it works just great. However, it seems to be very sensitive to
balance in RA. During guiding, the mount is kept heavy to the east.
This means that with the RA clutch loose, the scope will move and you
must pay attention when moving from the sky. If it is not that heavy,
the RA tracking suffers.
I have also found that the tracking rate that works best is 1.3 to 1.5
seconds with a delay between corrections (as set in MaxImCCD) of 0.8
seconds. If the delay is not set or is set too low, the mount seems to
chase corrections all over the place.
With the mount balanced and the guiding rate and delay properly set,
and when used with my 4" Tak (820 mm focal length), the tracking error
is usually +/- 0.2 pixels with an occassional flier of .7 or .8 that
gets corrected immediately. The camera is an ST-7E.

My latest images are:






The bubble nebula has been retouched to remove the blooming, as has
the cocoon. Tough images that will get another look next month.
I have learned that imaging at f/8 just requires lots of exposure. The
galaxy images could have used 2x the time I used here. That's also for
next month.

There will be more images posted later this week.

Thanks
Tom Carrico

Hi Gil, To get at the dual Roller Bearings inside the Dec. Assembly,
you must first remove the Saddle Plate, which is held on by 4 Allen Cap
Screws.
(You may have to tap the allen wrench with a hammer to break the bolts
loose, Mine were tight.)
Then you will need a large set of Snap Ring Pliers to remove the Snap
ring that is present under the Saddle Plate (I found a pair at Sears,
Small snap ring pliers will not do the job adequately, it is a large
ring)
There are a couple of washers then I believe to come out. (Don't lose
thier orientation0,
Then the Large Dec.Clutch Wheel will unscrew from the shaft.
You will then be able to lift the Sub-Saddle Assembly (What the Top
Saddle Plate bolts to) completely off the Dec Shaft.
Clean the two Rollers Bearings very well with a solvent like
Turpentine/Naptha/Gasoline (Don't smoke!), and then repack the bearings
with your finger with a high quality grease.
Reverse this order for reassembly.
The difference will be dramatic! (Two finger movement at the scope once
it's balanced) If you have any questions feel free to e-mail me, Mark

Hey Bill,
An easy fis would be to put a small square of plywood under the legs, when
on soft ground, it should do the trick.
CS
Jay

In a message dated 8/3/00 6:56:37 AM EST, dbell@... writes:

Not sure what you meant by again, but my attempts to access that URL have
been met with "Not Available"

Sorry for being a little obtuse by *again* I posted earlier
via the E Groups website a message about this. Never saw
it show up.

The address does work, I got the same message, but
the page loaded (it has no graphics)



I know others have used my method's, grease and had
excellent results Let me know what ya'all think (please)

Allan



A little bio on me here, and PIC as well...

Robert Leyland wrote:

Hi Bill,

On my GM-8 I use celestron anti-vibration pads. But the G-11 has much
larger legs, so you'd probably have to make something. It wouldn't be
difficult, to cut some plywood into 4-5" diameter circles, and put a
layer of "Sorbathane" (sp?) between them to reduce vibrations. A
doorstop, or similar knob, could act as a centering plug for the G-11
legs.

This could be quite elegant :-)

I use the G-11 with the Celestron anti-vibration pads. All you
have to do is turn the legs 180 degrees and the curved outer
end of the legs fits nicely in the cup of the pads. This combination
works very well.

Rockett Crawford

----------------------------------------------------------------------------

Capella's Observatory (CCD Imaging)

Hi Bill,

On my GM-8 I use celestron anti-vibration pads. But the G-11 has much
larger legs, so you'd probably have to make something. It wouldn't be
difficult, to cut some plywood into 4-5" diameter circles, and put a
layer of "Sorbathane" (sp?) between them to reduce vibrations. A
doorstop, or similar knob, could act as a centering plug for the G-11
legs.

This could be quite elegant :-)


Robert.

