DEC Balancing


 

Shailendra,

With an EXOS2, you're not going to be able to get a perfect DEC balance, and you probably don't want that anyway.  If you could achieve a perfect DEC balance, and then you pointed near-vertical, you would likely end up with the DEC axis rocking within its' gear lash (h/t Jerry).   If you're using a refractor, go camera-heavy, call it good, and don't worry about it being a little lopsided.  If you're using something else, then apply the concept as best you can.

Hope this helps...

Also - pls update your .sig with your gear - helps you get better responses.  :-)

- Bob

On Tue, Aug 11, 2020, at 07:41, Shailendra Sharma wrote:
How are you balancing your dec? Mine is near on impossible? Got a pic of how your cables are rooted? And how do you offset the balance due to the dec motor assembly?

Cheers



From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Mike Leemhuis <skislalom1@...>
Sent: Monday, August 10, 2020 7:59:03 PM
To: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io>
Subject: [ESPMC-Eight] Pluto blink comparator astrophotography #astrophotography #EXOS2 #VIDEO
 
I decided last week to try to photograph Pluto since it was the only "planet" that I hadn't photographed yet with my EXOS-2.  So I used my plate solver to aim my ES 102CF and took about 40 - 1 minute exposures.  After stacking the pictures I soon realized that Pluto must either be too small or it must look like just another star because I couldn't find it in the hundreds of stars in the picture.  So I decided to repeat the process the following day and then compare the pictures to see what moves.  That would have to be Pluto.  My friend who is the head of the Astronomy club here in Lexington told me that's how Clyde Tombaugh found Pluto in 1930 although he used a mechanical blink comparator contraption to look for movement.  So I did that the modern way by using Affinity Photo to align both pictures and then made a short movie switching back and forth between the them.  I'll attach a link to the video here:
You can play this video in a loop and replicate with today's technology what Clyde did back in 1930. Pluto pops out if you look closely.  This would be a terrific science experiment for a high school student if you ever need an idea!

Mike

--
Location: Nicholasville, KY
Mount: Explore Scientific Exos-2
Scope: Explore Scientific ED102CF, Orion 60mm guidescope
Camera: QHY163C and QHY5L-ii
Filter: Optolong L-eNhance 2"
Software: ASCOM, PHD2, CDC, Stellarium, Sharpcap Pro, NINA, Deep Sky Stacker, Affinity Photo, Lightroom
Computer:  ASRock X570 Steel Legend, AMD Ryzen 7 3700X 8-Core Processor, 3600Mhz
Extras:  Lots of 3D printed parts I designed for improved usability


--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Shailendra Sharma <sshailendrasharma@...>
 

Ahh cool thanks. Its not then dec balance in the normal sense at 90 degrees. Its when I release the dec clutch, in the home position it swings straight to the right. I have put my guide scope on the left to compensate. And some weights. But now weirdly. Either way left or right. It wants to drift to the north position slightly so upwards from left or right which is weird.!  Main reason I ask is if I play with it. In the guiding, the stats get better. Dec error is reduced. But its like move a cable slightly and hope it doesn't shift again!

Exos2 gt pmc-8
Skywatcher 102t refractor
Svbony 50mm guide scope
Zwi asi120mm mc-s

Thanks again.


From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Robert Hoskin <devonshire@...>
Sent: Tuesday, August 11, 2020 3:35:46 PM
To: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io>
Subject: [ESPMC-Eight] DEC Balancing
 
Shailendra,

With an EXOS2, you're not going to be able to get a perfect DEC balance, and you probably don't want that anyway.  If you could achieve a perfect DEC balance, and then you pointed near-vertical, you would likely end up with the DEC axis rocking within its' gear lash (h/t Jerry).   If you're using a refractor, go camera-heavy, call it good, and don't worry about it being a little lopsided.  If you're using something else, then apply the concept as best you can.

Hope this helps...

Also - pls update your .sig with your gear - helps you get better responses.  :-)

- Bob

On Tue, Aug 11, 2020, at 07:41, Shailendra Sharma wrote:
How are you balancing your dec? Mine is near on impossible? Got a pic of how your cables are rooted? And how do you offset the balance due to the dec motor assembly?

