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EXOS2 / mount level inconsistent with tripod level?


Alex Arjomand
 

Hi all,

I had a quick question about leveling the EXOS2 mount. I have noticed that if I: 
  1. Carefully level the tripod base surface using a 24" external ruler level,
  2. Next carefully attach the mount without moving the tripod
... it results in the bubble level on the mount being nowhere near level.

Is this expected (i.e. is the mount on a different plane than the tripod base)? Or should these two be different? Is it better to align using the bubble level or by leveling the tripod?

Thank you!
Alex

--
Mounts: ES EXOS2 PMC-8
Scopes: Celestron C8SE (OTA from Nexstar 8SE), 10" Antares Dobsonian
Software: ASCOM / Stellarium / Sharpcap
Computer: Lenovo X1 Carbon, Windows 10/64
Cameras: ASI385
Location: Toronto / Bortle 8


Jeny@
 

How I did - attach mount head to a tripod, put level on saddle and level it (saddle should be parallel to the ground)
Make a dot with a marker on mount's bubble where 'true' level is.
--
EXOS2-GT PMC8
Orion150 Mak, Polemaster, ZWO ASI178MM


Jeff Snell
 

Mine was nowhere close either but that is likely pretty common for small bubble levels like that.  They just won't overcome the friction inside the glass without a lot of "tapping."  I bought a small 8" builder's level from Lowe's.  It sits nicely with the mount attached on a little bit of a ledge along the left side of the mount as you face north.  Fits well across the back of the mount too underneath the polar scope.

Jeff

PMC-Eight w/Explore Stars
ES ED80mm APO
Celestron 8" Edge HD
Canon Ti-5 w/ Spencer Camera Astro-mod
Lenovo Serial Connection w/APT, CdC, PHD2, Orion Starshoot Auto Guider, Polemaster


On Mon, Jun 29, 2020 at 10:41 AM Jeny@ via groups.io <miachyn_yevhenii=yahoo.com@groups.io> wrote:
How I did - attach mount head to a tripod, put level on saddle and level it (saddle should be parallel to the ground)
Make a dot with a marker on mount's bubble where 'true' level is.
--
EXOS2-GT PMC8
Orion150 Mak, Polemaster, ZWO ASI178MM


Suarez Tizoc
 

hi,
could you post a photo of where you are setting the level on the mount?
an image is worth a thousand words :)
thanks and stay safe

On Jun 29, 2020, at 11:23 AM, Jeff Snell <Jeffery.snell1@...> wrote:

Mine was nowhere close either but that is likely pretty common for small bubble levels like that.  They just won't overcome the friction inside the glass without a lot of "tapping."  I bought a small 8" builder's level from Lowe's.  It sits nicely with the mount attached on a little bit of a ledge along the left side of the mount as you face north.  Fits well across the back of the mount too underneath the polar scope.

Jeff

PMC-Eight w/Explore Stars
ES ED80mm APO
Celestron 8" Edge HD
Canon Ti-5 w/ Spencer Camera Astro-mod
Lenovo Serial Connection w/APT, CdC, PHD2, Orion Starshoot Auto Guider, Polemaster


On Mon, Jun 29, 2020 at 10:41 AM Jeny@ via groups.io<miachyn_yevhenii=yahoo.com@groups.io> wrote:
How I did - attach mount head to a tripod, put level on saddle and level it (saddle should be parallel to the ground)
Make a dot with a marker on mount's bubble where 'true' level is.
-- 
EXOS2-GT PMC8
Orion150 Mak, Polemaster, ZWO ASI178MM




medin003 University of Minnesota
 

I don't understand the necessity of leveling the mount head (except to make it somewhat easier to polar align).  There are four axes of rotation; azimuth, altitude, ra, and dec.  The first two are only used to align the ra axis to the celestial pole; once that is accomplished, they are locked.  I suspect that the tripod feet could be glued to a vertical wall and if there was enough freedom of movement to align the ra axis the mount would track just fine.  I know levelness is necessary for altaz mounts, but I don't see that is the case for eq mounts.

