[TowerTalk] And now for something completely different(TrueNorth)

[Jim Lux]

At 01:38 PM 9/17/2006, K8RI on TowerTalk wrote:

> >From: "Jim Lux" <jimlux at earthlink.net>
><snip>
>
> > Actually, though, the other link I posted (about using polaris) is
> > fascinating.. It makes the point that with a standard theodolite
> > telescope, Polaris is visible in the daytime, and because it moves a lot
> > slower (angular wise) than the sun, it's easier to get a good north
> > direction.  I'll have to give it a try.
> >
>The spotting scope on my larger telescope 2500mm @ f10 (don't remember the
>spotting scope magnification, but the objective is 50mm for light gathering)
>has not only cross hairs, but a graduated rail road track so when things are
>properly aligned polaris will travel around that track.  Polaris is not all
>that bright and can be difficult to spot (naked eye) in heavily light
>poluted skys yet you can see it in the daytime in a scope. Even with a
>relatively low power eyepiece I have to crank the main scope off to one side
>or the other to find Polaris.  If not properly set up even being off a
>little will cause stars to drift noticeably in a shot time. OTOH the beam
>width of that 2500 f-10 is a some what narrower than that of my
>tri-bander.<:-))


Come on, Roger, you need a better antenna.. Let's see.. f/10 at 
2500mm means you've got 250mm aperture, at lambda of say 500 nm, or 
500 lambda.  So, on 20m, you only need an antenna with an aperture 
of, let's see, 10 km. But... real hams work on top band, so you'd 
need about 100 km. (hmm, you'd have trouble at Field day.. everything 
has to fit in a 1000 ft circle.) This is up in LOFAR antenna territory.

><snip>



>These are two different realms with far different requirments. Applying the
>far greater astronomical precision requirements to antenna alignment hurts
>nothing, but gains nothing as well. OTOH is good experience<:-))

I think everyone should try several alignment methods.. not just for 
their antenna, but just because it's fun and not particularly time 
consuming.  Especially the "stick and shadow" approaches.  It's easy 
to say, "mark when the shadow is shortest".. much tougher to actually do it.


Jim,W6RMK