Question on Nexstar 114GT

I was viewing saturn last night in my fairly nex nestar 114GT and it
kept going out of my FOV when I was using a fairly high
magnification.... I looked at the motors and noticed the Dec motor
doesn't seem to be running much...(if at all) is it normal
for the (I think) declination motor to run alot less then the RA
motor? In this case... the one not running seems to be the one
labeled Alt: The Azm: was chugging away just fine and the numbers
kept changing and incrementing... is this a problem? Or normal? The
motor runs fine otherwise.... perhaps I'm just putting too much
magnification on this scope for the price I payed and wanting it to
track too precisly?

"Matt" wrote in message
om...
I was viewing saturn last night in my fairly nex nestar 114GT and it
kept going out of my FOV when I was using a fairly high
magnification....

That sounds pretty typical. You need to man the hand controller.

What focal length eyepieces are you using and what are the results? What do
you think of the image in the eyepiece? Are you seeing the planet's ring?
Can you see that it's divided into two major rings (Cassini division)? Can
you see any differences in the color shading on the surface (belts and
zones)?

I hope you are otherwise enjoying the experience!! Though frustrating at
times, I had a lot of fun when I first started out.
--
-Stephen Paul

"Matt" wrote in message
om...
I was viewing saturn last night in my fairly nex nestar 114GT and it
kept going out of my FOV when I was using a fairly high
magnification.... I looked at the motors and noticed the Dec motor
doesn't seem to be running much...(if at all) is it normal
for the (I think) declination motor to run alot less then the RA
motor? In this case... the one not running seems to be the one
labeled Alt: The Azm: was chugging away just fine and the numbers
kept changing and incrementing... is this a problem? Or normal? The
motor runs fine otherwise.... perhaps I'm just putting too much
magnification on this scope for the price I payed and wanting it to
track too precisly?
Don't confuse Ra/Dec, with Alt/Az. If you are mounted using Ra/Dec (the RA
'axis', is pointed at the celestial pole), then the Dec motor, will not be
used at all. If however you are mounted in Alt/Az, the ratio of movements
will depend on what part of the sky you are viewing, and where you are.
Assuming you are in the northern temperate regions, looking at something in
the southerly part of the sky, then the motions in Az, will be a lot smaller
than those in Alt.
What you saw was normal.

Best Wishes

On 21 Nov 2003 04:43:34 -0800, (Matt) wrote:

I was viewing saturn last night in my fairly nex nestar 114GT and it
kept going out of my FOV when I was using a fairly high
magnification.... I looked at the motors and noticed the Dec motor
doesn't seem to be running much...(if at all) is it normal
for the (I think) declination motor to run alot less then the RA
motor? In this case... the one not running seems to be the one
labeled Alt: The Azm: was chugging away just fine and the numbers
kept changing and incrementing... is this a problem? Or normal? The
motor runs fine otherwise.... perhaps I'm just putting too much
magnification on this scope for the price I payed and wanting it to
track too precisly?

Tracking and GoTo accuracy of the little GT Nexstars is very dependent
on the care and method of alignment. The tracking is not great at its
best but taking care to compensate for gear backlash when doing the
alignment can make it pretty good. See Michael Swansen's Nexstar
Resources page at http://www.nexstarsite.com/ and look for the
Alignment Guides there.

Les Blalock
http://www.txastro.com

"Matt" wrote in message
om...
I was viewing saturn last night in my fairly nex nestar 114GT and it
kept going out of my FOV when I was using a fairly high
magnification.... I looked at the motors and noticed the Dec motor
doesn't seem to be running much...(if at all) is it normal
for the (I think) declination motor to run alot less then the RA
motor? In this case... the one not running seems to be the one
labeled Alt: The Azm: was chugging away just fine and the numbers
kept changing and incrementing... is this a problem? Or normal? The
motor runs fine otherwise.... perhaps I'm just putting too much
magnification on this scope for the price I payed and wanting it to
track too precisly?
As a question, how did you align the scope?.
Even with much more expensive models, alignment is critical, and small
errors will cause disproportionate errors in tracking on some parts of the
sky. Though to some extent, the movement was normal at high magnifications,
if you take the time to align very carefully, possibly even using a reticule
eyepiece, you may be astonished at how accurately the scope will then track.
:-)

Best Wishes

Les Blalock wrote in message . ..
On 21 Nov 2003 04:43:34 -0800, (Matt) wrote:

I was viewing saturn last night in my fairly nex nestar 114GT and it
kept going out of my FOV when I was using a fairly high
magnification.... I looked at the motors and noticed the Dec motor
doesn't seem to be running much...(if at all) is it normal
for the (I think) declination motor to run alot less then the RA
motor? In this case... the one not running seems to be the one
labeled Alt: The Azm: was chugging away just fine and the numbers
kept changing and incrementing... is this a problem? Or normal? The
motor runs fine otherwise.... perhaps I'm just putting too much
magnification on this scope for the price I payed and wanting it to
track too precisly?

