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Hi all,

Well, I'm reasonably pleased with the improvement that I have been able to
achieve in my G11's tracking and periodic error. Take a look at
to see the results.

I am curious how the PE shown on the web page above compares to other G11
mounts out there. I still am not sure if the problems with the mount I
received are typical or a fluke.

I have made the fix permanent since my original post back on 8/13, but I did
risk damaging the mount in the process. Specifically, I pressed in a new
needle bearing with .002" stainless steel shim stock wrapped around the
OUTSIDE of the bearing (I know, I was against it in an earlier post ;-) I do
not recommend this! You can easily damage your mount unless you are VERY
careful. Five things can go wrong.

1. The needles in the bearing can seize.
2. The bearing can easily distort due to the amount of force require to
press it in.
3. The fit can bee too good, and the shaft will bind due to the relative
misalignment of all three needle bearings.
4. You can permanently knock the RA wheel gear bearing sleeve off axis or
bend it.
5. You can expand the OD of the RA wheel gear bearing sleeve so that the
wheel gear will no longer fit.

However, this strategy did cause the ID of the needle bearing to shrink
(exactly the amount needed in my particular case) and I now have a very nice
on-axis fit with no measurable slop. The OD of the RA wheel gear sleeve
bearing did expand slightly (approx .0002") and I needed to lap it a bit to
ensure that it would not bind over an appreciable operating temperature
range.

Anyway, now that the RA shaft was not flopping around, I was finally able to
see how well the mount would track. Now I had a fairly regular PE of about
11-12 arc seconds. After lapping the RA worm and wheel gear it dropped to
under 10 and became even more regular. After training the SkyWalker II PEC,
it tracks within 2 arc seconds. Not too shabby given where this all started.

Neal

Hi Neal,it's looking good.I put a third 1"long bearing in each of my axies and it improved nicely but not like yours.
By coincidence,I offset my mount and took a few before and after startrails.
The after star trailsARE VERY REULAR AND i TOO USED A 101 POINTED AT THE M31 REGION.I used a 2x big barlow in front of my camera.

My star trails can be described as 2 different appearing trails:
the bright stars look loke a straight linr composed of light balls (stars )connecetd together like a string of pearls.
The dimmer stars leave wavy trails but are much thinner of course than the bright stars.
How would I measure the arcsec error?

I had tried to calculate my arcsec resolution with a 12.5mm ortho eyepiece and on the 60mm scale it took 300 seconds for a star to go end to end.I calculate dthe that give an st-4 pixel is 13.5 x 16 microns that on the ra side,1 pixel at prime focus would be 5.5 arcsecs.The 2x barlow would halve that would it not?
If correct,how then do you extrapolate that to a 4 by 6"photo?

I shot 30 minutes at the pleades and have round stars even under an 8 power magnifier.

Can you shed any light on this for me?

thanks
Jimmy

From: "Neal Barry" <nbarry@...>
Reply-To: Losmandy_users@...
To: <Losmandy_users@...>
Subject: [Losmandy_users] G11 Fix (III)
Date: Tue, 22 Aug 2000 12:55:59 -0700

Hi all,

Well, I'm reasonably pleased with the improvement that I have been able to
achieve in my G11's tracking and periodic error. Take a look at
to see the results.

I am curious how the PE shown on the web page above compares to other G11
mounts out there. I still am not sure if the problems with the mount I
received are typical or a fluke.

I have made the fix permanent since my original post back on 8/13, but I did
risk damaging the mount in the process. Specifically, I pressed in a new
needle bearing with .002" stainless steel shim stock wrapped around the
OUTSIDE of the bearing (I know, I was against it in an earlier post ;-) I do
not recommend this! You can easily damage your mount unless you are VERY
careful. Five things can go wrong.

1. The needles in the bearing can seize.
2. The bearing can easily distort due to the amount of force require to
press it in.
3. The fit can bee too good, and the shaft will bind due to the relative
misalignment of all three needle bearings.
4. You can permanently knock the RA wheel gear bearing sleeve off axis or
bend it.
5. You can expand the OD of the RA wheel gear bearing sleeve so that the
wheel gear will no longer fit.

