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Equipment Discussions >> Mounts

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yashi
super member


Reged: 11/15/11

GP-DX understanding Problem (RA Axis)
      #5481499 - 10/21/12 07:12 AM

Hi,

ive got an understanding issue with my new GP-DX. I dont get how the RA circle works



from left to right. theres an Arrow pointing to the black circle and a noniusscale on the green metal casing.
it would make sense if these + the black scale are used to find objects. BUT the small thumbscrew fixes the blackscale to the casing, which means it wont move if you rotate the scope around the RA axis.
The next ring with a scale(the shiny/silver/white one) is fixed to the axis, but i take it that this one is for the polarscope if i attach the protective cover im not even able to see that scale.

this is what i would see when im done setting the scope up. the black scale is fixable and isnt fixed to the axis. How am i suppost to use that if bose scales are fixed to eachother o_0



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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5481635 - 10/21/12 09:48 AM

It is a little confusing. If I recall--I have never used the tiny setting circles on GEMS much--you Leave the screw loose during object location. When you are on an object, you tighten it down so the RA reading will remain the same as the mount tracks. The black scale is a vernier to increase your accuracy somewhat.

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yashi
super member


Reged: 11/15/11

Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5481716 - 10/21/12 10:49 AM

thanks for your reply.

Quote:

en you are on an object, you tighten it down so the RA reading will remain the same as the mount tracks.




This would mean the ra axis and the ra circle dont have a hard connection, otherwise it would block the ra axis too if i tighten the thumbscrew.

Right now my ra circle is just "floating" on the ra axis. sometimes it moves sometimes it doesnt. i already opened the whole thing. but i dont see how this should work :/. circle and axis obviously can be connected with a screw -> would render the blocking screw useless

here are a few more pictures of the inside
http://arnholm.org/astro/gpdx/index.htm


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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5481752 - 10/21/12 11:13 AM

I'm not at all sure what you mean by "hard connection." You tighten the little screw above the circle to _keep it from changing as the scope tracks_. If you do NOT do that, your RA circle's reading will become progressively farther off. If it sometimes moves and sometimes does not move, you don't have the thumb screw either loose or tight enough.

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yashi
super member


Reged: 11/15/11

Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5481835 - 10/21/12 11:59 AM

with hard connection i mean screwed to the axis for example. this would mean i couldnt lock the ring because it would lock the axis too.

right now i can lock the ring. but if i do not lock it it will just float randomly around the axis. its not bound at all to the axis.


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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5481955 - 10/21/12 01:33 PM

The little setscrew doesn't have anything to do with locking the mount's axis. Don't believe me? Try it.

When it's not locked down, that exactly what SHOULD happen.


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yashi
super member


Reged: 11/15/11

Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5482040 - 10/21/12 02:25 PM

Quote:

The little setscrew doesn't have anything to do with locking the mount's axis. Don't believe me? Try it.




i know. if i screw it down i lock the circle

if i dont screw it down the circle rotates freely. with free i mean moving the axis has no effect on the circle because its not connected in any way to it


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Starhawk
Space Ranger
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Reged: 09/16/08

Loc: Tucson, Arizona
Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5482476 - 10/21/12 06:21 PM

It's free to move so you can align it with local time. The polar scope has to be aligned with the pole, so it is separate.

I know this sounds odd, but at the end of the day, they aren't really all that useful. It is vastly easier to point at an object (like Vega or Sirius, for example), and use it to set the setting circles if you want to use them.

-Rich


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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5482609 - 10/21/12 08:04 PM

Quote:



i know. if i screw it down i lock the circle

if i dont screw it down the circle rotates freely. with free i mean moving the axis has no effect on the circle because its not connected in any way to it




One last time:

Loosen the setscrew to find objects.
Tighten to track.

But it is your mount, and I think you should use it any cotton-picking way you want to...


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yashi
super member


Reged: 11/15/11

Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5483009 - 10/22/12 02:34 AM

losening the setscrew has virtually no effect. it still wont turn with the ra axis (its not connected to it in anyway, it just touches it)

if i losen the setscrew and put the protective cover on, the ra circle will be fixed, because the drag of the protective cover on the circle overcomes the drag between the circle and the axis. the cover is just an example it doesnt even need that much drag to stop the ra circle from moving. even without any resistance at all the ra circle wont follow properly


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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5483192 - 10/22/12 07:42 AM

Should definitely turn with the RA axis when the setscrew is fully loosened...

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yashi
super member


Reged: 11/15/11

Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5483246 - 10/22/12 08:50 AM

exactly.
and i want to know why my isnt doing it/ how the ra circle should be connected to the axis, because i can not find anything about it :/ i even took it apart but there is nothing to connect the axis with the circle.


