Astronomical Register: A Medium of Communication for Amateur Observers and ...

the reason is given: "A very sensitive eye, which would detect the spots more readily, would be more easily overpowered by the light of a brilliant star, so as to miss a very minute one in its neighbourhood." This I take to be a very correct explanation, as I find that, though I miss the companions of Polaris and Rigel with 2-inch aperture, yet I can well see the division of the ring of Saturn, especially if the planet is near the moon, and can always see the four stars in the Trapezium of Orion, which I think are both pretty severe tests for so small an aperture.

In conclusion, allow me to thank you for the greatly improved appearance of the Register, and the valuable drawings therein, which I doubt not will ensure it increased patronage.

I am, Sir, yours obediently,
CHARLES GROVER.

Red Lion Street, Chesham, Bucks:

Feb. 14, 1865.

HIND'S SCARLET STAR.

TO THE EDITOR OF THE ASTRONOMICAL REGISTER. Sir, I am induced to send you the following extract from my note-book, by seeing Mr. Chambers' notice in the February number of the Register.

"Monte Video: May 2, 1864-9-inch refractor. Hind's Scarlet Star; a beautiful scarlet, very beautiful, very bright scarlet, large star." Yours faithfully, G. L. T.

Fort Cumberland: March 15, 1865.

BRIGHT SPOTS ON THE MOON.

TO THE EDITOR OF THE ASTRONOMICAL REGISTER. Sir, I shall feel obliged to any of your correspondents who would kindly communicate through your columns any reliable information on the subject of lucid or bright spots on the dark side of the moon. It is, I believe, ascertained, that when the illuminated portion of the moon visible to the earth presents the appearance of a slender crescent, many of the darker and lighter spaces may be distinguished in the unilluminated portion, by means of the earth-shine, which is then very strong. I have met with a few notices of spots that seemed to be too bright for this explanation, but as to their real nature I have not found any satisfactory account. It is, I believe, on record that the brightest spot on the moon's surface, "Aristarchus," has been seen, although but rarely, shining with a lustre beyond that which it could acquire by earth-shine, if the usual appearance of the moon's dark side be taken as its normal condition under earth-shine; and, if I do not mistake, bright spots of a similar character have been seen in other parts of the moon's dark side. I suppose it may not be difficult to identify "Aristarchus" when it is not illuminated by the sun; and if so, the occasional brightly shining of this spot in the lunar night may be capable of being well authenticated. May I enquire if any other bright spot that may have been seen on the dark side of the moon has been identified with any bright mountain or crater? There

are on the illuminated side many bright spots that, although inferior in brilliancy to "Aristarchus," nevertheless come very close to it. Have any of these at any time been seen on the moon's dark side brighter than the earth-shine would ordinarily show them?

Feb. 20, 1865.

CORRESPONDENTS' QUERIES.

JUVENIS.

Is there any published explanation of the 500 numbers on Lohrmann's Map of the Moon of 15 inches diameter ?

F. A. W. There appear to be abundant evidences of the action of elevatory forces on the surface of the moon: what evidence do we possess of the action of opposite forces producing subsidence or degradation ?

A. L. S.

In the Great Exhibition of 1862 there were some very beautiful stereoscopic views of the moon. One of them presented the appearance of an elongated spheroid, the axis major being in the line of sight. I should be glad to hear if this peculiar projection has been noticed in any other photograph, as it did not appear to arise from any defect.

E. J.

It would be a good thing if the many persons in the country provided with instruments would agree to unite in some work-e. g., the careful mapping of limited portions of the heavens; say all the stars within a certain radius distance of some bright star. Something of this kind, I believe, has been done for the variable stars. It is a pity that in numerous cases time and means which might be directed on some combined effort should be wasted in desultory work.

G. J. W.

THE TEMPORARY STAR OF 1572.-From a careful reduction of the places recorded by Tycho Brahe, Argelander has arrived at the following figures, as giving i s position for 1865:

Decl.

