Re: ... and daytime polar alignment


Tyrel Smith
 

Just a thought. Instead of the level, why not just put marks on the RA and dec axis so you always know where an accurate park position is? Seems much more repeatable then eyeballing a level each time.

I did this once after a night of platesolving. Once you are well calibrated (platesolve and sync to remove zero position error) send the mount to your preferred park position.  Then just put some tape or some kind of mark across the axis that you can line up whenever you need to manually put the mount in park position. 

Maybe this doesn’t work for all mount, but I did this with my Mach1 just once. I’ve never needed to use a level. I’d like to know if I’m off-base with this, though. 

Ty Smith

On Apr 21, 2019, at 09:56, Mike Dodd mike@... [ap-gto] <ap-gto@...> wrote:

 

On 4/21/2019 8:38 AM, y.groups@... [ap-gto] wrote:
> 5) Using a carpenter's level, use pier adjustments to level the
> counterweight shaft.
> 6) Using a carpenter's level, use the mount's altitude adjustment to
> level the OTA.

I'd like to propose an alternative to a carpenter's level.

My AP1200 is pier-mounted and drift-aligned, so I don't have the same
situation you do. But I loosen the clutches to re-balance the mount
after changing imaging equipment. I use a level on the CW shaft and the
OTA to return to the Park 1 position after balance is achieved. (Yes,
I'm still using Park 1, not 4, and yes, I know the issues with Park 1.)

Instead of a carpenter's level, I use a Starrett #98-6 precision
machinist's level
<https://www.amazon.com/Precision-Machinists-NIST-Traceable-Calibration-Certificate/dp/B07579PWPL>.

This level is super-accurate! One division on the glass vial is 86
arc-seconds. It's easy to read to within 1/4 of a division, or 21.5
arc-seconds. That's MUCH better than I can get on my carpenter's bubble
level, or even on my electronic level that displays only to 1/10 degree.

Here's what I do:

1. Use the keypad to park the mount in Park 1.

2. Set the machinist's level on the CW shaft and take a photo of the
bubble position.

3. Set the level on the OTA and take a photo of the bubble position.

NOTE: Steps 2 and 3 record the MOUNT'S Park 1 position. So, if my
original Park 1 position was a bit off, I can return to the MOUNT'S
position.

NOTE: The level has a V-groove on the bottom that makes it easy to
position it accurately on the CW shaft and the OTA.

4. Remove the level, loosen the clutches, and do whatever I need to do.

5. Move the mount back close to the Park 1 position.

6. Set the machinist's level on the CW shaft and adjust the RA until the
bubble is in exactly the same spot as in the step-2 photo, then tighten
the RA clutches.

7. Set the machinist's level on the OTA and adjust the Dec until the
bubble is in exactly the same spot as in the step-3 photo, then tighten
the Dec clutches.

8. Power-up the mount, and select "Resume Ref-Park 1" on the keypad.

As a testament to the level's accuracy, when I complete this procedure,
I can GOTO a target star, and it will be within the central 15% of my
camera's sensor.

The Starrett #98-6 isn't cheap. I bought mine specifically for leveling
the telescope, and have never regretted spending the money.

I also use it to level the AP1200's mounting plate on my concrete pier:
<http://astronomy.mdodd.com/observatory.html#PierBolts>

Just a suggestion for an alternative to a carpenter's level....

--
Mike

Mike Dodd
http://astronomy.mdodd.com
Louisa County, Virginia USA

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