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Polar scope reticle orientation in home position.

Astrophotography Equipment Mount
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#1 DrummerDreamer

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Posted 13 June 2021 - 10:12 AM

Hello Fellow Stargazers,

 

I realize it doesn't have a lot of importance in precise polar alignment to have the polar scope reticle oriented to the home position of a mount or a tracker however, I really wonder why the manufacturers (especially Skywatcher) do not seem to be bothered at all about this detail. 

 

It really gets me frustrated to see my mount in home position but my polar reticle is wonky. Maybe it is just me, because of the **** nutbag I am, I just wonder whether it bothers anyone else as well?

 

As I own two (Star-Adventurer and a recently bought HEQ5Pro) from Skywatcher and one Celestron Alt-Az mount which obviously doesn't have a polar scope, I cannot say anything for other make and models but it honestly grinds my gears.

 

Especially after paying not so small amount, I suppose I expect any instrument which is supposed to be a precision one like a telescope mount should be in pristine condition in every sense of the word when it leaves the factory. Of course a number of things may require fine tuning and calibration as it would travel great distances before arriving to your door but I don't think this is one of them.



#2 Old Speckled Hen

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Posted 13 June 2021 - 10:43 AM

https://www.cloudyni...-brand-new-sct/

 

https://www.cloudyni...pped-secondary/

 

plenty of other examples on here


Edited by Andrew Brown, 13 June 2021 - 11:15 AM.


#3 Brainebula

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Posted 13 June 2021 - 11:32 AM

As long as you do the RA calibration to be sure the scope reticle is centered, you don't need to be concerned about whether the reticle is rotated because you can do a simple RA rotation to put the reticle in the vertical position before spotting polaris at the correct hour angle (I have far better success alinging that way then having to estimate the rotation error which is normally a very imprecise estimate, enter that estimated error into PSA Pro and then rely on PSA's fudge calculation for hour angle placement). Here's the polaris placement method that works the best for me:

  1. Do the RA calibration which centers the polari scope reticle (normally only needs to be done once when you use that mount the very first time). 
  2. Put Polaris at the center interesection of the reticle's crosshairs.
  3. Adjust the Alt so that Polaris move to the the top of the reticle ring.
  4. Rotate RA so that the "0" (or "12") hour mark of the crosshair line intersects Polaris, and then lock the RA in place. 

At this point your reticle is in true vertical alignment and you can proceed to change Alt and Azi to place Polaris at the proper hour angle and annular precession ring. 

 

After proper NCP placement, return the scope to home position and do the 2-star alignment. I use an illumated eyepiece on my scope when doing my 2-star alignment (I don't have plate solving, sharpcap, or any other automatic alignment equipment). This ensure very accurate for both stars with essentially zero error doing the fine adjustments to center each star in the FOV during that alignment process.

 

The RA calibration takes some time to complete, so thankfully it doesn't need to be done each time you use the scope. But the Polaris placement and 2-star processes only take a few minutes at the start of each session. 

 

And using this method I am able to get essentially perfect tracking with no noticeable drift on my EQ6-R Pro. For example, after I finish the above RA calibration, NCP placement on the PS reticle, and 2-star alignment using the illuminated eyepiece, when I hide a star behind the crosshairs of the scope's illuminated eyepiece reticle, that star remains hidden behind the crosshair intersection with zero drift for over an hour with no help from any other hardware or software. And I only use the hand controller because of the effectiveness of having the tactile feel of the slew buttons while I'm making fine adjustments nailing the 2-star alignment while looking through the scope's illuminated eyepiece. 


Edited by Brainebula, 13 June 2021 - 11:46 AM.