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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5483560 - 10/22/12 12:22 PM

I believe that typically there was no connection, friction caused the circle to move with the RA axis. Sounds like your circle is loose.

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yashi
super member


Reged: 11/15/11

Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5484797 - 10/23/12 05:55 AM

thanks for your help.

but the parts do not look worn down :/

it would be awesome if someone with the same or similar mount would take a look at it. i Really want to know how it is suppost to work.

Edited by yashi (10/23/12 05:56 AM)


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Wouter D'hoye
Carpal Tunnel
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Reged: 06/27/03

Loc: Belgium
Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5484802 - 10/23/12 06:14 AM

Hi,

I own a GP-DX and I have to agree with Rod. Now it's possible that the ring is loose and that you need to somehow tighten it on the shaft so it has better grip and rotates with the shaft. Mabe just applying some tape on the shaft so it fits more snugly could do the trick.

I have one too, i'll try to take a look at it when I get home this evening.

Kind regards.


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yashi
super member


Reged: 11/15/11

Re: GP-DX understanding Problem (RA Axis) new [Re: Wouter D'hoye]
      #5484871 - 10/23/12 08:32 AM

thanks this would be awesome!

if it all fails i will do it with tape. but seriously i thought the gp-dx is decently made...how worse could it be, if i have to fix a mechanical instrument with duct-tape O_O


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yashi
super member


Reged: 11/15/11

Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5486703 - 10/24/12 09:47 AM

so far i couldnt find a solution

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planet9
member


Reged: 01/23/13

Loc: UK
Re: GP-DX understanding Problem (RA Axis) new [Re: yashi]
      #5940936 - 06/26/13 06:23 AM

hi Sorry for digging out old thread, but this is very relevant to what I am up to these days. Have you got answers to this questions? cheers.

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orlyandico
Postmaster
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Reged: 08/10/09

Loc: Singapore
Re: GP-DX understanding Problem (RA Axis) new [Re: planet9]
      #5940943 - 06/26/13 06:33 AM

Search on Google for the Takahashi EM10 manual.

It has a very good description of how to use these setting circles.

They are actually very cool. Poor man's GoTo that works all the time...


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Happy Birthday John Carruthers
Skiprat
*****

Reged: 02/02/07

Loc: Kent, UK
Re: GP-DX understanding Problem (RA Axis) new [Re: orlyandico]
      #5942510 - 06/27/13 04:05 AM

You can find the gp-dx manual here;
http://arnholm.org/astro/gpmanual/

The verniers are good but take some getting used to. If you ever used vernier calipers it comes easier.

As mentioned, off set from a known target is a quick way to get aligned.


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photonhunter
member


Reged: 02/24/07

Re: GP-DX understanding Problem (RA Axis) new [Re: John Carruthers]
      #5945841 - 06/29/13 12:47 AM

You tighten the set screw when using the polar alignment scope to use the RA ring as an hour graduation ring. Normally when observing it should be loosened.

The RA ring (with the set screw loosened) should have enough friction to follow the RA axis as it turns.


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planet9
member


Reged: 01/23/13

Loc: UK
Re: GP-DX understanding Problem (RA Axis) new [Re: photonhunter]
      #5949242 - 07/01/13 08:30 AM

hi

Do I need some kind of auto tracking or GOTO interface for the auto tracking with GP-DX mount? I have just the GP-DX fitted with RA and DEC motor and DD-1 two axis controller. I can move the scope with the controller to both axis, but I do not know how to activate auto tracking.

When stationery, I can hear the GPDX motors ticking away, so I was under impression that they are auto tracking, but when I check the EP, they are not.

Thanks.

Edited by planet9 (07/01/13 08:31 AM)


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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: planet9]
      #5949379 - 07/01/13 10:11 AM

The mount will track when turned on. Remember, it will be very slow movement. For go-to you will need new motors and a new controller.

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planet9
member


Reged: 01/23/13

Loc: UK
Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5949772 - 07/01/13 02:15 PM

Is a lot slower than it should be?

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Happy Birthday John Carruthers
Skiprat
*****

Reged: 02/02/07

Loc: Kent, UK
Re: GP-DX understanding Problem (RA Axis) new [Re: planet9]
      #5950749 - 07/02/13 03:43 AM

how slow? it should track at 1 rev / day.

I suspect you have MT1 motors and a basic guiding handset.
If you can find an old Vixen Skysensor 2000 it might help. I fitted a Skywatcher Synscan goto drive set to my Vixen SP but the Ioptron drive set will also fit.


