Andre,

We have identified the problem and have a solution. Keypads with serial numbers below GTO1490 have smaller memory chips. The code associated with v4.15 interfered with the RTC on these older keypads due to space constraints. Charles has just fixed the code and we plan to have v4.16 uploaded to the website early next week after some additional testing. Thank you for bringing this to our attention.


Marj Christen
Astro-Physics, Inc
11250 Forest Hills Road
Machesney Park, IL 61115
Phone: 815-282-1513
Fax: 815-282-9847
www.astro-physics.com
Please include this e-mail with your response.

Thanks for the response, Roland.

As I said, so far it's not an issue at the focal lengths at which I
image, but it is very curious.

It's certainly possible that I am not aligned well enough, but with
PemPro, I am about 0.5 arcmin within polar align - I think, and there
is very little, if any dec drift evident on the real time graphs of
the guiding software.

Believe me, I have no desire to be constantly chasing slight
anomalies due to tube flexure, or any other reason.

Very curious, but your explanation is very informative.

Hunter

--- In ap-gto@..., chris1011@... wrote:

In a message dated 7/2/2008 11:10:52 AM Central Daylight Time,
hewholooks@... writes:

I seem to remember reading that sidereal rate, as applied by the

RA

motor in an AP mount (or any mount, for that matter) is only 100%
accurate at one declination in the sky. Further north or south

from

there, and the RA axis either moves slightly slower or slightly
faster than the earth's rotation.

I also seem to remember reading somewhere that some guiding

software

will automatically compensate for this, and if so, I would like

to

know how effective it is, and does anyone use it.

The reason I ask, is that since I have been using my Mach1, which

is,

as I have said before, much better quality than my last mount, I

have

noticed that when I am imaging in the extreme north that the
autoguiding software seems to make RA corrections only in one
direction (I think it was west), and does this relatively
frequently. I can then move more towards the equator, and I can
guide for many minutes without an RA correction.

Is it possible that I am actually seeing this, or is it some

illusion

that I am being fooled by. My stars are round, even up north, so
it's not a big deal, but it seems to me that if the guiding

software

or the AP driver simply would run the RA motor a little faster or
slower depending on the declination, guiding would be much

smoother.

Thanks for indulging me,

Well first, the rate of motion of the mount is constant. It moves

the same

with respect to the earth's rotation regardless of what declination

that you are

pointing to. It is the stars that are moving at a variable rate

depending on

their altitude. One can compensate somewhat for this by offsetting

the polar

alignment of the mount to the refracted pole, but it's only an

approximation.

Chances are that most of the motion you see is due to poor polar

alignment on

your part, however since you are getting round stars, there really

is not

much you need to do to make the situation better. Only in the case

of a

permanently mounted system would I advocate using fancy software

programs to model the

exact sidereal rate of every point in the sky. The reason is that

in a

portable setup, your slight polar misalignments will totally swamp

the actual

differential refraction motion of a star at the different

declinations. You will be

constantly chasing your tail trying to model a complex assortment

of motions

due to misalignments, refraction, tube flexures, etc.

Rolando


**************
Gas prices getting you down? Search AOL Autos for
fuel-efficient used cars.
(http://autos.aol.com/used?ncid=aolaut00050000000007)


[Non-text portions of this message have been removed]

I just lean the housing on it's side and swipe it with a rag. There
are a few scratches on the surface, but nothing big that would effect
the level.

Bryan

--- In ap-gto@..., "werner.pribil" <werner.pribil@...>
wrote:

Hello Bryan !

Thanks for your answer !

I want to know how I can clean the (white) underside of the

polar

axis assembly when I need two hands for lifing the R.A.

housing ?

Do you lay down your R.A. housing to wipe the surface with a rag or
how do you it ?

Dou you have also little scratches at the both surfaces ?

Werner




--- In ap-gto@..., "Bryan Henry" <behenry10@> wrote:

I suspect the need for a relatively clean surface is to avoid any
particles that would cause a small tilt to the polar axis

assembly.