However, this strategy did cause the ID of the needle bearing to shrink
(exactly the amount needed in my particular case) and I now have a very nice
on-axis fit with no measurable slop. The OD of the RA wheel gear sleeve
bearing did expand slightly (approx .0002") and I needed to lap it a bit to
ensure that it would not bind over an appreciable operating temperature
range.

Anyway, now that the RA shaft was not flopping around, I was finally able to
see how well the mount would track. Now I had a fairly regular PE of about
11-12 arc seconds. After lapping the RA worm and wheel gear it dropped to
under 10 and became even more regular. After training the SkyWalker II PEC,
it tracks within 2 arc seconds. Not too shabby given where this all started.

Neal









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Losmandy_users-unsubscribe@...

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Jimmy,

1. You can calculate arcseconds per pixel with the following formula:

ArcSec = 3600 * ARCTAN( (PixelWidth * 10^-6) / FL )

Where:
ArcSec = Width of Pixel in Arcseconds
PixelWidth = Width of CCD pixel in microns
FL = Objective focal length in meters

For Example, the TV 101 with ST8 would be:

ArcSec = 3600 * ARCTAN ( ( 9 * 10^-6) / .540 )
ArcSec = 3.44

2. If you want to find the dimensions of a projected image (ie, a large
format camera) the formula above works as well. Just pretend that a pixel is
the size of the negative. There is no direct way to state the angular
dimensions of a photographic print unless you know the FL of the objective
lens, size of the negative, AND the magnification used during printing.

3. You can estimate the arcsecond tracking error by visually measuring the
peak to peak pixel deviation of the star trail from an ideal mean trail.
Then multiply this deviation by the arcseconds per pixel resolution of your
CCD camera. I wrote a small Visual C program a while back to calculate it
more precisely directly from the image file. I'd send you a copy, but I
can't seem to find it right now.

4. Yes, doubling the FL roughly halves the arcseconds per pixel unless you
are dealing with very short focal lengths.

Neal

You know,my poblem has always been that I'm an economist and not a mathematician.I can tell you why or why not we'll never make any money at this but I can't figure out arctans...I'm going out to buy a scientific calculator this morning.
I presume the st7 pixels are same as st8 except more numerous in the 8.

Later this week I'll try to scan in my photo of trails so it can be atatched to the e-mail.My new scanner,(memorex) is supposed do handle this but the settings must be off because while it does great photo scans,doesn't seem to want to acknowledge stars.Everything comes out black.

In the meantime,I've got a 30 minute photo of pleades that's right on.Your 2" modulation is extrodinary but if I can get mine down to the point where the st-7(st4) can guide it to rms of less than .5 in each axis I'll be extatic.
ps check out www.aimcontrols.com for their 5arcsec shot.This is done with a $6000.us mount and yours seems pretty close.
My star trails look literally the same on the brighter stars (string of pearls) but my fainter stars have a definite regular wave.

hope for good seeing this week because I'm going up north to "God's country" for a week of shooting.
This is the first time I have confidence in the mount and now I can concentrate on the photography.
Thanks for your help....Jimmy

From: "Neal Barry" <nbarry@...>
Reply-To: Losmandy_users@...
To: <Losmandy_users@...>
Subject: RE: [Losmandy_users] G11 Fix (III)
Date: Tue, 22 Aug 2000 23:00:23 -0700

Jimmy,

1. You can calculate arcseconds per pixel with the following formula:

ArcSec = 3600 * ARCTAN( (PixelWidth * 10^-6) / FL )

Where:
ArcSec = Width of Pixel in Arcseconds
PixelWidth = Width of CCD pixel in microns
FL = Objective focal length in meters

For Example, the TV 101 with ST8 would be:

ArcSec = 3600 * ARCTAN ( ( 9 * 10^-6) / .540 )
ArcSec = 3.44

2. If you want to find the dimensions of a projected image (ie, a large
format camera) the formula above works as well. Just pretend that a pixel is
the size of the negative. There is no direct way to state the angular
dimensions of a photographic print unless you know the FL of the objective
lens, size of the negative, AND the magnification used during printing.

