2019

Mercury crosses the sun - Nov. 11/2019
by John Hylnialuk

Note: this entire event requires proper solar filters for viewing. Serious eye damage or blindness may result from looking at the sun without proper filters protecting your eyes, telescopes and/or cameras.

A once-in-a-lifetime transit of the Sun by Mercury occurs on the morning of Mon, Nov 11, Remembrance Day. The tiny disk of Mercury starts its pass across the Sun at 7:36 am EST locally and continues for 5 hours 28 minutes until 1:04 pm EST when it finally leaves the Sun’s face.

You cannot see Mercury without optical aid since it has such a small silhouette. A telescope at medium power with solar filter over the objective lens or mirror is required. Follow all precautions for proper solar viewing.

Mercury is tiny (only 10 arc-seconds across) compared to Venus which last transited the Sun in 2004 and 2012. Venus was 6 times larger than Mercury, but transits of Venus are very rare. The next two Venus transit occur in 2117 and in 2125, then another century or so elapses before another pair.

Mercury passes across the Sun much more often. We saw transits in 2003, 2006 and 2016 in this century, and 9 more are due before 2100. BAS members observed both the 2006 and 2016 transits. However, make sure to the attempt this November sighting because, the next Mercury transit does not happen until 2032 and that one will be over before sunrise in North America! Neither will the one that follows next in 2039 be visible from most of the western hemisphere. North Americans have to wait almost 30 years until May 7, 2049 to see a Mercury transit locally.

BAS members will set up telescopes (properly-filtered) at the Fox Observatory 7:00 am weather-permitting) on Nov 11 for viewing. There is a 5-½ hour window of opportunity and even if there are some clouds, we hope to have some clear sky over that interval. By an interesting astronomical coincidence, this is Remembrance Day which however, is not a statutory holiday in Ontario, Quebec and two other provinces.

Canon 60D at prime focus of the 10-inch Bishop scope at 2500 mm focal length, f/10, 1/1000 s. at 200 ISO. Photo May 9, 2016 by JH from Fox Observatory.

We will feature live views through our various telescopes during the transit. Once again note that all will be equipped with safe solar filters. Solar filter material can be obtained from various sources online but note that you will see nothing with solar eclipse glasses if you have a pair left over from 2017. Mercury is too small to be seen with the naked eye even as a silhouette against the sun’s surface.


Moon occults stars in Beehive Cluster - May 10, 2019
by John Hylnialuk

On Friday night, May 10, from 10 pm local time or so until after midnight, several stars in the southern part of the Beehive Cluster will be occulted by the 6.3 day-old crescent Moon. Some of the stars are double, one is triple and one is quadruple, and though these will be difficult to observe in the vicinity of the bright Moon, they may be still “observable” -read on.

Stars of 6th and possibly 7th magnitude will be detectable, but don’t count on seeing 12th magnitude in the bright moonlight. In any case, there may be a possibility of “detecting” the doubles or multiples as step-wise changes in the light level. First one, then the other of the close pair is occulted by the optically very shape moon’s edge -a sequence that may take only a fraction of a second, but if you look for it, it may be detectable. Event no. 5 and 9 are good candidates for these. If you see a drop in the light from the star that looks like it faded first, then went out entirely, that may be each star blinking out in succession.

In general, occultations of stars by the Moon are neat to watch and occur fairly often. In 2019, the RASC Observer’s Handbook list 32 of these (for Toronto) and though there are no 1st magnitude stars involved, there is Tejat, μ-Geminorum, a 2.9 magnitude star occulted twice late in the year. Also, for this area will be a daytime occupation of Venus by the very thin crescent Moon only 4 degrees from the Sun on July 31.

Occultations of stars by the dark limb of the Moon are almost instantaneous and especially neat if there are several total occultations in series like we get May 10 or during totality of lunar eclipse. One gets a real sense of the Moon’s motion through the heavens from events like these. Click on the diagram and/or table below to download a copy.

Diagram above from Sky Safari (with additional graphics added) illustrates the path of the 38% sunlit Moon passing through M44 from 10:10 pm EDT to just after midnight May 11. A pdf version of the star chart is available on the BAS website. Chart above does not show BS Cancri (BS Cnc) No.1 below, the first star to be occulted, and it will be faint, almost 9th magnitude.

The table above gives times of events determined manually from Sky Safari 5 Pro for Owen Sound, ON. Times will not vary too much from these values if you are within 20 or 30 km of Owen Sound and are conservative (early) by about a minute. But if you are farther west times can be several, meaning many, minutes early and the opposite, later, to the east. Check your own software for your own geographic location. Differences of 15 minutes or more will occur across a province like Ontario.


Mars near Pleiades
by John Hylnialuk

The end of March will go out with a nice view in the west just after sunset. Especially if you want to get a sense of how quickly planets move across the sky. The players involved are Mars and M45, the Pleiades Cluster. In the last week of March and the first week of April, Mars will be slipping past the Seven Sisters in the western sky. The closest approach (appulse) occurs on March 30 & 31 when the separation is about 3 degrees 9 minutes of arc. The spacing is under 5 degrees for a lot longer than that, from March 25 to April 6, so anytime during that interval will provide a nice photo opportunity.

The sky will be dark for the evening hours when Mars is above the horizon since the Moon is in last quarter (March 28) or new phase (April 6) and does not rise until the wee morning hours. The waxing 2 or 3 day old crescent does finally appear on the scene by Apr 7 or so -it is a nice addition to the group April 9.

The event will be visible nightly from sunset to about midnight when Mars finally sets below the western horizon so there is lots of time from sunset until midnight to catch a view of the planet and M45. Mars continues climbing eastwards in the SW sky for several more months crossing Taurus into Gemini and then finally getting lost in the Sun’s glare in Cancer in late June.

The diagram above shows the path of Mars from March 28 to Apr 3, 2019.

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