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planet9
member


Reged: 01/23/13

Loc: UK
Re: GP-DX understanding Problem (RA Axis) new [Re: John Carruthers]
      #5951476 - 07/02/13 03:00 PM

I will just use it as it is. I do not want to add any new GOTO or Digital accessories to the mount. It would have been good, if it was working AUTO Tracking with what it is got, but it is still good mount as is.

Thanks for your suggestion. cheers.


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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: planet9]
      #5951610 - 07/02/13 03:57 PM

Quote:

Is a lot slower than it should be?




It's a "clock" drive. It will move with a speed commensurate with that name: one revolution in a sidereal day, 23 hours, 56 minutes, 4 seconds.


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planet9
member


Reged: 01/23/13

Loc: UK
Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5951642 - 07/02/13 04:12 PM

Quote:

Quote:

Is a lot slower than it should be?




It's a "clock" drive. It will move with a speed commensurate with that name: one revolution in a sidereal day, 23 hours, 56 minutes, 4 seconds.




Yes, that is what I thought. But when I was viewing the Moon with ORION DX300, it was in the centre of the FOV. I thought the GP-DX clock drive will keep it in the centre of the FOV by compensating the Earth's movement, but it wasn't. The Moon moved away from the FOV quickly, even when the GP-DX motor was ticking away. I was using 9mm EP, which gave about 130x magnification.


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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: planet9]
      #5951738 - 07/02/13 04:57 PM

How good a polar alignment did you do?

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planet9
member


Reged: 01/23/13

Loc: UK
Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5951797 - 07/02/13 05:46 PM

Polar scope was set for rough alignment to the north, and then set for my location 52 degrees which is UK.

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rmollise
Postmaster
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Reged: 07/06/07

Re: GP-DX understanding Problem (RA Axis) new [Re: planet9]
      #5952746 - 07/03/13 09:16 AM

Whether that was good enough depends on how fast the Moon moved out of the field. Center on the Moon, see how it moves, then _turn off the drive_ and see if that changes things.

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comets4tom
professor emeritus


Reged: 02/08/05

Loc: Texas
Re: GP-DX understanding Problem (RA Axis) new [Re: rmollise]
      #5953003 - 07/03/13 12:11 PM

Two other things to check for.

Make sure you have tightened the clutches on the mount (the black levers)or it will not track.

If the mount is grossly imbalanced it will also fail to track properly. You will need to check the declination balance and then the right ascension balance.

Tom H.


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Happy Birthday John Carruthers
Skiprat
*****

Reged: 02/02/07

Loc: Kent, UK
Re: GP-DX understanding Problem (RA Axis) new [Re: planet9]
      #5955590 - 07/05/13 03:54 AM

Quote:

Polar scope was set for rough alignment to the north, and then set for my location 52 degrees which is UK.



check your polarity, Vixen sometimes use centre negative.
Is there a N/S hemisphere switch? it may be driving backwards ;-)
If you could post a pic of your handset it will help.(or if it's marked DD1, DD3 etc?)

As mentioned above, check the balance and make sure the clutches aren't slipping. The Vixen mounts are generally very well made and smooth in operation.

If you are anywhere near Kent I could have a look?


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planet9
member


Reged: 01/23/13

Loc: UK
Re: GP-DX understanding Problem (RA Axis) new [Re: John Carruthers]
      #5968544 - 07/13/13 04:44 AM

They are working OK now. What was wrong before was, I think, the clutches were not locked strong enough on both axis. Last night I was looking at a few double stars, and made sure they are tightened firmly, and hey voila, it was tracking OK.

But after about 15 minutes, it was slightly losing tracking, so I had to follow the target manually by handset - maybe this is due to low battery power (using 8x dry cell, and the light was flashing between green and red, before it was only green) on the handset.

I will go to Argos, and buy a 12v engine starter, which also gives 9 and 12v DC out from rechargeable battery.

I see one from Sky-Watcher on eBay, but they are crazy expensive over 115 quid, and some other seller asking even twice or more of that , when the same rating power tank from Argos costs £29.95.

They are all 17Ah, so same rating, the SW one has some extra bits like radios and lights which are not essential needs. Save money, and put it towards another scope.

I am at outside of Edinburgh. cheers.

Edited by planet9 (07/13/13 07:30 AM)


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Happy Birthday John Carruthers
Skiprat
*****

Reged: 02/02/07

Loc: Kent, UK
Re: GP-DX understanding Problem (RA Axis) new [Re: planet9]
      #5971704 - 07/15/13 05:26 AM

Maplin do a 5A 12V camera power supply ...
http://www.maplin.co.uk/xvision-12v-dc-5000ma-powersupply-535932

or I use an old PC psu.


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