CATALOGUE OF Silvered Glass Reflecting Telescopes, &c., AND THEIR ACCESSORIES,
Reading edition
OCTOBER, 1880.
G. Calver, while introducing the list of prices below, has the greatest confidence in calling the attention of the practical astronomer and the amateur to the very moderate prices charged, considering the principle and style of the mounting, and the firm and well-fitted arrangements in all the parts.
The principle of the mounting is that which is the most convenient to use, and with the greatest degree of steadiness with the easiest movements. Fig. 1 is the best mounting ever applied to the Reflecting Telescope.
He is also able to state that, with his processes and special facilities for working large specula, and substantially mounting them, he is prepared to construct automatic equatorials of large sizes, and with any special arrangements that may be required.
Fig. 1 is a very excellent mounting, and admirably suited for large instruments, especially when clock-power is applied; and as now manufactured by G. Calver, is the most complete and reliable, its details of construction being such as to give the greatest freedom of motion and steadiness. For large sizes the top of polar axis works on friction rollers; and, as a superior German stand, its arrangements and means of astronomical as well as optical adjustments, are such as to make it an instrument of precision.
To ensure these qualities many well considered arrangements—entailing careful and expensive workmanship—must be provided; details that do not easily admit of description in an ordinary catalogue, or can be shown in an engraving, but are duly appreciated by the observer, who will find their value by practice.
The cradle bar is compound with fine screw movement for perfecting collimation, but to make this adjustment perfect, the telescope tube must be centred in a powerful lathe, and the cradle and solid metal rings in which the tube revolves (see illustration) has to be turned and fitted with true flanges or working bearings; the mechanical and optical centres will then coincide.
The hour circle, to be truly divided, must be truly made, and is a solid wheel of good substance, working on a secondary axis, and rotated by mechanical means, truly concentric, with a very strong polar axis.
The declination circle has fine tangent screw movement, with double action for setting the readings by milled-headed screw, and also long driving rod from the eye-piece to set and adjust the object in centre of field. There is slow hand motion, by a separate wheel in right ascension.
The clock-power is connected and disconnected instantly, by touching with the finger a small lever, conveniently placed at a small door in the clock case. The clock will go at exactly the same rate, whether it is driving the telescope or not, and the latter begins to move at the proper speed the instant the lever is moved, and the connection of the telescope and clock made, which is instantly effected by another lever.
£ s. d.
14, 15, to 16 inch Speculum mounted as (Fig. 1), with rotating hour circle reading to 5 seconds and decimation to 1 minute (the diameter of the circles never less than that of the Speculum, and often larger)
8 powers, from 50 to 700, with first-rate and very powerful driving clock, first-class instrument, and complete from £250 to 350 0 0
17, 18, to 20 inch Speculum, with 10 powers, from 50 to 800, including Kellners, Huyghenians, and Achromatics, from £360 to 500 0 0
22 to 24 inch Speculum from £600 to 700 0 0
30 inch Speculum, with 12 powers and position micrometer, and transit eye-pieces 1000 0 0
Prices will be forwarded for special arrangements in any of these large sizes.
£ s.d.
DrivingClocks for 6to8inch 350 0
〃〃12 〃18〃400 0
〃〃20 〃30〃500 0
These are fitted with governor, regulator, and self-adjusting break. They are made of gun metal and steel, and every wheel is cut. They drive with most excellent regularity, and are, when desired, made to beat seconds on a bell. The whole is enclosed in a mahogany frame, with glass panels.
Fig. 2 admits of equal completeness, &c., but the stand is not so convenient for clock-power.
Silvered Glass Equatorial Telescopes, very substantially and well fitted as (Fig. 2). All these equatorials have revolving body.
£ s. d.
5-1/4 inch Speculum, from 4 to 6 feet focus, with 7 inch hour circles, reading to 5 seconds of time, and declination circle reading to 1 minute, 2 powers 30 0 0
6-1/2 inch Speculum, of from 5 to 6-1/2 feet focus, 10 inch rotating hour circle, reading to 5 seconds of time, and declination circle to 1 minute of arc, with 3 powers—100 to 500 45 0 0
8-1/2 inch Speculum, as above, with 10 inch circles, 4 powers 70 0 0
10 inch Speculum, as above, with 10 inch circles, 5 powers 90 0 0
12-1/2 inch Speculum, as above, with 10 inch circles, 5 powers 120 0 0
The Educational Reflector is a plain and very steady and satisfactory instrument, mounted on (Fig. 2) stand, without circles, has revolving body, and made so as to be portable.
£ s. d.
8-1/2 inch Speculum as above, with 3 powers400 0
The Popular Reflector (Fig 3), with Angle-Block stand, with endless screw-motion to follow the stars with equatorial motion.
£ s. d.
5-1/4 inch Speculum, of from 4 to 6 feet focus, with 2 powers15150
These are also made with rotating body.
Reflecting Telescope on Alt-azimuth Stand, fitted with silvered glass Speculum, and provided with two eye-pieces.
£ s. d.
5-1/4 inch Speculum, 4 to6 feet focus 19100
6-1/2 〃〃5 〃6-1/2 〃25 00
8-1/2 〃〃 〃6-1/2 〃33100
10 〃〃 〃7 〃50 00
12-1/2〃〃 〃8 〃70100
Silvered-Glass Specula (unmounted).
THE FINEST QUALITY GUARANTEED.
£ s. d.
5-1/4 inch diameter, 4to 6 feet focus 500
6-1/2 〃4〃6-1/2〃 6 50
8-1/2 〃 〃6-1/2〃 13 00
10 〃 〃7 〃 25 00
12-1/2〃 〃8 〃 38100
14 〃 〃8 〃 55 00
16 〃 〃10 〃 75 00
18 〃 〃12 〃100 00
20 〃 〃12 〃130 00
22 〃 〃15 〃165 00
24 〃 〃18 〃200 00
26 〃 〃 〃250 00
30 〃 〃 〃300 00
36 〃 〃 〃400 00
Silvered-Glass Diagonal Mirrors (unmounted).
FINEST QUALITY GUARANTEED.
£ s. d.
1 inch in the minor axis, or narrowest diameter of the ellipse 1 00
1-1/2 dittodittoditto1100
2 dittodittoditto2 00
2-1/2 dittodittoditto2100
3 dittodittoditto3 30
3-1/2 dittodittoditto4 40
4 dittodittoditto5 50
Silvering and Polishing Specula.
£ s. d.
5 inch 06 0
6-1/2 〃 08 0
8-1/2 〃 0106
10 〃 0150
12-1/2〃 11 0
Diagonal Planes 3s. to 050
ASTRONOMICAL EYE-PIECES.
OF BEST QUALITY.
Huyghenian Construction of the following magnifying powers on a 6-1/2 feet focus object-glass:—
£ s.d.
35, 60, 90, 130, 180, 200each0150
320, 450 1 10
610 1 76
All fitted with Sunshades.
Improved Achromatic, Ramsden’s Construction.
£s.d.
90, 130 each1 00
189, 250 1100
320, 450 1126
610, 750 2 20
850 2 20
Kellner’s Construction.
£ s.d.
30, 58, and 80each1 50
Solar Eye-Pieces.
£ s.d.
Solar Diagonal, with true plane 1126
Barlow’s Lens 1 10
Day Erecting Eye-piece 1 50
Coloured Eye-piece cap for observing the Moon 0 40
Transit Eye-pieces, for use with Equatorials £1 1s. to2 20
Adjusting Piece 0 26
Good Instruments will be taken in exchange, and liberally allowed for.
GEORGE CALVER,
HILL HOUSE, WIDFORD,
CHELMSFORD, ESSEX.