The planetary observer has to accept such opportunities as are given him; he must use his telescope at the particular seasons when his objects are well presented. These are limited in number, and months may pass without one of them coming under favourable review. In stellar work no such irregularities can affect the progress of observations. The student of sidereal astronomy has a vast field to explore, and a diversity of objects of infinite extent. They are so various in their lustre, in their grouping, and in their colours, that the observer’s interest is actively retained in his work, and we often find him pursuing it with unflagging diligence through many years. No doubt there would be many others employing their energies in this rich field of labour but for the uninteresting character of star-disks, which are mere points of light, and therefore incapable of displaying any detail. Those who study the Sun, Moon, or planets have a large amount of surface-configuration to examine and delineate, and this is ever undergoing real or apparent changes. But this is wholly wanting in the telescopic images of stars, which exhibit a sameness and lack of detail that is not satisfying to the tastes of every observer. True there are some beautiful contrasts of colour and many striking differences of magnitude in double stars; there are also the varying position and distance of binary systems, the curious and mysterious fluctuations in variable stars, and some other peculiarities of stellar phenomena which must, and ever will, attract all the attention that such important and pleasing features deserve. And these, it must be conceded, form adequate compensation for any other shortcomings. The observer who is led to study the stars by comparisons of colour and magnitude or measures of position, will not only find ample materials for a life-long research, but will meet with many objects affording him special entertainment. And his work, if rightly directed and accurately performed, will certainly add something to our knowledge of a branch in which he will certainly find much delectation. _Greek Alphabet._—The amateur must, at the outset of his career, thoroughly master the Greek alphabet. This will prevent many time-wasting references afterwards, and avoid the doubt and confusion that must otherwise result. The naked-eye stars in each constellation have Greek letters affixed to them on our celestial globes and star-maps. α Alpha β Beta γ Gamma δ Delta ε Epsīlon ζ Zēta η Eta θ Theta ι Iota κ Kappa λ Lambda μ Mu ν Nu ξ Xi ο Omīcron π Pi ρ Rho σ Sigma τ Tau υ Upsīlon φ Phi χ Chi ψ Psi ω Omĕga.