A faint comet is currently moving through the sky in the constellation Orion. Unfortunately, it is too dim (mag. +8) to seen by the unaided eye but binoculars, a small telescope, or most digital cameras will be adequate to see it.
Comet C/2020 M3 (ATLAS) moving through the constellation Orion.
As the comet was moving near the belt of Orion I captured about one hours worth of exposures and then did the typical stacking using Deep Sky Stacker. Post processing was done with rnc-color-stretch.
The comet is located to the right and slightly below the belt of Orion. The future path of the comet can be found at in-the-sky.org.
Since then I have been experimenting with different tools for postprocessing astro photos. Along the way I discovered some interesting software called rnc-color-stretch from Clarkvision.com.
The rnc-color-stretch algorithm does 3 main things. 1) Analyze the image histogram to maintain a black point or use set low level color throughout the stretching process. The histogram is analyzed at multiple stages from beginning to end. 2) A power stretch while maintaining the black point. 3) Recover lost color after the stretching process. How far you can stretch an image depends on the signal-to-noise ratio.
I’ve been testing this software on both recent and older images. I thought it might be interesting to try it on the Rho Ophiuchi images taken in 2015. Once again, I used Deep Sky Stacker to register and align the images. Then I ran rnc-color-stretch. The result is the image shown above. I thnk it did a fine job of pulling out the details and the color.
Three comets: C/2020 F3 (NEOWISE; C/2019 U6 (LEMMON); and C/2017 T2 (PANSTARRS)
Nikon D750, 85mm, ƒ/2.8, ISO 400, 30 x 120 seconds. Shot at Wupatki National Monument, an International Dark Sky Park, in northern Arizona. A direct link to the full-size image is available.
The Perseids meteor shower is an always popular sky event. Perhaps one reason is that it occurs during the warm summer months and can be a pleasant family event.
Photographing a meteor shower is always about trade offs. If you shoot with an ultra-wide lens the meteors are small and you will likely miss some of the dimmer ones. But the wide angle view ensures that you cover a large portion of the sky.
Another option is to shoot with a lens that is in the “normal” range or even a telephoto. The disadvantage is the field of view is greatly reduced while an important advantage is that the lens will capture the dimmer meteors.
The Lens Aperture Area versus Angular Coverage Trade Because meteors appear in random location across the entire night sky, one might think that an all sky camera would pick up the most meteors. But this is not the case. Wide angle lenses mean short focal lengths and short focal lengths have smaller physical lens apertures, so collect less light. Thus, there is a trade between lens technology to collect a lot of light and angular coverage…
Another factor in meteor capture is where to point. If one points closer to the radiant then the angular velocity of a meteor decreases and the longer focal lengths are not impacted as much.
For several years I shot with wide-angle and ultra-wide-angle lens (28mm, 24mm, and 16mm). More recently, I been shooting with 50mm and 85mm lens. Last year, with the 85mm lens I captured one (1) meteor. But the detail was great!
This year I shot with a 50mm lens. This is an old, legacy lens: Nikon 50mm ƒ/1.8 AI manual focus.
We set up the camera on a star tracker, dialed in the settings, and then let it go taking continuous shots at ƒ/2.8, 30 seconds, and ISO 1600. The camera was pointed with the radiant in the lower left corner. Also visible in the composite is Andromeda Galaxy (M31) in the upper right. Meanwhile, we pulled out the camp chairs and leaned back to stare at the sky for a few hours.
We saw a few dozen meteors in about 2-1/2 hours and the camera with its smaller FOV captured considerably fewer. As the Moon rose above the horizon we packed it all away and drove home. Reliable reports indicate that meteor activity picked up considerably in the pre-dawn hours. We were happily asleep at that time.
Perseid meteors (full crop)—2020.
The first image is a stack of the handful of shots containing meteors and downsized for this posting. The second image (full-size image), on the other hand, is a full-size crop of two meteors showing how much detail can be found when using a fast lens with a narrow field of view.
Comet C/2020 F3 (NEOWISE) is growing dimmer in the evening sky although is still visible in binoculars. Longer exposures are now necessary to reveal the fan-shaped tail.
Comet C/2020 F3 (NEOWISE) in the evening sky.Comets C/2020 F3 (NEOWISE), C/2019 U6 (LEMMON), and C/2017 T2 (PANTARRS).
The second image is a wider view that shows that Comet C/2017 T2 (PANSTARRS) and Comet C/2019 U6 (LEMMON) are also visible albeit both are very small and faint. M53, a globular cluster, and M64, a spiral galaxy, are also visible and labeled. A full-size version of this image (~2.1 MB) is also available.
