Monday, 14 September 2015

With Erik Høg on Parallax in New Catalogues

1) New blog on the kid : Natural Reason and Authority of Philosophers - are they Being Inverted? ; 2) Correspondence of Hans Georg Lundahl : With Erik Høg on Parallax in New Catalogues

Me to Erik Høg
Wednesday, September 02, 2015 1:55 PM
Different parallax ranges in Hipparcos, Tycho (and Tycho 2 too)?
First of all, on Tycho 2 I cannot on this formula search for parallax:

The Hipparcos and Tycho Catalogues
Multiparameter Search Tool

But second question is, how come Hipparcos and Tycho Main have different parallax ranges?

"Trigonometric parallax (in milliarcseconds): Field H11/T11 from the Hipparcos and Tycho Catalogues, Hipparcos range [-55, 772.33], Tycho range [-919, 701.5]"

from ReadMe

And finally, when I see the result, under T1 I see "2853 306 1" - how do I get to know what star it is?

Hans Georg Lundahl

Erik Høg to me
09/09/15 à 10h36
Re : Different parallax ranges in Hipparcos, Tycho (and Tycho 2 too)?
The Tycho experiment on the Hipparcos satellite did not give accurate parallaxes, but 2.5 million positions. They were used for the Tycho-2 Catalogue published in 2000. Please consult the catalogue descriptions.


Me to Erik Høg
Wed, 9 Sep 2015 11:58:44 +0200
Re : Different parallax ranges in Hipparcos, Tycho (and Tycho 2 too)?
So, if I get your position right ...

Quote: ESA's Hipparcos space astrometry mission was a pioneering European project which pinpointed the positions of more than one hundred thousand stars with high precision, and more than one million stars with lesser precision.

Launched in August 1989 Hipparcos successfully observed the celestial sphere for 3.5 years before operations ceased in March 1993. Calculations from observations by the main instrument generated the Hipparcos Catalogue of 118,218 stars charted with the highest precision. An auxiliary star mapper pinpointed many more stars with lesser but still unprecedented accuracy, in the Tycho Catalogue of 1,058,332 stars. The Tycho 2 Catalogue, completed in 2000, brings the total to 2,539,913 stars, and includes 99% of all stars down to magnitude 11, almost 100 000 times fainter than the brightest star, Sirius.

This web site presents background information describing the mission, the satellite and payload, operations and data reduction procedures. The Hipparcos and Tycho catalogues are described, and details on how to access the catalogues are provided. Some scientific highlights from the mission are noted. A number of resources are provided indicating how the Hipparcos and Tycho data can be used as educational tools. Visual material, in the form of photographs, images and animations are available for use.

... this means:

Hipparcos Catalogue gets parallax better than Tycho Main
Tycho Main gets lots more of stars and parallaxes, but gets parallaxes wrong
Tycho 2 corrects the parallaxes of Tycho Main - or doesnt it?

Which is it?

Hans Georg Lundahl

Erik Høg to me
09/09/15 à 13h25
Re : Different parallax ranges in Hipparcos, Tycho (and Tycho 2 too)?
No your statements are not correct:

Tycho-2 provides positions and proper motions besides of magnitudes.
Please red the catalogue descriptions.
I cannot help you any further...

Med venlig hilsen - With best regards

Erik Høg
Emeritus, Copenhagen University, Niels Bohr Institute
+45 44492008
ehoeg@hotmail.DK Important: NOT !!! because such a mail goes to Earl Hoeg in Halifax, Nova Scotia, a kind person who will forward to me, but please do not bother him.

Me to Erik Høg
09/09/15 à 21h56
Re : Different parallax ranges in Hipparcos, Tycho (and Tycho 2 too)?
But parallax is not searchable for Tycho 2 - only for Hipparcos and Tycho Main.

That was the reason I asked, partly.

Hans Georg Lundahl