Cheers



From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Mike Leemhuis <skislalom1@...>
Sent: Monday, August 10, 2020 7:59:03 PM
To: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io>
Subject: [ESPMC-Eight] Pluto blink comparator astrophotography #astrophotography #EXOS2 #VIDEO
 
I decided last week to try to photograph Pluto since it was the only "planet" that I hadn't photographed yet with my EXOS-2.  So I used my plate solver to aim my ES 102CF and took about 40 - 1 minute exposures.  After stacking the pictures I soon realized that Pluto must either be too small or it must look like just another star because I couldn't find it in the hundreds of stars in the picture.  So I decided to repeat the process the following day and then compare the pictures to see what moves.  That would have to be Pluto.  My friend who is the head of the Astronomy club here in Lexington told me that's how Clyde Tombaugh found Pluto in 1930 although he used a mechanical blink comparator contraption to look for movement.  So I did that the modern way by using Affinity Photo to align both pictures and then made a short movie switching back and forth between the them.  I'll attach a link to the video here:
You can play this video in a loop and replicate with today's technology what Clyde did back in 1930. Pluto pops out if you look closely.  This would be a terrific science experiment for a high school student if you ever need an idea!

Mike

--
Location: Nicholasville, KY
Mount: Explore Scientific Exos-2
Scope: Explore Scientific ED102CF, Orion 60mm guidescope
Camera: QHY163C and QHY5L-ii
Filter: Optolong L-eNhance 2"
Software: ASCOM, PHD2, CDC, Stellarium, Sharpcap Pro, NINA, Deep Sky Stacker, Affinity Photo, Lightroom
Computer:  ASRock X570 Steel Legend, AMD Ryzen 7 3700X 8-Core Processor, 3600Mhz
Extras:  Lots of 3D printed parts I designed for improved usability


--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


 

Yes, you won't be able to overcome that lopsided DEC motor's weight. Rotate your guidescope to one side of your imaging scope, and you just change the point at which your balance goes off, because their weights and weight distribution won't match..  
 
Your guide stats are a useful troubleshooting tool, but the goal is round stars in your images.  If you've got that, for the exposure length you require, you've done the job.  Perhaps you might tweak a bit more in hopes of tightening them, but round is round.
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Wade Prunty
 

I would like to make a suggestion too. Always get back to the DEC with your cables. You might have to work with them to keep from snagging elsewhere, but the cables have weight to them, and if you leave them hanging of of the back of your system they will affect the balance throughout the night. I have the iEXOS-100 and I've very loosely ran a zip-tie under the DEC plate. I make sure it can spin freely and I then run my cables through it. This keeps the weight of the cable consistent the entire time I'm imaging, and removes a variable that can cause balance/guiding issues. You can sort of see what I'm talking about in the attached image.


Shailendra Sharma <sshailendrasharma@...>
 

This is how they are routed. Image

Image

Image




From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Wade Prunty <wadeprunty@...>
Sent: Tuesday, August 11, 2020 4:45:41 PM
To: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io>
Subject: Re: [ESPMC-Eight] DEC Balancing
 
I would like to make a suggestion too. Always get back to the DEC with your cables. You might have to work with them to keep from snagging elsewhere, but the cables have weight to them, and if you leave them hanging of of the back of your system they will affect the balance throughout the night. I have the iEXOS-100 and I've very loosely ran a zip-tie under the DEC plate. I make sure it can spin freely and I then run my cables through it. This keeps the weight of the cable consistent the entire time I'm imaging, and removes a variable that can cause balance/guiding issues. You can sort of see what I'm talking about in the attached image.


Dan Kahraman <dkahra213@...>
 

Hi Robert:

Exactly! Small mounts cannot internalize the location of their declination motor housing so this creates an imbalance issue the fact that they are small structures to begin with enhances the impact. A suggestion at balancing, applicable to Newtonian scopes, is to rotate the tube so that the focuser/imaging camera and the guide-scope/guide-camera are at the bottom centred along the longitudinal axis of the tube...the "sweet spot" may be with the focuser closer to the axis than the finder scope yet both straddling it on either side.

Dan Kahraman

On Tue, 11 Aug 2020 at 11:39, Robert Hoskin <devonshire@...> wrote:
Yes, you won't be able to overcome that lopsided DEC motor's weight. Rotate your guidescope to one side of your imaging scope, and you just change the point at which your balance goes off, because their weights and weight distribution won't match..  
 
