The great astronomical correction

OK, so that’s done now.

I have read an enormous amount of repetition, watched a loop from SOHO a number of times before I copped on that it was the same each time, and had a look at a few topics online such as axial precession, heliacal rising (which even the poor autocorrect keeps trying to call “helical”) read Canopus decree - at least in part, and I now know what a hapax legomenon is. I’m just waiting for the chance to use it.

Seriously, I take my hat off to those posting what now, at least at first pass, seems a fact based view on a number of relatively complex concepts. It’s a fascinating subject, and I feel I’ve learned something about a matter that has always been of interest to me. Thank you, especially to ps200306 and Zubeneschamali

oriel36

Deleted User wrote: »

I have read an enormous amount of repetition, watched a loop from SOHO a number of times before I copped on that it was the same each time

Astronomy-by-satellite is not for everyone while others will take to it easily as they become familiar with the narrow corridor which is normally out of sight during that period between dawn and twilight.

https://sol24.net/data/html/SOHO/C3/96H/VIDEO/

The time lapse is not the same each time as Mercury is currently brightening in its phase before exiting the corridor and won't be seen again until it is seen moving behind the Sun around the same time as Venus will pass between the Earth and the stationary Sun as these planets did in 2012 -

https://www.youtube.com/watch?v=w2uCtot1aDg

Contributors have not sufficiently understood that this astronomy-by-satellite is for those who can interpret observations in context of a central Sun and moving planets hence all the downplaying and diminution of astronomers and astronomy inherited from other eras are ineffective.

In terms of daily rotation and the orbital cycle, come March 1st 2021, the orbital distance of 6 hours and 1/4 rotation will be omitted as we gauge the orbital cycles by the number of rotations across 4 orbital circuits. This is a point of departure for many avenues of research so those who adhere to celestial sphere software like stellarium as a true reflection of planetary motions, especially ours, are fooling themselves and others who know no better.

I don't feel sorry for you that you can't see something new every day with the SOHO Lasco C3 camera, I do feel sorry for those who can but have yet to experience this type of astronomy. It all depends on the input of the Earth's orbital motion and the change in position of the background stars parallel to the orbital plane thereby setting the Sun up as a central reference.

oriel36

Normally there would be a considerable amount to consider, however, stellarium enthusiasts are unlikely to appreciate the subtle distinctions and changes in the positions of the stars when freed of the Earth's daily rotation or what is effectively astronomy-by-satellite.

In terms of orientation, the Northern hemisphere view is the more accurate and productive as the stars change position parallel to the orbital plane from left to right of the stationary Sun -

https://www.youtube.com/watch?v=qRzqNK-1IHI

https://upload.wikimedia.org/wikipedia/commons/4/4e/Pleiades_large.jpg


The Southern hemisphere observers see the constellations upside down from the standpoint of the orbital change in positions where all circumpolar motion or RA/Dec factors are subtracted.

ps200306

oriel36 wrote: »

Normally there would be a considerable amount to consider, however, stellarium enthusiasts are unlikely to appreciate the subtle distinctions and changes in the positions of the stars when freed of the Earth's daily rotation or what is effectively astronomy-by-satellite...

Tell me, Gerald ... have you ever actually used Stellarium? You know you can advance the time by sidereal days, effectively eliminating diurnal rotation? Or you can fix any object at the centre of the view. Place the Sun there and you will see very much what you see from SOHO ... except without the limitations of the narrow fixed field of view, the short time span, and the solar radiation knocking lumps off your camera sensor. You really should try it. Expand your horizons, so to speak.

oriel36 wrote: »

In terms of orientation, the Northern hemisphere view is the more accurate and productive ... The Southern hemisphere observers see the constellations upside down ...

Try flipping your laptop screen upside down. Now the southern hemisphere view is the right one! Actually, none of them is right, as the constellations don't have a fixed orientation for observers on Earth. The Pleiades look a bit like that for a northern observer when they cross the meridian. They stand on their tail when rising and on their head when setting.

