AP 900 problem


nitemike1 <nitemike1@...>
 

I am new to the group. I have an AP 900 mount (V 4.12) that I bought
on Astromart. It tracks very well and the GOTO function works
flawlessly. However, I have been unable to get my ST4 to guide for
more than a few minutes at a time. I tried using the periodic error
function to correct any flaws in the RA worm but to no avail. I don't
know whether the problem is in the ST4 or the stepper motors. What
would you suggest? If it is the stepper motors is replacing them a
major expense/problem?

Thanks, Mike


Roland Christen
 

In a message dated 2/14/2008 6:02:21 AM Central Standard Time,
nitemike1@... writes:


I am new to the group. I have an AP 900 mount (V 4.12) that I bought
on Astromart. It tracks very well and the GOTO function works
flawlessly. However, I have been unable to get my ST4 to guide for
more than a few minutes at a time. I tried using the periodic error
function to correct any flaws in the RA worm but to no avail. I don't
know whether the problem is in the ST4 or the stepper motors. What
would you suggest? If it is the stepper motors is replacing them a
major expense/problem?
1) the 900 servo mount does not have stepper motors. If it tracks very well,
then certainly the servo motors are working properly.

2) An ST4 is not an easy beast to work with. If it does not work properly,
then it will not interact with the mount. If the relays are shot or stuck in an
open or closed position, then it will not work no matter what you do with the
mount, so the first thing you need to do is find out if the 4 relays are doing
their job properly. Next thing is to make sure that the connector cable from
the ST4 to the mount is of the proper type. You will need to the trace the
pins back to the relays with an ohmmeter to make sure that the proper pins are
opening and closing when the 4 direction buttons on the ST4 are pushed. If the
ST4 is not set up properly, you can forget about using it to guide the mount.

3) you mention that you tried to use the periodic error function to correct
any flaws in the worm. What flaws are in the worm that you are trying to
correct, and how are you setting up the periodic error compensation to do this? Are
you guiding by hand and loading the PE curve this way? Are you using PEMPro?
What is your method for loading the PE curve?

Rolando


**************
The year's hottest artists on the red carpet at the
Grammy Awards. Go to AOL Music.

(http://music.aol.com/grammys?NCID=aolcmp00300000002565)


Roland Christen
 

In a message dated 2/14/2008 10:36:37 AM Central Standard Time,
nitemike1@... writes:


I have had no problem with the calibration function of the ST4 as long as I
calibrate for about 10 seconds in both axis. When the guiding starts it
seems to work well for several minutes and then the numbers on the screen
progressively increase in the RA axis (as in periodic error).
1) In the old days when I was using one of these beasts, I figured out quite
quickly that I could not determine anything by looking at the numbers. I
placed a crosshair eyepiece on a seperate telescope, and while the ST4 was doing
its thing, I monitored the prosition of the star on the crosshair. So, if you
don't start out with this fundamental concept, you will probably be in the dark.
Start by watching the star motion when you calibrate. Is the star actually
moving in the 2 directions N-S and E-W? Next, press the 4 direction buttons.
Does the star actually move when you do this? If you don't do these things, then
you might as well forget trying to work with the ST4.

2) Your symptoms do not indicate periodic error. They do not indicate any
kind of mount electronics error besides maybe a slight polar misalignment (which
is not a mount problem). They indicate simply that the ST4 is probably not
sending any correction signals to the mount, and the star is simply drifting
slowly away from the center (stars will always drift for a variety of reasons not
related to the mount electronics, so this is quite normal).

Finally, your heading is misleading. It should not read "AP 900 Mount
problem", rather it should say "SBIG ST4 Problem".

Rolando


**************
The year's hottest artists on the red carpet at the
Grammy Awards. Go to AOL Music.

(http://music.aol.com/grammys?NCID=aolcmp00300000002565)


observe_m13
 

If the mount works and tracks the sky without the ST4 then it's almost
definitely the ST4. It is either incorrectly set up or the cable
connecting it to the mount is damaged or broken. Does this ST4 work
with another mount you have? Since I have never had an ST4 I would
have no idea of how to go about testing and calibrating it. There
should be lots of info on the internet though.

