All Sky HIPP2+GAIA All Sky Image Collection generated from Hipparcos2 and GAIA DR2 catalogues	19, Jul, 2018 Japanese

About

All-sky images of 1.3 billion stars generated from Hipparcos-2 and GAIA DR2 catalogues are downloadable in this page.
Images with various settings are available because the preferred setteings are different dependent on the purposes.

For image generation, the ratio of brightness are retained as possible. Color of stars is calculated from effective temperature approximated from B-V of Hipparcos catalogue, BT-VT of Tycho2 catalogue, BP-RP of GAIA DR2, and also effective temperatures provided in GAIA DR2.

Tha total number of GAIA DR2 is 1.7 billion, but the stars with both BP and RP are 1.3 billion, and 1 billion stars contains positive parallax, BP and RP. Stars without BP and RP are not shown in the current images.

Description

Epoch:

The original epoch of GAIA DR2 is 2015.5, and Hipparcos2 is 1991.25. Position for other epoch is calculated using proper motion and parallax.
Hence, 1.3 billion stars are shown at epoch 2015.5, but 1 billion for the other epoch because stars with positive parallax are shown.

The value 2000 means AD2000, 0 means BC1, -2000 means BC2001 in Julian year.

Brightness:

This value is proportional to the plotted star brightness. When a stars is plotted in one pixel, the RGB color value per pixel becomes the same and independent to image size. When the color becomes larger than 255, the brightness is proportional to circle area of the star.

Saturation, threshold radius:

The RGB color values are proportional to the brightness of star unless the RGB value exceeds 255. When one of the RGB values are over 255, circular image is drawn on the image and the area of the circle become proportional to the brightness.

linear: When one of the RGB values are over 255, circular image is drawn on the image and the area of the circle become proportional to the brightness.

Func3: The same as linear unless the circular radius is below threshold. When circular value is over threhold, the actual radius drawn becomes; actual radius = threshold * sqrt(radius from brigheness/threshold). As a result, circles become smaller and star become darker.

min. distance:

Stars closer than this value is not plotted. Unit is persec.

image type:

ER：currently, only equirectangular available.

Credits and References

The following data are used for generation of images donloadable in this page.

Hipparcos and Tycho Catalogues

ESA, 1997, The Hipparcos and Tycho Catalogues, ESA SP-1200.

Hipparcos-2 Catalogue

F. van Leeuwen, "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474, (2007) 653-664.
F. van Leeuwen, "Hipparcos, the New Reduction of the Raw Data", 2007, Springer Netherlands.

Tycho-2 catalogue

Hog, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A., "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy and Astrophysics, 355, (2000) L27-L30.

Hipparcos Input catalogue

ESA, 1992, The Hipparcos Input Catalogue, ESA SP-1136.

GAIA DR2

Licenses

The works provided in this page are licensed under a Creative Commons Attribution 4.0 International License.

If you have space to show credits, creator's name to show is NOMOTO Tomonori. Also, the source URL of this download site is http://T.NOMOTO.org/AllSkyHipp2GAIA/

Also, please follow the instructions of the credits for each star catalogues.

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Copyright (C) 2018 NOMOTO Tomonori, All rights reserved.