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Adjusting altitude scale on Meade GEM

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#1 atsidor

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Posted 21 July 2021 - 11:22 AM

I recently got my LX85 mount up and running (as you all may know from a prior thread). I've discovered that the altitude scale on the mount is pretty far off. I say this because I leveled the tripod, put the mount in it's home position, and measured the angle of the dovetail saddle. I did all of this with a digital protractor/inclinometer to make sure it was (fairly) precise. 

 

Turns out the digital protractor read about ~5-6 degrees lower than the scale on the mount. I know, I know... these scales are not the most accurate but this seems pretty far off. Am I missing a larger issue here?

 

I would like to get the scale tuned a little closer to actual (I realize there are other solutions here but I'm a little bit of a perfectionist). Does anyone have any experience adjusting this on a Meade GEM? I assume other models are probably similar. I attached pictures. There are two caps on either side - one with the altitude scale and one without. It seems like one or both of these could be pried off but not sure. I tried but didn't want to apply too much force. 

Attached Thumbnails

  • IMG_1496.jpg
  • IMG_1495.jpg


#2 wrvond

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Posted 21 July 2021 - 12:01 PM

Two things you can do:

1. Check the scale using Polaris.

2. Move the arrow sticker.



#3 atsidor

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Posted 21 July 2021 - 01:17 PM

2. Move the arrow sticker.

Duh! Can't believe I didn't think of that. That is a much easier solution :)

 

And good idea to check with Polaris. I will confirm with that.


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#4 photoracer18

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Posted 21 July 2021 - 01:19 PM

Pretty sure that is just a plastic plug glued into the hole there based on other Meade models. Trick is melting the glue a little to aid in prying it out so you don't crack the plug.



#5 Andynator

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Posted 21 July 2021 - 01:23 PM

It's a "set it and forget it" thing for me. Even traveling a few counties any direction isn't going to make a meaningful change when you're tweaking it after setting up and during alignment (I use Polemaster).

#6 atsidor

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Posted 21 July 2021 - 02:01 PM

Pretty sure that is just a plastic plug glued into the hole there based on other Meade models. Trick is melting the glue a little to aid in prying it out so you don't crack the plug.

Thank you - good tip. These plugs are definitely metal which should be easier. I could try heating up with a hair dryer to see if I can loosen up the glue.

 

 

It's a "set it and forget it" thing for me. Even traveling a few counties any direction isn't going to make a meaningful change when you're tweaking it after setting up and during alignment (I use Polemaster).

Understood and I agree. My use case is that I don't always have a view of the pole and want to get "close enough" for quick visual sessions / go-tos. Maybe there's another approach to dial in alignment that's quick though?



#7 Andynator

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Posted 21 July 2021 - 04:54 PM

Understood and I agree. My use case is that I don't always have a view of the pole and want to get "close enough" for quick visual sessions / go-tos. Maybe there's another approach to dial in alignment that's quick though?


I just bore-sight through the empty hole where the polar scope would be (if it was installed) and once I can see Polaris anywhere in the view, that's aligned enough for me! (for visual observation)

#8 atsidor

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Posted 26 July 2021 - 04:52 PM

Quick update: I checked the angle measurement against Polaris and it's definitely off. And unfortunately the sticker is more robust than I thought, and it's in a small indentation in the metal, so it would make moving it a bit awkward. Not impossible but not ideal. Anyway, I think I'll just be content to add ~5 deg to whatever my latitude is and call it good, rather than go messing around any further with the mount.



#9 jeff clarke

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Posted 28 July 2021 - 04:02 PM

With a label-maker, you could overlay the sticker with a new index mark.

 

Jeff



#10 wrvond

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Posted 28 July 2021 - 04:57 PM

With a label-maker, you could overlay the sticker with a new index mark.

 

Jeff

Or make a simple mark with a Sharpie...




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