Your guide stats are a useful troubleshooting tool, but the goal is round stars in your images.  If you've got that, for the exposure length you require, you've done the job.  Perhaps you might tweak a bit more in hopes of tightening them, but round is round.
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Shailendra Sharma <sshailendrasharma@...>
 

Yes stars are round.  Heres one stacked image very little editing. 

Image



From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Dan Kahraman <dkahra213@...>
Sent: Tuesday, August 11, 2020 5:00:58 PM
To: MAIN@espmc-eight.groups.io <MAIN@espmc-eight.groups.io>
Subject: Re: [ESPMC-Eight] DEC Balancing
 
Hi Robert:

Exactly! Small mounts cannot internalize the location of their declination motor housing so this creates an imbalance issue the fact that they are small structures to begin with enhances the impact. A suggestion at balancing, applicable to Newtonian scopes, is to rotate the tube so that the focuser/imaging camera and the guide-scope/guide-camera are at the bottom centred along the longitudinal axis of the tube...the "sweet spot" may be with the focuser closer to the axis than the finder scope yet both straddling it on either side.

Dan Kahraman

On Tue, 11 Aug 2020 at 11:39, Robert Hoskin <devonshire@...> wrote:
Yes, you won't be able to overcome that lopsided DEC motor's weight. Rotate your guidescope to one side of your imaging scope, and you just change the point at which your balance goes off, because their weights and weight distribution won't match..  
 
Your guide stats are a useful troubleshooting tool, but the goal is round stars in your images.  If you've got that, for the exposure length you require, you've done the job.  Perhaps you might tweak a bit more in hopes of tightening them, but round is round.
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Shailendra Sharma <sshailendrasharma@...>
 

Here is an image of what my guiding nor.ally looks alike after a while.
Image

Thanks
Exos 2 gt pmc-8
Skywatcher 102t
Svbony 50mm
Canon 600d
Zwo asi 120mm mc-s



From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Shailendra Sharma <sshailendrasharma@...>
Sent: Tuesday, August 11, 2020 5:07:39 PM
To: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io>
Subject: Re: [ESPMC-Eight] DEC Balancing
 
Yes stars are round.  Heres one stacked image very little editing. 

Image



From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Dan Kahraman <dkahra213@...>
Sent: Tuesday, August 11, 2020 5:00:58 PM
To: MAIN@espmc-eight.groups.io <MAIN@espmc-eight.groups.io>
Subject: Re: [ESPMC-Eight] DEC Balancing
 
Hi Robert:

Exactly! Small mounts cannot internalize the location of their declination motor housing so this creates an imbalance issue the fact that they are small structures to begin with enhances the impact. A suggestion at balancing, applicable to Newtonian scopes, is to rotate the tube so that the focuser/imaging camera and the guide-scope/guide-camera are at the bottom centred along the longitudinal axis of the tube...the "sweet spot" may be with the focuser closer to the axis than the finder scope yet both straddling it on either side.

Dan Kahraman

On Tue, 11 Aug 2020 at 11:39, Robert Hoskin <devonshire@...> wrote:
Yes, you won't be able to overcome that lopsided DEC motor's weight. Rotate your guidescope to one side of your imaging scope, and you just change the point at which your balance goes off, because their weights and weight distribution won't match..  
 
Your guide stats are a useful troubleshooting tool, but the goal is round stars in your images.  If you've got that, for the exposure length you require, you've done the job.  Perhaps you might tweak a bit more in hopes of tightening them, but round is round.
 
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Mike Leemhuis
 

I have to agree with the various suggestion people have made.  I'll attach a few pictures of my setup.  My concept is to route the cables in a path that has the least amount of motion.  That means keeping them very near the DEC and RA pivot axes.  As you can see in the pictures, I gather all the cables under the OTA and then route them off the front of the dovetail bar and then go to a clamp on the counterweight bar and then to the tripod legs.  This path seems least likely to get snagged on something.  It's the best of what I've found although there may be even better solutions.

I might add that a few months ago I made a DEC axis torsion spring to put a light bias torque on the DEC axis so the stepper only had to work in one direction.  After a lot of work, I wasn't able to show any improvement so I gave up.  But it was a good learning experience.  I even learned how to make torsion springs!

