I tend to regard the cataclysmic variables (also known as dwarf novae) as the fun objects of observing. The planets have a special entitlement to out interest as members of the same family as Mother Earth; galaxies, clusters and nebulae inspire awe, but the cataclysmic variables have the rare characteristic in astronomy of high unpredictability. When you take out the scope to observe a cataclysmic, you never know what to expect.
Cataclysmic variables - or dwarf novae - consist of close binaries, one component of which is a white dwarf and the other an expanding object which is shedding material more or less continuously on to the white dwarf. The white dwarf is an extremely dense, compact object and the material received from the companion blankets its surface where it gets hotter and hotter. In due course an explosion of a thermonuclear character takes place, the material is thrown off and the cycle begins again. The explosion brightens the object greatly - sometimes by as much as four or five magnitudes for periods ranging from a day to a fortnight or so.
So far, I have observed the fluctuations of five cataclysmals. Following are short notes on each of the five objects - they each have their special characteristics.
SS Aur: I find this object by moving N about 3° from Pi Aur to 36 Aur and then E for 10' of RA to the field of SS Aur. The object is normally of mag 15 (and so is invisible in my telescope) but brightens to mag 10 or 11 at intervals averaging about 100 days. Occasionally it gets into a dither and fluctuates erratically all the way between successive outbursts.
U Gem: I find this by going south about 2° from kappa Gem to the southern-most of a little curve of three 6th mag stars and then eastwards for 13' of RA. The pattern of outbursts of U Gem is rather similar to that of SS Aur but the erratic phase seems to be absent. Normally of mag 14 (and invisible to me), it can rise to mag 9 in outbursts. There are two types of outburst - the long (e.g., that of Mar/Apr 1993) and the short (e.g., that of Apr 1990). The long outbursts last about 17 days and the short about 9 days.
SS Cyg: Easily found about 1° E of 5th mag 75 (or UU) Cygni. SS is normally about mag 12 and has outbursts to mag 8 or 9 which may last for several weeks.
Z Cam: Rather difficult to find, located as it is in an area devoid of bright stars. My usual route to it starts at 24 UMa, goes N to 27 and 22 UMa and thence W to the 6th Mag double Struve 1193. Z Cam is about a degree NNE of the double. Z Cam differs from the other cataclymals which I have listed in having little in the way of a base magnitude. It varies in an unpredictable way between about mag 10 and 13.5.
SU UMa: My route to SU starts at 3rd mag Omicron Ursae Majoris, goes W rather more than a degree to just beyond an unnumbered 6th mag star, then N nearly two degrees to another unnumbered 6th mag star and then W again rather less than a degree to the location of SU. SU is normally of mag 14.5 and invisible in my telescope. It has short lived outbursts (lasting at most a few days) to mag 12 or 11.5 every fortnight or so and occasional "supermaxima" to mag 11 or even brighter. The "supermaxima" last for about a fortnight. I have observed only one of the latter - in Feb/Mar 1993.