 |
Alessi 2
Size: 30' Type: IV 3 m Notes: Br * 8.8 |
Sunday, 10 January 2016
Sunday, 4 October 2015
Deep Sky column 7/2015: NGC 7789 & NGC 7243
NGC 7789 is one of the finest open clusters in the northern hemisphere. It was discovered by Caroline Herschel on 30th of October 1789 using a modest 10 centimeter f/6.4 Newton. It features roughly 600 stars within 20' of which the brightest is 10th magnitude. Visually the object is less than 10' in size.
Loosely translated my friend Iiro described the object as "a labyrinth of dark pathways and starless regions".
NGC 7243 is an old favorite of mine. Several shapes can be discerned from the object most common one being a bird flying directly to the viewer. Brightest star in the cluster is 8.5 magnitude. Size of the object is 17' with a total number of stars visible with an 8 inch Orion DSE: ~150. Illustration (from my part) featured a sketch of NGC 7243:
 |
| 4.5 " Orion SkyQuest @ 101x (30') |
Wednesday, 1 July 2015
Deep Sky column 5/2015: Dwarfs and Giants
Massive star: LBV candidate Cyg OB2 #12 (HIP 101364). 11.4 magnitude star with ~110 M☉ and bolometric magnitude ~10.9. Dwarfed by R136a1 (~256 solar masses) in NGC 2070 (LMC - Dorado).
A star close to us: Lalande 21185 in Ursa Major. The star is only 8,3 light years away. At magnitude 7.5 is it also a naked eye object under excellent conditions. Absolute magnitude is quite faint: ~10.5.
Tiny star: Barnard's star. Closer to us than Lalande 21185 but a lot smaller: 0.14 M☉and with an absolute magnitude of only 13,2. The star has only 150 times more mass the Jupiter. Moves 10" in the sky per year - that's 90 km/s. Not discovered by E. E. Barnard.
Far far away: 6th magnitude Rho Cassiopeia. Distance estimates vary greatly: between 6000 and 16 000 light years. Commonly referred as the most distant (single) star visible to the naked eye. Radius is at least 400 R☉ then again dwarfed by UY Scuti (~1700 solar radii). Another distant star to the naked eye: V762 Cas, possibly even 15 000 light years away.
Monday, 6 April 2015
Deep Sky column 3/2015: The three phases of galaxy mergers
Second phase in galactic collision - NGC 4676A & NGC 4676B (Mice Galaxies): Galaxies visible with 8 inch Orion DSE, both galaxies of same size and brightness. Failed to spy with 4.5" SkyQuest. "Tails" commonly described as being difficult to observe, NGC 4676A's tail has been seen with 12 inch telescope. Pair discovered by William Herschel in 1785. IC designations (819 & 820) from Rudolf Spitaler (1849 – 1946).
Third phase in galactic collision - NGC 4038 & NGC 4039 (Antennae Galaxies): Beaten up, tormented shape. 400 million years from now the two will merge as a giant elliptical galaxy. Southern "tail" is 10' long with the northern one being at least 7'. Brightening in southern tail is NGC 4038S - a presumed Tidal Dwarf Galaxy (TDG). Visually NGC 4039 is smaller and fainter. Both components have fairly faint surface brightness. Brightest H II regions are roughly magnitude 15 and within reach of medium to large apertures.
Monday, 2 February 2015
Deep Sky column 1/2015: Orion Redux
NGC 1684: Fairly faint elliptical galaxy. Visible as a faint smudge paired with NGC 1682 using 8 inch Orion DSE @ 133x. Brightest galaxy in Orion.
NGC 2194: Beautiful open cluster with 150* within 5'. East of the cluster lies Luginbuhl-Skiff 1 discovered visually by astronomer Brian Skiff in 1975.
Abell 12 (PK 196-6.1): Glued to brilliant 4th magnitude Mu Orionis. Barely visible with 4.5 SkyQuest using an occulting bar. Using larger aperture and an OIII filter a darker center is visible.
Barnard's Loop (Sh 2-276): Massive size of over 25 degrees. Visible with any optical instrument, usually best with small widefield refractors. UHC or H-Beta filter improves contrast. Edward Emerson Barnard called it "Orion Loop".
The original version included: NGC 1662+1663, NGC 1684, NGC 1788, NGC 1999, NGC 2141, NGC 2194, Cederbland 59 and Sh 2-276.
Subscribe to:
Posts (Atom)