Nautical almanac 2022, November 11, Aries

[Lasse Karagiannis (Lasse_Karagiannis)]

Hi, I am  running the 0.18.0 version and looking at the Nautical Almanac 2022
https://thenauticalalmanac.com/TNARegular/2022_Nautical_Almanac.pdf
and I am trying to verify the entries for Aries which I think means
the vernal point -the zero hour on the blue equatorial grid.
According to the almanac at 06:00:00 GMT the 11th of November 2022 the longitude (Greewhich Hour Angle measured from 0 to 360 degrees)
is 140 degrees 22.0 minutes.

I've enabled "Equator (of date)" and "Eqliptic (of date)"  so that I can see the veneral crossing points and also enabled the blue equatorial grid and the green azimutal grid but the veneral point is on around 315 degrees of the green grid and the zodiac sign of Aries is between 290 and 300 degrees longitude on the green grid. 

Could somebody please explain what I am missing?
Kindest regards,
Lasse

[Georg Zotti]

Hi!

First, upgrade to 1.0 or later.

Then, activate the Navigational Stars plugin.

Click on the Sun or any other object.

Verify GHA(Aries) is 140°22.2'. This means, hour angle of the Vernal Equinox point as seen from Greenwich is 140°22.2'.   (Our results seem to deviate from yours by 1 temporal second.)

Putting Vernal (not "veneral") Equinox point (First point of Aries) onto azimuth 315° for 6h UT puts you anywhere on a small circle through (roughly) Sardinia, Calais and the Shetlands. Adding an altitude could reveal your position.

The "Zodiacal Sign of Aries" means the section of the ecliptic with Ecliptical Longitudes 0...30°. 0° ecl. longitude is equivalent to the Vernal Equinox point, so that your added info of 290...300° contradicts the 315°. If you mean the stars of the Aries constellation, they are meanwhile outside their "sign". (Read about precession e.g. in Wikipedia)

HTH, G.

[Georg Zotti]

You can additionally set yourself to Greenwich and show the "Fixed Equatorial" Grid (or just "Fixed Equator") to verify that Vernal Equinox is at hour angle 140.3°.

[Lasse Karagiannis (Lasse_Karagiannis)]

Thanks you but I still don't get how I am supposed see the Vernal Equinox point as seen from Greenwich is 140°22.2 .  The 1.1  version Stellarium appimage got corrupted on my Linux station after running different versions simultaneously, so I have to stick to 0.18 little bit longer until I am confident to uninstall and compile from sources. 

I have the following settings in the 0.18 version:
-Position: Royal Observatory Greenwich
-Time 2022-11-11, 06:00:00 .Time-stepping is paused.
in the "Sky and view options window (F4)"-> Markings tab has the following settings:
 -Equator (of date)
 -Eqliptic (of date)
-Equinoxes (of date), which shows the ram-symbol at the Vernal Equinox point, the crossing between the Eqliptic and the Equator.

 -Equatorial grid (of date), blue color grid, 0h line passes through Vernal Equinox point. 140 deg/ 15 deg per hour is 9.333h, and between 9h and 10h  the star 38 Lyn at the tail of the Lynx is seen
 -Ecliptic grid (of date), bronze color grid, 0 degree passes through Vernal Equinox point,  140 degree is around Merak in Ursa Major
-Azimutal grid, light green color grid, Vernal Equinox point is between +310  and +320 degree meridians, at 140 deg it passes through Centaurus

 
I still don't understand how the Vernal Equinox point as seen from Greenwich is 140°22.2
Please help a little bit more.
/Lasse

[Georg Zotti]

Since 2018 we have added features as described that allow you to see GHA. I would try to reinstall 1.1 AppImage and avoid running different versions simultaneously. Esp. avoid running obsolete versions. Likely you don't need to compile from sources, but also this takes just ~30 minutes on a slow PC, following BUILDING.md instructions on our Github site. 

Do you understand what hour angle is? It is the sidereal time elapsed after meridian transit, and therefore counted in the opposite direction from RA. GHA(ARI) of 140° means First point of Aries (which has RA=0 per definition) is 140° after meridian transit (HA=140°), or that objects with RA=140° like 38 Lyn are in the Meridian. This is what you have. On version 1.0 we have the Fixed Equator that shows hour angles.