locked Moon Dx #general


Michael Black
 

Trying to determine accuracy of moon distance.

Using WSJTX Astronomy window, PSTRotator and https://www.mooncalc.org

All 3 seem to agree pretty well on Az and El but distance is off by about 5000km comparing WSJTX to the others.


As of 13:00 or so I see
WSJTX 383,115
PSTRotator 388074
MoonCalc  388199

The equatorial radius of the moon is 1,738km so that doesn't explain the difference (of about 1.3%).

It seems the code in wsjtx was done with certain deliberation so I'm hoping WSJTX is more accurate.  But how to resolve who's right?

Mike W9MDB


Svend, OZ7UV
 

Hi Mike.

I just got this answer:

PstRotator v17.28.
The displayed Moon distance is now the distance between your location and
the Moon surface.
It is still a difference around 100km between PstRotator and WSJT-X, and I
will try to find the reason.

Codrut - YO3DMU
\Svend, OZ7UV

man. 26. sep. 2022 01.02 skrev Michael Black via groups.io <mdblack98=
yahoo.com@groups.io>:

Trying to determine accuracy of moon distance.

Using WSJTX Astronomy window, PSTRotator and https://www.mooncalc.org

All 3 seem to agree pretty well on Az and El but distance is off by about
5000km comparing WSJTX to the others.


As of 13:00 or so I see
WSJTX 383,115
PSTRotator 388074
MoonCalc 388199

The equatorial radius of the moon is 1,738km so that doesn't explain the
difference (of about 1.3%).

It seems the code in wsjtx was done with certain deliberation so I'm
hoping WSJTX is more accurate. But how to resolve who's right?

Mike W9MDB










w6de
 

They could all be correct depending on the assumptions. Your position on the earth and the distance to the to the moon constantly varies. Examine what each of the three programs assume for the reflection point on the moon and your position on the earth.

73,
Dave, w6de

-----Original Message-----
From: main@WSJTX.groups.io <main@WSJTX.groups.io> On Behalf Of Michael Black via groups.io
Sent: Sunday, September 25, 2022 22:31
To: WSJTX Group <main@wsjtx.groups.io>
Subject: [WSJTX] Moon Dx #general

Trying to determine accuracy of moon distance.

Using WSJTX Astronomy window, PSTRotator and https://www.mooncalc.org

All 3 seem to agree pretty well on Az and El but distance is off by about 5000km comparing WSJTX to the others.


As of 13:00 or so I see
WSJTX 383,115
PSTRotator 388074
MoonCalc  388199

The equatorial radius of the moon is 1,738km so that doesn't explain the difference (of about 1.3%).

It seems the code in wsjtx was done with certain deliberation so I'm hoping WSJTX is more accurate.  But how to resolve who's right?

Mike W9MDB


Julian
 

I recently looked into this. There is no simple answer. The Apogee and Perigee vary considerably over time.
See the following paper from NASA:

https://eclipse.gsfc.nasa.gov/SEhelp/moonorbit.html


Over the period 2008-2010, the radius of the orbit varies between 356,568 and 406,602km.
Over a 5000 year period, it varies between            356,355 and 406,725km.
It depends on what the programmes have assumed...


Julian, G3YGF

On 26/09/2022 00:52, w6de wrote:
They could all be correct depending on the assumptions. Your position on the earth and the distance to the to the moon constantly varies. Examine what each of the three programs assume for the reflection point on the moon and your position on the earth.

73,
Dave, w6de

-----Original Message-----
From: main@WSJTX.groups.io <main@WSJTX.groups.io> On Behalf Of Michael Black via groups.io
Sent: Sunday, September 25, 2022 22:31
To: WSJTX Group <main@wsjtx.groups.io>
Subject: [WSJTX] Moon Dx #general

Trying to determine accuracy of moon distance.

Using WSJTX Astronomy window, PSTRotator and https://www.mooncalc.org

All 3 seem to agree pretty well on Az and El but distance is off by about 5000km comparing WSJTX to the others.


As of 13:00 or so I see
WSJTX 383,115
PSTRotator 388074
MoonCalc  388199

The equatorial radius of the moon is 1,738km so that doesn't explain the difference (of about 1.3%).

It seems the code in wsjtx was done with certain deliberation so I'm hoping WSJTX is more accurate.  But how to resolve who's right?

Mike W9MDB













 

This probably doesn't answer the question but it's pretty interesting!

https://en.m.wikipedia.org/wiki/Lunar_distance_(astronomy)

--
John P.
WA2FZW


Michael Black
 

I had an older version of PSTRotator and they agree much better now with 17.28 -- differing by around 100km as of right now so only 0.026% between them.

WSJTX 390620
PSTRotator 390506
MoonCalc 386676

MoonCalc is now the odd one out and off by approx 3900km but I imagine they are doing the orbital distance and not surface-to-surface.

Mike W9MDB

On Sunday, September 25, 2022 at 06:51:13 PM CDT, Svend, OZ7UV <spanget@...> wrote:





Hi Mike.

I just got this answer:

PstRotator v17.28.
The displayed Moon distance is now the distance between your location and
the Moon surface.
It is still a difference around 100km between PstRotator and WSJT-X, and I
will try to find the reason.

Codrut - YO3DMU
\Svend, OZ7UV

man. 26. sep. 2022 01.02 skrev Michael Black via groups.io <mdblack98=
yahoo.com@groups.io>:


Trying to determine accuracy of moon distance.

Using WSJTX Astronomy window, PSTRotator and https://www.mooncalc.org

All 3 seem to agree pretty well on Az and El but distance is off by about
5000km comparing WSJTX to the others.


As of 13:00 or so I see
WSJTX 383,115
PSTRotator 388074
MoonCalc  388199

The equatorial radius of the moon is 1,738km so that doesn't explain the
difference (of about 1.3%).

It seems the code in wsjtx was done with certain deliberation so I'm
hoping WSJTX is more accurate.  But how to resolve who's right?

Mike W9MDB










Charles Suckling
 

Hi Mike

Yes, I think its the difference between geocentric and topocentric
calculations. If you look at Moonsked, the 'Range' changes continuously in
one direction (today centre of moon is moving closer to centre of earth).
Watch' Dist' in WSJT-X and you should see it increase again after transit,
as the observer moves away from the moon.

For comparison, I suggest using JPL Horizons to provide definitive data for
comparison. At the present time, JPL and WSJT-X differ at my location by
about 5-6km.


73

Charlie DL3WDG

On Mon, 26 Sept 2022 at 10:57, Michael Black via groups.io <mdblack98=
yahoo.com@groups.io> wrote:

I had an older version of PSTRotator and they agree much better now with
17.28 -- differing by around 100km as of right now so only 0.026% between
them.

WSJTX 390620
PSTRotator 390506
MoonCalc 386676

MoonCalc is now the odd one out and off by approx 3900km but I imagine
they are doing the orbital distance and not surface-to-surface.

Mike W9MDB









On Sunday, September 25, 2022 at 06:51:13 PM CDT, Svend, OZ7UV <
spanget@...> wrote:





Hi Mike.

I just got this answer:

PstRotator v17.28.
The displayed Moon distance is now the distance between your location and
the Moon surface.
It is still a difference around 100km between PstRotator and WSJT-X, and I
will try to find the reason.

Codrut - YO3DMU
\Svend, OZ7UV

man. 26. sep. 2022 01.02 skrev Michael Black via groups.io <mdblack98=
yahoo.com@groups.io>:


Trying to determine accuracy of moon distance.

Using WSJTX Astronomy window, PSTRotator and https://www.mooncalc.org

All 3 seem to agree pretty well on Az and El but distance is off by about
5000km comparing WSJTX to the others.


As of 13:00 or so I see
WSJTX 383,115
PSTRotator 388074
MoonCalc 388199

The equatorial radius of the moon is 1,738km so that doesn't explain the
difference (of about 1.3%).

It seems the code in wsjtx was done with certain deliberation so I'm
hoping WSJTX is more accurate. But how to resolve who's right?

Mike W9MDB



















Charles Suckling
 

Hi Mike

I forgot to add, that discrepancies may arise between programs that use a 6
character grid locator to define your home location, and JPL Horizons where
you can enter your exact location, due to the potential inaccuracy in
determining your exact location from a 6 digit Maidenhead locator.

We see this sometimes on microwave EME, where the computed Doppler shifts
may be a few Hz out. Similar effects might well happen with moon
distance. Its all negligible, however!

73

Charlie

On Mon, 26 Sept 2022 at 10:57, Michael Black via groups.io <mdblack98=
yahoo.com@groups.io> wrote:

I had an older version of PSTRotator and they agree much better now with
17.28 -- differing by around 100km as of right now so only 0.026% between
them.

WSJTX 390620
PSTRotator 390506
MoonCalc 386676

MoonCalc is now the odd one out and off by approx 3900km but I imagine
they are doing the orbital distance and not surface-to-surface.

Mike W9MDB









On Sunday, September 25, 2022 at 06:51:13 PM CDT, Svend, OZ7UV <
spanget@...> wrote:





Hi Mike.

I just got this answer:

PstRotator v17.28.
The displayed Moon distance is now the distance between your location and
the Moon surface.
It is still a difference around 100km between PstRotator and WSJT-X, and I
will try to find the reason.

Codrut - YO3DMU
\Svend, OZ7UV

man. 26. sep. 2022 01.02 skrev Michael Black via groups.io <mdblack98=
yahoo.com@groups.io>:


Trying to determine accuracy of moon distance.

Using WSJTX Astronomy window, PSTRotator and https://www.mooncalc.org

All 3 seem to agree pretty well on Az and El but distance is off by about
5000km comparing WSJTX to the others.


As of 13:00 or so I see
WSJTX 383,115
PSTRotator 388074
MoonCalc 388199

The equatorial radius of the moon is 1,738km so that doesn't explain the
difference (of about 1.3%).

It seems the code in wsjtx was done with certain deliberation so I'm
hoping WSJTX is more accurate. But how to resolve who's right?

Mike W9MDB



















Lawrence Godek
 

Extremely interesting!

On 9/25/2022 8:03 PM, John P wrote:
This probably doesn't answer the question but it's pretty interesting!

https://en.m.wikipedia.org/wiki/Lunar_distance_(astronomy)