Remote Planets, Uranus, Neptune and Beyond!
February 16, 17, 2019. The above is my best image of Uranus to date. It is based upon 12 minutes of 251 ms exposures taken with the ASI290MM CMOS video camera fitted with a filter having a long pass cutoff at 850 nm and 2 minutes of 11 ms exposures taken with the ASI224MC one-shot color CMOS video camera and 1.5x Barlow lens. My 7.25" f/14 Schupmann Medial telescope was used for both sets of video data. The best 25% of the frames of each video were aligned and stacked in Autostakkert 2 and the final image composed in PhotoShop elements using the NIR image as luminance and the one-shot color image as chrominance. I believe the bright spot on the left side of the image is the north polar hood of Uranus. Terrestrial South is up in this image, and the north pole of Uranus is to the left.
Note that the NIR image (as well as the nirRGB image) is lower in resolution than the visible light image. This is because the average wavelength of visible light is around 500 nm whereas in the NIR bandpass it is about 900 nm. The Airy disk at 500 nm for a 7.25 inch aperture is about 0.75 sec arc in diameter while at 900 nm it is 1.23 arc second and the planetary disk size is only 3.45 arc seconds. We are certainly working at the limits of my little telescope! If I could get better seeing, the C1100EdgeHD scope would have Airy disks at those wavelengths of 0.49 and 0.81 arc seconds and the image would be considerably sharper. With the C14 it would be 0.39 and 0.64 arc seconds, however the probability of getting diffraction limited seeing for the 14 inch aperture is pretty much negligible at sea level in NJ.
February 16, 2019. I had been trying unsuccessfully to image the north polar hood of the planet Uranus. Using one-shot color cameras all I got was a featureless light blue disk. Hypothesizing that the blue color might be high altitude haze in the atmosphere scattering blue light, I reasoned that if I imaged in the near infrared, I might be able to penetrate to the level where the bright polar hood became visible. So, I took three 120 second videos of Uranus using the ASI224MC one shot color video camera coupled to the 7.25" Schupmann medial with a 1.5x Barlow lens. This combination delivers f/24. I then replaced the color camera and Barlow with the ASI290MM monochrome camera fitted with an 850 nm cutoff high pass filter. This gives me a bandpass from 850 nm out to the 1 micron cutoff of silicon photodetectors. I took another three 120 second videos with this setup. I had to use a shutter speed of 251 ms and a much higher gain for the NIR imaging compared with only 11 ms for the color imaging. And still got only 478 frames from each video in the NIR compared with 1356 frames from the color videos. I processed the videos using Autostakkert 2, keeping the best 25% of the frames from the color videos and the best 50% from the NIR videos. The individual stacked images were then combined in Photoshop using the NIR image as luminance and the color image as chrominance. Results from the three sets of videos is shown below. The top row are the color images from the ASI224MC, the middle raw are the NIR images from the ASI290MM and the bottom row is the result of using the NIR images as the luminance and the color images as the chrominance. The left side of the combined images is definitely brighter and that is where the north polar hood should be.
August 23, 2016 Beautiful clear night with well above average seeing. Got home from Jenny Jump remote site around 3:30 am and set up CPC-1100EdgeHD on Uranus using the ASI-1600MM and 3x Barlow. Took a set of 2000 FITS files of Uranus and a nearby single star, SAO109964, for deconvolution purposes. Sent them to Dave Rowe to try his bispectrum routine. I then took a one minute video of Uranus. Since seeing was good and I was using a lower focal ratio, I was able to use very short exposures. I processed this monochrome image and used it as the luminance for the image obtained on the 20th with the color camera. Composite result is above.
October 8, 2015. After finishing my double star program for tonight, I realized that Neptune was near the meridian and lined up on the distant planet, only 2.3 arc seconds in diameter at its distance of 2.7 billion miles. Not much to see at that distance.
Project for this coming summer. Catch Pluto in Sagittarius. It has passed the bulge of the Milky Way galaxy and should be relatively easy to image. Try with C1100EdgeHD with 0.7x reducer and the ASI-1600MM camera. Starfields below from the DSS show positions (purple crosses) at 1 am on June 21, 22, and 23 2019.