3. You can estimate the arcsecond tracking error by visually measuring the
peak to peak pixel deviation of the star trail from an ideal mean trail.
Then multiply this deviation by the arcseconds per pixel resolution of your
CCD camera. I wrote a small Visual C program a while back to calculate it
more precisely directly from the image file. I'd send you a copy, but I
can't seem to find it right now.

4. Yes, doubling the FL roughly halves the arcseconds per pixel unless you
are dealing with very short focal lengths.

Neal

-----Original Message-----
From: James A. Thibert [mailto:thibertj@...]
Sent: Tuesday, August 22, 2000 7:14 PM
To: Losmandy_users@...
Subject: Re: [Losmandy_users] G11 Fix (III)


Hi Neal,it's looking good.I put a third 1"long bearing in each of
my axies
and it improved nicely but not like yours.
By coincidence,I offset my mount and took a few before and after
startrails.
The after star trailsARE VERY REULAR AND i TOO USED A 101 POINTED
AT THE M31
REGION.I used a 2x big barlow in front of my camera.

My star trails can be described as 2 different appearing trails:
the bright stars look loke a straight linr composed of light balls

(stars

)connecetd together like a string of pearls.
The dimmer stars leave wavy trails but are much thinner of course
than the
bright stars.
How would I measure the arcsec error?

I had tried to calculate my arcsec resolution with a 12.5mm ortho
eyepiece
and on the 60mm scale it took 300 seconds for a star to go end to end.I
calculate dthe that give an st-4 pixel is 13.5 x 16 microns that
on the ra
side,1 pixel at prime focus would be 5.5 arcsecs.The 2x barlow
would halve
that would it not?
If correct,how then do you extrapolate that to a 4 by 6"photo?

I shot 30 minutes at the pleades and have round stars even under
an 8 power
magnifier.

Can you shed any light on this for me?

thanks
Jimmy

From: "Neal Barry" <nbarry@...>
Reply-To: Losmandy_users@...
To: <Losmandy_users@...>
Subject: [Losmandy_users] G11 Fix (III)
Date: Tue, 22 Aug 2000 12:55:59 -0700

Hi all,

Well, I'm reasonably pleased with the improvement that I have

been able to

achieve in my G11's tracking and periodic error. Take a look at
to see the results.

I am curious how the PE shown on the web page above compares to other

G11

mounts out there. I still am not sure if the problems with the mount I
received are typical or a fluke.

I have made the fix permanent since my original post back on 8/13, but

I

did
risk damaging the mount in the process. Specifically, I pressed in a

new

needle bearing with .002" stainless steel shim stock wrapped around the
OUTSIDE of the bearing (I know, I was against it in an earlier

post ;-) I

do
not recommend this! You can easily damage your mount unless you are

VERY

careful. Five things can go wrong.

1. The needles in the bearing can seize.
2. The bearing can easily distort due to the amount of force require to
press it in.
3. The fit can bee too good, and the shaft will bind due to the

relative

misalignment of all three needle bearings.
4. You can permanently knock the RA wheel gear bearing sleeve off axis

or

bend it.
5. You can expand the OD of the RA wheel gear bearing sleeve so that

the

wheel gear will no longer fit.

However, this strategy did cause the ID of the needle bearing to shrink
(exactly the amount needed in my particular case) and I now have a very
nice
on-axis fit with no measurable slop. The OD of the RA wheel gear sleeve
bearing did expand slightly (approx .0002") and I needed to lap

it a bit to

ensure that it would not bind over an appreciable operating temperature
range.

