Mesu e200 bent knee pier - GEM vs EQ


Dan Gray
 

Hi Jonk,
Here's an image with settings.  Look carefully on the right side, you'll see the meridian flip lines.
In the upper left is the settings:


On Wed, Feb 17, 2021 at 7:31 AM Don W <westergren@...> wrote:
Hi Jonk,

A GEM is not a FORK/Equatorial.  It really is best to use a GEM as a GEM.

Set the Meridian West to 90° and leave the Meridian East at zero.  That will make all motion looking east with counter weight Down, and all looking west counter weight Up.  The mount will never do a meridian flip.

Set your altitude limit to whatever you want, either with the fixed alt limit in Mount Parms or using the SiTech.hrz file.  Generally astrophotography is badly affected by refraction below 30° altitude.  However you can move below the altitude limit with the handpad to set a lower Park position if desired.

DEC motion is either North (toward the North Pole) or South toward the South Pole.  If you move toward a Pole from above, when you get to the pole, the DEC motion reverses when pointed BELOW the pole.  This is true regardless of a GEM or EQUATORIAL.  Parking at the pole is truly ambiguous and will cause you problems.  Parking at the pole can not initialize RA.

The reversal of Dec you experienced when set as EQ is exactly why I say don't set it as EQ.

Don W


Don W
 

Hi Jonk,

A GEM is not a FORK/Equatorial.  It really is best to use a GEM as a GEM.

Set the Meridian West to 90° and leave the Meridian East at zero.  That will make all motion looking east with counter weight Down, and all looking west counter weight Up.  The mount will never do a meridian flip.

Set your altitude limit to whatever you want, either with the fixed alt limit in Mount Parms or using the SiTech.hrz file.  Generally astrophotography is badly affected by refraction below 30° altitude.  However you can move below the altitude limit with the handpad to set a lower Park position if desired.

DEC motion is either North (toward the North Pole) or South toward the South Pole.  If you move toward a Pole from above, when you get to the pole, the DEC motion reverses when pointed BELOW the pole.  This is true regardless of a GEM or EQUATORIAL.  Parking at the pole is truly ambiguous and will cause you problems.  Parking at the pole can not initialize RA.

The reversal of Dec you experienced when set as EQ is exactly why I say don't set it as EQ.

Don W


Jonk
 

I have a Mesu e200 which is destined for installation on a custom bent knee / flipless pier. I wanted this to avoid meridian flips and also to eliminate the possibilty of any crashes.

In the Sitech settings as we know, there are choices for how you wish to use it. The Mesu e200 comes set as default to GEM, with meridian limits set.

I have played with these limits and it would seem as though the only way to completely remove all limits (which is what I want), is to set it as an EQ mount.

I played with EQ mode last night on the bench, and I have a question. I'm using the latest Sitechexe 95H and the controller is as far as I know, contains the latest firmware.

In GEM mode, starting in the typical park position (DEC at 90 degrees, weights down, facing NCP), clicking on a star due E or W (so DEC at 0 degrees), syncing, pushing N towards NCP and setting park all works as expected. The mount is now initialised and parked. Removing power, closing sitech then starting it all back up again works as expected, no need to reinitialise, gotos work etc.

So, changing onto EQ mode, this removes all meridian limits etc. Good. Repeat the procedure - weights down, DEC at 90 degrees, click on a star due E or W (so DEC at 0 degrees), sync. All good so far. Pressing N (software or hand controller) to move back to the park position, the DEC moves the opposite direction. Gotos do the same, so does park (after setting park in the correct place). I'm not sure I understand this, as skyview shows the reticle behaving correctly, i.e it moves DEC N towards the NCP whereas the mount DEC moves in the opposite direction.
 
My question - is it just a case ot setting the 'reverse DEC servo / encoder' in the servo setup or is there something else I'm missing?

I am certain that I want to remove all GEM limits, not just extend them to max, I don't have any possibility of the mount crashing the scopes into anything.

Here's a render of my pier and Mesu. You can see that a crash is not possible.

2003782277_Mountonpierwithweightsrender2.jpg.264c5d37b74969c953dd1cfa1ce039ae.jpg