Autumnal Equinox

The fall equinox will occur at 21:50HST today.

Sunrise over Georgia Strait
Sunrise over Georgia Strait

The equinox is defined as the time at which the Sun passes through the plane of the Earth’s equator. Until the next spring equinox occurs in 2020, the Sun will be located in the southern hemisphere with a negative declination coordinate.

Today the length of the day and night will be very near equal, thus the term equinox. the Sun will rise and set nearly exactly due east and due west.

Today is considered the start of fall for most cultures in the northern hemisphere, or the start of spring for those in the southern hemisphere.

2019 Apsides and Seasons
Event Universal TimeHawaii Standard Time
Perihelion Jan 0305:20UTJan 0219:20HST
Spring Equinox Mar 2021:58UTMar 2011:58HST
Summer SolsticeJun 2115:54UTJun 2105:54HST
Aphelion Jul 0422:11UTJul 0412:11HST
Fall Equinox Sep 2307:50UTSep 2221:50HST
Winter SolsticeDec 2204:19UTDec 2118:19HST
Data from US Naval Observatory Data Services

A First Attempt

Just getting back into astrophotography after quite a few years of observing visually. A new camera, updated software, it seems like I am learning all over again.

For a first run I processed a monochrome image of M31, the Andromeda Galaxy. A quick run of fourteen luminance frames, 8 at 5 minutes, 6 at 60 seconds combined into a single frame.

M31 or the Andromeda Galaxy, with M110 visible above and M32 visible below the core
M31 or the Andromeda Galaxy, with M110 visible above and M32 visible below the core

I have color data for this image, but that will be a lot more processing. Given all of the various filters and calibration frames I really need to get the automated batch processing running before I do much color work.

Neptune at Opposition

Today the planet Neptune will pass through opposition, directly opposite the Sun in our sky. The planet will be well placed for observation all night long, rising at sunset, transiting at midnight, and setting at sunrise. If you are looking to observe Neptune, it is currently shining at magnitude 7.8 in the center of the constellation Aquarius.

Neptune from Voyager 2
Neptune from Voyager 2, Credit: NASA /JPL

As the outer planets Uranus and Neptune move so slowly across the sky, the timing of oppositions is driven by the Earth’s orbit and occur each year at nearly the same time. Neptune’s orbital period is 164.8 years, taking over a century and a half to circle the celestial globe once. As Neptune was discovered in 1846, it has completed a little over one orbit since discovery.

Venus Appears in the Sunset

Crescent Venus
Venus approaching inferior conjunction, 24Dec2013

Over the next weeks Venus will appear above the sunset. Look for a brilliant, star-like object low in the glow of sunset, right above the setting Sun.

Over the following months the planet will rise high above the sunset, reaching maximum elongation on March 24th, 2020.

When Venus does reappear we can expect a few UFO reports by people unfamiliar with the normal workings of our skies. In late 2018, when it last emerged in the dawn we had a few such reports here on the island, including a very nice video and folks who could not accept the fact that the “strange light” was simply a bright planet.

Rising with Venus on this particular apparition is Mercury, the pair getting higher each evening until Mercury reaches maximum elongation on October 19th.