Thread: Pointing Ku dish using Sun, not compass

Finding the satellite azimuth by turning the dish could be time consuming and frustrating. For beginners, and not pressed for time, perhaps this trick would help? First, the data from dishpointer should be written down: coordinates of the area where the dish will be used, and the azimuth and elevation of the desired satellite. Next, google the words "Sun or Moon altitude" and find the web site which calculates azimuth of Sun and Moon in any chosen day and time. Interval 1 minute can be chosen. The coordinates of the town should be converted to degree - minute format (dishpointer provides degrees with 4 digit decimal fraction) and entered into the proper space. Time zone also has to be input (for example, Toronto is in zone 5, but in summer, zone 4 works). The calculated table should be scrolled until the needed Sun azimuth is found, and the corresponding hour and minute written down. A piece of string, or shoelace, should be attached to the top of the dish and the back of the LNB. At certain time, when the Sun is (hopefully) shining, the dish should be turned until the shadow of the string is in the exact centre of the dish. This position can be marked on the mast and bracket. Pictures follow.

I used a similar method, differing only in that I found a program (
Satellite Antenna Alignment

) which I can run at anytime that gives the exact position of the sun at my location at every minute of the day. So I know from this program the exact time when the sun is at its peak elevation. Using the shadow cast is more accurate than trying to use the type of compasses we usually have, including adjusting for our local magnetic declination. Using dishpointer.com is good in theory, but there isn't much that's unique for me to reference to when using dishpointer.com; all trees look about the same in the fuzzy image.

Added: I should add that dishpointer.com clearly shows me after-the-fact why I can't get 123W or 125W. The LOS runs right into my neighbour's house! I wish I knew about this website before I installed. On the first sunny warm day, I'll be picking up my mini-tower, moving it about 15 feet and start all over again. But this time I know what I'm doing. It will be fun to see if USALS will work 15W through 125W.

Originally Posted by cyberham

Added: I should add that dishpointer.com clearly shows me after-the-fact why I can't get 123W or 125W. The LOS runs right into my neighbour's house! I wish I knew about this website before I installed. On the first sunny warm day, I'll be picking up my mini-tower, moving it about 15 feet and start all over again. But this time I know what I'm doing. It will be fun to see if USALS will work 15W through 125W.

Are you looking at just the azimuth to get 123w or 125w or allowing for the impingement angle of the sat beam when looking at your LOS. I understand you may be pretty low to the horizon for both sats but while I haven't used the feature, dishpointer is supposed to be able to give you the required set back distance and/or needed dish height to clear a known obstruction. Havng seen lots of working dishes looking like they are pointed directly at walls or trees or even pointed down to the ground, apparent obstructions may only be perceptual.


I find my dish and h to h motor will swing almost a full 180 azimuth arc but as a practical matter the horizon gets in the way too far e or w. With USALS being simply a programming function of the STB it rotates the dish left-right to whatever limits it has programmed or you've set. Haven't noticed as I don't use it much but it seems like USALS tries to move to the dish to any sat you ask it to and only gvies an error for an out of range sat when the dish can't move any more or its at the limit. Doesn't seem to have any programmed sense of the horizon based on user location. So I'd think no reason it can't mechanically swing 15w or 125w if dish is aligned e-w properly but whether or not you get reception on the higher dish skew sats is another discussion.

I am considering both azimuth and satellite elevation. To be neighbour friendly, I had to move my dish location far down a steep hill in my backyard, 200 feet from the house. Visually, you might think I couldn't receive much from there low on the western horizon. The offset dish does appear to be pointing at ground and even into the hillside. But I can receive 121W well (ERT World on Ku when it was ITC). I've learned it's best to use tools and not try to guess what you will be able to see. dishpointer.com indicates I may only be able to see about 20 feet above ground at the neighbour's 2-storey house location. If so, the house blocks me to 125W for elevation reason. However, I think the easier-to-determine problem is that the azimuth runs through his house. By moving the dish about 15 feet to the south, I should be able to avoid both issues. I know I can get 125W since I received it from a different location at this property last year. Elevation of 125W for me is 11 degrees.

I read that USALS software has a limitation of as little as 40 or 50 degrees swing on either side of due south. I know this is not correct at least for my receiver / motor combination since I can use USALS for more than 65 degrees to the west of due south. I've also used it for 58 degrees to my east of due south. You're right...USALS does not consider satellite elevation in its calculation since its purpose is only to determine azimuth. Elevation-wise, if not for objects in the near ground, I can see beyond where satellite footprints will provide a signal for me. That is, azimuths for my +5 elevation points to the west and east are 133W and 7E. So elevation is not the limiting factor, satellite footprint is.

