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Star hops to Uranus, Neptune, Mira

Sky Notes from Bob Victor.

On Saturday morning, July 25, from Palm Springs, California, I observed all seven of the planets (all except Earth) with my 6-inch Orion SkyQuest Dobsonian reflecting telescope. using eyepieces of focal length 32 mm (giving about 37x) and 6 mm (200x). To locate Uranus and Neptune, I used the excellent Sky & Telescope Pocket Sky Atlas, and coordinates of those planets precessed to 2000.0. 

I was not able to observe all seven planets simultaneously, because the San Jacinto Mountains nearby to my west blocked the view of Jupiter and Saturn before Mercury came into view. Seeing conditions were quite good, except for Jupiter and Saturn which were just above the mountains when I started, and Mercury, which I observed last, low in ENE.  

Nevertheless, working from west to east, within an hour's time, I had satisfying views of Jupiter's cloud belts and four Galilean satellites, Saturn's rings and largest moon Titan, Neptune's tiny 2"3 disk, Mars' obviously gibbous phase and bright South Polar Cap, Uranus' easily discernible 3".5 disk, Venus' brilliant crescent, and finally, Mercury's discernible phase, about half full. 

It would have been handy to have the annual Sky & Telescope Uranus and Neptune finder charts, usually available by early in their apparitions; but as of today, they still haven’t been published. I realize that the majority of folks wait until evening visibility to make use of such charts, but there are often worthwhile events before the planets' oppositions, so I wrote S&T to request that they make finder charts for Uranus and Neptune available soon, even if only online at first. 

I urged them to make the charts user-friendly for observers who would like to locate these planets by star hopping with just binoculars or a good quality finder scope. 

For the Uranus finder chart during the 2020-21 apparition, that would mean including the stars Xi-2, Mu, and Lambda Ceti, and perhaps Alpha and Gamma Ceti as well, to complete the head of Cetus; and the stars 29, 31, Omicron, and 38 Arietis. The stars 38 and Omicron Ari are almost due north of Mu Ceti; Mu Cet (mag. 4.3) to 38 Ari (mag. 5.2) is 2.3°. Omicron Ari (mag. 5.8) is another 2.9° farther north of 38 Ari. 

Currently (on July 27), a line from 4.3-mag. Mu Cet NNW to 5.7-mag. 31 Ari, 3°.1 long, extended 2°.3 farther, locates 5.8-mag. Uranus. The slightly fainter 6.0-mag. star 29 Ari is now about 0°.6 NNE of Uranus. 

An article or posting about the upcoming maximum of Mira (expected in late September) on https://skyandtelescope.org might have the finder chart for Uranus expanded in area to include Alpha, Gamma and Delta Ceti, and Mira. The position of Mira, and positions of Uranus and Neptune for mid-October 2020 are plotted on our map October Evening Skies, on the reverse side of the Abrams Planetarium Sky Calendar for that month. Note that the “V” comprising the Hyades and Aldebaran points to Alpha and Delta Ceti and Mira, and beyond to Beta Ceti. A line from Alpha to Delta Ceti, 7° long, extended 6° farther, locates Mira. At last report (July 25), Mira glows at only mag. 7.0, but it will brighten during the next two months. Handy comparison stars for use near Mira’s peak are Alpha Ceti (mag. 2.5), Gamma (3.5), and Delta (4.1), and, if needed, Alpha Arietis (2.0). 

A finder chart for Neptune in 2020-21 could include stars as far afield as the Water Jar of Aquarius, or at least a smaller scale, wider angle chart could be included to show the location of Neptune's field in relation to the Water Jar. The Neptune finder chart itself should include at least these stars in Aquarius: Lambda, Phi, Chi, Psi-1, Psi-2, Psi-3, 96, and V14515.  The stars 96 Aqr (mag. 5.6) and HR8879 (mag. 6.2), 0°51' apart, are 1°.6 ENE and 1°.6 E of 4.2-mag. Phi Aqr, forming an isosceles triangle with it. Neptune is on the other (east) side of 96 Aqr and HR8879, also forming an isosceles triangle with them, nearly 1°.8 from those stars on the morning of July 27. By the morning of Aug. 6, Neptune will be 1°.6 from 96 and HR8879, forming a rhombus (quadrilateral with four equal sides) with Phi at the western vertex. (But, alas, the Moon will be only 6° away.) On the evening of October 3, Neptune will pass midway between 96 Aqr and HR8879. 

On Nov. 11, Neptune will find itself surrounded by the three stars, Phi, 96, and HR8879, 49' from each. Neptune will end retrograde on Nov. 28, 0°44' ENE of Phi Aqr, and about 0°53' from the other two stars. 

So an easy star hop to Neptune can begin with the Water Jar of Aquarius, and a high-power inspection of its central star Zeta, a close double star with components of mag. 4.3 and 4.5, separated by 2".3, comparable to the diameter of Neptune's disk. The position angle of the fainter star from the brighter is currently 154°, with a period of revolution of about 540 years. 

From Zeta Aqr, go nearly 10° (9°.6) SE to 3.8-mag. Lambda. Next, go 5°.6 ENE to 4.2-mag. Phi. Next, look for stars 5.6-mag. 96 Aqr 1°.6 ENE of Phi and HR8879 1°.6 E of Phi, forming an isosceles triangle with Phi as described above. Then locate 7.8-mag. Neptune, forming an isosceles triangle with 96 and HR8879. Neptune is east of those stars until it passes between them on Oct. 3, and again after it passes between them, while going east, on Jan. 20, 2021. 

Robert C. Victor 

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