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Position Angles in the Era of clutchless Goto AltAz mounts.

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#1 gdjsky01

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Posted 28 August 2020 - 09:27 PM

Directions in the eyepiece when using AltAz goto mount...

I was attempting a few nights ago to see if I could guess a Position Angle or two. It's been a long time. I was picking Izar with a 90mm StellarVue SV90T on a Meade LX-65 mount... and it hits me... which way is which?

 

Back in the day, using a dob or anything AltAz that was not driven, west was where the object was going, east was where it came from, and north was 90 degrees counter-clockwise or clockwise depending on the scope. Also back in the day, if I was using an EQ mount, establishing directions was pretty obvious...

 

Now enter something like my original NexStar 5, or the recent LX-65 mount. Using the controls gets you nowhere (without a wedge) as the controls are not moving in the four cardinal directions. Stopping the mount, ah that would be grand... you know, hold a button and stops tracking, let up and starts again. Alas I see no such feature. Turn off the power? Well yeah that works! But now these blasted mounts won't start tracking again until aligned... that's sort of a pain point per star.  Worse yet they don't have clutches. So you can't move them manually.

 

So given those circumstances, how would you / do you establish N-S-E-W in the eyepiece? Or at least west. Probably something I am missing. Using an undriven mount like the StellarVue MG2 is childs play. I was just wondering however given prevalence of clutchless goto mounts, what do you do? And who came up with the very popular idea of no clutches on these goto mounts anyway? I guess it saved $30 or something.

 

Clear skies

 



#2 AstroBrett

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Posted 28 August 2020 - 09:52 PM

Turn off the drive, let the star drift, and align your reticle, then immediately take your measurement. You'll have to repeat for each measurement you want to take. Field rotation will be a constant unwanted companion ….

 

Brett



#3 gdjsky01

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Posted 28 August 2020 - 11:22 PM

Thank you for the reply. Turning off the drives in the case of these mounts means turning off the mount. And that, as I said means a new alignment (at least a basic one) after every star. Or worse everytime I need to center the star since that can not be done manually. However even that is not feasible as their is with no way to unlock the motors and let the mount move manually, so I would have seconds before the star is gone. Does not seem like a feasible solution. There may be no solution. It cloudy out :) so I was just asking what others do. Maybe the only answer is to not use an alt az mount if it is driven and lock to motors. But I was just wondering if I missed something. 



#4 mauigazer

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Posted 29 August 2020 - 02:16 AM

Does your Meade LX65 Mount have a "hybernate" or "sleep" mode in "Utilities"? Most driven mounts have something similar - check your manual. If you don't have a hard copy you can find it online.

#5 mauigazer

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Posted 29 August 2020 - 02:30 AM

I just found the manual for your mount online. Go to "Utilities" on pp. 25 &26 and it explains how to "sleep" the mount while keeping the clock running. 

S. McG. 


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#6 John Fitzgerald

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Posted 31 August 2020 - 08:37 AM

Use a mount that has auxiliary encoders.  Like the AZ/EQ-6.   Then you can move manually without losing alignment.


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#7 lionel

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Posted 02 September 2020 - 11:32 PM

I don’t see a way to easily tell directions in a driven alt-az mount unless you stop both drive motors to allow the target to drift west.  I bought an AZ Mount Pro partly because iOptron was smart enough to include a stop button on the hand pad.  Press it once, the tracking stops. Press it again and tracking resumes.

 

Having determined west drift for the pair one should be able to use a goniometer to guesstimate the position angle of the companion. I say that, but I haven’t spent any time working out a convenient way to do this,...it would probably involve a goniometer app on my iPhone.

 

Lionel


Edited by lionel, 03 September 2020 - 12:03 AM.


#8 gdjsky01

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Posted 03 September 2020 - 04:55 PM

Use a mount that has auxiliary encoders.  Like the AZ/EQ-6.   Then you can move manually without losing alignment.

So a different mount? Sure. But mount like the NexStar and LX-65 do not have clutches. You have to move them with the motors.




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