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TPoint: Making Polar Alignment Adjustments
Paramount ME Altitude/Azimuth Adjustment KnobsThe Elevation and Azimuth adjusting knobs on the Paramount ME allow for very precise polar adjustments to be made easily and accurately. When you loosen one axis to make the necessary adjustment the other axis will remained fixed. For example, when the Paramount ME is completely free to be moved in elevation the only change you will see is in the up and down direction. The same is true for azimuth East - West movement only. When the mount is moved in azimuth you see movement in only the left and right or East and West direction. Perform the adjustments one axis at a time. When the star doesn't jump all over the place after tightening the mount back down after making the necessary adjustments it is extremely easy to make the proper precise adjustment based on the TPoint information.
HINT: Live Video Users
If you have a live video camera it is quite easy to see what is happening when you are adjusting the mount in real-time. For the price of a live video camera under $100.00 these are hard to beat for polar alignment. By accurately centering a star you can see precisely what happens to the stars position when you loosen the mount knobs to make adjustments. Even when all 4 elevation knobs are loose and the mount is free to be raised or lowered the star will stay put. After making an adjustment up or down when you lock the mount down it again stays put!
The Final Adjustments - precisely calibrated with feed back
At the point where the polar alignment numbers are very good, say 1 to 2 arcminutes in error or less you may find it hard to make smaller than 2 arcminute adjustments. That is adjustments that are smaller than the calibrated tic marks on the adjustment knobs 2 arcminutes.
By using TheSky's Motion controls as a tool you can make very accurate adjustments at varying increments. Here is exactly how! <----- Click here!
Note that by shooting for slightly higher than the pole (the refracted position based on your latitude ~90 arcseconds too high for 39 degrees north latitude) you have accomplished the same thing as trying to use the King’s Rate to help compensate for the effect of atmospheric refraction during tracking. However, when employing ProTrack the polar alignment, the above off-set, along with many other tracking related issues like flexure, out-of-roundness of the gears, refraction, and many more can be completely taken care of by the low level TPoint tracking kernel ProTrack, so you need not be too concerned with the polar alignment when it is reasonably small say an arcminute or less.
Azimuth Adjustment knob
Azimuth adjustment
Elevation Adjustment
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TPoint reports polar alignment relative to the true pole, not the refracted pole. If you're aiming for the refracted pole, adjust the values reported by TPoint accordingly. See "Optimum Location of the Polar Axis" in the TPoint User's Manual for a detailed description on how to adjust your mount to the refracted pole.
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In this example, TPoint reports the following information for the polar alignment (only after mapping enough points as described above AND after adding the proper new terms also described above). The relatively low sigma values indicate that you can "trust" the data.
Example Data
We are going to use the following actual TPoint data to demonstrate.
Northern Hemisphere
************* AZIMUTH ************
MA: +315 seconds (+5.2 minutes).
Rotate axis West (counterclockwise).
For latitude 34.22°, the azimuth adjustment is 5.3 minutes.
Sigma=11.904
************* ALTITUDE ************
ME: -182 seconds (-3.0 minutes).
The polar axis should be lowered -182 seconds (-3.0 minutes).
Sigma=7.507
Use TheSky's Telescope | Motion Controls dialog in the Altitude/Azimuth mode and "JOG" the telescope as close to 5.2 arcminutes to the West and as close to 1.5 arcminutes South or down as you can. With the Paramount ME the JOG will be extremely accurate.
First pick the right amount to "Jog" the telescope. There should be enough increments to suit any amount of adjustment here.
TheSky's Telescope
Motion Controls
TheSky's Motion Controls
Offset Slew Alt-Az
In the case of the elevation adjustment we are shooting for the refracted pole which is about 1.5 arcminutes too high for a latitude of 40 degrees, as described earlier in the text. These jogs must be made only after centering on a bright star near the meridian at declination ZERO. Use a star at declination zero as close to the Celestial equator as possible. Use TheSky to easily identify such a star that meets the declination requirements. See above. Also, note that you will have to adjust the "Jog" amount's according to the amount of adjustments needed.
CCDSoft users
HINT: By using CCDSoft's feature to place the cross hairs on your CCD images or piped in video you can easily center stars in the field! If you have calibrated the CCD camera you can use CCDSoft or you can also use TheSky's telescope motion control!
Nice! Click image for details!
After the mount has been JOGGED the proper amount in Altitude and Azimuth (offset based on TPoint values for polar alignment) use the mount's polar alignment adjustments to bring the star back to center, as accurately as you can. That is, the mount is physically being moved in each direction as needed to re-center the star making a precise calibrated polar alignment adjustment.
If you have made very large adjustments to the mount it may require a finder scope, flip mirror, Telerad (c) or other method, to aid in placing the star back in the smaller live video field of view after the adjustment. Or just work in small moves (small moves Elly small moves - Contact). When the star has been accurately re-centered using the mount's polar adjustments that match the values reported by TPoint, you have made a near perfect adjustment limited primarily by your ability to keep the star centered after locking the mount back in place! Paramount ME users do not have to be concerned with this!
