Re: PemPro Polar Alignment differs East to West

Roland Christen

Hi Joe,

Thanks for your thoughts.

One could try the zenith to see if the drift in Dec is the same on either side.

By the way, I got to thinking about your daytime polar alignment routine and decided to modify it for our new mounts that have the 90 degree engraving marks on the axes. You must have the pier or tripod level for this to work. All you have to do is line up the RA and Dec engraved marks with the scope pointing to Park3 position (Home position) and tighten both sets of clutches. Then send the mount to either Park1 or Park4 and level the telescope tube assembly using the altitude adjuster.
That's it, and now all you need to adjust is the azimuth angle and that can be done by sending the scope to the Sun (with proper filter or use the ring shadow method). Turn the azimuth until the Sun lines up with the scope. You may have to move the RA axis a small amount using the E-W buttons if your keypad time is off, then press Recal. Now you are ready to slew to other bright planets or stars.


-----Original Message-----
From: 'Joseph Zeglinski' J.Zeglinski@... [ap-gto] <ap-gto@...>
To: ap-gto
Sent: Sat, Mar 3, 2018 2:32 pm
Subject: Re: [ap-gto] PemPro Polar Alignment differs East to West

Hi Rolando,
    I too have seen that PemPro curve results discrepancy on runs east vs. west side of the mount.
I REALLY like your explanation, on the cause – even if the results might sometimes be slight. They could be further exaggerating with poor seeing, besides the atmospheric component adding to the discrepancy.
    Yes - if you run PemPro with the “standard” setting of 5 minutes  (deg ?) looking toward the east of PM, the OTA is “rising” and the atmospheric refraction is “actually improving”, all during the hour long RAW data sampling.
    On the flip side, running with exactly the same PemPro meridian target offset, the atmospheric refraction  can ONLY  “degrade” steadily for the entire western sky target  run.
    So, you have the worst of both situations. You can either trust the optimum raw data when PemPro runs from the west side of the pier on eastern targets, or the twice as bad situation with “STEADILY declining”  target Altitude ... when running with the scope on the east side (looking west).
    I brought this up, on this Group probably more than a couple of years ago, suggesting that PemPro could be run twice, and the two raw data curves averaged – or their samples interleaved – to come to some averaged curve result. Requires some further thinking, whether the results “should be weighted” more toward eastern targets, Something for Ray to consider, based on your premise.
    Anyway, Rolando, thanks for this explanation of what has been frustrating me about my own PemPro results ... for a VERY long time. Unfortunately, in the short term, we just have to live with this minor discrepancy.

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