APV
member
Reged: 08/17/04
Posts: 87
Loc: Greenwich, CT
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I am new to GEMs and I bought this mount used. I am having all sorts of problems with the GOTO alignment on the CG-5 -- unfamiliar stars, pointing to ground, refractor OTA flipping over where the diagonal inverts. I have a Nexstar 8i and the GOTO function is a dream. I started to look for pictures of what the GEM is suppose to look like and I found a picture of the wrong DEC which is exactly what my mount looks like. 
Does anyone have a suggestion of what exactly is wrong and how to fix it? I also notice the setting circles seems to misaligned.
Any help would be appreciated. 
Albert
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jrcrilly
Refractor wienie again
Reged: 04/30/03
Posts: 22365
Loc: NE Ohio
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The orientation doesn't make any functional difference; the mount doesn't know which initial position you used. I prefer to use it the other way only because it prevents the secondary dovetail bolt from bending or slipping.
The alt/az rigs such as the N8i are certainly easier to set up. On the other hand, you can certainly use the same alignement stars with which you are familiar (except for Polaris) so that shouldn't make it strange. Flipping of the optical tube is required when crossing the meridian so you'll need to accomodate yourself to that with any GEM. Pointing to the ground should only be possible if alignment is done improperly so the mount thinks it's pointed somewhere other than where it is.
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John C
Urban Observatory
Tele Vue Pronto
A&M/Astreya 76mm F/6 APO
TMB/LOMO 80mm F/7.5 APO
Tak FSQ-106N F/5 APO
Meade 152ED F/9 "APO"
152mm F/10 achromat
Tak CN-212 8" F/12 classical Cass/ F/4 Newt
Teeter 20" F/3.8 truss Newt w/ServoCat
LXD750, EM-200, CI-700
ST-10XME
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APV
member
Reged: 08/17/04
Posts: 87
Loc: Greenwich, CT
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John,
Why does the picture show the DEC is wrong? You mentioned that you use it another way. Why? any advantages?
Albert
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APV
member
Reged: 08/17/04
Posts: 87
Loc: Greenwich, CT
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John,\
Do you have a picture of the better setup? or a link on how to set this up? I have looked in Yahoo but not much luck and unfortunately I am one of these visual types that like to see the config and work my way there.
Albert
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jrcrilly
Refractor wienie again
Reged: 04/30/03
Posts: 22365
Loc: NE Ohio
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Quote:
John,
Why does the picture show the DEC is wrong? You mentioned that you use it another way. Why? any advantages?
Albert
Hi, Albert.
You'd have to ask the fellow who posted the photo for his opinion. I use it the other way for purely mechanical reasons, as I described. It'll work precisely the same either way except for the secondary dovetail bolt being more effective one way than the other. The same is true for the GP clones (LXD55, LXD75, CG5-GT).
I describe it in more detail here.
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John C
Urban Observatory
Tele Vue Pronto
A&M/Astreya 76mm F/6 APO
TMB/LOMO 80mm F/7.5 APO
Tak FSQ-106N F/5 APO
Meade 152ED F/9 "APO"
152mm F/10 achromat
Tak CN-212 8" F/12 classical Cass/ F/4 Newt
Teeter 20" F/3.8 truss Newt w/ServoCat
LXD750, EM-200, CI-700
ST-10XME
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jrcrilly
Refractor wienie again
Reged: 04/30/03
Posts: 22365
Loc: NE Ohio
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Quote:
John,\
Do you have a picture of the better setup?
There are photos in the article to which I refer above.
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John C
Urban Observatory
Tele Vue Pronto
A&M/Astreya 76mm F/6 APO
TMB/LOMO 80mm F/7.5 APO
Tak FSQ-106N F/5 APO
Meade 152ED F/9 "APO"
152mm F/10 achromat
Tak CN-212 8" F/12 classical Cass/ F/4 Newt
Teeter 20" F/3.8 truss Newt w/ServoCat
LXD750, EM-200, CI-700
ST-10XME
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John M
professor emeritus
Reged: 12/01/03
Posts: 570
Loc: Phoenix, AZ
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Albert,
JR addressed the declination issue above so I won't here. I had some of the same 'electronic' issues you described with the OTA ending up pointed at the ground and other alignment issues. After much hair pulling it turned out to be a bad power cable. Process of elimination guided me to a third power cable and 'poof' problems went away. Low battery charge can have the same symptoms. Pretty much if there are 'electronic' issues with these mounts I think power is the first place to look.
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John M
Mesa/Tucson, AZ
8" Sky View Pro Newt
90mm Meade 386D Refractor
60 mm Monlux Refractor
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jrcrilly
Refractor wienie again
Reged: 04/30/03
Posts: 22365
Loc: NE Ohio
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Quote:
I had some of the same 'electronic' issues you described with the OTA ending up pointed at the ground and other alignment issues. After much hair pulling it turned out to be a bad power cable. Process of elimination guided me to a third power cable and 'poof' problems went away. Low battery charge can have the same symptoms. Pretty much if there are 'electronic' issues with these mounts I think power is the first place to look.
Thanks, John.
You are correct and my response was way too short. Battery condition and power connections do cause the symptoms he described. Good catch!
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John C
Urban Observatory
Tele Vue Pronto
A&M/Astreya 76mm F/6 APO
TMB/LOMO 80mm F/7.5 APO
Tak FSQ-106N F/5 APO
Meade 152ED F/9 "APO"
152mm F/10 achromat
Tak CN-212 8" F/12 classical Cass/ F/4 Newt
Teeter 20" F/3.8 truss Newt w/ServoCat
LXD750, EM-200, CI-700
ST-10XME
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APV
member
Reged: 08/17/04
Posts: 87
Loc: Greenwich, CT
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John,
Is there a method to measure the amperage coming through a DC adapter? I am using a new battery from Costco which recharges my surburban. It is a Xantrex with 15 Amps. From the Internet I found the CG-5 needs 2-3 amps verus 1.5 amps for the nexstar. Nevertheless the mount seems to slew quickly and efficiently without any hesitation. I would be surprized if it is the DC adapter but you can never know. It also turns out that my setup is identical to your setup. Kudos to the previous owner who probably read your article and followed your suggestion.
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John M
professor emeritus
Reged: 12/01/03
Posts: 570
Loc: Phoenix, AZ
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Albert,
I never could figure out a way to measure the amperage at the mount. I asked some electricians at work without luck. I'm sure an electronics shop could do it, but not with the simple equipment I have.
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John M
Mesa/Tucson, AZ
8" Sky View Pro Newt
90mm Meade 386D Refractor
60 mm Monlux Refractor
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Charlie Hein
Postmaster
Reged: 11/02/03
Posts: 6534
Loc: 26.06.08N, +80.23.08W
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Quote:
Albert,
I never could figure out a way to measure the amperage at the mount. I asked some electricians at work without luck. I'm sure an electronics shop could do it, but not with the simple equipment I have.
The simplest way I can think of is to cut the positive leg of your power cord and measure the current there. Maybe rather than cutting up your good power cord you might consider making one up just for this purpose, putting bananna plugs on the cord where you'll "jack in" the VOM. They even sell bananna plug "barrel connectors", so you could join the two bananna plugs together and have a usable power cord without the VOM. The whole thing shouldn't cost more than about $10.00 to build, and you would have it on hand whenever you needed it.
Charlie
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Weston CSC:
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