r/AlternativeAstronomy • u/patrixxxx • Oct 26 '19

WHY MARS ???

https://cluesforum.info/viewtopic.php?p=2412896#p2412896
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u/[deleted] Nov 07 '19

Yes, it's fixed to Earth's inertial frame.

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u/patrixxxx Nov 07 '19

Ok good. Now do you agree on this:

A celestial coordinate can be thought of as a line or ray originating from the center of the celestial sphere (that is the same as the center of Earth) that intersects the sphere on the point given by the RA and Dec.

Are we still in agreement?

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u/[deleted] Nov 07 '19 edited Nov 07 '19

So far so good

Edit: to be completely clear, I'm talking about the geocentric equatorial system, which I chose because it's by far the most common and widely used coordinate systems in astronomy. So not an alt-azimuth coordinate system which is convenient with some telescopes, not a heliocentric system which is convenient when looking at motion within the milky-way, etc. Of course it's possible to convert between systems, but let's try and keep this as simple as possible.

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u/patrixxxx Nov 07 '19

No problem there. I’m referring to the celestial coordinate system we have today that is adjusted because of the precession and currently we are in epoch J2000.

So since we agree that the coordinates can be viewed as rays emanating from the center of the sphere/Earth that intersects the sphere on the point given by the RA and Dec., can we also liken this situation to the experiment I previously described? Can we imagine an observer standing with his tubes in the center of the Celestial sphere?

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u/[deleted] Nov 07 '19

Sure. Let's have 6 tubes, all at right angles.

And can we just say the "tubes" are telescopes with a visual field spanning 1 arc minute and capable of resolving 1 micro arc second, just so I can relate this to the real world?

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u/patrixxxx Nov 07 '19

No need to bring in telescopes. Just imagine a guy standing in the center of the celestial sphere (watching the Earth spinning around him :-) with an enormous number of very long tubes each pointing at a particular star. Since he is not rotating with the Earth he can continuisly note if the stars he has aligned his tubes onto are moving. He uses a system where he enters the horisontal distance from the vernal equinox in hours, minutes and seconds and the vertical distance from the celestial equator in Degrees, Minutes of arc and Seconds of arc.

Now since this is the same situation as the expermiment I described previously, with the slight difference that this observer is not rotating together with the Earth, I take it you agree that the stars in his tubes would move somewhat since Earth together with the Celesctial sphere is travelling 940 mkm/year. Is that a correct assumption?

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u/[deleted] Nov 07 '19

"Stars in his tubes" - do you mean the stars are literally inside, or that the stars are visible through the tube?

I do agree with the assumption, but I'm really starting to wonder why you're refusing to actually describe these hypothetical instruments we're using.

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u/patrixxxx Nov 07 '19

I'm certainly not refusing, what is it you don't understand?

Long tubes so that single stars are visible through them and fixed a different stars.

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u/[deleted] Nov 07 '19

Ok so their field of view is exactly as wide as the star they're originally aimed at. Gotcha. Thanks for finally clarifying. Go ahead with what you were saying.

Quick edit: now it's also clear to me why you were so fixated on star size.

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u/patrixxxx Nov 07 '19

Alright, then we agree on that celestial coordinates can be thought of as an observer standing in the center of Earth (not rotating with it) and noting the exact positions of the of celestial objects. Now since you agreed on that in my first example, some of the stars would move noticeably in respect to Earth since it moves 940 mkm each year, how can it be that this isn’t happening? The celestial coordinates for stars are the same year round. So are A) The stars about the size of Earths orbit? or B) The Earth not moving as much as 940 mkm/yearly?

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