Moon and the Ring Nebula – September 30, 2014
Lately I had time to do some night-time astrophotography due both to a bit of free time and to clear skies.
So, I’ve tried to catch up with lunar imaging and some short exposures deep-sky imaging technique.
All of the images below were acquired with the TS APO 115mm F/7 Refractor, at F/7 for the deep-sky images, and at F/18 and F/7 for the lunar shots. The camera used was the ASI120MM with Baader RGB and UV/IR cut filters.
First, a different lunar shot, showing the Earth-illuminated part (Earthshine) of the Moon within a few days of the First Quarter. The final image is a stack of 380 frames, each a 1 second exposure through a Baader Red CCD filter, with the refractor working at F/7.
The above image might not show many or interesting details, but the simple fact that it shows the Earthshine in close proximity to the Sunshine (overexposed area at right) is what is interesting. Normally one can observe the imaged areas under similar illumination at or very near the Full Moon phase.
The second image, again a lunar one, is an LRGB image, meaning that I’ve captured one series of frames using the Red filter, a second one with the Green filter, and the third series with the Blue filter; afterwards I’ve combined them into a single image to render the colors, then I’ve placed the result onto the Red filter image, in which the details were better resolved. All channels were stacks of 600 frames out of 1500, in 2-3/10 seeing conditions due mostly to the very low altitude of the Moon above the horizon (under 19 degrees). The refractor was working this time at F/18.
The image above shows an area centered on the apparently double impact (could be possible that it is actually a double impact site?) craters Stevinus A and Furnerius E. Between the two lies Stevinus, the rather well defined crater without “blue” material on it’s floor. Another interesting formation can be seen in the upper-right corner of the image, a large crater with a rimae system inside it’s rim: Janssen. Part of the white-blue materials from the nearby impact craters is covering Janseen’s floor.
And now for the deep-sky images….
Well, I’ve only got enough time to acquire some sub-frames of a single object: the planetary nebula Messier 57, or “the Ring Nebula”. It’s name is in direct connection with it’s appearance both at the eyepiece or in not-too-long exposures.
The image above, with the refractor working at F/7, and acquired using the UV’IR cut filter, is a stack of only 50 frame,s each a 20 seconds exposure. The details inside the nebula are the result of 100 frames of 10 seconds each.
Due to the light pollution both from Bucharest (to the North) and from the Moon (to the South) the limiting visual magnitude was around +5, but there are some Mag +18 (!) galaxies present in the final image. I’m sure that on darker skies I could go a lot deeper with this setup on this object. For now, I’m posting two slightly differently processed versions of the same image (resized to 148% from original), each with it’s advantages and disadvantages.
I’ve also processed a detailed image of this object (resized to 300% from original), again in two ways, one in grayscale, the other being a LRGB version using the color data acquired in the same night (20x12s for each channel).
The result shows some rather fine details for a 4.5 inch refractor under far from perfect sky conditions.
While processing the images with M 57, I’ve stretched the results a bit to see if it could be possible to catch a glimpse of the outer ring of the nebula, which normally requires very long exposures. It seems that a glimpse I did catch, as is shown in the animation below where the outer margin of the diffuse glow is marked with a red ellipse:
I can’t wait to get to a dark skies location and try longer exposures with this object, and perhaps revealing the true shape of it’s outer ring…
(October 1, 2014)
UPDATE (October 17, 2014)
I’ve just finished the mosaic from the September 30th session, with the Moon hanging just 22 degrees above the horizon. The image is a mosaic of 14 zones, each a 450 frame stack out of 1500 in 2-3/10 seeing conditions. The equipment: TS APO 115mm Refractor working at F/18, ASI120MM and Baader Red filter.