Pretoria Centre of the Astronomical Society of Southern Africa Observer: Neville Young Site: Soniville, Faerie Glen, Pretoria 25°47’2.5”S 28°19’42.8”E Date: 4 January 2018 Time: (from to) 22h00 to 22h30
Sky Cloud Cover Clear Conditions Light Pollution Full Moon rising 40 degrees away. Air Pollution Clear Naked Eye Limiting Mag 4.0
Telescope Make and Model Meade 10” Eyepiece, Mag, 35mm, 71x, 1.5° FOV Focal Length 2500mm Aperture 250mm Binoculars 7 x 50
Camera Make and Model SONY DSC-H10, Fixed Lens, 10x Optical zoom, Piggyback on Meade Focal Length 63mm Aperture 4.4 FOV: 4° x 3° Exposure 15 sec ISO 3200 Stacking 5 stacked images
Map / Book / Software Used: TheSky6, DeepSkyStacker, XNView for some image processing
Object(s) Name(s) NGC2287, M41, ASSA100-21 Constellation Canis Major Type Object, Open Cluster, 4.6 Magnitude Alt & Azimuth Alt 90° RA & Dec 06h46 -20°46’ Notes: (magnitude, Shape, size, colour, etc) Image or Drawing: Visual: About 50 stars, size maybe 60’. ASSA100-21 NGC2287 M41 anno.jpg Dark-adapted naked eye in moonlight not visible. This photograph taken 4 Jan 2018 with a rising just-past-full Clear in binoculars. Easy to find. Moon. A small fish hook made up of equally bright stars near the centre is only asterism I . noticed. About 3’ long.
Navigation: (how to get to the object) From Sirius 4º SE to the triangle of stars and then 2º W to M41
Verified by:
For the Pretoria ASSA Deep Sky Observers (or any observer) How to analyse and record what you are observing. What to fill in on the Observing Log Sheet. Open Clusters (a) relation to the surrounding field stars Through binoculars and panning around with the 40mm eyepiece, the cluster stands out distinctly from the surroundings. (b) how many stars are there? About 50. (c) range of brightness / magnitudes The stars I could see ranged from 6.0 (SAO 209132) to about 10. (d) how are the stars concentrated? Randomly concentrated, (not evenly spread like OmegaCen). (e) look for prominent empty spaces None (f) are there clumps/chains of stars? Cannot imagine a butterfly. Perhaps a long-legged, gangly crayfish. Or better still, a Dragon Fly. (g) glow of unresolved stars/nebulosity? Nebulosity not evident. (h) central / prominent individual stars? SAO 209132 at mag 6.0 on the eastern side of the cluster. (i) any striking double stars resolved? No (j) Stars with a particular colour? SAO 209132 very orange – type K3 Globular Clusters (a) are individual stars seen? (unresolved – granular – partially resolved – well resolved) (b) how are the stars concentrated towards the nucleus? (c) estimate the size of the nucleus (compare with the size of the halo) (d) look for prominent empty spaces / starless patches (e) any clumps/chains of stars? Galaxies (a) galactic nucleus shape/brightness? (b) are there stars very nearby, or within the galaxy? (c) are there darker areas within galaxy? (d) any areas of uneven brightness? Planetary Nebulae (a) is a disk seen? (b) edge sharply defined? (c) colour of the nebula? (d) central star visible? Dark Nebulae (a) how well does the nebula stand out (b) is it isolated, or part of larger complex? (c) how dark is it? (d) are the edges sharp or diffuse? (e) stars superimposed on the nebula? Bright Nebulae (a) are there areas of uneven brightness? (b) dark lanes/patches? (c) any other structure Other – from Wikipedia
Messier 41 was discovered by Giovanni Batista Hodierna before 1654 and was perhaps known to Aristotle about 325 BC. M41 lies about four degrees almost exactly south of Sirius, and forms a triangle with it and Nu2 Canis Majoris—all three can be seen in the same field in binoculars. The cluster itself covers an area around the size of the full moon. It contains about 100 stars including several red giants, the brightest being a spectral type K3 giant of apparent magnitude 6.3 near the cluster's center, and a number of white dwarfs. The cluster is estimated to be moving away from us at 23.3 km/s. The diameter of the cluster is between 25 and 26 light years. It is estimated to be 190 million years old, and cluster properties and dynamics suggest a total life expectancy of 500 million years for this cluster, before it will have disintegrated.