Polar Mount Prime Focus .What changes when it is an off set dish.

Declination angle is increased by a value equal to the offset angle of the dish, for example many Channel Master dishes have a 22.5° offset angle.
 
Many thanks that is the answer I was looking for.
 
As as matter of interest should one install the dish with the LNB on top facing down ,how will the angles change.
 
With an "upside down" offset dish, the declination angle is deminished by a value equal to the offset angle of the dish (as the offset angle then is negative).
 
Many thanks a33 in the Netherlands. Appreciated.
 
To add:
The rotation axis has an elevation angle towards due south or due north, that suits your place on earth, to best follow the clarke belt. The rotation axis will be about parallel to the earth rotation axis.

The dish should then be aimed a little bit lower than that angle: it must point down to the equatorial plane, where the satellites are (instead of pointing parallel to the equatorial plane). Hence the "declination offset angle" (offset angle, from the axis).
When the dish is an offset dish (positive or negative offset angle), the dish face angle has to be corrected with this offset angle; as is described above.
If the dish has an "elevation scale", this scale of the dish would already take this offset angle into account. This means that the needed elevation scale value would always be the declination offset angle. Declination means the opposite of elevation, so the elevation scale angle would be negative!
(With an upside down dish, the upside down elevation scale values are even more complicated to calculate.)

Hope this might help a bit more?

Greetz,
A33
 
Many thanks again for the valuable input Greetz.A lot to digest for this 90 year old.
 
wium78 said:
A lot to digest for this 90 year old.
Click to expand...

Well, the brain might not have the the same speed as before, but it is nice to see that you still want to understand!
I hope I will still have the same curiosity, when I grow that 'mature'.

I guess you found the website How to Install a Motorized FTA Satellite TV System How to Install a Motor on a Free To Air Satellite TV Dish for KU Band and How to , as you used one of its drawings?
Maybe my text helps to understand the different angles shown on that website, by 'explaining' them with different words.

Greetz,
A33
 
Thanks Greetz for the complement.I go way back to 1986 in Zimbabwe under Mugabe when I was the second person to get satellite TV via a 6 meter dish.At first it was banned but that changed .
 
Back
Top