But the SOHO view of the Pleiades is not quite right either, being rotated a little anti-clockwise. I'm surprised such an astute satellite astronomer missed that. What's more, the stars don't move directly left to right. Have a look at the sequence from 0:25 to 0:50 in the video below. Follow any star entering from the bottom left corner. Does it travel straight across the screen? Just before the end of the sequence, your faves the Pleiades appear at top left. They drift upward, trying to escape at the top of the screen.

That's because SOHO isn't aligned with the ecliptic, it's aligned with the solar equator which is tilted 7.25 degrees to the ecliptic. If you didn't find coordinate systems so offensive, you'd know that SOHO has its own*.

* From SOHO's standard operating procedures manual:

Solar rotation axis

The solar rotation axis will be calculated using the Carrington ephemeris elements. These elements define the inclination of the solar equator to the ecliptic as 7.25 degrees, and the longitude of the ascending node of the solar equator on the ecliptic as , where T is the time in years from J2000.0.

The solar rotation axis used for alignment of the SOHO spacecraft will be determined from the Carrington ephemeris elements. The Experiment Interface Document Part A (Issue 1, Rev 3) lists the longitude of the ascending node of the solar equator as 75.62° and the position of the pole of the solar equator in celestial coordinates as 286.11° right ascension and 63.85° declination. This definition is consistent with a solar rotation axis determined from the Carrington elements for a date of 1 January 1990. As mentioned in the EID Part A, this information must be updated for the actual launch date.

Heliographic longitudes on the surface of the Sun are measured from the ascending node of the solar equator on the ecliptic on 1 January 1854, Greenwich mean noon, and are reckoned from 0 to 360° in the direction of rotation. Carrington rotations are reckoned from 9 November 1853, 00:00 UT with a mean sidereal period of 25.38 days, and are designated as etc.

Inter-instrument flag reference coordinates

The spacecraft optical axes are defined with respect to the optical alignment cube of the Fine Pointing Sun Sensor, with the optical X axis (X₀) nominally perpendicular to the spacecraft launcher separation plane and pointing from the separation ring through the spacecraft. The spacecraft optical Y axis (Y₀) is along the direction of the solar panel extension with positive Y₀ pointing from the interior of the spacecraft towards the UVCS instrument.

The orientation of the SOHO spacecraft is planned to have the spacecraft optical X axis (X₀) pointing towards the photometric center of the Sun, and the spacecraft optical Z axis (Z₀) oriented towards the north ecliptic hemisphere such that the (X₀,Z₀) plane contains the Sun axis of rotation. As such the Y₀ axis will be parallel to the solar equatorial plane pointing towards the east (opposite to the solar rotation direction). ESA will be responsible for achieving this orientation with the misalignment margins defined in the EID-A...

oriel36

ps200306 wrote: »

Try flipping your laptop screen upside down. Now the southern hemisphere view is the right one! Actually, none of them is right, as the constellations don't have a fixed orientation for observers on Earth. The Pleiades look a bit like that for a northern observer when they cross the meridian. They stand on their tail when rising and on their head when setting.

In this case, the principle refers not just to the orbital orientation of the stars to the Sun using a left/right marker for the Earth's orbital motion but also the relationship of individual stars to the galactic structure for some stars will be closer to the galactic centre than others.


The satellite tracking with the Earth's orbital motion is free from daily rotation and any hemispherical concerns so that leaves the direction of the Earth as the main factor in assigning a left/right to the stationary Sun, after all, observers should know by now why stars go from an evening appearance (left) to dawn appearance (right) with stars close to the orbital plane out of view for a number of weeks.

https://www.youtube.com/watch?v=qRzqNK-1IHI

It is an astronomical beachhead and a project rather than a finished article so all the observer does is make allowances for the limitations of the satellite, the quality of its imaging, the rough tracking and things like that. The observer no longer has to deal with hemispherical concerns but neither are they trapped by them in a celestial sphere framework where there is no pretense to structural depth perception or long term observations rendered into structural context. Celestial sphere software like stellarium is excellent for relative positions of celestial objects to each other as dates and times within those dates.

For the purpose of this thread, the first step is subtracting any daily rotational and hemispherical component so the curtain rises on the astronomical symphony of timekeeping and orbital comparisons in a stationary Sun centred system.

Thanks for the accompanying video by the way as it is informative up to a point, however, the use of the material here is original hence a level playing field.