Observers looking towards South in clear nights during the Southern Autumn can notice a beautiful asterism. In the border between the constellations Carina and Vela (once part of the “Argo Navis” ship) four bright stars outline a cross in the sky – Delta Velorum, Epsilon Carinae, Iota Carinae and Kappa Velorum, all about 2nd magnitude (V). However, this cross should not be mistaken with the “real” Southern Cross, some 20 degrees to the East of this field. The South Celestial Pole (and therefore the cardinal point) can be found by extending the major axis of the southern cross about 4 times towards the horizon. However, due to their proximity in the sky, unaware observers might do the same with the cross depicted in this image, leading to an erroneous location of the pole. Thus, this asterism is frequently referred to as “the False Cross”.

Besides the bright stars and the rich Milky Way starfield (especially in the upper left of the image), some interesting deep sky objects can be found around the area. Despite not poiting towards the South, the False Cross does point to a beautiful open cluster – NGC 2516. It was discovered by Abbe Lacaille in 1751-52, and is also known as the “Southern Beehive”, about 1300 light years distant [1]. Between 1872 and 1882, Benjamin Apthorp Gould and assistants took several plates of 35 Southern open star clusters from Cordoba, Argentina, in “Fotografia Cordobesas”, and likely photographed this cluster. [2, 3]. IC2220 is to the north of the cluster. On the upper right edge, some faint extended reddish emission nebulae can be seen, part of the Gum Nebula.

__________________________________

This image is the result of a quick set, in between deeper observations. The result was surprising, and I decided to process it as a “final” image. I was especially happy about how the faint Ha loops of the Gum nebula turned out, in the upper right, and how the field revealed some very faint dust, especially in the lower right around NGC 2516. This dust appears in astronomical surveys, but they are rarely captured by amateur images such as this one, and are likely part of the Galactic Cirrus (or IFN). The image could be improved were more time invested in integration, but since the target is already too far West, this will have to be a project for the coming seasons. Overall, I am happy, especially given the really short half-hour integration time!

Constructive criticism, comments and suggestions are more than welcome in the comments section!

Date: 10 April 2021

Location: My Observatory, MG, Brazil. Rural Skies (Bortle 3, calculated SQM ~21.6)

Camera: Canon EOS 6D (mod) at ISO 1600

Optics: Samyang 135mm f/2.0, operated at f/2.4

Mount: Sky-Watcher Star Adventurer, tracking.

Exposure Detail: 16x120s. Total integration 32min or 0.5h.

[1] SIMBAD Astronomical Database, CDS.

[2] S. Hughes. Catchers of Light: The Forgotten Lives of the Men and Women Who First Photographed the Heavens. ArtDeCiel Publishing, 2012. pp. 526 - 533

[3] S. Paolantonio, E. R. Minniti. Fotografías Cordobesas: Obra pioneira de fotografia astronómica em Latinoamérica y el mundo. Revista Universo Nº 55, 2006.