I

just wipe both surfaces prior to mounting them with a rag to make
sure they are free of particles. Since I use a pier and rely on

the

polar alignment achieved a few months back, the clean surface

ensures

a relatively accurate return to that alignment.

Bryan

--- In ap-gto@..., "werner.pribil" <werner.pribil@>
wrote:

In the manual of the AP 1200 you can read on p.11 "Ensure both

pier

top and polar axis assembly mating surfaces are clean and free

of

dirt" before you place the polar axis assembly onto the pier

top.

I want to know how I can clean the (white) underside of the

polar

axis assembly when I need two hands for lifing the R.A.

housing ?

Do you always clean the white mating surface of the polar axis
assembly before you place the polar axis on the pier adapter

and

if

yes - how ?

I have a new mount and I have assembled the R.A. housing only

one

time onto the standart pier adapter (without special cleaning)

and

now I can see one little scratch in the black surface of the

standart

pier adapter and three little scratches in the white surface of

the

R.A. housing ! I did´not think that this will happen, because I

keep

the mount and the adapter in my home.

I think that this scratches are not critical, because they will

not

influence the function of the mount.

Please tell me your experiences.

Hello Andre,



This issue has now come up with 4 keypads that I am aware of. We are
still trying to find a common denominator. Version 4.15 has worked
perfectly in many keypads now, and all the new keypads that we are
shipping have this firmware installed. Many older keypads have also
been successfully upgraded with v.4.15 without the clock dying. Yet,
for these 4 units, v.4.15 kills the clock, and restoring v.4.12 brings
it back to life. Since v.4.12 restores the clock function, the clock
itself has to be OK and one would blame the firmware. Yet, v.4.15 does
not normally cause a clock to fail. Why has it happened with these 4
keypads, and only these 4 keypads? So far, the only common
denominator is that the 4 affected keypads are all older units, but
other keypads of the same vintage have not had the problem.



Can you please contact me directly, off group, to discuss this (info
below)? I will need some additional information that we don't need to
bother the group members with. I did feel that the group should get an
explanation of the problem so that they are "forewarned" of the
possibility.



If anyone else has had this issue, please contact me (also off group,
please) so that I can build my knowledge database and hopefully find a
solution.



Mag. 7 skies!



Howard Hedlund

howard@...

Astro-Physics, Inc.

815-282-1513

________________________________

From: ap-gto@... [mailto:ap-gto@...] On Behalf
Of nightowl662003
Sent: Wednesday, July 02, 2008 9:10 AM
To: ap-gto@...
Subject: [ap-gto] Re: Keypad update and real time clock.



Hello,

sorry to bring this up again, but I seem to have the same problem.

I have upgraded from v4.12 to v4.15 and the RTC (when entering the
Time/LST menu)is just frozen at the time it's been set upon
initialization. I've tried re-installing v4.15 several times to no
avail.

Also I don't think there's a problem with the battery because after
downgrading to v4.12 the clock is working perfect.
Is there a fix other than the one Howard decribes below to make the
RTC working and have the full functionality of v4.15? Did I miss
anything?

thanks for your help,

Andre

--- In ap-gto@... <mailto:ap-gto%40yahoogroups.com> ,
"bill_lombardo_bill"
<bill_lombardo@...> wrote:

First class support and answer, Mr. Howard,
the keypad beeps when I set time (obviously after I press GOTO)and
the time stays as settled (no random garbage of digits).
In the next few days I'll try a "time-blind" alignment and

tracking,

as you kindly suggested, and a reinstallment of the 4.15 firmware
(freshly charged). I'll keep you informed about everything even if,
as a last resource, I'm prepared to let you have my keypad through
the gentle UNITRON: your mount is a jewel and I desire it in full
performance as a Rolex watch deserves.
Thanks indeed for the time beeing, Mr. Howard.
--- In ap-gto@... <mailto:ap-gto%40yahoogroups.com> ,

"Howard" <howard@> wrote:

Hello Mr. Mella



It may be that your Real Time Clock's (RTC) built in battery has

died.