Anyway, now that the RA shaft was not flopping around, I was

finally able

to
see how well the mount would track. Now I had a fairly regular

PE of about

11-12 arc seconds. After lapping the RA worm and wheel gear it dropped

to

under 10 and became even more regular. After training the

SkyWalker II PEC,

it tracks within 2 arc seconds. Not too shabby given where this all
started.

Neal









To unsubscribe from this group, send an email to:
Losmandy_users-unsubscribe@...

________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at




To unsubscribe from this group, send an email to:
Losmandy_users-unsubscribe@...

To unsubscribe from this group, send an email to:
Losmandy_users-unsubscribe@...

________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at

A simpler formula for #1 below is:

Arc-secs per pixel = (pixel width / FL) * 206

You can nearly do this one in your head. Certainly with a simple
calculator.

It provides almost exactly the same results. This is the formula
recommended in several articles including the S&T website (Sky Pub).

Paul Sterngold

--- Neal Barry <nbarry@...> wrote:

Jimmy,

1. You can calculate arcseconds per pixel with the following formula:

ArcSec = 3600 * ARCTAN( (PixelWidth * 10^-6) / FL )

Where:
ArcSec = Width of Pixel in Arcseconds
PixelWidth = Width of CCD pixel in microns
FL = Objective focal length in meters

For Example, the TV 101 with ST8 would be:

ArcSec = 3600 * ARCTAN ( ( 9 * 10^-6) / .540 )
ArcSec = 3.44

2. If you want to find the dimensions of a projected image (ie, a large
format camera) the formula above works as well. Just pretend that a pixel
is
the size of the negative. There is no direct way to state the angular
dimensions of a photographic print unless you know the FL of the
objective
lens, size of the negative, AND the magnification used during printing.

3. You can estimate the arcsecond tracking error by visually measuring
the
peak to peak pixel deviation of the star trail from an ideal mean trail.
Then multiply this deviation by the arcseconds per pixel resolution of
your
CCD camera. I wrote a small Visual C program a while back to calculate it
more precisely directly from the image file. I'd send you a copy, but I
can't seem to find it right now.

4. Yes, doubling the FL roughly halves the arcseconds per pixel unless
you
are dealing with very short focal lengths.

Neal

-----Original Message-----
From: James A. Thibert [mailto:thibertj@...]
Sent: Tuesday, August 22, 2000 7:14 PM
To: Losmandy_users@...
Subject: Re: [Losmandy_users] G11 Fix (III)


Hi Neal,it's looking good.I put a third 1"long bearing in each of
my axies
and it improved nicely but not like yours.
By coincidence,I offset my mount and took a few before and after
startrails.
The after star trailsARE VERY REULAR AND i TOO USED A 101 POINTED
AT THE M31
REGION.I used a 2x big barlow in front of my camera.

My star trails can be described as 2 different appearing trails:
the bright stars look loke a straight linr composed of light balls

(stars

)connecetd together like a string of pearls.
The dimmer stars leave wavy trails but are much thinner of course
than the
bright stars.
How would I measure the arcsec error?

I had tried to calculate my arcsec resolution with a 12.5mm ortho
eyepiece
and on the 60mm scale it took 300 seconds for a star to go end to end.I
calculate dthe that give an st-4 pixel is 13.5 x 16 microns that
on the ra
side,1 pixel at prime focus would be 5.5 arcsecs.The 2x barlow
would halve
that would it not?
If correct,how then do you extrapolate that to a 4 by 6"photo?

I shot 30 minutes at the pleades and have round stars even under
an 8 power
magnifier.

Can you shed any light on this for me?

thanks
Jimmy

From: "Neal Barry" <nbarry@...>
Reply-To: Losmandy_users@...
To: <Losmandy_users@...>
Subject: [Losmandy_users] G11 Fix (III)
Date: Tue, 22 Aug 2000 12:55:59 -0700

Hi all,

Well, I'm reasonably pleased with the improvement that I have

been able to

achieve in my G11's tracking and periodic error. Take a look at
to see the results.

