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Astrolabe or inclinometer?



 
 
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  #11  
Old September 8th 16, 09:44 AM posted to uk.tech.digital-tv
Max Demian
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Posts: 3,720
Default Astrolabe or inclinometer?

On Thu, 8 Sep 2016 01:08:40 +0100, Davey
wrote:
On Wed, 7 Sep 2016 13:44:31 -0700 (PDT)
Andrew Rowland wrote:


Been to a couple of houses recently surrounded on all sides by

tall
trees. One in particular was very keen to get Sky and we spent

some
time looking for locations where a dish might be able to peer

through
a small gap in the foliage. I used an inclinometer app on my

phone,
but found it next to impossible to hold it steady at 23.1 while
sighting along it to see if we were looking at sky or forest

canopy.
Does anyone know of a device that lets you look along or through

it
while simultaneously being able to see the bubble or plumb line so
you know you are holding the thing level? Or has anyone found an
different solution to the problem? Bill said recently 'look SSE

and
slightly up' but I need a bit more accuracy than that when things

are
tight! I'll probably construct myself a gadget out of cardboard

but I
am not sure the best way to go about it...


Would a sextant work?


Since they're designed to work on board ship, it won't matter if
you've had a few.

--
Max Demian
  #12  
Old September 8th 16, 10:07 AM posted to uk.tech.digital-tv
Java Jive[_2_]
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Posts: 1,654
Default Astrolabe or inclinometer?

On Thu, 08 Sep 2016 09:30:42 +0100, Chris Green wrote:

Bill Wright wrote:

On 07/09/2016 23:20, Java Jive wrote:

You can create an inclinometer using a protractor. If you really
want to be fancy, you can also tape it to a spirit level for the
duration.


Because the difference between being screened and not being screened
can be a fraction of a degree, it is far beyond the accuracy of this
sort of device to give a definite answer. That's unless of course the
proposed dish location is obviously screened or obviously not screened,
in which case...


If you need to be that accurate surely other factors are going to change
things from day to day anyway. If you are going to "peer through a
small gap in the foliage" then being accurate to a fraction of a degree
isn'g going to help at all is it?


Quite, and if it really is a question of peering through foliage, what is
visible this summer likely will not be next. I've tried both the
inclinometer and the cardboard template from my own page that I linked, so
I know that both work and thus are certainly better than many other like
contraptions, but I used them to find a place on the end wall of my house
that could see the satellite over things that don't move or grow, in my
case a neighbour's roof.

--
Please reply to newsgroup
  #13  
Old September 8th 16, 10:25 AM posted to uk.tech.digital-tv
Java Jive[_2_]
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Posts: 1,654
Default Astrolabe or inclinometer?

On Thu, 08 Sep 2016 10:13:28 +0100, Woody wrote:

Get the free Satellite Director. Turn on your GPS, set the satellite you
want, and set it into camera mode. It will place a vertical line on the
screen on top of which is a circle where the satellite sits. As it is
superimposed on the camera picture you will be able to easily find a
clear view.


I've given a lot of thought to this sort of problem, because I've wondered
how best I can convert my satellite calculator page to work as a mobile
app, using photographs, and thus, while I admit freely that I haven't
actually tried Satellite Director, immediately I can see the same
potential problems with it as prevented me from taking any further the
ideas I was mulling over:

:-( GPS on my phone is only accurate to a few metres both
horizontally and vertically, so it's unlikely to be able
to pinpoint a satellite's position sufficiently accurately
to be of any use.

:-( The precise position of a satellite in a photo will depend
critically on the focal length of the camera used, which
is likely to vary from mobile to mobile, and if the camera
has an optical, as opposed to a digital, zoom will even
vary from photo to photo. It MIGHT be possible to obtain
the camera's focal length from the photo's metadata, but
my guess is that the writer(s) of neither this app nor any
other similar one will understand the need to do this.

So I suspect that like most such over-simplifying methods, Satellite
Director is unlikely to be accurate to better than a few degrees, perhaps
not even that, and since dishes have to be aligned to ~0.1 degrees,
probably ~0.05 degrees for a rotor, I wouldn't even begin to trust it.

I can see no alternative to using something like an inclinometer. If the
results from that are marginal, in the case of trees, forget it, because
their growth will obscure the satellite sooner rather than later, but if
it's something unchanging like a neighbour's roof, try to borrow a dish
and a receiver from somewhere to test in the intended location.

--
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  #14  
Old September 8th 16, 11:13 AM posted to uk.tech.digital-tv
Paul Ratcliffe
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Posts: 2,425
Default Astrolabe or inclinometer?

On Thu, 8 Sep 2016 10:25:33 +0000 (UTC), Java Jive
wrote:

since dishes have to be aligned to ~0.1 degrees,
probably ~0.05 degrees for a rotor, I wouldn't even begin to trust it.


What utter rubbish from Charley McFarley.
Don't think he lives in the real world...
  #15  
Old September 8th 16, 11:28 AM posted to uk.tech.digital-tv
Peter Duncanson
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Posts: 4,190
Default Astrolabe or inclinometer?

