Even simpler methods carefully applied may serve to give a view of Mercury.  To show this, I may describe how I obtained my first view of this planet.  On June 1st, 1863, I noticed, that at five minutes past seven the sun, as seen from my study window, appeared from behind the gable-end of Mr. St. Aubyn’s house at Stoke, Devon.  I estimated the effect of Mercury’s northerly declination (different of course for a vertical wall, than for the cross-rod in fig. 8, which, in fact, agrees with a declination-circle), and found that he would pass out opposite a particular point of the wall a certain time after the sun.  I then turned the telescope towards that point, and focussed for distinct vision of distant objects, so that the outline of the house was seen out of focus.  As the calculated time of apparition approached, I moved the telescope up and down so that the field swept the neighbourhood of the estimated point of apparition.  I need hardly say that Mercury did not appear exactly at the assigned point, nor did I see him make his first appearance; but I picked him up so soon after emergence that the outline of the house was in the field of view with him.  He appeared as a half-disc.  I followed him with the telescope until the sun had set, and soon after I was able to see him very distinctly with the naked eye.  He shone with a peculiar brilliance on the still bright sky; but although perfectly distinct to the view when his place was indicated, he escaped detection by the undirected eye.[12]

Mercury does not present any features of great interest in ordinary telescopes; though he usually appears better defined than Venus, at least as the latter is seen on a dark sky.  The phases are pleasingly seen (as shown in Plate 6) with a telescope of moderate power.  For their proper observation, however, the planet must be looked for with the telescope in the manner above indicated, as he always shows a nearly semi-circular disc when he is visible to the naked eye.

We come next to Venus, the most splendid of all the planets to the eye.  In the telescope Venus disappoints the observer, however.  Her intense lustre brings out every defect of the instrument, and especially the chromatic aberration.  A dark glass often improves the view, but not always.  Besides, an interposed glass has an unpleasant effect on the field of view.

Perhaps the best method of observing Venus is to search for her when she is still high above the horizon, and when therefore the background of the sky is bright enough to take off the planet’s glare.  The method I have described for the observation of Mercury will prove very useful in the search for Venus when the sun is above the horizon or but just set.  Of course, when an object is to be looked for high above the horizon, the two rods which support the cross-rods must not be upright, but square to the line of view to that part of the sky.

But the observer must not expect to see much during his observation of Venus.  In fact, he can scarcely do more than note her varying phases (see Plate 6) and the somewhat uneven boundary of the terminator.  Our leading observers have done so little with this fascinating but disappointing planet, that amateurs must not be surprised at their own failure.