Jump to content


Photo

Atlas EQ-G Wiggle in RA

This topic has been archived. This means that you cannot reply to this topic.
9 replies to this topic

#1 jmasin

jmasin

    Mercury-Atlas

  • -----
  • Posts: 2784
  • Joined: 22 Dec 2008

Posted 19 May 2009 - 07:31 PM

Hi all,

I'm pretty new to this, so this may be normal.

I have an Atlas, on that is mounted Orion's 8" Newt. Orion dovetail and rings, and another Orion dovetail on top of the rings.

I've noticed with everything off, clutches tight that I can wiggle the mount a noticeable amount by grabbing the top dovetail and wiggling back and forth. I found this by accident when mounting the OTA.

Is this normal?

If not, does it mean a tear-down or warranty work?

Thanks for any pointers.

#2 Charlie Hein

Charlie Hein

    Voyager 1

  • *****
  • Administrators
  • Posts: 12359
  • Joined: 02 Nov 2003

Posted 19 May 2009 - 08:45 PM

It's got a little backlash. Does this interfere with your observing?

#3 jmasin

jmasin

    Mercury-Atlas

  • -----
  • Posts: 2784
  • Joined: 22 Dec 2008

Posted 19 May 2009 - 10:13 PM

No, definitely not with my observing.

I am trying to image and just starting out with guiding. I'm going through the normal growing/learning pains and was just wondering if this was something to sweat.

(I've been on a lot of boards for different hobbies and seen a lot of newbies with "is this normal" questions, and now I'm one of 'em :) ).

Thanks!

#4 red

red

    Explorer 1

  • -----
  • Posts: 56
  • Joined: 23 Apr 2008

Posted 20 May 2009 - 12:20 AM

I just solved this problem when it popped up after I rebuilt my Atlas. What you need to do is to back out the 3 small allen screws holding the saddle on. After the saddle is removed, you will see a black ring with two small holes in it around the center shaft. Use an adjustable spanner wrench to tighten up this ring and your problem should go away. If you still have questions you can always PM me.

#5 Charlie Hein

Charlie Hein

    Voyager 1

  • *****
  • Administrators
  • Posts: 12359
  • Joined: 02 Nov 2003

Posted 20 May 2009 - 06:14 AM

Hi Jon - Just to make sure we're all on the same page here, when you say this...

I can wiggle the mount a noticeable amount by grabbing the top dovetail and wiggling back and forth


...you're definitely talking about play only in the RA direction, or does it wiggle in pretty much every direction, indicating a loose part?

If it's the latter you can certainly try red's suggestion. Note also that the entire Dec shaft can get loose over time and need to be tightened up. The "nut" that holds the whole Dec shaft together is the part that has the counterweight shaft lock on it. There are three allen screws that lock this nut down once you get it tight enough. If it is indeed loose do not over tighten it. You need just enough "tightness" to remove any up/down play in the shaft without introducing any binding.

Note: If it's significantly loose and you mount is under warranty then you may consider calling your vendor to see what they will do for you.

If it's only play in the RA direction, I'm going to say something that some may call heresy - it may be that your mount will need to have a certain amount of backlash in RA in order to work at its best. Many do. This can easily be worked around for imaging by slightly unbalancing your load toward the east to ensure that the gear stays "loaded up".

If your mount is still under warranty and the backlash is not excessive (how far does the end of the extended counterweight shaft move when you rock it back and forth?) it's pretty much the only way to deal with it until you can try a mesh adjustment anyway - and it's likely that at the end of the day you'll still need to leave a little "play" in there.

#6 jmasin

jmasin

    Mercury-Atlas

  • -----
  • Posts: 2784
  • Joined: 22 Dec 2008

Posted 20 May 2009 - 09:25 AM

Guys, thanks for the continued comments.

I can say definitely YES, it is play in RA only, and it certainly seems to be rotating around the RA axis. By moving the top dovetail back and forth, the movement in the bottom of the CW shaft is 1-3mm (eyeballing this).

Charlie, your point is taken though regarding just letting it go. I must admit I have an MO of obsessing with new hobbies about things that are potentially wrong (as much as I hate that)... I probably just need to step back and leave it until it presents itself as a problem. I've just been struggling with erratic autoguide results (still very new) and I'm trying to figure out why.

Thanks for all the inputs, I will also check the above mentioned nuts/screws and make sure things are snug.

Thanks for the input.

#7 astro_baby

astro_baby

    Viking 1

  • -----
  • Posts: 998
  • Joined: 17 Jun 2008

Posted 20 May 2009 - 02:28 PM

It might also be sloppy worm gear engagement and or the worm end float is loose.

the RA worm gear is a complete swine to set up and you need the patience of Job to pull it off. I spent ages getting mine perfect.

Too tight and the motors will bind ( and let you know by making a real racket ), too loose and play appears.

You could take a look here if you want to try adjusting it.

http://www.adur-astr...ld/heq5-we1.htm

#8 averen

averen

    Vendor Main Sequence Software

  • *****
  • Vendors
  • Posts: 578
  • Joined: 20 Jan 2009

Posted 20 May 2009 - 02:31 PM

I would also just let it go...and I have in my CG-5. I tend to worry more about the rigidity of the dec rather than the RA. Your RA will tend to be loaded on one side or the other, depending on which side of the meridian it's on. Any wiggle is really only a problem when you're imaging through the meridian and gear backlash allows the mesh to flip to the other side of the gear...if that makes any sense.

All gears are going to have some amount of backlash in them. If it ain't broke...

Jared

#9 jmasin

jmasin

    Mercury-Atlas

  • -----
  • Posts: 2784
  • Joined: 22 Dec 2008

Posted 20 May 2009 - 03:23 PM

astro_baby, thanks for the link, I'll file that info away.

Jared, you are probably right!

Cheers.

#10 Charlie Hein

Charlie Hein

    Voyager 1

  • *****
  • Administrators
  • Posts: 12359
  • Joined: 02 Nov 2003

Posted 20 May 2009 - 03:30 PM

Guys, thanks for the continued comments.

I can say definitely YES, it is play in RA only, and it certainly seems to be rotating around the RA axis. By moving the top dovetail back and forth, the movement in the bottom of the CW shaft is 1-3mm (eyeballing this).

Charlie, your point is taken though regarding just letting it go. I must admit I have an MO of obsessing with new hobbies about things that are potentially wrong (as much as I hate that)... I probably just need to step back and leave it until it presents itself as a problem. I've just been struggling with erratic autoguide results (still very new) and I'm trying to figure out why.

Thanks for all the inputs, I will also check the above mentioned nuts/screws and make sure things are snug.

Thanks for the input.


1-3mm of movement in the counterweight bar is small enough to leave alone IMO. You'd spend a good amount of time re-doing the mesh and at the end of the day you may not get it any better - or you could even make things much worse by over-tightening the mesh.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics