Celestron CG-5 GT question (GEM question in general)

I decided to get a goto GEM for my TV102 and although I read manual, I
can't figure out what's going on...

I'm testing the mount in my living room. I have the scope balanced in
Dec and RA. I have the index marks lined up and locked. I entered my
exact time, lat and long. The mount is set to my latitude and I think I
have it lined up within a few degress of North.

First, I tried a quick align. The scope immediatly started to rotate in
RA, so that the tube is going down toward the tripod legs and the
counterweight is heading for the ceiling. I cut the power when the tube
was 1 inch from smacking into the tripod leg with no sign of slowing down.

I reset the index marks and tried an auto align. It choose Arcturus and
proceeded to move the other direction in RA a bit and then started to
point the scope up until it almost smacked the diagonal into one of the
tripod legs. Again I cut the power with an inch to spare.

1. Anyone know what I'm doing wrong?

2. Is there a way to train the mount not to ram the scope into the
tripod legs?

3. Anyone want to buy a barely used CG-5 GT :-) ?

--
Clear Skies,

Paul Murphy


(remove gemini to email me)

Paul Murphy wrote:
I decided to get a goto GEM for my TV102 and although I read manual, I
can't figure out what's going on...


I'm not familiar with this particular Go-To device. But some Go-To
mounts/controllers, Celestron (e.g., my Nexstar8GPS) and Meade, have a
menu option for Az-El or Polar (RA-Decl) Go-To operation.

Perhaps you have the scope mounted Polar in the GEM but have not told
the computer to do Polar vs. Az-El in the setup menu.

Phil

Paul Murphy wrote:
I decided to get a goto GEM for my TV102 and although I read manual, I
can't figure out what's going on...

I'm testing the mount in my living room. I have the scope balanced in
Dec and RA. I have the index marks lined up and locked. I entered my
exact time, lat and long. The mount is set to my latitude and I think I
have it lined up within a few degress of North.

First, I tried a quick align. The scope immediatly started to rotate in
RA, so that the tube is going down toward the tripod legs and the
counterweight is heading for the ceiling. I cut the power when the tube
was 1 inch from smacking into the tripod leg with no sign of slowing down.

I reset the index marks and tried an auto align. It choose Arcturus and
proceeded to move the other direction in RA a bit and then started to
point the scope up until it almost smacked the diagonal into one of the
tripod legs. Again I cut the power with an inch to spare.


There is a review of this mount he

http://www.cloudynights.com/documents/asm.pdf

There is some discussion there about declination axis labels being 180
deg off. I don't know if this relates or not, not having this mount.

There is some discussion there about declination axis labels being 180
deg off. I don't know if this relates or not, not having this mount.


Well, I tried again and not only did it again immediately proceed to put
the scope on a collision course with the tripod legs, hitting a
direction button and then enter didn't stop the slew at all, it just
slewed in the direction of the button I pressed while I held it and as
soon as I let go, before I could even hit enter, it contined on the
previous collision course.

I disassembled the mount and tossed it off my second floor balcony. Just
kidding. I put everything in my car and I'm going to bring it to the
telescope shop where I bought it to see where I (or the mount) am going
wrong.

I'm kicking myself for getting rid of my Gibraltar. I could carry the
whole thing assembled down the two flights of stairs and take quick
looks. Now all I have is a homicidal computer (HAL's little brother)
that's out to smash my telescope. Mixed in with the declination motor
whine, I can hear it chuckling to itself...better motors and 2 inch
tripod legs...all the better to smash you with...goooohaaaaaaa.

Well, I hope everyone else has clear skies...I'm getting buried under
lake effect snow...Paul Murphy

Paul Murphy wrote:

Now all I have is a homicidal computer (HAL's little brother)
that's out to smash my telescope. Mixed in with the declination motor
whine, I can hear it chuckling to itself...better motors and 2 inch
tripod legs...all the better to smash you with...goooohaaaaaaa.


Welcome to the Twilight Zone, Paul.

I bought one of the early ETX-90EC's. I've never gotten it to work
correctly or consistently. But every few years, when I feel the urge
(i.e., masochism) I take it out, update the firmware, carefully level
the tripod, put it in the "home" position and give it a try. It never
fails to frustrate me, to give me that real "hobbiest" ambience: In
fact, I relived that experience just last evening. But I have used it
successfully on a (hand driven) Az-Alt mount (Microstar) at low power:
Really nice optics!

But, for relief, I also have a Nexstar8GPS which works quite well in the
Az-Alt mode (do not yet have a wedge for it). Since I suspect the
electronics for your CG-5 GT are related to the NS8GPS (and *not* to the
ETX), I am confidence you will soon be pleased with your new mount.

Phil

I bought one of the early ETX-90EC's. I've never gotten it to work
correctly or consistently. But every few years, when I feel the urge
(i.e., masochism) I take it out, update the firmware, carefully level
the tripod, put it in the "home" position and give it a try. It never
fails to frustrate me, to give me that real "hobbiest" ambience: In
fact, I relived that experience just last evening. But I have used it
successfully on a (hand driven) Az-Alt mount (Microstar) at low power:
Really nice optics!

