Quote:
Originally Posted by snyper1982
Quote:
Originally Posted by wejones
Then even more reason to be careful. What you should be doing, is first calculate your declination. Most tables will tell you that for your latitude to use a declination of 5.99, however this is a rather crude approximation. You should use 5.30. Then, subtract this declination from the bend angle in the motor shaft. The old SG2100 motors had a 30 deg bend, so 30-5.99=24.01 (pretty much what you're quoting), however the newer SG2100s have a 35 degree bend, which means 35-5.99=29.01. So you have to figure out which motor shaft you have. And again, I'd recommend using 5.3 instead of 5.99 as your declination, but if you do that, you need to use 38.3 for your latitude setting instead of 37.6.
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I already did that. Then used that page and it came up with nearly the exact same calculations I did. So I figured what the heck, I will just use it. Anyways, How do you go about calculating the declination, because all I have seen was charts with latitude. Since my lat is pretty close to a half a degree, I added the declination for 37 lat and the declination for 38 lat, and divded that number by 2. I came out with 24.04, the calculator I used came out with 24.03.... I appreciate your help, but I am curious as to where you are getting your numbers, and what makes them better than the other numbers that the calculators give? Dish Elevation: 24.03
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There are charts that cover what I'm referring to. Look at:
Footprints by Dish Size - Latitude Declination Chart - C/Ku-Band Satellite Listing
At this page, there is a chart for declination and a chart for "modified" tracking angles, which is the more accurate values. (Note, this chart incorrectly refers to the latitude value as being an elevation, when actually the elevation is 90 minus this value).
The declination of a sat to your south is very easy to calculate, which is why most charts (such as you'll find on the
Sadoun site) use these values. I just drew up a little picture describing the calculation.
Basically, the declination angle is the "d", which is described by a right triangle with one side being the distance above the earth's equatorial plane you are located ( "A"), and the other side being the distance to the sat in the equatorial plane, ( H + C ).
The problem is that the declination of sats toward either your east or west horizon is less, up to about 0.6 degrees less, so if you use the south declination, you will be off by up to 0.6 degrees in your aim on other sats. I drew another diagram from the perspective above the north pole with south up.
For sats not to your south, the declination calculation still has the same "A" dimension, however the ( H + C ) dimension has increased, which is what causes the declination angle to get less. BTW, the DL angle is the delta longitude, ie the difference between the sat's longitude and your longitude, and the U angle is the so called USALS angle, ie the actual angle that the motor shaft has to turn to go to a satellite. But back to the declination, I can't remember the equations off hand, but I always look up the equation for calculating the angles of a non-right triangle, given two sides and an angle. Years ago I used to just spit that out from memory, but with age, I generally struggle for hours trying to do the calculations.
HOWEVER, a pretty good approximation for the declination angle for sats to your east or west is obtained by using ATAN ( A/(H+RE) ).
Basically, if you use this smaller declination, you have to increase the latitude setting on your motor by the difference between the south declination and the east/west declination, and this will correct the setting on south satellites, and the motor elevation's effect decreases proportionally as you motor east or west since it is orthogonal, so it is still correct to the east or west.
Quote:
Originally Posted by snyper1982
Quote:
Originally Posted by wejones
No,all the back and forth is at the easterly sat. Ie, I'm saying motor to the easterly sat, get a signal quality reading, then make an adjustment by moving the entire mount on the pole, then bump the motor back and forth very small amounts, trying to find the best signal. When you find the best signal quality, compare this reading to what you had originally. If better, adjust more in that direction, if worse, adjust in the other direction, then bump motor back and forth in small steps, and again compare your best reading to your original. It will take a few back and forths, but once you get the best possible signal at the easterly sat, you should be done.
There are some other ways of doing this, but if you start out with the proper declination and motor elevation, and then spend a little more time working on your easterly sat, things will end up taking you much less time in the long run.
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So you mean, move the motor+dish setup once I get to the easterly sat, and peak the signal there?
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Yeah, I think that's what I mean. Basically, *IF* the true south alignment was done properly, you won't have to do this adjustment, but usually you'll be off a bit. Also, if your motor is properly calibrated re the zero position, then you won't need to do the motoring back and forth after each adjustment, but I've found that my SG2100 was not calibrated properly.