Then, leaving the telescope clamped in declination as it was after adjustment 1, turn it in azimuth across the pole until the pole star enters the field which, if the finder inverts it will do on the other side of the center; i.e. if it stands at IV to the naked eye it will enter the field apparently from the XVI o’clock quarter. When just comfortably inside the field, the axis of the telescope is pointing substantially at the pole. It is better to get Polaris in view before slipping in the stop and if it is clearly coming in too high or too low shift the altitude of the polar axis a trifle to correct the error. This approximate setting can be made even with the smallest finder and on any night worth an attempt at observation. With a finder of an inch or more aperture a very quick and quite accurate setting to the meridian can be made by the use of Fig. 170, which is a chart of all stars of 8 mag. or brighter within 1° 30′ of the pole. There are only three stars besides Polaris at all conspicuous in this region, one quite close to Polaris, the other two forming with it the triangle marked on the chart. These two are, to the left, a star of magnitude 6.4 designated B. D. 88 112, and to the right one of magnitude 7.0, B. D. 89 13. The position of the pole for the rest of the century is marked on the vertical arrow and with the stars in the field of the finder one can set the cross wires on the pole, the instrument remaining clamped in declination, within a very few minutes of arc, quite closely enough for any ordinary use of a portable mount. All this could be done even better with the telescope itself, but it is very rare to find an eyepiece with sufficient field. [Illustration: FIG. 170.—The Pole among the Stars.] At all events the effect of any error likely to be made in these adjustments is not serious for the purpose in hand, since if one makes an error of a minute of arc in the setting the resulting displacement of a star in the field will even in the most unfavorable case reach this full amount only after 6 hours following. I.e. with any given eyepiece an error of adjustment equal to the radius of the field will still permit following a star for an hour or two before it drifts inconveniently wide of the center. Considerable space has been devoted to these easy approximations in setting up, since the directions commonly given require circles and often a clock drive. In some cases one has to set up a portable equatorial where from necessity for clear sky space, Polaris is not visible. The best plan then is to set up with great care where Polaris can be seen, paying especial attention to the levelling. Then establish two meridian marks on stakes at a convenient distance by turning the telescope 180° on its declination axis and sighting through it in both directions. Now with a surveyor’s tape transfer the meridian line East or West as the case may be until it can be used where there is clear sky room.