By Hassan Dadashi . Arani | 2024-03-11
![Community photo entitled by Andrea Iorio on 03/12/2024 at Marino, Rome, italy](https://earthsky.org/upl/gravity_forms/6-d184048789a60d766a02a8e43117298b/2024/03/SH2-274_HOO_def.jpg)
On 03/12/2024 08:00 pm by Andrea Iorio| Marino, Rome, italy
Although Abell 21, or Sh2-274, has a large apparent diameter of 10 arcminutes, its surface brightness is so low, with features ranging from magnitude 16-25, that it was not discovered until 1955. It is a planetary nebula lying at a distance of 1,500 light-years in the constellation Gemini, which gives it an estimated diameter of 4 light-years. The parent star, now a white dwarf, is thought to be the deep blue star near the center of the nebula.
RIG1:
ZWO ASI533MC Pro (gain 101, offset 40, -10°C)
ZWO OAG & ASI 120MM for guiding
Skywatcher 130PDS f5 with 1X coma corrector
Optolong L-eNhance filter
RIG2:
Tecnosky 60ED APO
ZWO ASI 715MC (gain 50, offset 40)
Optolong L-eNhance filter
Skywatcher EQM-35 Pro
Pixinsight and Photoshop