On Thu, 8 Sep 2016 01:08:40 +0100, Davey wrote:

On Wed, 7 Sep 2016 13:44:31 -0700 (PDT)
Andrew Rowland wrote:

Been to a couple of houses recently surrounded on all sides by tall
trees. One in particular was very keen to get Sky and we spent some
time looking for locations where a dish might be able to peer through
a small gap in the foliage. I used an inclinometer app on my phone,
but found it next to impossible to hold it steady at 23.1 while
sighting along it to see if we were looking at sky or forest canopy.
Does anyone know of a device that lets you look along or through it
while simultaneously being able to see the bubble or plumb line so
you know you are holding the thing level? Or has anyone found an
different solution to the problem? Bill said recently 'look SSE and
slightly up' but I need a bit more accuracy than that when things are
tight! I'll probably construct myself a gadget out of cardboard but I
am not sure the best way to go about it...


Would a sextant work?


As far as I know a sextant deals with the angle of elevation. It doesn't
have a compass.

--
Peter Duncanson
(in uk.tech.digital-tv)
  #16  
Old September 8th 16, 12:34 PM posted to uk.tech.digital-tv
Max Demian
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Posts: 3,720
Default Astrolabe or inclinometer?

On Thu, 8 Sep 2016 10:07:49 +0000 (UTC), Java Jive
wrote:

Quite, and if it really is a question of peering through foliage,

what is
visible this summer likely will not be next. I've tried both the
inclinometer and the cardboard template from my own page that I

linked, so
I know that both work and thus are certainly better than many other

like
contraptions, but I used them to find a place on the end wall of my

house
that could see the satellite over things that don't move or grow,

in my
case a neighbour's roof.


What about loft extensions? Does the mediaeval right of "ancient
lights" extend through the EM spectrum?

--
Max Demian
  #17  
Old September 8th 16, 12:41 PM posted to uk.tech.digital-tv
Max Demian
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Posts: 3,720
Default Astrolabe or inclinometer?

On Thu, 08 Sep 2016 12:28:52 +0100, Peter Duncanson
wrote:
On Thu, 8 Sep 2016 01:08:40 +0100, Davey

wrote:

Would a sextant work?


As far as I know a sextant deals with the angle of elevation. It

doesn't
have a compass.


Go out at night and take a site line off Polaris. Hold it
horizontally.

--
Max Demian
  #18  
Old September 8th 16, 01:15 PM posted to uk.tech.digital-tv
Java Jive[_2_]
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Posts: 1,654
Default Astrolabe or inclinometer?

On Thu, 08 Sep 2016 13:34:54 +0100, Max Demian wrote:

What about loft extensions? Does the mediaeval right of "ancient lights"
extend through the EM spectrum?


That's a really interesting idea! I wonder who would be rich enough and
interested enough to fund a case to test that in the courts - not, me,
sadly!-)

--
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  #19  
Old September 8th 16, 01:18 PM posted to uk.tech.digital-tv
Java Jive[_2_]
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Posts: 1,654
Default Astrolabe or inclinometer?

On Thu, 08 Sep 2016 11:13:08 +0000, Paul Ratcliffe wrote:

On Thu, 8 Sep 2016 10:25:33 +0000 (UTC), Java Jive

wrote:

since dishes have to be aligned to ~0.1 degrees,
probably ~0.05 degrees for a rotor, I wouldn't even begin to trust it.


What utter rubbish from Charley McFarley.
Don't think he lives in the real world...


What is your figure for the required accuracy then? I note that you don't
offer one.

--
Please reply to newsgroup
  #20  
Old September 8th 16, 01:22 PM posted to uk.tech.digital-tv
Davey
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Posts: 2,176
Default Astrolabe or inclinometer?

On Thu, 08 Sep 2016 12:28:52 +0100
Peter Duncanson wrote:

On Thu, 8 Sep 2016 01:08:40 +0100, Davey
wrote:

On Wed, 7 Sep 2016 13:44:31 -0700 (PDT)
Andrew Rowland wrote:

Been to a couple of houses recently surrounded on all sides by tall
trees. One in particular was very keen to get Sky and we spent some
time looking for locations where a dish might be able to peer
through a small gap in the foliage. I used an inclinometer app on
my phone, but found it next to impossible to hold it steady at
23.1° while sighting along it to see if we were looking at sky or
forest canopy. Does anyone know of a device that lets you look
along or through it while simultaneously being able to see the
bubble or plumb line so you know you are holding the thing level?
Or has anyone found an different solution to the problem? Bill
said recently 'look SSE and slightly up' but I need a bit more
accuracy than that when things are tight! I'll probably construct
myself a gadget out of cardboard but I am not sure the best way to
go about it...


Would a sextant work?


As far as I know a sextant deals with the angle of elevation. It
doesn't have a compass.


Next idea: My star-gazer telescope has scales for elevation and
direction, and it might even show the satellite at the right time of
night. Once it's pointing where you want, just lock it all down.

--
Davey.

 




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