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Allen Gilchrist's polar alignment calculator
Allen Gilchrist in 2002 wrote a simple 2 page 11 line (22kb) Excel spreadsheet where you enter a few parameters and it tells you the magnitude of polar alignment corrections you have to do.
I have it and would love to see it posted on IIS - does anyone else use it?
Basically you enter the elevation and enter the drift time, observed drift in DEC and it gives you your precise correction.
So if you say zoomed to Acrux or Rigel Kentarus binary stars to check how far say 4 or 9 arc seconds is in your illuminated reticle, you can drift align at a known elevation - enter the paramters and it tells you how many arc seconds to correct by!
Anyone else use this? (I'd be happy to e-mail or attach this file - but don't think you can upload .xls files!
e.g.
To correct polar alignment errors in azimuth: Allen Gilchrist, 2002
Find a star near the meridian and celestial equator.
Determine how far it drifts in declination during a known period of time.
Using a positive number if the star drifts to the north or a negative number if the star drifts south, enter the time and amount of drift in the table below.
Note that the distance between the 0.2 mm spaced lines on the
12mm guiding eyepiece is about 15 arc seconds with the C-11.
Drift Time = 1200 seconds
Dec Drift = -10 arc sec
The computed azimuth error is
Delta Az = -0.03 degrees,
where a positive number means that the mount is pointed too far west.
To correct this error:
Enter your latitude
Latitude = 33 degrees
The required correction is,
Corr = 0.017 degrees
1.04 arc min
62 arc sec
Adjust the mount azimuth so as to move the star in RA by this amount.
A positive delta Az requires that the star be moved toward the east in the FOV.
The FOV of the 12mm guiding eyepiece on the C-11 is 10 arc minutes.
Note: The value of pi used for these calculations was 3.142
* * *
To correct polar alignment errors in altitude:
Allen Gilchrist, 2002
h m s Set the scope to 0o dec., point it level toward the horizon, and note the RA. RAHorizon = 0 0 0 Find a star near 0o dec. and about 20 - 30 degrees up. Note its RA.
RAStar = -2 30 30 The elevation that the star is above the horizon measured along the celestial equator is 22.38 degrees Determine how far the star drifts in declination during a known period of time.
Using a positive number if the star drifts to the north or a negative number if the star drifts south, enter the time and amount of drift in the table below. Note that the distance between the 0.2 mm spaced lines on the 12mm guiding eyepiece is about 15 arc seconds with the C-11.
Drift Time = 1200 seconds
Dec Drift = 10 arc sec
The computed altitude error is:
Delta Alt = 0.03 degrees, where a positive number means that the mount is pointed too high. The correction required to correct this error:
Corr = 0.012 degrees
0.73 arc min
44 arc sec
Adjust the mount altitude so as to move the star in Dec. by this amount. A positive correction requires that the star be moved south in the FOV. The FOV of the 12mm guiding eyepiece on the C-11 is 10 arc minutes.
Note: The value of pi used for these calculations was 3.142
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