--- In ap-gto@..., "nitemike1" <nitemike1@...> wrote:

I am new to the group. I have an AP 900 mount (V 4.12) that I bought
on Astromart. It tracks very well and the GOTO function works
flawlessly. However, I have been unable to get my ST4 to guide for
more than a few minutes at a time. I tried using the periodic error
function to correct any flaws in the RA worm but to no avail. I don't
know whether the problem is in the ST4 or the stepper motors. What
would you suggest? If it is the stepper motors is replacing them a
major expense/problem?

Thanks, Mike


Michael Cater <nitemike1@...>
 

I have had no problem with the calibration function of the ST4 as long as I calibrate for about 10 seconds in both axis. When the guiding starts it seems to work well for several minutes and then the numbers on the screen progressively increase in the RA axis (as in periodic error). After a few minutes the values improve only to increase again in a few minutes of guiding. Eventually, the values reach the E value (>9) which means the ST4 can't find the guide star. I will probably try my friends ST4 this weekend to see if the issue is my ST4.

Mike

chris1011@... wrote:
In a message dated 2/14/2008 6:02:21 AM Central Standard Time,
nitemike1@... writes:

I am new to the group. I have an AP 900 mount (V 4.12) that I bought
on Astromart. It tracks very well and the GOTO function works
flawlessly. However, I have been unable to get my ST4 to guide for
more than a few minutes at a time. I tried using the periodic error
function to correct any flaws in the RA worm but to no avail. I don't
know whether the problem is in the ST4 or the stepper motors. What
would you suggest? If it is the stepper motors is replacing them a
major expense/problem?
1) the 900 servo mount does not have stepper motors. If it tracks very well,
then certainly the servo motors are working properly.

2) An ST4 is not an easy beast to work with. If it does not work properly,
then it will not interact with the mount. If the relays are shot or stuck in an
open or closed position, then it will not work no matter what you do with the
mount, so the first thing you need to do is find out if the 4 relays are doing
their job properly. Next thing is to make sure that the connector cable from
the ST4 to the mount is of the proper type. You will need to the trace the
pins back to the relays with an ohmmeter to make sure that the proper pins are
opening and closing when the 4 direction buttons on the ST4 are pushed. If the
ST4 is not set up properly, you can forget about using it to guide the mount.

3) you mention that you tried to use the periodic error function to correct
any flaws in the worm. What flaws are in the worm that you are trying to
correct, and how are you setting up the periodic error compensation to do this? Are
you guiding by hand and loading the PE curve this way? Are you using PEMPro?
What is your method for loading the PE curve?

Rolando

**************
The year's hottest artists on the red carpet at the
Grammy Awards. Go to AOL Music.

(http://music.aol.com/grammys?NCID=aolcmp00300000002565)








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Michael Cater <nitemike1@...>
 

I have had no problem with the ST4 calibration mode. The problems develops after a few minutes of guiding and then the accuracy drops off. I will try my friend's ST4 to see if the problem is duplicated; if his works then my ST4 is defective.

Mike

Rick K <JunkMailGoesHere@...> wrote:
If the mount works and tracks the sky without the ST4 then it's almost
definitely the ST4. It is either incorrectly set up or the cable
connecting it to the mount is damaged or broken. Does this ST4 work
with another mount you have? Since I have never had an ST4 I would
have no idea of how to go about testing and calibrating it. There
should be lots of info on the internet though.

--- In ap-gto@..., "nitemike1" <nitemike1@...> wrote:

I am new to the group. I have an AP 900 mount (V 4.12) that I bought
on Astromart. It tracks very well and the GOTO function works
flawlessly. However, I have been unable to get my ST4 to guide for
more than a few minutes at a time. I tried using the periodic error
function to correct any flaws in the RA worm but to no avail. I don't
know whether the problem is in the ST4 or the stepper motors. What
would you suggest? If it is the stepper motors is replacing them a
major expense/problem?

Thanks, Mike





---------------------------------
Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now.


Michael Cater <nitemike1@...>
 

Thank you, for your input. I have a feeling that it's an ST4 problem.

