- Both observatories lie at altitude about 2400 meters and latitude 29 degrees (La Palma north, La Silla south)
- Southern part (La Silla) was taken on 13 April 2016, morning (a month after vernal eqionox). Northern part (La Palma) almost perfectly to fit – evening of 20 February 2020 (month before vernal equinox)
- On northern part (Casado) can be seen prominent reddish airglow from OH radicals, which is mostly visible after dusk, southern one (Horálek) shines with green (oxygen) airglow of which visibility is favorable also in mornings before dawn.
- Same equipment gave same resolution and same spectral sensitivity so HII regions are visible in both images. For both views were used modified Canon 6D cameras, 24mm lenses, f2.2, ISO 10000 and 15s exposures stitched to panorama. Most prominent HII regions are, of course – Gum nebula (behind MAGIC telescope), Barnard’s Loop, Orion Nebula, Rosetta Nebula, California Nebula, Heart and Soul… (Casado, north), Lagoon Nebula, Cat Paw Nebula, Rho Ophiuchi region, Carina Nebula, North America… (Horálek, south)
- In this time of year the 2 northern and 2 southern galaxies, except the Milky Way, are visible to naked eye in dark sky (in Casado’s La Palma view Andromeda galaxy and Triangulum galaxy, in Horálek’s one from La Silla the Magellanic clouds)
- Gegenschein can be seen as well – as a faint both-hemispheres belt 180 deg. away from Zodiacal Light columns
- Domes of one of world’s largest telescopes can be seen: Grand Telescopio Canarias (Casado, behind MAGIC telescope) and ESO 3.6 Telescope (Horálek, behind dome of New Technology Telescope)
The images would not have been taken without support of ESO – European Southern Observatory, IAC – Institute of Astrophysics of the Canary Islands and TWAN – The World At Night. Full credit of all images is Petr Horálek/ESO, Juan Carlos Casado/IAC/TWAN.
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