Tracking and GoTo accuracy of the little GT Nexstars is very dependent
on the care and method of alignment. The tracking is not great at its
best but taking care to compensate for gear backlash when doing the
alignment can make it pretty good. See Michael Swansen's Nexstar
Resources page at http://www.nexstarsite.com/ and look for the
Alignment Guides there.

Yet there are major issues with the firmware in the 114GT as were discussed
here in SAA circa August when the "Costco Special" sales began.

No matter how carefully one sets up and aligns the 114GT, tracking sucks and
has been so (bad) since (at least) 2000 (3+ years now).

For just a simple example of how bad the 114GT tracking is, follow all the
setup and alignment steps, tips and suggestions at the above-cited site and
also the two Yahoo groups ("BabyNexstar" and "nexstar"), then goto some fixed
object (i.e., a star), then select the RA/Dec display from the handcontroller
and watch the numbers change (!) at a moderate rate which I originally termed
the "gas pump meter" effect.

The flaw in the 114GT seems to be twofold: incorrect tracking values are
initially sent to the motor controller board (in the arm), and though the
changing RA/Dec values clearly indicate there's feedback between the motor
controller and the handcontroller the second error is that nothing is done
about it and, thus, any object will swiftly leave the scope's FOV.

Even "tracking" Polaris will show the errors in the 114GT's firmware.

On 21 Nov 2003 12:02:39 -0800, (Thad Floryan) wrote:
Yet there are major issues with the firmware in the 114GT as were discussed
here in SAA circa August when the "Costco Special" sales began.

No matter how carefully one sets up and aligns the 114GT, tracking sucks and
has been so (bad) since (at least) 2000 (3+ years now).

For just a simple example of how bad the 114GT tracking is, follow all the
setup and alignment steps, tips and suggestions at the above-cited site and
also the two Yahoo groups ("BabyNexstar" and "nexstar"), then goto some fixed
object (i.e., a star), then select the RA/Dec display from the handcontroller
and watch the numbers change (!) at a moderate rate which I originally termed
the "gas pump meter" effect.

The flaw in the 114GT seems to be twofold: incorrect tracking values are
initially sent to the motor controller board (in the arm), and though the
changing RA/Dec values clearly indicate there's feedback between the motor
controller and the handcontroller the second error is that nothing is done
about it and, thus, any object will swiftly leave the scope's FOV.

Even "tracking" Polaris will show the errors in the 114GT's firmware.

Hi Thad,

I've wondered about these later 114GT questions/issues since there has
been so much discussion about them lately. I had one of the very
first 80GTs (faulty HC and all) and found that careful alignment
allowed it to work pretty well. Not great, mind you, but it would
track an object at ~80x pretty well for ~20 minutes. That 80GT was
pretty comparable to my old N5. My N8i tracks *much* better.

So, I wonder if there was some changes in the firmware. Especially
with these that were sold by Costco?

Les Blalock
http://www.txastro.com

On 11/22/03 00:00 +0900, Roger Hamlett wrote:

Don't confuse Ra/Dec, with Alt/Az. If you are mounted using Ra/Dec (the RA
'axis', is pointed at the celestial pole), then the Dec motor, will not be
used at all. If however you are mounted in Alt/Az, the ratio of movements
will depend on what part of the sky you are viewing, and where you are.
Assuming you are in the northern temperate regions, looking at something in
the southerly part of the sky, then the motions in Az, will be a lot smaller
than those in Alt.

That applies for an EQ-mounted OTA, of course, but the NexStar
114 GT on the as-supplied tripod always operates in altaz.

What you saw was normal.

Yes, but not for the reasons you state. The GT series scopes
require critical alignment and anti-backlash setting. Even then,
it's not uncommon for one of the motors to stall and let the
image drift out of the FOV.