But, for relief, I also have a Nexstar8GPS which works quite well in the
Az-Alt mode (do not yet have a wedge for it). Since I suspect the
electronics for your CG-5 GT are related to the NS8GPS (and *not* to the
ETX), I am confidence you will soon be pleased with your new mount.

Phil

Hi Phil:

Sorry your little ETX has proven to be a source of frustration. I've
used quite a few of 'em, and own a couple at the moment. My
observation? They can work pretty well. Remember that their long focal
lengths can make landing dead center on a target a bit challenging, but
mine are always able to put what I request in the field. Tips? Other
than generally taking care with the alignment, drive training, at least
occasionally is a must. And a "calibrate motors" is also a good idea
after changing batteries. The little scopes very much like fresh
batteries as well.

As for the CG5 GT, once you get used to a few of its quirks, it is very
accurate indeed, as (or slightly more) accurate than the Celestron GPS
scopes.

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
http://skywatch.brainiac.com/astroland/index.htm

Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers:
http://groups.yahoo.com/group/sct-user

See: http://journals.aol.com/rmollise/UncleRodsAstroBlog/
For Uncle Rod's Astro Blog.

RMOLLISE wrote:
I bought one of the early ETX-90EC's. I've never gotten it to work
correctly or consistently. But every few years, when I feel the urge
(i.e., masochism) I take it out, update the firmware, carefully level
the tripod, put it in the "home" position and give it a try. It never
fails to frustrate me, to give me that real "hobbiest" ambience: In
fact, I relived that experience just last evening. But I have used it
successfully on a (hand driven) Az-Alt mount (Microstar) at low power:
Really nice optics!

But, for relief, I also have a Nexstar8GPS which works quite well in the
Az-Alt mode (do not yet have a wedge for it). Since I suspect the
electronics for your CG-5 GT are related to the NS8GPS (and *not* to the
ETX), I am confidence you will soon be pleased with your new mount.

Phil


Hi Phil:

Sorry your little ETX has proven to be a source of frustration. I've
used quite a few of 'em, and own a couple at the moment. My
observation? They can work pretty well. Remember that their long focal
lengths can make landing dead center on a target a bit challenging, but
mine are always able to put what I request in the field. Tips? Other
than generally taking care with the alignment, drive training, at least
occasionally is a must. And a "calibrate motors" is also a good idea
after changing batteries. The little scopes very much like fresh
batteries as well.


Thanks for the tip, Rod. Hmmm .. I have trained the drives (two days
ago, in fact, was the last time) but never calibrated the motors; did
not know that was available. I always use an external Gel Cell (same
one i use on NS8GPS) vs. internal batteries; since it is pretty much
fully charged when I start, the voltage should be pretty much the same
each time. And I use the 26mm Plossl for acq.

It seems functionally correct (motors sound right, it does not go
bonkers!) but just does not quite do what it should .. and always misses
the first star by 20 deg or so.

Anyway, a friend who has success with his ETX-125EC is going to give it
a shot over the holidays. When you try something too many times you
often repeat the same operator error(s).

Phil

Phil Wheeler wrote:

It seems functionally correct (motors sound right, it does not go
bonkers!) but just does not quite do what it should .. and always misses
the first star by 20 deg or so.

Anyway, a friend who has success with his ETX-125EC is going to give it
a shot over the holidays. When you try something too many times you
often repeat the same operator error(s).

Phil

Hi Phil:

That's possible, but--for sure--try the old litany:

Reset
Calibrate (motors)
Train Drives

I wouldn't worry too much about how much you miss the first star by,
either. Just center it carefully (a reticle eyepiece is a good tool).

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
http://skywatch.brainiac.com/astroland/index.htm

Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers:
http://groups.yahoo.com/group/sct-user

See: http://journals.aol.com/rmollise/UncleRodsAstroBlog/
For Uncle Rod's Astro Blog.

I've got a CG5 GT on the way, maybe arriving today. What are some of the
quirks I should look out for? Thanks.

-John Banister

"RMOLLISE" wrote in message
oups.com...

As for the CG5 GT, once you get used to a few of its quirks, it is very
accurate indeed, as (or slightly more) accurate than the Celestron GPS
scopes.

Peace,
Rod Mollise

RMOLLISE wrote:
Phil Wheeler wrote:

It seems functionally correct (motors sound right, it does not go
bonkers!) but just does not quite do what it should .. and always misses
the first star by 20 deg or so.

Anyway, a friend who has success with his ETX-125EC is going to give it
a shot over the holidays. When you try something too many times you
often repeat the same operator error(s).

Phil


Hi Phil:

That's possible, but--for sure--try the old litany:

Reset
Calibrate (motors)
Train Drives

I wouldn't worry too much about how much you miss the first star by,
either. Just center it carefully (a reticle eyepiece is a good tool).


Yes. I found a very good five part procedure for getting the best from
an ETX-EC at Mike Weisner's site yesterday and will execute that process
as soon as I get the scope back from my friend. It includes mechanical
fixes and the steps above re Reset, Calibrate and Train .. with details
re how best to do the training.

Astronomy is a hobby for me and the ETX-90EC will let me pursue the "fix
it" aspect. Given I've had this scope for 5-6 years and never found it
useful (except with the OTA on a Microstar), I have nothing to lose!

Phil