Caldwell’s planetary nebulae
The Caldwell list offers a total of 13 fine planetary nebulae and most of them can be seen well from the northern hemisphere. A wealth of detail and structure become visible, especially on nights with good seeing when magnification can be cranked up.
NCG 40 (C2), the “Bowtie Nebula”, is the most northern one and it’s characteristic for its opposing, somewhat brighter arcs that appear a bit angular. The central star can be seen well, surrounded by a darker area. a loose “tuft” can be seen on one tip. Sketched with the 16″ Alkaid @362x.
NGC 6543 (C6), the “Cat’s Eye Nebula” is a beautiful object, very bright and even with high magnification the blue color remains visible. the central star is very prominent and shines brightly in the oval shaped nebula. With AV the nebula has a more rhomboid shape. Some structure can be seen in the nebulosity and around the central star a darker cavity is seen, although it’s difficult to estimate how large it is. An easier feature is the curl on the right side, or actually it’s more like a dark intrusion. The outer shell of the nebula can’t be seen, except for one small comet-shaped part: IC 4677 (up in the sketch). Sketched with the 16″ Alkaid @362x.
NGC 7662 (C22), the famous “Blue Snowball” is a fine autumn planetary. Increasing magnification on this nebula helps to see some interesting details; an inner bright ring in the shape of a horseshoe, a soft outer halo and of course the color blue. Things really started to get blurry at this power, but the nebula took it quite well and the view was still nice. The central star was not seen, however. Sketched with the 16″ Alkaid @518x.
One of the most famous winter planetaries must be NGC 2392 (C39), or the “Eskimo Nebula”. At low power it’s very bright, round and fluffy, but it takes magnification well and then some more interesting details become visible. The central star is easy and around it an uneven dark cavity and a double shell can be seen, showing the well known and structured “fur collar”. The face of the Eskimo was not seen however. A very bright star is close by. Sketched with the 16″ Alkaid @259x.
NGC 3242 (C59) was a real showpiece when viewed with (only) 10″ from La Palma with superb seeing. The “Ghost of Jupiter” is razor sharp, very bright, slightly oval and consists of two rings. The inner ring is the brightest and sharply defined and two “tufts” at the end are a bit brighter. The outer ring is a bit rounder and much softer. The color of the nebula is a definite light-blue and the central star can just be glimpsed. Sketched with the 10″ Alkaid @240x