Your keypad is now over eight years old. However, to date, we

have

had so few RTC problems, that we really aren't sure what to

expect

when

one does go bad. One question: when entering the time in the

setup

menu, does your keypad give you a "beep" when you press GOTO to

save the

new time setting? (I hope that you are pressing GOTO and not

MENU!)

Also, does the keypad remember the time that you set, even though

it no

longer advances, or does the keypad just display random garbage

for

the

time and date?



I do not believe that the keypad firmware update has anything to

do

with

the RTC failure, but you are certainly welcome to try re-loading

the

firmware. If you do this, I would delete your current v.4.15

loader

from your computer and download a new copy from the internet,

just

in

case a bit or two was lost in cyberspace on your original

download

from

the internet. It won't do any good to re-load something that is
already corrupted!



Some of the keypads produced over the years have RTC's that are

held in

place by a soldered retaining bar. Others are simply held in

place by

a clip on either side. If your keypad has the version with the

clips,

it will be relatively easy to change the RTC. If it has the

soldered

retaining bar, you may wish to send it in for service (through

Unitron,

of course).



I am currently researching the RTC issue with our manufacturer

for

you

and one other customer. Please contact me directly for more
information.



In the mean time, you can use the mount, but you will want to do

the

following, since the keypad can no longer keep time. I am

assuming

that the keypad's time will remain as you set it and simply won't
advance. In other words, the time value won't corrupt into

nonsense;

it just won't go forward after it is set. If the time and date

turn to

garbage, you will need to initialize the mount via a computer -

see

below.

1. When you start out, power up the mount just long enough to set
the correct time and date in the setup menu. You may want to

set

it a

minute or so fast, since it will no longer advance the time, and

you

need a minute or so for the next step. You must be in auto-

connect =

NO to proceed. If you need to change the auto-connect setting,

do

that

now also.
2. Power down the mount, wait a few seconds and then power it

back

up again. As long as the time hasn't corrupted in the short

time

since

you set it, the keypad will now send the correct starting time

and

date

to the GTOCPx control box.
3. Go through your normal start up routine: enter your location

#,

and then either polar align or do a star sync. You should

probably not

use resume from park or resume from reference park.
4. Once you are at the main menu, press 4=Time/LST
5. The time and date that you entered in step one should be
showing. This step is just to verify that garbage time was NOT

sent to

the GTOCPx control box.
6. The GTOCPx control box will now be keeping its own time. It
only needs the initial time and date from the keypad. After

that,

the

GTOCPx will perform all of its own calculations based on its own
internal oscillator. It will perform goto's as it should, and

will

know when to flip sides. The GTOCPx will know the correct LST,

even

though the keypad will not. You can verify that time is being

kept in

the control box by using the 3=Get Time/Loc FrMnt command in the
keypad's 2=Setup -> 1=Locations and Time -> 2=Set Date and Time

menu.

7. Keep in mind as you observe, that the Keypad's LST or "Z"

value

will be wrong. This could be confusing since the Keypad

displays

the Z

value every time you choose a star as your observing target.
8. Do not use a park position at the end of your session. The
keypad sends calculated RA and Dec coordinates to the mount for a

park,

and it will not calculate these correctly without the correct

time.

You could send the scope into the pier.



Another possibility is to initialize the mount with a computer

program

like PulseGuide. You can still use the keypad for all of your

GoTo's,

you simply will not use it to establish time and location or to

park the

mount. Good luck, and let me know if I can be of further help.



howard@



Mag. 7 skies!



Howard Hedlund

Astro-Physics, Inc.

815-282-1513

________________________________

From: ap-gto@... <mailto:ap-gto%40yahoogroups.com>

[mailto:ap-gto@... <mailto:ap-gto%40yahoogroups.com> ] On

Behalf

Of bill_lombardo_bill
Sent: Saturday, April 12, 2008 11:54 AM
To: ap-gto@... <mailto:ap-gto%40yahoogroups.com>
Subject: [ap-gto] Keypad update and real time clock.