GTs are "fiddly" scopes.

trane
--
//------------------------------------------------------------
// Trane Francks Tokyo, Japan
// Practice random kindness and senseless acts of beauty.
// http://mp3.com/trane_francks/

labeled Alt: The Azm: was chugging away just fine and the numbers
kept changing and incrementing... is this a problem? Or normal? The
motor runs fine otherwise.... perhaps I'm just putting too much
magnification on this scope for the price I payed and wanting it to
track too precisly?

Tracking and GoTo accuracy of the little GT Nexstars is very dependent
on the care and method of alignment. The tracking is not great at its
best but taking care to compensate for gear backlash when doing the
alignment can make it pretty good. See Michael Swansen's Nexstar
Resources page at http://www.nexstarsite.com/ and look for the
Alignment Guides there.


Well I took the scope out again tonight...
Looking at a star in the North-east it tracked fine and looking at the
Azm/Alt read-out they were tracking well... for a while... then a few
times while viewing the star through a 15mm.. I could hear the motor
stop and the star moved out of the bottom of the field of view. Then
I re-centered it and it was fine for a while, then the motor would
stop and the star would move out of the bottom. Each time the motor
stopped and the star moved the Alt read-out would stop incrementing..
as soon as the motor started up again it would start incrementing
again and everything would be happy when I re-aligned. I moved to
another star (this time in the east) and the same thing happened.
I took the side off the telescope to look
at the motors and the Azm: motor (one connect to the base) turns
almost continually no matter what position I am in. The Alt
(connected to scope via gear) seems to pulse on and off ... as in it
will stay off for 3-8 seconds or so... then come on.. and sound like
it is trying harder and harder to move (for about 10 seconds).. then
the gear will move a very small amount (sometimes it doesn't move at
all) and it will shut off. I have tried re-balancing the
telescope... that seemed to have little effect... is this perhaps
what is causing things like mars/saturn/stars to shoot across my FOV?
Is
that by design or a defect?
What prognosis do you make from all this?

That's normal then I take it?
To the other person who asked about image.. yes the view of saturn was
great! And I saw several nebulae... which seemed to track fairly
well... so this is just how the scope works then? I can live with
that.. I just want to make sure it's working correctly and not in need
of repair.

"Matt" wrote in message
m...
labeled Alt: The Azm: was chugging away just fine and the numbers
kept changing and incrementing... is this a problem? Or normal? The
motor runs fine otherwise.... perhaps I'm just putting too much
magnification on this scope for the price I payed and wanting it to
track too precisly?

Tracking and GoTo accuracy of the little GT Nexstars is very dependent
on the care and method of alignment. The tracking is not great at its
best but taking care to compensate for gear backlash when doing the
alignment can make it pretty good. See Michael Swansen's Nexstar
Resources page at http://www.nexstarsite.com/ and look for the
Alignment Guides there.


Well I took the scope out again tonight...
Looking at a star in the North-east it tracked fine and looking at the
Azm/Alt read-out they were tracking well... for a while... then a few
times while viewing the star through a 15mm.. I could hear the motor
stop and the star moved out of the bottom of the field of view. Then
I re-centered it and it was fine for a while, then the motor would
stop and the star would move out of the bottom. Each time the motor
stopped and the star moved the Alt read-out would stop incrementing..
as soon as the motor started up again it would start incrementing
again and everything would be happy when I re-aligned. I moved to
another star (this time in the east) and the same thing happened.
I took the side off the telescope to look
at the motors and the Azm: motor (one connect to the base) turns
almost continually no matter what position I am in. The Alt
(connected to scope via gear) seems to pulse on and off ... as in it
will stay off for 3-8 seconds or so... then come on.. and sound like
it is trying harder and harder to move (for about 10 seconds).. then
the gear will move a very small amount (sometimes it doesn't move at
all) and it will shut off. I have tried re-balancing the
telescope... that seemed to have little effect... is this perhaps
what is causing things like mars/saturn/stars to shoot across my FOV?
Is
that by design or a defect?
What prognosis do you make from all this?

That's normal then I take it?
To the other person who asked about image.. yes the view of saturn was
great! And I saw several nebulae... which seemed to track fairly
well... so this is just how the scope works then? I can live with
that.. I just want to make sure it's working correctly and not in need
of repair.
What power source?...
Most scopes, are very critical of their power. These are no exception. The
problem is that if you run off a small battery pack, their voltage, and the
power they can deliver, declines when cold. The 'fine' movements, are the
first to show problems. It sounds as though, when the motor is only having
to move a small amount, the system is 'sticking' a little, and the motor is
having trouble overcoming it. This could either be the power available to
the motor, or a friction problem (something is stuck...).

Best Wishes