Here's this week's Mars image (as we await closest approach on Oct. 6, opposition on Oct. 13). This image was captured from my back patio on the night of 2020, Sept. 18th.
The South Polar Cap can be seen at the bottom.
The dark band spanning from left center to right center is is called the Mare Cimmerium starting at the left side, becoming the Mare Sirenum at the right side.
Olympus Mons, the largest volcano in our solar system, is visible at the upper right, near the edge. If, in the image, you start at the very right side at the equator, and then follow the edge North to about 20 deg. N latitude, you can make out a little dimple near the edge. That dimple is Olympus Mons.
The weird halo-like effect along the left and bottom edge is not a feature of the planet itself, but rather is primarily caused by diffraction in my telescope, exacerbated a little by some sharpening I did in post processing. There's some interesting physics going on there, if you like diffraction theory. I'm pushing my telescope's magnification to its limits here. The only real, reliable way to reduce the effect without sacrificing focus is to get a bigger telescope, or to wait until other conditions cause the boundary between Mars and space to appear less abruptly.
Acquisition and processing details below.
Midpoint timestamp: 2020-09-19 10:21.3 UT
Equipment:
Meade LX200-ACF 10", fork mounted on an equatorial wedge.
Tele Vue 4x Powermate (this is the item's first light, btw) to bring optical system to f/40, focal length of 10,000 mm. Sweet, fancy Moses. That's 10 meters. Ten. Meters. Good lordy.
ZWO EFW electronic filter wheel.
Astronomik Deep Sky RGB filter set.
ZWO ASI290MM monochrome camera.
The reason I chose the 4x Powermate instead of the 2x Powermate was not to increase resolution -- I'm already past the diffraction limitations of my optics given the camera's pixel size, even with the 2x PowerMate. Rather my goal with the 4x Powermate was to use my camera's internal 2x2 software binning feature to quadruple the full sensor frame rate over the USB, making it comparable to the 2x Powermate with a smaller region of interest (ROI), all while effectively doubling the signal to noise ratio (SNR). Unfortunately, FireCapture, the acquisition software that I'm using, doesn't seem to recognize the camera's internal 2x2 binning feature (FireCapture can do 2x2 software binning
after the data transfer, but that defeats the point entirely). So, in the end, I skipped any 2x2 binning altogether and decided to just work with the larger image of Mars since I had it, faster framerate and beter SNR be damned.
Acquisition and processing:
Red: Exposure = 10.4 ms, Gain = 331, Framerate = 96 fps
Green: Exposure = 10.4 ms, Gain = 387, Framerate = 96 fps
Blue: Exposure = 9.6 ms, Gain 439, Framerate = 104 fps
Approximately 12,000 frames captured, per 2 minute video, per color.
Nine videos were stacked using Lucky Imaging process (18 minutes of integration time).
FireCapture was used to take data in the form of a series of 2-minute uncompressed video (.SER files), alternating between red, green, and blue filters for 9 videos per set (RGBRGBRGB, 18 minutes of capture time per set). Refocusing was performed between sets. Nine sets were captured but not all were used. (Btw, on a side note, I filled up an entire terabyte [that's 1000 GB] on my hard drive that night. Jaysus.)
Autostackkert! was used to evaluate and process each video into an image. The sharpest data came at the end of one set and the beginning of the next (specifically, Set6:xxxRGBRGB and Set7:RGBxxxxxx) -- but still, three contiguous groups of RGB data. That data was kept.
Registax wavelet sharping was used individually for each of the 9 images.
WinJUPOS was used to derotate and combine each of the color channels individually (beginning with 3 images for Red, 3, images for Green, and 3 images for Blue), producing a combined Red image, a combined Blue image, and a combined Green image.
Gimp's healing brush was used to repair derotation artifacts. Gimp was also used to combine the Red, Green, and Blue images into their respective color channels (i.e., combine into a single, color image), and finally to perform some color curves adjustments, saturation adjustments and contrast adjustments.
