Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Clarification on East Heavy Balancing...please fill in the blank

  • Please log in to reply
11 replies to this topic

#1 DuiA1

DuiA1

    Mariner 2

  • *****
  • topic starter
  • Posts: 218
  • Joined: 07 May 2012
  • Loc: Ontario, Canada

Posted 01 June 2015 - 03:42 PM

I've read a few threads on this and still not clear.  Please help me fill in the blank so I can get this right.

 

1.  Imaging East of the Meridian (Scope Pointing East):

- Telescope should fall slightly to the East or West? Slightly Nose heavy or Diagonal heavy?

 

2.  Imaging West of the Meridian (Scope Pointing West):

- Telescope should fall slightly to the East or West? Slightly Nose heavy or Diagonal heavy?

 

I believe to engage the gears continuously for 

1.  Scope falls slightly East and nose heavy

2.  scope falls slightly West and Diagonal heavy

 

is this correct?

 

thx 

Dui



#2 Cotts

Cotts

    Just Wondering

  • *****
  • Moderators
  • Posts: 9667
  • Joined: 10 Oct 2005
  • Loc: Madoc, Ontario

Posted 01 June 2015 - 04:01 PM

Dui. 

 

For a German EQ mount like your AZEQ whatever is on the EAST side of the mount should be a few ounces heavier than the west.  This causes the mount to be lifting that extra weight.   If you are imaging toward the east then the counterweight will be on the east side and you can velcro a beanbag* onto the counterweights.   If you are imaging toward the west then the telescope will be on the east side and you velcro the beanbag* to the telescope.

 

For a fork-mounted SCT like the LX90  you put the beanbag on the east 'end' of the telescope.  So, if you are imaging toward the east the objective end of the scope will require the beanbag*.  If you are imaging toward the west then put the beanbag* near the eyepiece end.  Difficulty:  The fork mount is able to image as your target crosses the meridian.  If you load the east side before the meridian crossing (good) the balance will shift suddenly just after the scope crosses the meridian and will likely cause a shudder and a bump which will wreck your image (bad).

 

Don't think of the scope 'falling' one way or the other.  Think of putting a slight lifting load on your scope.  That load will always be on the east side of the scope/mount system, no matter what sort of driven equatorial mount you have.

 

* Using a beanbag is the easiest method to put the load on.  Much easier than trying to slide counterweights a bit this way or that way....

 

Dave


  • samuelpkco likes this

#3 Midnight Dan

Midnight Dan

    Voyager 1

  • *****
  • Posts: 13165
  • Joined: 23 Jan 2008
  • Loc: Hilton, NY, Yellow Zone (Bortle 4.5)

Posted 01 June 2015 - 04:54 PM

I've read a few threads on this and still not clear.  Please help me fill in the blank so I can get this right.

 

1.  Imaging East of the Meridian (Scope Pointing East):

- Telescope should fall slightly to the East or West? Slightly Nose heavy or Diagonal heavy?

 

2.  Imaging West of the Meridian (Scope Pointing West):

- Telescope should fall slightly to the East or West? Slightly Nose heavy or Diagonal heavy?

 

I believe to engage the gears continuously for 

1.  Scope falls slightly East and nose heavy

2.  scope falls slightly West and Diagonal heavy

 

is this correct?

 

thx 

Dui

 

1. if on the east side, and clutches are released, the telescope should move *down*.

 

2. if on the west side, and clutches are released, the telescope should move *up*

 

In both of these cases, the mount will *rotate* towards the east on the RA axis when the clutches are released.  With RA rotation, you want east-heavy because, as Dave points out, the RA motor is driving the mount towards the west and you want it to be pushing against the weight.

 

Nose or diagonal heavy is completely separate and has to do with Dec rotation, not RA rotation.  For Dec rotation, the motors are normally not driving one way or the other.  When guiding, you will get some motion in the motors, but you don't know which direction it will be, and will in fact change from moment to moment.  Since you can't provide weight against the motor direction, you can't preload in one particular direction.  

 

Nonetheless, to avoid backlash, it's good to have the Dec axis a little imbalanced too.  But it can be in either direction.  Doesn't really matter.

 

-Dan



#4 DuiA1

DuiA1

    Mariner 2

  • *****
  • topic starter
  • Posts: 218
  • Joined: 07 May 2012
  • Loc: Ontario, Canada

Posted 01 June 2015 - 05:35 PM

Dan, I think I'm getting closer.  In your answer, 1 means the telescope is east of the pier correct? Because the stars rotate counterclockwise when you look at Polaris, you want the telescope  to go down slightly on the east side to engage the gears correct?

When the telescope is on the west side of the pier, would one have to adjust the weights?  Or is east heavy good for both scenarios listed. 

Thx Dan and Dave for your help.

 

Dave, i think light just went on...whatever is on the east side has to be heavier.  Like your bean bag analogy.  So there is a slight adjustment of the weights when shifting from east to west imaging. Thx.  I think I got it.  

 

Trying my my first guiding tomorrow night...weather permitting.

Dui


Edited by DuiA1, 01 June 2015 - 05:47 PM.


#5 sazam

sazam

    Sputnik

  • -----
  • Posts: 44
  • Joined: 31 Aug 2013

Posted 01 June 2015 - 08:57 PM

This may help clarify.

 

"When using a German Equatorial mount, you need the gear to be lifting the weight, not allowing it to drop.  This means when the telescope is on the East side -- it is coming up -- that the counterweight should be adjusted so the telescope end is a little heavier. With the telescope on the West side, the counterweight (which is on the east side) end should be a little heavier.  If it isn't set this way, the telescope will move in little jerks as the gears bounce back and forth, and it will be impossible to guide." 