Help me to understand.
After upgrading the keypad to firmware 4.15 and after favourably
checking Status "All system go", in a mount 400GTO purchased in

October

2000, the Time, Date,GMT,LST and Photo Timer no more update and

no

more

advance as before (red lights blink but do not change digits in
Time/LST).
Could it be Real Time Clock Battery exhausted or could it be for

some

other reason I can't understand?
Do you think I can still make use of the mount or I have to

change

RTC

chip?

In a message dated 7/2/2008 3:18:07 PM Central Daylight Time,
hewholooks@... writes:

It's certainly possible that I am not aligned well enough, but with
PemPro, I am about 0.5 arcmin within polar align - I think, and there
is very little, if any dec drift evident on the real time graphs of
the guiding software

Dec drift is governed by the azimuth position. RA drift is governed by the
altitude. Theoretically you should offset the pole position to the refracted
pole for lowest RA drift.

Everyone always first assumes that the mount is drifting, but it's not the
mount drifting or not tracking correctly. It's the sky that is drifting due to
refraction. Also many times this is compounded by tube flexure and mirror
shifting, something very common in SCTs.

Rolando

Rolando


**************
Get the scoop on last night's hottest shows and the live
music scene in your area - Check out TourTracker.com!

(www.tourtracker.com ?NCID=aolmus00050000000112)

Hello Bryan !

Thanks for your answer !

I want to know how I can clean the (white) underside of the polar
axis assembly when I need two hands for lifing the R.A. housing ?

Do you lay down your R.A. housing to wipe the surface with a rag or
how do you it ?

Dou you have also little scratches at the both surfaces ?

Werner




--- In ap-gto@..., "Bryan Henry" <behenry10@...> wrote:

I suspect the need for a relatively clean surface is to avoid any
particles that would cause a small tilt to the polar axis assembly.

I

just wipe both surfaces prior to mounting them with a rag to make
sure they are free of particles. Since I use a pier and rely on the
polar alignment achieved a few months back, the clean surface

ensures

a relatively accurate return to that alignment.

Bryan

--- In ap-gto@..., "werner.pribil" <werner.pribil@>
wrote:

In the manual of the AP 1200 you can read on p.11 "Ensure both

pier

top and polar axis assembly mating surfaces are clean and free of
dirt" before you place the polar axis assembly onto the pier top.

I want to know how I can clean the (white) underside of the polar
axis assembly when I need two hands for lifing the R.A. housing ?
Do you always clean the white mating surface of the polar axis
assembly before you place the polar axis on the pier adapter and

if

yes - how ?

I have a new mount and I have assembled the R.A. housing only one
time onto the standart pier adapter (without special cleaning)

and

now I can see one little scratch in the black surface of the

standart

pier adapter and three little scratches in the white surface of

the

R.A. housing ! I did´not think that this will happen, because I

keep

the mount and the adapter in my home.

I think that this scratches are not critical, because they will

not

influence the function of the mount.

Please tell me your experiences.

I am sorry that I cannot find the reference that I would like to
discuss, but maybe some of you can remember it.

I seem to remember reading that sidereal rate, as applied by the RA
motor in an AP mount (or any mount, for that matter) is only 100%
accurate at one declination in the sky. Further north or south from
there, and the RA axis either moves slightly slower or slightly
faster than the earth's rotation.

I also seem to remember reading somewhere that some guiding software
will automatically compensate for this, and if so, I would like to
know how effective it is, and does anyone use it.

The reason I ask, is that since I have been using my Mach1, which is,
as I have said before, much better quality than my last mount, I have
noticed that when I am imaging in the extreme north that the
autoguiding software seems to make RA corrections only in one
direction (I think it was west), and does this relatively
frequently. I can then move more towards the equator, and I can
guide for many minutes without an RA correction.