I am curious how the PE shown on the web page above compares to other

G11

mounts out there. I still am not sure if the problems with the mount I
received are typical or a fluke.

I have made the fix permanent since my original post back on 8/13, but

I

did
risk damaging the mount in the process. Specifically, I pressed in a

new

needle bearing with .002" stainless steel shim stock wrapped around

the

OUTSIDE of the bearing (I know, I was against it in an earlier

post ;-) I

do
not recommend this! You can easily damage your mount unless you are

VERY

careful. Five things can go wrong.

1. The needles in the bearing can seize.
2. The bearing can easily distort due to the amount of force require

to

press it in.
3. The fit can bee too good, and the shaft will bind due to the

relative

misalignment of all three needle bearings.
4. You can permanently knock the RA wheel gear bearing sleeve off axis

or

bend it.
5. You can expand the OD of the RA wheel gear bearing sleeve so that

the

wheel gear will no longer fit.

However, this strategy did cause the ID of the needle bearing to

shrink

(exactly the amount needed in my particular case) and I now have a

very

nice
on-axis fit with no measurable slop. The OD of the RA wheel gear

sleeve

bearing did expand slightly (approx .0002") and I needed to lap

it a bit to

ensure that it would not bind over an appreciable operating

temperature

range.

Anyway, now that the RA shaft was not flopping around, I was

finally able

to
see how well the mount would track. Now I had a fairly regular

PE of about

11-12 arc seconds. After lapping the RA worm and wheel gear it dropped

to

under 10 and became even more regular. After training the

SkyWalker II PEC,

it tracks within 2 arc seconds. Not too shabby given where this all
started.

Neal









To unsubscribe from this group, send an email to:
Losmandy_users-unsubscribe@...

________________________________________________________________________

Get Your Private, Free E-mail from MSN Hotmail at

To unsubscribe from this group, send an email to:
Losmandy_users-unsubscribe@...

__________________________________________________
Do You Yahoo!?
Yahoo! Mail - Free email you can access from anywhere!

Hi Paul...I've got that one but what I'm trying to do is extrapolate that to the 4x6"photo print of my star trails.
If I had used the st-4 or st7e I know this would be a lot easier than photo analysis.

jimmy

From: Paul Sterngold <psterngold@...>
Reply-To: Losmandy_users@...
To: Losmandy_users@...
Subject: RE: [Losmandy_users] G11 Fix (III)
Date: Wed, 23 Aug 2000 06:50:25 -0700 (PDT)

A simpler formula for #1 below is:

Arc-secs per pixel = (pixel width / FL) * 206

You can nearly do this one in your head. Certainly with a simple
calculator.

It provides almost exactly the same results. This is the formula
recommended in several articles including the S&T website (Sky Pub).

Paul Sterngold

--- Neal Barry <nbarry@...> wrote:

Jimmy,

1. You can calculate arcseconds per pixel with the following formula:

ArcSec = 3600 * ARCTAN( (PixelWidth * 10^-6) / FL )

Where:
ArcSec = Width of Pixel in Arcseconds
PixelWidth = Width of CCD pixel in microns
FL = Objective focal length in meters

For Example, the TV 101 with ST8 would be:

ArcSec = 3600 * ARCTAN ( ( 9 * 10^-6) / .540 )
ArcSec = 3.44

2. If you want to find the dimensions of a projected image (ie, a large
format camera) the formula above works as well. Just pretend that a

pixel

is
the size of the negative. There is no direct way to state the angular
dimensions of a photographic print unless you know the FL of the
objective
lens, size of the negative, AND the magnification used during printing.

3. You can estimate the arcsecond tracking error by visually measuring
the
peak to peak pixel deviation of the star trail from an ideal mean trail.
Then multiply this deviation by the arcseconds per pixel resolution of
your
CCD camera. I wrote a small Visual C program a while back to calculate

it

more precisely directly from the image file. I'd send you a copy, but I
can't seem to find it right now.

4. Yes, doubling the FL roughly halves the arcseconds per pixel unless
you
are dealing with very short focal lengths.

Neal

-----Original Message-----
From: James A. Thibert [mailto:thibertj@...]
Sent: Tuesday, August 22, 2000 7:14 PM
To: Losmandy_users@...
Subject: Re: [Losmandy_users] G11 Fix (III)


Hi Neal,it's looking good.I put a third 1"long bearing in each of
my axies
and it improved nicely but not like yours.
By coincidence,I offset my mount and took a few before and after
startrails.
The after star trailsARE VERY REULAR AND i TOO USED A 101 POINTED
AT THE M31
REGION.I used a 2x big barlow in front of my camera.

My star trails can be described as 2 different appearing trails:
the bright stars look loke a straight linr composed of light balls

(stars

)connecetd together like a string of pearls.
The dimmer stars leave wavy trails but are much thinner of course
than the
bright stars.
How would I measure the arcsec error?

I had tried to calculate my arcsec resolution with a 12.5mm ortho
eyepiece
and on the 60mm scale it took 300 seconds for a star to go end to

end.I

calculate dthe that give an st-4 pixel is 13.5 x 16 microns that
on the ra
side,1 pixel at prime focus would be 5.5 arcsecs.The 2x barlow
would halve
that would it not?
If correct,how then do you extrapolate that to a 4 by 6"photo?

I shot 30 minutes at the pleades and have round stars even under
an 8 power
magnifier.

Can you shed any light on this for me?

thanks
Jimmy

From: "Neal Barry" <nbarry@...>
Reply-To: Losmandy_users@...
To: <Losmandy_users@...>
Subject: [Losmandy_users] G11 Fix (III)
Date: Tue, 22 Aug 2000 12:55:59 -0700

Hi all,

Well, I'm reasonably pleased with the improvement that I have

been able to

achieve in my G11's tracking and periodic error. Take a look at
to see the

results.

I am curious how the PE shown on the web page above compares to other

G11

mounts out there. I still am not sure if the problems with the mount

I

received are typical or a fluke.

I have made the fix permanent since my original post back on 8/13,

but

I

did
risk damaging the mount in the process. Specifically, I pressed in a

new

needle bearing with .002" stainless steel shim stock wrapped around

the

OUTSIDE of the bearing (I know, I was against it in an earlier

post ;-) I

do
not recommend this! You can easily damage your mount unless you are

VERY

careful. Five things can go wrong.

1. The needles in the bearing can seize.
2. The bearing can easily distort due to the amount of force require

to

press it in.
3. The fit can bee too good, and the shaft will bind due to the

relative

misalignment of all three needle bearings.
4. You can permanently knock the RA wheel gear bearing sleeve off

axis

or

bend it.
5. You can expand the OD of the RA wheel gear bearing sleeve so that

the

wheel gear will no longer fit.

However, this strategy did cause the ID of the needle bearing to

shrink

(exactly the amount needed in my particular case) and I now have a

very

nice
on-axis fit with no measurable slop. The OD of the RA wheel gear

sleeve

bearing did expand slightly (approx .0002") and I needed to lap

it a bit to

ensure that it would not bind over an appreciable operating

temperature

range.

Anyway, now that the RA shaft was not flopping around, I was

finally able

to
see how well the mount would track. Now I had a fairly regular

PE of about

11-12 arc seconds. After lapping the RA worm and wheel gear it

dropped

to

under 10 and became even more regular. After training the

SkyWalker II PEC,

it tracks within 2 arc seconds. Not too shabby given where this all
started.

Neal









To unsubscribe from this group, send an email to:
Losmandy_users-unsubscribe@...

________________________________________________________________________

Get Your Private, Free E-mail from MSN Hotmail at

To unsubscribe from this group, send an email to:
Losmandy_users-unsubscribe@...

__________________________________________________
Do You Yahoo!?
Yahoo! Mail - Free email you can access from anywhere!




To unsubscribe from this group, send an email to:
Losmandy_users-unsubscribe@...

________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at