 

Whichever part of the sky you plan on imaging, i.e. telescope pointing east while imaging vs west, use the above methods to adjust the weight.

 

 

-Sal



#6 Cotts

Cotts

    Just Wondering

  • *****
  • Moderators
  • Posts: 9667
  • Joined: 10 Oct 2005
  • Loc: Madoc, Ontario

Posted 01 June 2015 - 09:13 PM

Dui, the beanbag is a method, for actual use, not just an analogy.  A bit of velcro or elastic bands or whatever to hold it on...   It's the easiest way to add a bit of weight to the East side.

 

Dave 



#7 DuiA1

DuiA1

    Mariner 2

  • *****
  • topic starter
  • Posts: 218
  • Joined: 07 May 2012
  • Loc: Ontario, Canada

Posted 01 June 2015 - 10:00 PM

Awesome folks.  I now understand...thanks to your help.  Dave, I have Velcro ankle weights which I will use for this purpose.  Thanks again. Clear skies.

Dui


Edited by DuiA1, 01 June 2015 - 10:03 PM.


#8 Per Frejvall

Per Frejvall

    In Memoriam

  • *****
  • In Memoriam
  • Posts: 893
  • Joined: 28 Sep 2012
  • Loc: Saltsj√∂baden, Sweden

Posted 01 June 2015 - 11:05 PM

Do you have enough slack in your gears to warrant using this "method"? If everything is tight you shouldn't need to. For those who practice this art and have remote or unattended setups, how do you image all night?

 

My NEQ6 never needed it as far as I can tell... Perhaps in its delivered state, but not after adjustments and tweaks.

 

/per


  • nomosnow likes this

#9 Hawkdl2

Hawkdl2

    Viking 1

  • *****
  • Posts: 674
  • Joined: 22 Feb 2015
  • Loc: Claremont, CA

Posted 03 June 2015 - 06:54 PM

I "East bias" in RA with great results but had trouble continuously imaging near or through the meridian because of the need to change the balance bias, so I built a system that provides consistent, measurable and linear bias to the East regardless of the target location. A bit more complex than taping weights to the OTA, but it works perfectly and requires no adjustment once I dialed in the proper amount of weight to hang (currenly an otherwise unused 5.8oz deep socket I had in my shop).  

 

DSC_6392_zpstn5adufq.jpg 


  • rkayakr likes this

#10 Midnight Dan

Midnight Dan

    Voyager 1

  • *****
  • Posts: 13165
  • Joined: 23 Jan 2008
  • Loc: Hilton, NY, Yellow Zone (Bortle 4.5)

Posted 04 June 2015 - 11:35 AM

Hi Dui:

 

 

Just getting back to this thread.

 

 

 

 Dan, I think I'm getting closer.  In your answer, 1 means the telescope is east of the pier correct? Because the stars rotate counterclockwise when you look at Polaris, you want the telescope  to go down slightly on the east side to engage the gears correct?

 

 

Correct.

 

 

 

 When the telescope is on the west side of the pier, would one have to adjust the weights?  Or is east heavy good for both scenarios listed.

 

You want east-heavy in both scenarios.  But to achieve that, you have to adjust the weights depending on where the scope is.  So, when the telescope is on the east side, you want it's side to be slightly heavier, so the weights have to move slightly in towards the mount to make the weight-side lighter.  When the telescope is on the west side, you want the weight-side to be heavier because it is now on the east.  So you need to move the weights outward a bit from the balance point.

 

Again, you want whichever "thing" is on the east side (scope or weights) to be heavier.  When you get to a meridian flip, the "thing" that's on the east side changes so you have to adjust the weights accordingly.

 

Adjusting the weights after a meridian flip can be a pain, so that's why some people use the string method shown above.  With that technique, the extra weight is always on the east side, no matter which side of the meridian you're on.  It has the added advantage of always applying the same additional force regardless of the mount position.  When you adjust the weights, they have the most effect when sticking straight out to the side, less effect as they move down, and zero effect when pointing straight down.

 

-Dan


Edited by Midnight Dan, 04 June 2015 - 11:36 AM.


#11 Jason1970

Jason1970

    Explorer 1

  • -----
  • Posts: 99
  • Joined: 25 May 2009

Posted 09 November 2016 - 08:28 AM

Let me ask....

I am imaging remotely,
If the weight needs to be heavier on the east, what should i do when imaging the west skies?
Any recommendations?

Thank you

#12 Midnight Dan

Midnight Dan

    Voyager 1

  • *****
  • Posts: 13165
  • Joined: 23 Jan 2008
  • Loc: Hilton, NY, Yellow Zone (Bortle 4.5)

Posted 09 November 2016 - 10:42 AM

Let me ask....

I am imaging remotely,
If the weight needs to be heavier on the east, what should i do when imaging the west skies?
Any recommendations?

Thank you

 

When imaging remotely, obviously you cannot shift the weights for pre and post meridian situations.  So you have two options.  One is to make everything as perfectly balanced as you can and hope for the best.  If your mount design has little to no backlash, you might be ok.

 

For the other option, you'd need to create an arrangement on your mount where you have a cable that wraps around the RA hub, and hangs down on the east side.  A small weight placed on that cable will provide added weight on the east side, regardless of whether you're pre or post meridian.

 

-Dan


Edited by Midnight Dan, 09 November 2016 - 10:55 AM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics