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.
Comet C/2014 Q2 Lovejoy is still visible in the sky in the constellation Cassiopeia. It is not as bright as it was a few months ago but can still be seen with a pair of binoculars. It is probably best viewed in the evening as Cassiopeia moves lower in the sky overnight and in the early morning hours. This makes it more difficult to see as there is more atmospheric attenuation at these lower elevation angles.
Using my recently acquired iOptron Skytracker for tracking night sky objects I took numerous exposures totaling 14 minutes (9x60s@iso1600; 10x30s@iso3200). These were then stacked in Deep Sky Stacker (DSS), a very good and free program designed for astrophotography.
This will probably be the final entry for Comet C/2011 L4 PanSTARRS. The comet is heading farther away from Earth each day and its brightness has diminished substantially. I have still been able to photograph it using long exposures or by stacking* many shorter exposures.
Here is an image from a few days ago that clearly shows the fan-shaped tail of the comet.
From a month ago — this stacked image shows both the comet and M31 (Andromeda Galaxy).