Argelander, taking up the theory that this Temporary Star is really a long-period variable, has been enquiring whether any suspicious star exists in or near the above place. He finds that D'Arrest has observed a star in the following position:

of the 10 magnitude. Now Argelander many years ago sought in vain for a star in this position, and he throws out the idea that D'Arrest's star may be the great Temporary Star of 1572 slowly recovering its light. He expresses an earnest wish that astronomers would keep on the watch for any increase in the lustre of this little

star.

The Astronomical Register-Miscellaneous Notices. 121

URANUS AND NEPTUNE.-In his communication to the Astronomical Society, dated Dec. 31, 1864, Mr Lassell, after detailing the great attention which had been given to these planets, says"I feel tempted to express an opinion that it is high time that in all future treatises on astronomy the proper number of known satellites should be assigned to these two planets,-namely, to Uranus four, and to Neptune one." He also adds-"It may be worth remarking that in March next (1865) Uranus will be very nearly in the same position as when first discovered, just completing one sidereal period."

ECLIPSE OF THE MOON.

A partial Eclipse of the Moon takes place early in the morning on the 11th of April, which will be partly visible at Greenwich: h. m.

The Moon sets at 17h. 12 m., the last contact with the shadow taking place 19 minutes afterwards. The first contact takes place 43° from the north point of the Moon's limb, towards the east.-Magnitude of the eclipse (Moon's diameter 1) 0 192.

THE PLANETS FOR APRIL.

Mercury passes from Pisces to Aries during April, and may be favourably observed about the middle of the month, having a consi- ́ derable altitude, and not setting until about an hour and a half after the sun.

Venus arrives at its greatest brilliance on the 2nd of the month, and is now a magnificent object in the north west sky in the evening, while its great altitude and conspicuous brightness adapt it splendidly for daylight observation. It can readily be seen by a tolerable eye in the middle of the day, without any optical assistance, provided its exact position is known. By looking along the tube of an equatorially mounted telescope, properly directed, the little white speck of the planet is easily made out.

Dec. N. 23 27
23 263

Diameter 36" *2

56" 0

Illuminated portion of the disc of Venus=0'143.

Mars remains in the constellation Gemini, and is visible in the evenings in the north west, setting about two o'clock in the morning at the beginning, and about one o'clock at the end of the month.

Jupiter continues in the constellation Sagittarius, rising on the first of the month about twenty minutes past one in the morning, and about twenty minutes past eleven in the evening at the end of April.

Saturn remains in Virgo, and will be tolerably well fixed for observation, as it comes to opposition on the 17th of April. At the beginning of the month it rises at about a quarter to eight o'clock in the evening.

Dec. S. 8 15

7 28

Diameter 17" 0
17" 2

Ist R.A. 13 48 39 30th 13 40 27 Dimensions of Ring: Outer Major Axis, 43"; Outer Minor Axis, 11". Uranus continus visible in the evenings in the constellation Taurus. Diameter 3".8

Dec. N. 23 35

3d 27th

R. A.

5 42 2

The following are the Minor Planets which will arrive at opposition this month: full particulars will be found in the Supplement to the Nautical Almanac for 1868.

EPHEMERIS OF THE SMALLER SATELLITES OF SATURN.

Calculated by Mr Marth, and presented to the Royal Astronomical Society by Mr Lassell.

In observing the closest satellites, we have found the most accurate mode to be to note the times when they respectively reached elongations, preceding or following, equal to the distance of a tangent to the end of the ring from its minor axis. The Ephemeris gives the distance, in semi-diameters of the ring, of the satellites from its minor axis, the letter p, of course, indicating preceding, and the letter f, following. The other co-ordinate need not be given, bearing in mind that if the motion be from p to f, the satellite passes on the north side of the major axis, and if from ƒ top, on the south side. At the end of the Ephemeris is a short Table of the lengths of the apparent semi-minor axes of the orbits of the several satellites, in the same terms, from which it may be inferred how much, north or south, of the ring's transverse axis the satellite is, when it passes these imaginary tangents.

It may be useful in observations for determining the dimensions

of the rings to state that the times required for the satellites respectively to traverse the whole length of the ring are, for