California nebula, NGC 1499 plus burnt-orange interstellar dust, reaching past magnitute 23 per square arc-second.
Canon 7D mark 1 stock camera, Canon EF 70-200mm f/2.8L IS II USM Lens. at f/2.8. Thirty nine 60-second exposures at ISO 1600 were added (39 minutes total
exposure). The California nebula is a very faint nebula, so this image demonstrates that the standard 7D Mark I is an excellent low
light camera for it to record so much detail in this exposure. Full size image is at 4.4 arc-seconds per pixel, and this view is
about 1/3 of full scale. No dark frame subtraction, no flat fields. Tracking with an astrotrac and no guiding.
This is a natural color image. The high dynamic range of astrophotos must be stretched to bring out the range of details the camera recorded. But the typical image stretch process loses color for brighter subjects (e.g. stars and the brighter parts of deep sky objects become whiter as they are made brighter). This image uses a new algorithm, rnc-color-stretch that does not lose color during the stretch. How do we know the colors are reasonable? The star colors can be checked against stellar photometry. Red stars have B-V > 2, orange stars have B-V of 1 to about 2. The blue-white stars have B-V in the range of 0 to -0.5. The colors closely follow the color sequence in Table 1 at Color of Stars. Solar-type stars have a B-V of 0.63 and appear close to white (daylight white balance).
More info at:
http://www.clarkvision.com/galleries/gallery.astrophoto-1/web/california_nebula_200mm.c12.29.2016.IMG_2982-3020-rs.g-c1-1500s.html
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