Mike




--
Location: Nicholasville, KY
Mount: Explore Scientific Exos-2
Scope: Explore Scientific ED102CF, Orion 60mm guidescope
Camera: QHY163C and QHY5L-ii
Filter: Optolong L-eNhance 2"
Software: ASCOM, PHD2, CDC, Stellarium, Sharpcap Pro, NINA, Deep Sky Stacker, Affinity Photo, Lightroom
Computer:  ASRock X570 Steel Legend, AMD Ryzen 7 3700X 8-Core Processor, 3600Mhz
Extras:  Lots of 3D printed parts I designed for improved usability


Shailendra Sharma <sshailendrasharma@...>
 

That's great thanks. I might try out the front then.

Its OK atm. It works. Lol.


From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Mike Leemhuis <skislalom1@...>
Sent: Tuesday, August 11, 2020 6:04:27 PM
To: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io>
Subject: Re: [ESPMC-Eight] DEC Balancing
 
I have to agree with the various suggestion people have made.  I'll attach a few pictures of my setup.  My concept is to route the cables in a path that has the least amount of motion.  That means keeping them very near the DEC and RA pivot axes.  As you can see in the pictures, I gather all the cables under the OTA and then route them off the front of the dovetail bar and then go to a clamp on the counterweight bar and then to the tripod legs.  This path seems least likely to get snagged on something.  It's the best of what I've found although there may be even better solutions.

I might add that a few months ago I made a DEC axis torsion spring to put a light bias torque on the DEC axis so the stepper only had to work in one direction.  After a lot of work, I wasn't able to show any improvement so I gave up.  But it was a good learning experience.  I even learned how to make torsion springs!

Mike




--
Location: Nicholasville, KY
Mount: Explore Scientific Exos-2
Scope: Explore Scientific ED102CF, Orion 60mm guidescope
Camera: QHY163C and QHY5L-ii
Filter: Optolong L-eNhance 2"
Software: ASCOM, PHD2, CDC, Stellarium, Sharpcap Pro, NINA, Deep Sky Stacker, Affinity Photo, Lightroom
Computer:  ASRock X570 Steel Legend, AMD Ryzen 7 3700X 8-Core Processor, 3600Mhz
Extras:  Lots of 3D printed parts I designed for improved usability


Wes Mcdonald
 

Shailendra 

It looks to me that your rig is very heavy in the rear. So much mass back.   This will cause your dec axis to swing to 90 degrees when the ra is not at 0.  This is what most people want to do but to a controlled extent. Your guide graph shows that you have a lot of dec backlash though which should not be the case if you are very heavy in the rear.

The way you correct excessive heaviness in the rear is to slide the rig forward in the saddle.  Not sure you can but that is the cure.  Or add more weight way forward on the tube.

What are the rms values for your dec guiding?  If they are in the under 2” sec range then you are going to have round stars mostly, provided you are not getting periodic long excursions.

Your guide graph in dec at least does not look that bad....pending the numbers

I agree with all the cable management comments. It is most important.  I am redoing all my power and usb wiring now to reduce the number of cables that have to cross the rotating axis.  My current arrangement is a nightmare.



Wes 

--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Shailendra Sharma <sshailendrasharma@...>
 
Edited

It looks it but its not that back heavy at all. Vid attached. See hiw it just wants to go back to the centre either way. 
 


From: MAIN@ESPMC-Eight.groups.io <MAIN@ESPMC-Eight.groups.io> on behalf of Wes Mcdonald <wesmcd6@...>
Sent: Tuesday, August 11, 2020 6:16:28 PM
To: MAIN@espmc-eight.groups.io <MAIN@espmc-eight.groups.io>
Subject: Re: [ESPMC-Eight] DEC Balancing
 
Shailendra 
 
It looks to me that your rig is very heavy in the rear. So much mass back.   This will cause your dec axis to swing to 90 degrees when the ra is not at 0.  This is what most people want to do but to a controlled extent. Your guide graph shows that you have a lot of dec backlash though which should not be the case if you are very heavy in the rear.
 
The way you correct excessive heaviness in the rear is to slide the rig forward in the saddle.  Not sure you can but that is the cure.  Or add more weight way forward on the tube.
 
What are the rms values for your dec guiding?  If they are in the under 2” sec range then you are going to have round stars mostly, provided you are not getting periodic long excursions.
 
Your guide graph in dec at least does not look that bad....pending the numbers
 
I agree with all the cable management comments. It is most important.  I am redoing all my power and usb wiring now to reduce the number of cables that have to cross the rotating axis.  My current arrangement is a nightmare.
 
 
 
Wes 

--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired