The Caldwell Objects

Star in Collo Ceti" about the star we know as
Mira in Cetus.
A star (a Sun I should say) perhaps sur-
rounded with a system of Planets depending
upon it, undergoes a change, which, were it to
happen to our Sun would probably be the total
destruction of every living creature. What an
amazing alteration from the first magnitude
down to the 6th, 7th or 8th.
Regarding the star Algol, Herschel penned
the following comments in a paper presented to
the Royal Society and read on May 8, 1783:
The most extraordinary Phenomenon of the
occultation of Algol is so interesting a subject,
that we cannot too soon collect every
observation that we may serve to ascertain its
period, or permit us to find what quantity of
light the star [loses] on these occasions. That
stars are Suns has long been inferred from the
intensity of their light at such great distances,
and that these suns may have Planets around
them. It has even been surmised that the
change in the appearance of periodical stars
might be owing either to spots revolving on
their surfaces or to dark clouds in their atmo-
spheres. The likes of a small sun revolving
around a large opaque body has also been
mentioned in the list of such conjectures.
Today we know Algol as one of the beststudied
eclipsing binary stars in the heavens.
While undertaking his variable-star studies
in January 1778, Herschel wondered if the
annual parallax of stars could be used to
determine their distances, as Galileo had suggested.
He reasoned that if one were to look at
double stars that appeared to be connected but in
reality were widely separated in distance from
the Earth, that the motion of the Earth
around the Sun would cause the closer of the two
stars to appear to move back and forth relative to
the more distant star. This led him to search for,
and measure, hundreds of double stars, which he
called his "First Stellar Review." This review
covered all stars down to 4th magnitude and was
made with a 7-foot Newtonian telescope (4½
inches in aperture) at 222x. His "Second Review"
was made with a far superior 7-foot instrument
(with an aperture of 6.2 inches) at 227x and
included all stars down to 8th magnitude. This
work resulted in his first Catalogue of Double Stars,
published in January 1782. The catalog contained
269 double stars, 227 of which, to Herschel's
knowledge, had not been noticed by anyone
before. Herschel's catalog was submitted to the
Royal Society, and the discovery of Georgium
Sidus (Uranus) was a result of this survey.
At the end of December 1781 Herschel
started his third sky review using the same
instrument. He measured the relative magnitudes,
colors, and positions of the paired stars at
460x and reviewed all of John Flamsteed's stars
for companions as faint as 12th magnitude. These
observations were published on December 9,
1784, as the Second Double Star Catalogue, and it
included 434 additional double stars. Many years
later, on June 8, 1821, he published his last listing,
"On the places of 145 new Double Stars."
Suspecting that many stars had changed
their brightnesses since Flamsteed had published
his stellar catalog, Herschel began a series of
naked-eye observations to compare the
brightnesses of stars within each constellation.
He soon discovered that Flamsteed's magnitudes
were inconsistent and of little use. Herschel's first
catalog of comparative stellar brightnesses was
published in 1796 and was followed by five more
such publications. (Incidentally, Flamsteed's
observations of the "star"
Appendix C 461