Near the Equator

[daveb]

I'm setting up a motorized installation, using a Dish Network 25" dish. I'm in Hawaii at 20 degrees latitude. There are only two echostar birds with signals beamed into this area - those are 110 and 119. In the future, I believe 121 and 148 may be received from here.

The problem I'm having is "This far south, requires a very large arc. If I set up with the standard due south 0 degree reference, I run out of travel on my setup before getting to the two echostar birds.

From my location:

Azimuth to 110 is 108.3 degrees true.
Elevation to 110 is 33.9 degrees.
Azimuth to 119 is 114.5 degrees true.
Elevation to 119 is 42.6 degrees.

Heres the question:

Is there any way I can set up with the zero reference of my motor at 114.5 degrees (119 satellite) and arc correctly to the 110 satellite to the east?

The standard motor elevation for my latitude is not going to work, since the elevation angle change is 6.2 degrees between the two birds. Over the short azimuth change between the two birds, the elevation is only going to drop a degree or two with the normal latitude angle set on the motor. I'm sure it's possible if enough tweaking is done with the motor elevation and possibly moving the basic mount from vertical. However, I'd like to know if anyone has figured out any kind of formula, so I don't have to spend days working it out with trial and error.

Thanks in advance!

[dtsexpert]

I thought that the Diseqc 1.2 mount is universal, meaning it should work regardless your location. Anyways, back to your questions, I have not seen any formular for "tweaking" the mount to make the dish movement more flat/curve. The only thing I know is the curve of the arc depends on the declination, in this case, use an incorrect h-h mount elevation to make the dish moves the way to want (more flat).
Check out the link below, it's for C-band setup, scroll down the bottom of the page, you'll see the box "Philosophi of Tuning Dish to Sat Arc"

http://www.geo-orbit.org/sizepgs/tun...l#anchor807714
It's perfect info for what you are trying to accomplish.

Michael

Originally Posted by daveb

I'm setting up a motorized installation, using a Dish Network 25" dish. I'm in Hawaii at 20 degrees latitude. There are only two echostar birds with signals beamed into this area - those are 110 and 119. In the future, I believe 121 and 148 may be received from here.

The problem I'm having is "This far south, requires a very large arc. If I set up with the standard due south 0 degree reference, I run out of travel on my setup before getting to the two echostar birds.

From my location:

Azimuth to 110 is 108.3 degrees true.
Elevation to 110 is 33.9 degrees.
Azimuth to 119 is 114.5 degrees true.
Elevation to 119 is 42.6 degrees.

Heres the question:

Is there any way I can set up with the zero reference of my motor at 114.5 degrees (119 satellite) and arc correctly to the 110 satellite to the east?

The standard motor elevation for my latitude is not going to work, since the elevation angle change is 6.2 degrees between the two birds. Over the short azimuth change between the two birds, the elevation is only going to drop a degree or two with the normal latitude angle set on the motor. I'm sure it's possible if enough tweaking is done with the motor elevation and possibly moving the basic mount from vertical. However, I'd like to know if anyone has figured out any kind of formula, so I don't have to spend days working it out with trial and error.

Thanks in advance!

[daveb]

dtsexpert,

Thanks for getting back to me. You are right that the mount is universal. The less the declination, the larger and flatter the arc. At the equator, the arc would pass directly overhead. In my case at 20 degrees N latitude, the motor runs into it's physical rotation limit before reaching the easternmost satellite. Since there are no birds of interest west of 119 position, the challenge is to set up an arc that will at least include the 119 and 110 positions. The arc needs to have more declination and be less flat than the standard.

Guess I'll just have to play with it until I get it right. Was hoping there would be an easier way.

I think the ideal would be a two axis motor with a position memory. That would sure make life easier setting up. Drive the azimuth to the proper position for your location, and then set the elevation. Do this for each satellite, and fine tune it before locking in the final setting.

[dtsexpert]

Daveb,
To me, playing arround with the declination is a way to go since these 2 birds are not far away to each other. I am sure you will find the "correct" declination which makes the mount track these 2 birds.
2 axis motor would be overkill in this case.
Let us know how things going. If possible, take some pictures, we want to see how the angles look like...:-)
Michael

Originally Posted by daveb

dtsexpert,

Thanks for getting back to me. You are right that the mount is universal. The less the declination, the larger and flatter the arc. At the equator, the arc would pass directly overhead. In my case at 20 degrees N latitude, the motor runs into it's physical rotation limit before reaching the easternmost satellite. Since there are no birds of interest west of 119 position, the challenge is to set up an arc that will at least include the 119 and 110 positions. The arc needs to have more declination and be less flat than the standard.

Guess I'll just have to play with it until I get it right. Was hoping there would be an easier way.

I think the ideal would be a two axis motor with a position memory. That would sure make life easier setting up. Drive the azimuth to the proper position for your location, and then set the elevation. Do this for each satellite, and fine tune it before locking in the final setting.

[daveb]

I think that I've got some time ahead playing with the declination.

Is there such a thing as a two axis motor that will remember preset positions?

Another question that is giving me trouble:

I'm trying to figure out how to physically measure the azimuth and elevation of my dish when it is rotated off the zero point of the motor scale - say to 65 degrees east. It's no problem getting those measurements when the dish is straight up and down at the due south position. However, when you move off the zero position on the motor scale, the dish rotates as it swings across the arc. Since the LNB is offset, I can't figure out how to physically measure the elevation with a protractor level. I also don't know what to use for a reference to measure the azimuth with a compass. It would be easy if the dish was round and the LNB pointed at the center, however that is not the case.

This whole process may end up causing me to dust off my books and review my spherical trig and 3D geometry!

Thanks for your help.