Originally Posted by polgyver

Finding the satellite azimuth by turning the dish could be time consuming and frustrating. For beginners, and not pressed for time, perhaps this trick would help? First, the data from dishpointer should be written down: coordinates of the area where the dish will be used, and the azimuth and elevation of the desired satellite. Next, google the words "Sun or Moon altitude" and find the web site which calculates azimuth of Sun and Moon in any chosen day and time. Interval 1 minute can be chosen. The coordinates of the town should be converted to degree - minute format (dishpointer provides degrees with 4 digit decimal fraction) and entered into the proper space. Time zone also has to be input (for example, Toronto is in zone 5, but in summer, zone 4 works). The calculated table should be scrolled until the needed Sun azimuth is found, and the corresponding hour and minute written down. A piece of string, or shoelace, should be attached to the top of the dish and the back of the LNB. At certain time, when the Sun is (hopefully) shining, the dish should be turned until the shadow of the string is in the exact centre of the dish. This position can be marked on the mast and bracket. Pictures follow.

Thanks for sharing this. Usually I just set the elevation very carefully, and slowly sweep the area of the sky my compass indicates is correct. Your method will be useful for dishes with elevation scales of unknown accuracy. I will print it out and put it in my FTA INFO notebook, along with Iceberg's Tips, and FaTAir's C-band Manual. The original post should be a sticky in the FAQ section.

Originally Posted by cyberham

...I've learned it's best to use tools and not try to guess what you will be able to see. dishpointer.com indicates I may only be able to see about 20 feet above ground at the neighbour's 2-storey house location...

I realize now that dishpointer's obstacle height is calculated using the dish location as its reference, not the location of the obstacle. In this case, a 20-foot house sitting on a 30-foot high hill means that the house is not the problem, the hill is the problem. I realize moving the dish in its local area will never see over that hill. I can dedicate a different fixed dish much closer to my receiver and aim it exclusively at 125W and maybe catch 123W too.

Originally Posted by hwm

Thanks for sharing this. Usually I just set the elevation very carefully, and slowly sweep the area of the sky my compass indicates is correct. Your method will be useful for dishes with elevation scales of unknown accuracy. I will print it out and put it in my FTA INFO notebook, along with Iceberg's Tips, and FaTAir's C-band Manual. The original post should be a sticky in the FAQ section.

Thank you for words of appreciation. I, too, used to sweep horizon with dish, and it was time consuming. Regarding the FAQ section, I hope that the site of Naval Observatory
Sun or Moon Altitude/Azimuth Table: Locations Worldwide — Naval Oceanography Portal

would be popularized and used much more, also with its Moon data. Cheers, Polgyver

more good stuff polgyver. any prole can use an iphone but it takes a real MacGyver to use a shoelace and the sun

maybe for your next project you could build a homemade dish using a
cardboard and aluminum tape Fresnel lense

Originally Posted by cyberham

I realize now that dishpointer's obstacle height is calculated using the dish location as its reference, not the location of the obstacle. In this case, a 20-foot house sitting on a 30-foot high hill means that the house is not the problem, the hill is the problem. I realize moving the dish in its local area will never see over that hill. I can dedicate a different fixed dish much closer to my receiver and aim it exclusively at 125W and maybe catch 123W too.

I believe,when searching for obstacles, nothing can substitute your presence under your dish and looking up towards the Moon from behind of your dish at certain day and time. This Naval site can also provide you with minute-after-minute positions of Sun and Moon. I do not know your exact location, but assumed you are in Halifax area. Coordinates of this city are 44 deg 39 min ; 63 deg 35 min. Satellite 125 has azimuth 249,1 and elevation 11.4 degree in this city. On Jan.14, 8.53 AM, the moon (70 % face) will be at azimuth 249.1 with elevation 13.1 - almost 2 degrees above your satellite 125. Moon's face, similarly like Sun's is seen at the angle of half a degree, so, to imagine location of satellite, you have to look below Moon's face 3 to 4 its diameters. Next day, Jan. 15, at 10.04 AM, the Moon (59 % face) will be at the same azimuth, but the elevation will be only 5.9 degree. If there will be no clouds (and it is big IF ...) you could estimate the best location for your tower, just looking towards the Moon at these hours. Cheers, polgyver