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Tag: 67/P Churyumov-Gerasimenko
I’m still processing images from last month’s imaging sessions and am finally getting around to Comet 67P/Churyumov-Gerasimenko images captured on January 23rd. Although Comet 67P passed perihelion in November, it was, and as of this writing still is, well placed for viewing in the evening sky.
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| This image of 67P consists of seven 240-second images stacked to produce a single image. Field of view 20×15 arcminutes. North is up. East is left.[1] | 67P moves across the sky over a 24-minute period. On this night, 67P was moving westward at 0.5 arcseconds per minute, or approximately one-half an arcminute per hour. Field of view 20×15 arcminutes. North is up. East is left.[2] |
On images captured during this session, I measured 67P’s magnitude as 12.25. By this time, the comet had faded considerably from its peak near magnitude 8.0 in November when it passed perihelion. In these images you can see a faint tail extending approximately 8 arcminutes to the west-northwest (north is up and west is to the right).
If you click on either of the two images, the larger image that appears in your browser may show dark artifacts in the upper left corner, lower left corner, and along the left edge of the image. You also may notice a faint bright glow in the upper right corner. Unfortunately, the dark frames I captured this session for calibrating my images were not done correctly. Thus, the ugly artifacts. Plain old operator error.
Notes:
1. January 23, 2022, 03:51:45-04:15:52 UT. Stack of seven images, each a stack of 2 frames at 120 seconds (total 240 seconds). Gain: 250. Telescope: Meade SN-8 (203mm f/4). Camera: ZWO ASI224MC with UV/IR cut filter. Mount: Celestron CGEM.
2. January 23, 2022, 03:51:45-04:15:52 UT. 24-minute, 7-image, animation sequence. Each image a stack of 2 frames at 120 seconds each (total 240 seconds). Gain: 250. Telescope: Meade SN-8 (203mm f/4). Camera: ZWO ASI224MC with UV/IR cut filter. Mount: Celestron CGEM.
I was processing and analyzing some images of Comet 67P/Churyumov-Gerasimenko from a January 29th imaging session when the program I was using (Astrometrica) alerted me to the fact that there were two known, but faint, asteroids in the same field of view. This was a real bonus!
Astrometrica detected these two small main belt asteroids barely above the noise level. There was just enough signal, however, to measure their magnitudes. Asteroid 33651 was measured at magnitude 17.0 and asteroid 103516 as magnitude 17.3. JPL’s online Horizons System predicted magnitudes for 33651 as 17.3 and 103516 as 17.0. Comet 67P’s magnitude was measured as 12.5.
I was pretty surprised by the detections of these two asteroids. I image from a heavily light polluted backyard under Bortle 7-8 skies. These two objects were quite faint, and the images were only 30-second exposures.
Neither the JPL’s Small-Body Database, nor the Lowell Observatory’s Asteroid Information Database give sizes for these objects. But, both databases gave absolute magnitudes (H) for them: 14.6 for asteroid 103516, and 13.5 for asteroid 33651. According to the JPL’s Asteroid Size Estimator, objects with these absolute magnitudes should have diameters in the range of 3-12 km (2-8 miles).
At the time of this imaging session, Asteroid 103516 was 174 million km (108 million miles) from Earth and asteroid 33651 was 263 million km (163 million miles) distant.
All things considered, I am amazed that my small backyard observing rig detected both of these tiny chunks of rock that were well beyond the orbit of Mars.
Notes:
1. January 29, 2022, 06:28:19-06:58:36 UT. Stack of three images, each a stack of 4 frames at 30 seconds (total 120s). Gain: 250. Telescope: Meade SN-8 (203mm f/4). Camera: ZWO ASI224MC with UV/IR cut filter. Mount: Celestron CGEM.
Sunday morning, November 14th, I caught two comets between midnight and dawn. The conditions weren’t ideal with occasional periods of gusty winds, the Moon approaching full, and waves of thin moon-illuminated clouds moving across the sky. Nevertheless, I took a chance and captured images of comets 67/P Churyumov-Gerasimenko and C/2021 A1 (Leonard).
Both comets were in the eastern sky while the bright Moon was to the west. Over at the Comet OBServation website (COBS), observers were reporting these comets between magnitude 8-9.
Comet 67/P Churyumov-Gerasimenko
During the hour that I was imaging C/2021 A1 Leonard, the waves of moonlit clouds passing through the field of view increased in frequency. As a result, the captured images wouldn’t produce a good animation. I did, however, capture enough useable images for a single stacked image of the comet.
Equipment
The telescope used for capturing these images was a Meade SN-8, an 8-inch Schmidt-Newtonian (203mm f/4). I pulled this scope out of the attic where it had been in retirement for the last 15 years. The camera was a ZWO ASI224MC. The 224MC is primarily a planetary imaging camera, but for deep sky objects in the magnitude range of these comets it seems to work pretty good.
Notes:
1. Stack of 6 Images. Each image is a stack of 17 subimages at 15 seconds each. The subimages captured and live-stacked in SharpCap. The resulting six images were stacked in Deep Sky Stacker. Color adjustment, crop, resize in GIMP. Telescope: Meade SNT-8 (203mm f/4). Camera: ZWO ASI 224 MC.
2. Animation stack of 9 Images. Each image is a stack of 16 subimages of 15 seconds each (total exposure for each image 240 seconds). The subimages were captured and live-stacked in SharpCap. Animation, color adjustment, crop, in GIMP. Telescope: Meade SNT-8 (203mm f/4)
Camera: ZWO ASI 224 MC.
3. Animation stack of 15 images. Each image is a stack of 17 subimages of 15 seconds each (total exposure for each image 255 seconds). The subimages were captured and live-stacked in SharpCap. Animation, color adjustment, crop in GIMP. Telescope: Meade SN-8 (203mm f/4) Camera: ZWO ASI224MC.
4. Stack of 12 Images. Each image a stack of 17 subimages at 15 seconds each. Subimages captured and live-stacked in SharpCap. The resulting 12 images were stacked in Deep Sky Stacker. Color adjustment, crop, resize in GIMP. Telescope: Meade SNT-8 (203mm f/4). Camera: ZWO ASI 224 MC.