Pear Tree Observatory

Due to prompting from some of my west coast friends, I stayed up way too long and got these images of the “green comet” just before encroaching clouds and pending dawn stopped the session. Additional interference was light from a 16-day old Moon. But this stack shows the comet is developing a nice tail.

C/2022 E3 (ZTF)
[CV:2x60s]

The comet is a long period comet. JPL says the orbital period is not defined; other sources just say the orbit is greater than 50,000 yrs. It spends most of that orbit below the ecliptic, but right now is above it and just outside Earth’s orbit. It will cross below the ecliptic around the 12th of February roughly halfway between the Earth and Mars. It will be closest to the Earth on the 1st of February.

C/2022 E3’s orbit.
(Graphic courtesy of the JPL Small-Body Database Browser)

So, this is just a preview. In a couple of weeks, the comet will be above the tree line at a more convenient time (0300), the Moon will not be up, and I will be able to take the necessary exposures to put together a color photo.

Near-Earth asteroid 2015 RN35 flew past the Earth on the 15th of December 2022 at a distance of roughly 426,000 mi (686,000 km). The size of the asteroid is estimated to be in the of 200 to 460 feet in diameter. This is close enough and large enough to get the usual internet suspects to issue dire warnings. But as usual, those predictions were way overblown.

Due to the proximity of the event to year-end holidays some were even calling it a “Christmas Asteroid”. However, with the closest approach on the 15th and the predicted visibility ending by the 19th I would argue that “Hanukkah Asteroid” would be a better moniker.

Unfortunately, on the 15th, the PTO was configured to image main belt asteroids, not near-Earth asteroids. So, it was quite a challenge to find and image something moving as quick as the asteroid was. I fully expected to get a streak as the asteroid flew through the telescope field-of-view. However, I was not expecting this.

The image shows a sparce star field with three streaks running from top to bottom, each a different brightness due to their color. There are an additional two short streaks paralleling the others where the aircraft lights were flashing.

Aircraft formation lights [CV:1x60s]

Even though I live less than a mile from the end of a major airport’s runway, I rarely get photo-bombed by one of the aircraft. There is a lot of traffic, but I am looking at too small of a chunk of sky to have one pass through that little spot. By pointing the scope in front of the anticipated path of RN35 and taking a series of blind exposures, I was able to get a quick look at it as it passed by.

The image shows a star field with a long streak as asteroid 2015 RN35 passes from middle center to upper right.

2015 RN35 [CV:1x300s]

This image was enough to encourage me to set up a different software configuration on the next night (the 16th) and take the series of images used to make the following animation. This is a series of sixty 60 second shots. Yes, you do see a satellite pass through the FOV right at the end of the video.

The asteroid is in a 654 day orbit with its aphelion just outside of Mars’ orbit.

2015 RN35’s orbit.
(Graphic courtesy of the JPL Small-Body Database Browser)

Even though the occultation of Mars by the Moon was not visible in the Florida panhandle, we were close enough that it was a near miss. While this is not one of my normal occultation targets, I was able to come up with a combination of scope and camera to get both objects into one field of view. I was able to live stream about 12 minutes of the Moon closing on Mars before clouds ended any possibility of watching the rest of the event.

Moon / Mars

This is one frame of the streamed video. I was pleasantly surprised that surface detail was still visible on Mars with the camera gain set as low as it was to prevent overexposure of the Moon.

Comet 29P is known for its periodic outbursts. It grabbed earth-based astronomer’s attention again on the 22nd of November. On average, the comet brightens 7.3 times per year. Normally, the comet’s magnitude is around 16.0 but current measurements show the comet at 12.2. Remember, the lower the number, the brighter the object. This image shows the characteristic ‘notch’ in the comet’s coma and close examination shows a slight, barely visible twist in it.

Comet 29P (Schwassmann–Wachmann 1) [C:1x60s]

Because its orbit lies entirely between Jupiter and Saturn, it is classified as a Centaur object. Its year is 14.7 earth years long and currently lies above the ecliptic. The nucleus of the comet is estimated to be roughly 60 km (37 mi) in diameter.

29P’s orbit.
(Graphic courtesy of the JPL Small-Body Database Browser)

As of the 2nd of December, the comet is visible in the constellation Gemini. It rises around 1830, transits the meridian at 0155 and sets well after sunrise at 0914.

Cosmic ray/Muon track

Also visible top-center in the first image is an excellent example of how sensitive modern CCD chips are.
The tracks visible are attributed high energy particles impacting the chip. Straight tracks are expected from cosmic rays or muons created by cosmic rays hitting atoms in our atmosphere. Curved tracks, known as worms, indicate somewhat less energetic particles thought to be generated by “Compton scattering” due to emissions by physical components in the immediate area of the chip. Some glass formulae (e.g. BK7) are notorious for this. However, the proximity, directionality and time constraints of this image could indicate that the straight and curved tracks are related to the same event.

The seeing tonight was much steadier than the last time I took a look at Mars. This of course led to much finer detail being visible. Once again, the clouds covering the northern polar ice cap are very obvious. You can identify several additional surface markings using the Mars map on the PTO web page. The central meridian is 1.8° but you must remember the image is south at the top unlike the map. Right now Mars is coming out of its winter season with the spring equinox just around the corner on the 26th of December.

Mars
[(V)L:2361×0.6ms; R:1857×1.4ms; G:2311×1.9ms; B:1190×3.9ms]

Pear Tree Observatory
temp:	38℉ (3℃)
humidity:	85%
wind (MPH):	From the N at 0
pressure:	30.16 inHg
station:	KFLVALPA4
hardware:	Davis Vantage Pro 2
software:	VWS V15.00
updated(L):	24-11-23 06:08
updated(Z):	24-11-23 12:08

Pear Tree Observatory

C/2022 E3 (ZTF) (08 Jan 2023)

2015 RN35 (Near-Earth asteroid) (16 Dec 2022)

Moon / Mars near occultation (07 Dec 2022)

Comet 29P/Schwassmann–Wachmann (28 Nov 2022)

Mars (23 Nov 2022)