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NGC 7023, also known as Iris Nebula, is the bright blue region top left of the center. The bright nebula that lies left to it, is VdB 4141 (Ghost Nebula).
The deep red star between these two nebulae is T Cephei, a Mira variable star.
These stars are dying a red giants characterized by strong infrared emission (that's why it appears red here).
In near infrared T Cephei is about 100 times brighter than in visible light (-0.496 mag in J band vs. 4.644 mag in G band).
Another bright red giant is AC Draconis in top right corner, a long periodic variable star.
The red and green artifacts below AC Draconis are probably caused by reflections on a part within the lens (due to the strange shape). The artifacts around the bright stars are residuals from the aggressive star reduction (by up to factor 40) and the fact that the PSF
(point spread function) strongly varies across the field of view.
The color of the nebulae is influenced by scattering which makes dense region more opaque for blue light than for (infra)red radiation.
For that reason regions known as dark nebulae are reddish in that image.
FOV: | 6.25° × 4.0° | ||||||
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Date: | 12/2021 to 01/2022 | ||||||
Location: | Pulsnitz, Germany | ||||||
Instrument: | 2-3 × 100mm lens at f=300mm (3× array was not fully operational at beginning) | ||||||
Camera Sensor: | 2-3 × IMX455 (3× array was not fully operational at beginning) | ||||||
Orientation: | North is up (exactly) | ||||||
Scale: | 3 arcsec/pixel (at full resolution) | ||||||
Total exposure times: |
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Image processing steps where:
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