Southern Cross Constellation
Crux

Crux

The southern cross (Crux) constellation is the smallest of the 88 modern constellations.
Used since the earliest times to get oriented at night in the Southern Hemisphere, Crux is characterized by four bright stars that give it its name.
In the photograph you can see these stars: below/left, the brightest, alpha Crux (Acrux, a triple star), center/up Beta Crux (Mimosa), up/right Gacrux and below/Right the less bright of the four main stars of the constellation, delta Crucis (Imai).
Although viewed from Earth they seem to form a cross in the same plane, these stars are at distances ranging from 88 to 353 light-years.
At the upper left, part of the Coalsack dark nebula and as background, the dense star field of the Milky Way.
The photograph clearly shows the color difference between Gacrux (an optical binary star, where one of the components is one of the closest red giants to Earth) and the other three bluish stars.
For the latitudes of southern Argentina Crux is a circumpolar constellation, so it is visible throughout the year.

This photograph is a two tiles mosaic and it was acquired in La Banderita observatory, La Pampa, Argentina with a total integration time of about 5 hours.
The used equipment setup: Astrotech 65 mm F6.5 APO refractor, unmodified Canon 6D camera, Sky Watcher Star Adventurer mount (modified for DEC guiding) and homemade anti-dew system.

Technical data

Acquisition site La Banderita Observatory , La Pampa, Argentina
Acquisition date 06-08-2019
Instrument Astrotech 65 mm F6.5 APO Refractor.
Mount Sky-Watcher Star Adventurer, (modified: DEC Guiding capable)
Guide QHY Miniguider, with QHY5L-II-M camera (RA and DEC guiding)
Camera Canon 6D (Unmodified)
Camera sensor temperature 13°C approx.as reported by camera (non refrigerated)
Integration Tile 1: 44 subframes @ ISO 1600, 200 seconds each
Tile 2: 47 subframes @ ISO 1600, 200 seconds each
Total integration time: approx. 5 hours
Calibration 49 flats, 100 bias, 35 darks.
Resolution 3.19 arcsec/pixel
420 mm focal lenght, 6.5 um x 6.5 um pixels
Native size (tile) 5496 x 3670 pixels
Mosaic size 6400 x 5247 pixels
FOV 5°40’ x 4° 39'
Image center coordinates RA: 12 h 31 min
Dec: -60° 16'
Rotation: -57°
Acquisition Maxim DL
Process PixInsight 1.8