The prices of this instrument, as marked in Mr. Tulley’s Catalogue, are as follows:--
£ s. d. The 3-1/2 feet achromatic telescope 2-3/4 inches aperture, on plain pillar and claw stand, 2 eye pieces for astronomical purposes, and 1 for land objects to vary the magnifying power, packed in a mahogany box 21 0 0
Ditto, ditto, with elevating rack and achromatic finder, 2 eye pieces for astronomical purposes, and 1 for day objects to vary the magnifying power, packed in a mahogany box 26 5 0
The following are the prices as marked in Messrs. W. and S. Jones’ Catalogue.
£ s. d. The 3-1/2 feet achromatic, plain mahogany tube 18 18 0
Ditto, all in brass, with rack work motions, &c. 26 5 0
Ditto, the object glass of the largest aperture, and the rack motions on an improved principle _from_ 37l. 16s. to 42 0 0
Ditto, fitted up with Equatorial motion, framed mahogany stand, divided altitude, and azimuth arches, or declination and right ascension circles, &c. &c. _from_ 60l to 80 0 0
This is the telescope which I would particularly recommend to astronomical amateurs, whose pecuniary resources do not permit them to purchase more expensive instruments. When fitted up with the eye pieces and powers already mentioned, and with a finder and elevating rack,--price 25 guineas--it will serve all the purposes of general observation. By this telescope, satisfactory views may be obtained of most of the interesting phenomena of the heavens, such as the spots of the sun--the mountains, vales, and caverns on the lunar surface--the phases of Mercury and Venus--the spots on Mars--the satellites and belts of Jupiter--the ring of Saturn--many of the more interesting nebulæ, and most of the double stars of the second and third classes. When the object glass of this telescope is accurately figured and perfectly achromatic, a power of from 200 to 230 maybe put upon it, by which the division of Saturn’s ring might occasionally be perceived. It is more easily managed and represents objects considerably brighter than reflecting telescopes of the same price and magnifying power, and it is not so apt to be deranged as reflectors generally are. A telescope of a less size would not in general be found satisfactory for viewing the objects I have now specified, and for general astronomical purposes. It may not be improper for the information of some readers, to explain what is meant in Mr. Tulley’s catalogue, when it is stated that this instrument has ‘one eye piece for day objects, _to vary the magnifying power_.’ The eye piece alluded to is so constructed, that by drawing out a tube next the eye, you may increase the power at pleasure, and make it to vary, say from 40 to 80 or 100 times; so that such a construction of the terrestrial eye piece (to be afterwards explained) serves in a great measure, the purpose of separate eye-pieces. The whole length of the 3-1/2 feet telescope, when the terrestrial eye piece is applied, is about 4-1/2 feet from the object glass to the first eye glass.