Seeing EnckePosted By Larry Thaxton |
There are several references to observations of Encke's divison in A.F.O'D.Alexander's "The Planet Saturn: A History of Observation, Theory and Discovery" among those mentioned:
Captain Henry Kater did most of his observing with a pair of Newtonian reflectors, a 6 1/4" F/6 and a 6 3/4" . On 17 December 1825 "the conditions were very favorable: no wind and a very slight fog. With the larger reflector (6 3/4") he saw a very distinct image but nothing unusal, but with the 6 1/4-inch Watson and his most perfect single eyepiece (power about 280)....'I fancied that I saw the outer ring separated by numerous dark divisions, extremely close, one stronger than the rest dividing the ring about equally...'
On 7 September 1843 W. R. Dawes viewed Encke's through a 9" reflector belonging to W. Lassel- "I presently perceived the outer ring to be divided in two.....The outline of the planet was very hard and sharply defined at a power of 450; and the primary (Cassini's) divison...very black and steadily seen all around the southern side." At 400x he could glimpse Encke's but could not see it at all at lower power.
On 25 November 1850 Dawes was armed with a 6 1/3" achromat of "very fine" quality. Using powers of 282 to 425 "Dawes ... was satisfied that in finest moments, a very narrow and short line was discernible on the outer ring near it's extremities."
On November 29: "having applied higher powers, and viewed the planet steadily for a considerable time, I obtained several satisfactory glimpsesof a division near the extremity of the outer ring. It was occasionally seen with power 323; but far more certainly with 460."
On 26 November 1854 Dawes, using a 7 1/2" achromat, described Encke's as " a very dark, narrow, well defined line concentric with the ring, and about one-fifth of it's breadth."
In 1852 W.S. Jacobs appears to have observed Encke's division with a 6.2" refractor at Madras Observatory at a power of 365.
Captain Henry Kater did most of his observing with a pair of Newtonian reflectors, a 6 1/4" F/6 and a 6 3/4" . On 17 December 1825 "the conditions were very favorable: no wind and a very slight fog. With the larger reflector (6 3/4") he saw a very distinct image but nothing unusal, but with the 6 1/4-inch Watson and his most perfect single eyepiece (power about 280)....'I fancied that I saw the outer ring separated by numerous dark divisions, extremely close, one stronger than the rest dividing the ring about equally...'
On 7 September 1843 W. R. Dawes viewed Encke's through a 9" reflector belonging to W. Lassel- "I presently perceived the outer ring to be divided in two.....The outline of the planet was very hard and sharply defined at a power of 450; and the primary (Cassini's) divison...very black and steadily seen all around the southern side." At 400x he could glimpse Encke's but could not see it at all at lower power.
On 25 November 1850 Dawes was armed with a 6 1/3" achromat of "very fine" quality. Using powers of 282 to 425 "Dawes ... was satisfied that in finest moments, a very narrow and short line was discernible on the outer ring near it's extremities."
On November 29: "having applied higher powers, and viewed the planet steadily for a considerable time, I obtained several satisfactory glimpsesof a division near the extremity of the outer ring. It was occasionally seen with power 323; but far more certainly with 460."
On 26 November 1854 Dawes, using a 7 1/2" achromat, described Encke's as " a very dark, narrow, well defined line concentric with the ring, and about one-fifth of it's breadth."
In 1852 W.S. Jacobs appears to have observed Encke's division with a 6.2" refractor at Madras Observatory at a power of 365.