Hi Bill,

There are small ground platforms (usually metal) available that are
used in the world of surveying. These often have small spikes on
their underside and are stamped firmly into the ground. They are
used for supporting the tripod feet of theodolites and leveling
staffs etc on soft ground. I couldn't tell you where to get them but
I hope this is of some help.

Ian.

--- In Losmandy_users@..., "Bill Faatz" <faatz1@l...> wrote:

OK, enough of the teflon washer. I wonder if anyone has a solution

to

this problem. Over the course of an evening's observing, I notice
that the front leg of my G11 starts sinking into the dirt (according
to
the bubble level). This is the one directly below the dec
counterweights,
so it sees the bulk of the weight distribution. The other legs are
probably wandering too. This causes my initial alignment to wander
off, and consequently makes it harder to locate objects with the
setting circles. The ground out here in northern California where I
observe is
largely adobe. Anyway, I wonder if there is some aftermarket

product

like a shoe that would slip into or over the ends of the existing
legs
and help distribute the weight over a larger area. Another observer
with a G11 uses old TV Guide mags under the legs, but I was thinking
of a more elegant solution.

Bill

OK, enough of the teflon washer. I wonder if anyone has a solution to
this problem. Over the course of an evening's observing, I notice
that the front leg of my G11 starts sinking into the dirt (according
to
the bubble level). This is the one directly below the dec
counterweights,
so it sees the bulk of the weight distribution. The other legs are
probably wandering too. This causes my initial alignment to wander
off, and consequently makes it harder to locate objects with the
setting circles. The ground out here in northern California where I
observe is
largely adobe. Anyway, I wonder if there is some aftermarket product
like a shoe that would slip into or over the ends of the existing
legs
and help distribute the weight over a larger area. Another observer
with a G11 uses old TV Guide mags under the legs, but I was thinking
of a more elegant solution.

Bill

On Thu, 3 Aug 2000, Bill Faatz wrote:

Steve, my point is that the teflon clutch washer IS a solution that
works very well to solve this problem. There is plenty of resistance
to
hold the telescope in position when taking out Negler EPs. You
actually
have to apply some force to move the scope, but the breakaway force
is
constant and repeatable, qualities that are necessary for using the
manual setting circles and moving fractions of a hash mark.I don't
want
the added complications of GoTo when I can locate objects very well
with the manual setting circles. I like to keep equipment as simple
as
possible in the field.

Bill

Bill, I agree - my answer was an attempt at humor, hence the smiley.

- Steve -

*
* Steve Linscott Information Technology Division *
* linscot@... Rice University Houston, Texas *
*

--- In Losmandy_users@..., "Stephen M. Linscott"
<linscot@r...>
wrote:

On Wed, 2 Aug 2000, Bill Faatz wrote:

Steve
Good point, I stand corrected on this issue. However, the force
applied
to the clutches is different...in the case of the Dec axis, the
weight
of the load, plus the tension of the clutch combine to make the
stiction load greater then the RA axis, which sees only the

clutch

tension. The difference in the breakaway stiction force necessary
between the two axis is very noticeable. Thanks for correcting my
analysis. I am beginning to enjoy this group.

Bill

Bill, you're absolutely right - the DEC setting is a balance

between easy

to move, and having to hold the scope when you take out that heavy
eyepiece! It's not so bad on the MCT, but the large refractor is a
challenge. I guess the solution is to install Scott's GoTo, and do
electric slewing! :-)

Steve, my point is that the teflon clutch washer IS a solution that
works very well to solve this problem. There is plenty of resistance
to
hold the telescope in position when taking out Negler EPs. You
actually
have to apply some force to move the scope, but the breakaway force
is
constant and repeatable, qualities that are necessary for using the
manual setting circles and moving fractions of a hash mark.I don't
want
the added complications of GoTo when I can locate objects very well
with the manual setting circles. I like to keep equipment as simple
as
possible in the field.

Bill

开云体育