Virus-free. www.avast.com


On Mon, Jun 29, 2020 at 12:23 PM Jeff Snell <Jeffery.snell1@...> wrote:
Mine was nowhere close either but that is likely pretty common for small bubble levels like that.  They just won't overcome the friction inside the glass without a lot of "tapping."  I bought a small 8" builder's level from Lowe's.  It sits nicely with the mount attached on a little bit of a ledge along the left side of the mount as you face north.  Fits well across the back of the mount too underneath the polar scope.

Jeff

PMC-Eight w/Explore Stars
ES ED80mm APO
Celestron 8" Edge HD
Canon Ti-5 w/ Spencer Camera Astro-mod
Lenovo Serial Connection w/APT, CdC, PHD2, Orion Starshoot Auto Guider, Polemaster


On Mon, Jun 29, 2020 at 10:41 AM Jeny@ via groups.io <miachyn_yevhenii=yahoo.com@groups.io> wrote:
How I did - attach mount head to a tripod, put level on saddle and level it (saddle should be parallel to the ground)
Make a dot with a marker on mount's bubble where 'true' level is.
--
EXOS2-GT PMC8
Orion150 Mak, Polemaster, ZWO ASI178MM


Jerry Hubbell - Explore Scientific VP Engineering
 

On Mon, Jun 29, 2020 at 01:38 PM, medin003 University of Minnesota wrote:
I know levelness is necessary for altaz mounts, but I don't see that is the case for eq mounts.
The reason to level the mount generally is to provide a consistent result every time you set up your mount night after night after taking it down after a session. I would also suggest as discussed previously to mark where your tripod feet are located (as precisely as you can manage). This provides a good starting point to touch up your polar alignment from the previous session instead of starting from scratch, this assumes that you set you mount up at the same location every session of course. 

The north south level does not matter as much as the east west level because the north south axis is taken care of with the altitude adjustment.
If the east west is not level, the tilt will impact the pointing even if you have a "perfect" polar alignment as the mounts coordinate system is tilted in relation to the celestial coordinate system in that case.

Wes can talk more about this, but this is generally why you would want to level the mount.
 
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


Wes Mcdonald
 

Medin003

As Jerry mentioned the level will impact your goto performance should the mount be tilted west-east.  Now I like to think of miss-level as being resolvable into two orthogonal components, one east-west and one north-south.  Thus it is best to realize that if you are not level it is very likely there is an error east-west.

The simplest thought experiment you can do is rotate the DEC to 0 with the RA at 0.  You will notice the telescope is pointing east and should be level relative to the local gravity vector.  Note that if your mount is tilted, the telescope will not be level -- corresponding to an error in DEC pointing.  This error will be manifest everywhere the scope points in one form or another.

Another reason to have the mount level involves another setup error that affects your goto performance -- polar home.  Polar home is the position where the mount is pointing at DEC =90, RA = 0 and the RA axis is aligned with the north (south) celestial pole.  In the Exos2 mount this is approximately where the alignment marks are on the mount.  But note what happens should your DEC polar home position be off by a few degrees and you should repeat the 90 degree movement of DEC as above, even with a level mount.  The telescope tube will not be level.  For this reason I advise people to make sure they find polar home and mark the mount appropriately.  This allows you to set up correctly each time.

The problem is DEC polar home looks alot like a mislevel in regard to how the mount goto performs.  Thus it is important to get your mount level, find polar home, mark polar home, and always level the mount prior to each use (once you have moved it for storage etc).  I have written a note on this describing how to find polar home, which can be found in the Files section of the Mounts subgroup. 

Hope this helps.

Wes.




--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired


brian skinner
 

I generally use the same location for my viewing, which is my patio, a good hard surface, which is almost level. Before I place my mount on a table (such that the mount is more stable due to not having to extend the tripod legs at all) on the patio, I first check that the table is level. To take the time to ensure the table is level is advisable and I do this using an 18inch long spirit level and don't rely wholly on the mounts bubble level. 

Having said that the bubble level appears to be sufficiently sensitive to show any significant non level in the tripod, but you do need to peer at the bubble level from vertically above it for accuracy, which can be a bit tricky depending on the mounts height.