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#4 DrummerDreamer

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Posted 13 June 2021 - 04:06 PM

Thank you Andrew. I see your point. Well it obviously is quite disappointing. Well, mine is clearly nothing to lose sleep over, I guess it is because of the compulsive person that I am it bothers me probably a little more than most. grin.gif



#5 DrummerDreamer

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Posted 13 June 2021 - 04:18 PM

As long as you do the RA calibration to be sure the scope reticle is centered, you don't need to be concerned about whether the reticle is rotated because you can do a simple RA rotation to put the reticle in the vertical position before spotting polaris at the correct hour angle (I have far better success alinging that way then having to estimate the rotation error which is normally a very imprecise estimate, enter that estimated error into PSA Pro and then rely on PSA's fudge calculation for hour angle placement). Here's the polaris placement method that works the best for me:

  1. Do the RA calibration which centers the polari scope reticle (normally only needs to be done once when you use that mount the very first time). 
  2. Put Polaris at the center interesection of the reticle's crosshairs.
  3. Adjust the Alt so that Polaris move to the the top of the reticle ring.
  4. Rotate RA so that the "0" (or "12") hour mark of the crosshair line intersects Polaris, and then lock the RA in place. 

At this point your reticle is in true vertical alignment and you can proceed to change Alt and Azi to place Polaris at the proper hour angle and annular precession ring. 

 

After proper NCP placement, return the scope to home position and do the 2-star alignment. I use an illumated eyepiece on my scope when doing my 2-star alignment (I don't have plate solving, sharpcap, or any other automatic alignment equipment). This ensure very accurate for both stars with essentially zero error doing the fine adjustments to center each star in the FOV during that alignment process.

 

The RA calibration takes some time to complete, so thankfully it doesn't need to be done each time you use the scope. But the Polaris placement and 2-star processes only take a few minutes at the start of each session. 

 

And using this method I am able to get essentially perfect tracking with no noticeable drift on my EQ6-R Pro. For example, after I finish the above RA calibration, NCP placement on the PS reticle, and 2-star alignment using the illuminated eyepiece, when I hide a star behind the crosshairs of the scope's illuminated eyepiece reticle, that star remains hidden behind the crosshair intersection with zero drift for over an hour with no help from any other hardware or software. And I only use the hand controller because of the effectiveness of having the tactile feel of the slew buttons while I'm making fine adjustments nailing the 2-star alignment while looking through the scope's illuminated eyepiece. 

Many thanks Brainebula. Much appreciate your detailed post as a response.

 

As far as I can see, what you describe is similar to the drift method or at least I assume it was inspired partly by it. I will try that for sure. As my HEQ5Pro just arrived on Saturday and there was nothing better to do due to the **** Berlin weather, I did my best to calibrate/align the polar scope.

 

The wobble at the crosshairs is very minimal at the moment if not for being dead center. I basically did it the classical way during daytime pointing the polar scope to the tip of a close by roof corner. That was the best I could achieve. I need to try the mount the first clear night to see how it performs guided but I will definitely fine tune my RA alignment with your described method. 



#6 Brainebula

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Posted 13 June 2021 - 05:16 PM

Many thanks Brainebula. Much appreciate your detailed post as a response.

 

As far as I can see, what you describe is similar to the drift method or at least I assume it was inspired partly by it. I will try that for sure. As my HEQ5Pro just arrived on Saturday and there was nothing better to do due to the **** Berlin weather, I did my best to calibrate/align the polar scope.

 

The wobble at the crosshairs is very minimal at the moment if not for being dead center. I basically did it the classical way during daytime pointing the polar scope to the tip of a close by roof corner. That was the best I could achieve. I need to try the mount the first clear night to see how it performs guided but I will definitely fine tune my RA alignment with your described method. 

Thanks Drummer. To be clear, the procedure I posted wasn't for the RA calibration. That calibration is described well enough in the mount's manual. I was focusing more on NCP positioning on the polar scope reticle and also the 2-star scope alignment using an illuminated eyepiece. 


Edited by Brainebula, 13 June 2021 - 05:16 PM.

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#7 DrummerDreamer

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Posted 13 June 2021 - 06:53 PM

Thanks Drummer. To be clear, the procedure I posted wasn't for the RA calibration. That calibration is described well enough in the mount's manual. I was focusing more on NCP positioning on the polar scope reticle and also the 2-star scope alignment using an illuminated eyepiece. 

waytogo.gif Apologies. Sure. Many thanks for the clarification. My mistake on typing RA alignment there but rest assured I got your point. It would be odd if I edit/change my post now.  




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