Mike

chris1011@... wrote:
In a message dated 2/14/2008 10:36:37 AM Central Standard Time,
nitemike1@... writes:

I have had no problem with the calibration function of the ST4 as long as I
calibrate for about 10 seconds in both axis. When the guiding starts it
seems to work well for several minutes and then the numbers on the screen
progressively increase in the RA axis (as in periodic error).
1) In the old days when I was using one of these beasts, I figured out quite
quickly that I could not determine anything by looking at the numbers. I
placed a crosshair eyepiece on a seperate telescope, and while the ST4 was doing
its thing, I monitored the prosition of the star on the crosshair. So, if you
don't start out with this fundamental concept, you will probably be in the dark.
Start by watching the star motion when you calibrate. Is the star actually
moving in the 2 directions N-S and E-W? Next, press the 4 direction buttons.
Does the star actually move when you do this? If you don't do these things, then
you might as well forget trying to work with the ST4.

2) Your symptoms do not indicate periodic error. They do not indicate any
kind of mount electronics error besides maybe a slight polar misalignment (which
is not a mount problem). They indicate simply that the ST4 is probably not
sending any correction signals to the mount, and the star is simply drifting
slowly away from the center (stars will always drift for a variety of reasons not
related to the mount electronics, so this is quite normal).

Finally, your heading is misleading. It should not read "AP 900 Mount
problem", rather it should say "SBIG ST4 Problem".

Rolando

**************
The year's hottest artists on the red carpet at the
Grammy Awards. Go to AOL Music.

(http://music.aol.com/grammys?NCID=aolcmp00300000002565)








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William R. Mattil <wrmattil@...>
 

Michael Cater wrote:
I have had no problem with the ST4 calibration mode. The problems develops after a few minutes of guiding and then the accuracy drops off. I will try my friend's ST4 to see if the problem is duplicated; if his works then my ST4 is defective.
Mike,

It is extremely doubtful that your ST-4 is defective. The scenario that you describe isn't at all uncommon and the root cause of it is that the parameters selected are not appropriate. Just because you successfully calibrate is no guarantee that the guiding will be successful. You haven't provided nearly enough information for anyone to actually help you with this either. I would suggest that you check the group archives as Roland has explained the mount parameters needed a number of times. Then it is up to you to provide the following.

1) A known good Autoguider Cable

2) Accurate Polar Alignment

3) Reasonable Parameter Settings for the ST-4.

I can assure you that both of my ST-4's worked well with my AP900 Mount.

The situation that you describe indicate that the feedback loop is out of kilter. Assuming that the Polar Alignment is good enough.


Regards

Bill


--

William R. Mattil : http://www.celestial-images.com


drgert1
 

Hi,

How much effort did you put into focusing? If the ST4 is not properly
focused the guiding can be erratic.

Clear Skies,
Gert

--- In ap-gto@..., Michael Cater <nitemike1@...> wrote:

I have had no problem with the ST4 calibration mode. The problems
develops after a few minutes of guiding and then the accuracy drops
off. I will try my friend's ST4 to see if the problem is duplicated;
if his works then my ST4 is defective.

Mike

Rick K <JunkMailGoesHere@...> wrote:
If the mount works and tracks the sky without the ST4 then
it's almost
definitely the ST4. It is either incorrectly set up or the cable
connecting it to the mount is damaged or broken. Does this ST4 work
with another mount you have? Since I have never had an ST4 I would
have no idea of how to go about testing and calibrating it. There
should be lots of info on the internet though.

--- In ap-gto@..., "nitemike1" <nitemike1@> wrote:

I am new to the group. I have an AP 900 mount (V 4.12) that I bought
on Astromart. It tracks very well and the GOTO function works
flawlessly. However, I have been unable to get my ST4 to guide for
more than a few minutes at a time. I tried using the periodic error
function to correct any flaws in the RA worm but to no avail. I don't
know whether the problem is in the ST4 or the stepper motors. What
would you suggest? If it is the stepper motors is replacing them a
major expense/problem?

Thanks, Mike





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