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Old 16-01-2013, 08:00 AM
acotiga (Andrei)
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Lightbulb Hypothetical dirty polar alignment

I've never experienced with it but maybe one of you has. What would happen is my mount would be decently well leveled and home positioned (RA and DEC set with the bubble level etc) and after execution the first Go to, I would center on the star not using the pad but using EL/AZ screws. Then shut down, reset RA and DEC and power again.

I think I should be way closer to PA then just by starting fresh. Or will I?
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Old 16-01-2013, 08:11 AM
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ZeroID (Brent)
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You are assuming that your 'level' is level and your Nth\Sth alignment is correct which is not necessarily true. A single star alignment would not prove correct alignment or position.
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Old 16-01-2013, 08:34 AM
acotiga (Andrei)
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Let me ellaborate.

Normally one would position the mount as level as possible, align with compass (magnetic deviation or not), align for latitude. Power up, slew to one star, sync, 2nd star, sync and 3rd star, sync. Then do drift alignment or Allstar..whatever. The 3 star alignment would create a skewed triangle to compensate for a miriad of errors but because it's easier to be level than to be perfectly N-S, the biggest contribution to the overall errors will be from Azimuth. That why, even when I'm very carefull with my compass, PA is usually 3-5 deg out of AZ and 1-3 deg of EL. That is requiring me to make a huge compensation when I start drifting.

Now, considering that AZ and EL will be the biggest source of erros, what I am suggesting is powering up, slewing. The distance between the slew and the star will then be covered by moving the actual mount. Reset RA and dec to 6hr and 90deg. Powering on and slewing again should be better than it was the first time. Only then, after hopefully killing 3 deg of your errors, start honing in on the others by doing drift, 3 star alignment and so on.

Mmm? Any ideas?
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Old 16-01-2013, 09:52 AM
SteveInNZ
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If you are using a Celestron EQ mount and starting with the OTA parallel to the RA axis and the counterweight bar pointing down, yes you can do this to get in the ballpark. Set the time and location correctly and use the "Quick Align" function. Then slew to something easily identifiable (I use the Jewel box cluster or 47-Tuc) and adjust the Alt-Az to get the target into the finder. Power off and start over with your preferred polar alignment method. I usually find that I'm within a turn or so of the pole when I do the drift or ASPA alignment. The mount has the brains and the capability so you may as well use it. It saves a ton of time and fluffing about with the bubble level, compass, etc.

Steve.
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Old 17-01-2013, 11:16 AM
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ZeroID (Brent)
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I used delayed tracking to isolate AZ error using 1 min exposure on the DSLR. Gives me a 'V' trace on screen which I then adjust to eliminate. Usually gets it with about 5 iterations.
Tablet level sets Dec angle accurately.
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