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Originally Posted by hoster
Good morning rainman
Can't you use a angle meter on the lnbf support arm and get the proper reading?
The other issue is having a hard time understanding the use of the compass when you are around the metal dish, it will not be c9orrect. With fiberglass dishes it is different.
How do you use the compass Ino it is a stupid question.
Rich
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Unfortunately, there is no surface on these little offset dishes that seem to relate to where the dish is actually
aiming.
I'm not sure from the above whether you are talking about the portion of the lnbf arm that is directly behind the dish (which is close but not exactly the same as being perpindicular to the apparent aim of the dish), or the portion between the bottom edge of the dish and the LNBF. The former comes close to being useful, assuming that you know the offset angle accurately (and while you can look up the offset angle, I'm convinced that each dish is slightly different, due to irregularities in the way the bracket attaches to the dish), however the latter isn't even close. It's often stated that the true center of the parabolic surface is just below the bottom edge of the dish, so it seems intuitive that the lnbf support arm would be roughly aiming pretty close to the direction that the dish is aiming. However, when I measured this on my 90CM dish, it wasn't close. I aimed at something with a 43 deg elevation, and an inclinometer on the support arm indicated 32 degrees, ie an 11 deg difference.
Since these small dishes don't need nearly the aiming accuracy of a bigger dish, it SHOULD be possible to get near perfect alignment without ever tuning a satellite, just by using an inclinometer, if only there was some surface on the darn things to measure from. However, from the best that I can determine, there is no suitable surface.
And BTW, there are numerous posts here about how to use the USNO
solar tables to determine true azimuths using shadows, if you are confused about using a compass. It's more accurate than a compass.