If you have to position the mount and tripod on soft ground you obviously run the risk of the mount moving out of level as it beds down.

I can't believe the mount and tripod can be different in level, if the tripod is level surely  mount level is assured.

Thankyou, Brian


Gord Farmer
 




On Jun 29, 2020, at 1:23 PM, Jeff Snell <Jeffery.snell1@...> wrote:


Mine was nowhere close either but that is likely pretty common for small bubble levels like that.  They just won't overcome the friction inside the glass without a lot of "tapping."  I bought a small 8" builder's level from Lowe's.  It sits nicely with the mount attached on a little bit of a ledge along the left side of the mount as you face north.  Fits well across the back of the mount too underneath the polar scope.

Jeff

PMC-Eight w/Explore Stars
ES ED80mm APO
Celestron 8" Edge HD
Canon Ti-5 w/ Spencer Camera Astro-mod
Lenovo Serial Connection w/APT, CdC, PHD2, Orion Starshoot Auto Guider, Polemaster


On Mon, Jun 29, 2020 at 10:41 AM Jeny@ via groups.io <miachyn_yevhenii=yahoo.com@groups.io> wrote:
How I did - attach mount head to a tripod, put level on saddle and level it (saddle should be parallel to the ground)
Make a dot with a marker on mount's bubble where 'true' level is.
--
EXOS2-GT PMC8
Orion150 Mak, Polemaster, ZWO ASI178MM


Gord Farmer
 




On Jun 29, 2020, at 1:23 PM, Jeff Snell <Jeffery.snell1@...> wrote:


Mine was nowhere close either but that is likely pretty common for small bubble levels like that.  They just won't overcome the friction inside the glass without a lot of "tapping."  I bought a small 8" builder's level from Lowe's.  It sits nicely with the mount attached on a little bit of a ledge along the left side of the mount as you face north.  Fits well across the back of the mount too underneath the polar scope.

Jeff

PMC-Eight w/Explore Stars
ES ED80mm APO
Celestron 8" Edge HD
Canon Ti-5 w/ Spencer Camera Astro-mod
Lenovo Serial Connection w/APT, CdC, PHD2, Orion Starshoot Auto Guider, Polemaster


On Mon, Jun 29, 2020 at 10:41 AM Jeny@ via groups.io <miachyn_yevhenii=yahoo.com@groups.io> wrote:
How I did - attach mount head to a tripod, put level on saddle and level it (saddle should be parallel to the ground)
Make a dot with a marker on mount's bubble where 'true' level is.
--
EXOS2-GT PMC8
Orion150 Mak, Polemaster, ZWO ASI178MM


Gord Farmer
 

Get a small mirror hold it out of 45° angle makes it easy to centre the bubble


On Jun 30, 2020, at 4:17 PM, Gord Farmer <gordfarmer@...> wrote:


<image1.jpeg>



On Jun 29, 2020, at 1:23 PM, Jeff Snell <Jeffery.snell1@...> wrote:


Mine was nowhere close either but that is likely pretty common for small bubble levels like that.  They just won't overcome the friction inside the glass without a lot of "tapping."  I bought a small 8" builder's level from Lowe's.  It sits nicely with the mount attached on a little bit of a ledge along the left side of the mount as you face north.  Fits well across the back of the mount too underneath the polar scope.

Jeff

PMC-Eight w/Explore Stars
ES ED80mm APO
Celestron 8" Edge HD
Canon Ti-5 w/ Spencer Camera Astro-mod
Lenovo Serial Connection w/APT, CdC, PHD2, Orion Starshoot Auto Guider, Polemaster


On Mon, Jun 29, 2020 at 10:41 AM Jeny@ via groups.io <miachyn_yevhenii=yahoo.com@groups.io> wrote:
How I did - attach mount head to a tripod, put level on saddle and level it (saddle should be parallel to the ground)
Make a dot with a marker on mount's bubble where 'true' level is.
--
EXOS2-GT PMC8
Orion150 Mak, Polemaster, ZWO ASI178MM