Is it possible that I am actually seeing this, or is it some illusion
that I am being fooled by. My stars are round, even up north, so
it's not a big deal, but it seems to me that if the guiding software
or the AP driver simply would run the RA motor a little faster or
slower depending on the declination, guiding would be much smoother.

Thanks for indulging me,

Hunter

I suspect the need for a relatively clean surface is to avoid any
particles that would cause a small tilt to the polar axis assembly. I
just wipe both surfaces prior to mounting them with a rag to make
sure they are free of particles. Since I use a pier and rely on the
polar alignment achieved a few months back, the clean surface ensures
a relatively accurate return to that alignment.

Bryan

--- In ap-gto@..., "werner.pribil" <werner.pribil@...>
wrote:

In the manual of the AP 1200 you can read on p.11 "Ensure both pier
top and polar axis assembly mating surfaces are clean and free of
dirt" before you place the polar axis assembly onto the pier top.

I want to know how I can clean the (white) underside of the polar
axis assembly when I need two hands for lifing the R.A. housing ?
Do you always clean the white mating surface of the polar axis
assembly before you place the polar axis on the pier adapter and if
yes - how ?

I have a new mount and I have assembled the R.A. housing only one
time onto the standart pier adapter (without special cleaning) and
now I can see one little scratch in the black surface of the

standart

pier adapter and three little scratches in the white surface of the
R.A. housing ! I did´not think that this will happen, because I

keep

the mount and the adapter in my home.

I think that this scratches are not critical, because they will not
influence the function of the mount.

Please tell me your experiences.

In the manual of the AP 1200 you can read on p.11 "Ensure both pier
top and polar axis assembly mating surfaces are clean and free of
dirt" before you place the polar axis assembly onto the pier top.

I want to know how I can clean the (white) underside of the polar
axis assembly when I need two hands for lifing the R.A. housing ?
Do you always clean the white mating surface of the polar axis
assembly before you place the polar axis on the pier adapter and if
yes - how ?

I have a new mount and I have assembled the R.A. housing only one
time onto the standart pier adapter (without special cleaning) and
now I can see one little scratch in the black surface of the standart
pier adapter and three little scratches in the white surface of the
R.A. housing ! I did´not think that this will happen, because I keep
the mount and the adapter in my home.

I think that this scratches are not critical, because they will not
influence the function of the mount.

Please tell me your experiences.

Hello,

sorry to bring this up again, but I seem to have the same problem.

I have upgraded from v4.12 to v4.15 and the RTC (when entering the
Time/LST menu)is just frozen at the time it's been set upon
initialization. I've tried re-installing v4.15 several times to no
avail.

Also I don't think there's a problem with the battery because after
downgrading to v4.12 the clock is working perfect.
Is there a fix other than the one Howard decribes below to make the
RTC working and have the full functionality of v4.15? Did I miss
anything?

thanks for your help,

Andre


--- In ap-gto@..., "bill_lombardo_bill"
<bill_lombardo@...> wrote:

First class support and answer, Mr. Howard,
the keypad beeps when I set time (obviously after I press GOTO)and
the time stays as settled (no random garbage of digits).
In the next few days I'll try a "time-blind" alignment and

tracking,

as you kindly suggested, and a reinstallment of the 4.15 firmware
(freshly charged). I'll keep you informed about everything even if,
as a last resource, I'm prepared to let you have my keypad through
the gentle UNITRON: your mount is a jewel and I desire it in full
performance as a Rolex watch deserves.
Thanks indeed for the time beeing, Mr. Howard.
--- In ap-gto@..., "Howard" <howard@> wrote:

Hello Mr. Mella



It may be that your Real Time Clock's (RTC) built in battery has

died.

Your keypad is now over eight years old. However, to date, we

have

had so few RTC problems, that we really aren't sure what to

expect

when

one does go bad. One question: when entering the time in the

setup

menu, does your keypad give you a "beep" when you press GOTO to

save the

new time setting? (I hope that you are pressing GOTO and not

MENU!)

Also, does the keypad remember the time that you set, even though

it no

longer advances, or does the keypad just display random garbage

for

the

time and date?



I do not believe that the keypad firmware update has anything to

do

with

the RTC failure, but you are certainly welcome to try re-loading

the

firmware. If you do this, I would delete your current v.4.15

loader

from your computer and download a new copy from the internet,

just

in

case a bit or two was lost in cyberspace on your original

download

from

the internet. It won't do any good to re-load something that is
already corrupted!



Some of the keypads produced over the years have RTC's that are

held in

place by a soldered retaining bar. Others are simply held in

place by

a clip on either side. If your keypad has the version with the

clips,

it will be relatively easy to change the RTC. If it has the

soldered

retaining bar, you may wish to send it in for service (through

Unitron,

of course).



I am currently researching the RTC issue with our manufacturer

for

you

and one other customer. Please contact me directly for more
information.



In the mean time, you can use the mount, but you will want to do

the

following, since the keypad can no longer keep time. I am

assuming

that the keypad's time will remain as you set it and simply won't
advance. In other words, the time value won't corrupt into

nonsense;

it just won't go forward after it is set. If the time and date

turn to

garbage, you will need to initialize the mount via a computer -

see

below.

1. When you start out, power up the mount just long enough to set
the correct time and date in the setup menu. You may want to

set

it a

minute or so fast, since it will no longer advance the time, and

you

need a minute or so for the next step. You must be in auto-

connect =

NO to proceed. If you need to change the auto-connect setting,

do

that

now also.
2. Power down the mount, wait a few seconds and then power it

back

up again. As long as the time hasn't corrupted in the short

time

since

you set it, the keypad will now send the correct starting time

and

date

to the GTOCPx control box.
3. Go through your normal start up routine: enter your location

#,

and then either polar align or do a star sync. You should

probably not

use resume from park or resume from reference park.
4. Once you are at the main menu, press 4=Time/LST
5. The time and date that you entered in step one should be
showing. This step is just to verify that garbage time was NOT

sent to

the GTOCPx control box.
6. The GTOCPx control box will now be keeping its own time. It
only needs the initial time and date from the keypad. After

that,

the

GTOCPx will perform all of its own calculations based on its own
internal oscillator. It will perform goto's as it should, and

will

know when to flip sides. The GTOCPx will know the correct LST,

even

though the keypad will not. You can verify that time is being

kept in

the control box by using the 3=Get Time/Loc FrMnt command in the
keypad's 2=Setup -> 1=Locations and Time -> 2=Set Date and Time

menu.

7. Keep in mind as you observe, that the Keypad's LST or "Z"

value

will be wrong. This could be confusing since the Keypad

displays

the Z

value every time you choose a star as your observing target.
8. Do not use a park position at the end of your session. The
keypad sends calculated RA and Dec coordinates to the mount for a

park,

and it will not calculate these correctly without the correct

time.

You could send the scope into the pier.



Another possibility is to initialize the mount with a computer

program

like PulseGuide. You can still use the keypad for all of your

GoTo's,

you simply will not use it to establish time and location or to

park the

mount. Good luck, and let me know if I can be of further help.



howard@



Mag. 7 skies!



Howard Hedlund

Astro-Physics, Inc.

815-282-1513

________________________________

From: ap-gto@... [mailto:ap-gto@...] On

Behalf

Of bill_lombardo_bill
Sent: Saturday, April 12, 2008 11:54 AM
To: ap-gto@...
Subject: [ap-gto] Keypad update and real time clock.



Help me to understand.
After upgrading the keypad to firmware 4.15 and after favourably
checking Status "All system go", in a mount 400GTO purchased in

October

2000, the Time, Date,GMT,LST and Photo Timer no more update and

no

more

advance as before (red lights blink but do not change digits in
Time/LST).
Could it be Real Time Clock Battery exhausted or could it be for

some

other reason I can't understand?
Do you think I can still make use of the mount or I have to

change

RTC

chip?





[Non-text portions of this message have been removed]

In a message dated 7/2/2008 9:10:22 AM Central Daylight Time, andre66@...
writes:

sorry to bring this up again, but I seem to have the same problem.

I have upgraded from v4.12 to v4.15 and the RTC (when entering the
Time/LST menu)is just frozen at the time it's been set upon
initialization. I've tried re-installing v4.15 several times to no
avail.

Howard is looking into this and he will get back to you with an answer.

Rolando


**************
Gas prices getting you down? Search AOL Autos for
fuel-efficient used cars.
(http://autos.aol.com/used?ncid=aolaut00050000000007)

Dear friends,

I had the opportunity last week to pursue an additional two exoplanet transits. To be more
specific, the first catch was TrES-2b in Draco whose orbit is almost certain to be decaying
given the shortening of the transit duration from the initial 90 minutes at discovery to the
current 76-80 minutes and which is quite visible in my light curve as well.

The second catch involves HD189733b in Vulpecula. This exoplanet is less than 0.30
degrees from the beautiful planetary nebula M27 and I recall reading a recent article
surrounding the suggestion that water may be present on this exoplanet!

For further details, I kindly direct you to:

(1) http://www.perseus.gr/Astro-Photometry-TrES-2-20080626.htm
(2) http://www.perseus.gr/Astro-Photometry-HD189733-20080627.htm

July promises to be a very busy month and there will be lots of material becoming
available to share with everyone.

Clear skies!

Anthony.

In a message dated 7/2/2008 11:10:52 AM Central Daylight Time,
hewholooks@... writes:

I seem to remember reading that sidereal rate, as applied by the RA
motor in an AP mount (or any mount, for that matter) is only 100%
accurate at one declination in the sky. Further north or south from
there, and the RA axis either moves slightly slower or slightly
faster than the earth's rotation.

I also seem to remember reading somewhere that some guiding software
will automatically compensate for this, and if so, I would like to
know how effective it is, and does anyone use it.

The reason I ask, is that since I have been using my Mach1, which is,
as I have said before, much better quality than my last mount, I have
noticed that when I am imaging in the extreme north that the
autoguiding software seems to make RA corrections only in one
direction (I think it was west), and does this relatively
frequently. I can then move more towards the equator, and I can
guide for many minutes without an RA correction.

Is it possible that I am actually seeing this, or is it some illusion
that I am being fooled by. My stars are round, even up north, so
it's not a big deal, but it seems to me that if the guiding software
or the AP driver simply would run the RA motor a little faster or
slower depending on the declination, guiding would be much smoother.

Thanks for indulging me,

Well first, the rate of motion of the mount is constant. It moves the same
with respect to the earth's rotation regardless of what declination that you are
pointing to. It is the stars that are moving at a variable rate depending on
their altitude. One can compensate somewhat for this by offsetting the polar
alignment of the mount to the refracted pole, but it's only an approximation.

Chances are that most of the motion you see is due to poor polar alignment on
your part, however since you are getting round stars, there really is not
much you need to do to make the situation better. Only in the case of a
permanently mounted system would I advocate using fancy software programs to model the
exact sidereal rate of every point in the sky. The reason is that in a
portable setup, your slight polar misalignments will totally swamp the actual
differential refraction motion of a star at the different declinations. You will be
constantly chasing your tail trying to model a complex assortment of motions
due to misalignments, refraction, tube flexures, etc.

Rolando


**************
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In a message dated 7/1/2008 7:09:21 PM Central Daylight Time,
twade35@... writes:

The link you provided helped immensely. I believe I had both
problems. Turning the worm gear was not as easy as it should have been
so I backed off on the pressure to the worm wheel. It now turns
easily, but not so easily to create "backlash". Next, the spur gear
was slightly loose on the worm shaft so I made sure the set screw was
flush with the flat part of the worm shaft, and I tightened it. The
set screw is tight and the spur gear turns easily.

This will make all the difference in the world, you will see. The Dec
reversal action should now be smooth and accurate and your guiding should be accurate
also.

Rolando


**************
Gas prices getting you down? Search AOL Autos for
fuel-efficient used cars.
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Rolando,

What do you mean by "worms are in full mesh"? I'm just making sure I
did everything correctly and did not misinterpret any steps.

Thanks,

Wade

Joe, et al,

The link you provided helped immensely. I believe I had both
problems. Turning the worm gear was not as easy as it should have been
so I backed off on the pressure to the worm wheel. It now turns
easily, but not so easily to create "backlash". Next, the spur gear
was slightly loose on the worm shaft so I made sure the set screw was
flush with the flat part of the worm shaft, and I tightened it. The
set screw is tight and the spur gear turns easily. Hopefully, I'll
have a clear enough sky tomorrow night to run some tests.

Thanks for all your help,

Wade

Hi Jeff,

The dialog is not finished yet so there will be changes, most importantly
the list of horizon points is hidden, to which is what the add/delete apply.

The colors were chosen to look readable behind red plexiglass, which is what
I keep by the side of my desk.

-Ray

Ray --

A couple of suggestions (none of them major):

I found the box to the lower left a bit confusing. I believe it shows a particular set of coordinates, and then several operations that can be performed on that set (GoTo, Add Point, Delete Point). But the layout almost makes it look like Add Point goes with Azimuth and Delete Point goes with Altitude (particularly as the Move +/- minus buttons *do* indeed go with each).

I'm used to seeing horizon limits shaded in green. (I'm not sure, though, if that's a common standard or if it's just the apps I use.)

Since I can save/load horizon sets, it'd be nice to show the filename of the one I'm currently looking at (perhaps with a "(modified)" after it if changes have been made.

Cheers,
-- Jeff.

Wade, although these links are for the "AP1200" gearboxes I'm hoping they are similar enough to your AP900 to give you an idea of your gearbox layout. I stress again, these documents are for the AP1200, not your AP900.

Be sure you work in a clean environment, dust and dirt will stick to lubrication easily. If this happens you 'will' hear the dust or dirt when you drive the motor.

You have to 'remove' the s/s shoulder bolt screw in the center of the large aluminum gear then remove the gear itself. The gear revealed below the large aluminum gear is the one which needs to have its set screw tightened. The flat spot on the shaft is easily seen. DO NOT OVER TIGHTEN this very small set screw or you could strip the threads and be in a worse condition.

DEC http://www.astroccd.freeserve.co.uk/AP1200/DecGear.htm
RA http://www.astroccd.freeserve.co.uk/AP1200/RaGears.htm

Thkx to Davie Rowe for his simple but effective "AP1200" documents...joe :)


"May You Go Among The Imperishable Stars"
Joe Mize www.cav-sfo.com
Chiefland Astronomy Village, Fla.

Hi Wade



Call me at Astro-Physics, and I will happily guide you through this.
The Allen wrench that you need will be either a 5/64 or a 1/16 depending
on the age of the mount. Both wrenches are included in the set that
came with the mount.



Mag. 7 skies!



Howard Hedlund

Astro-Physics, Inc.

815-282-1513

________________________________

From: ap-gto@... [mailto:ap-gto@...] On Behalf
Of chris1011@...
Sent: Monday, June 30, 2008 11:51 PM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Strange Declination Backlash Problem?



In a message dated 6/30/2008 11:48:44 PM Central Daylight Time,
twade35@... <mailto:twade35%40yahoo.com> writes:

I removed the six screws on the plate of the Declination gear box.
When looking inside, I first see a large gray gear, then a medium
sized white gear, and then a small gear with a set screw.

That is NOT the gear that is attached to the worm shaft. That is the
gear
that is attached to the motor shaft, and that must be left alone. Look
for the
gear that is the final drive gear, the one attached to the worm shaft.

Roland

**************
Gas prices getting you down? Search AOL Autos for
fuel-efficient used cars.
(http://autos.aol.com/used?ncid=aolaut00050000000007
<http://autos.aol.com/used?ncid=aolaut00050000000007> )