interacting – Page 9 – Astronomy Sketch of the Day

Dynamic Duo

M81 and M82

Here is another digital sketch. It’s the first one made with a digital tablet and a
pressure sensitive pen. It feels more natural than using a mouse to draw nebulosity
or to smudge out an area. The application (Photo-Paint) controls the relationship
between the pressure you apply with the pen to the tablet, and the effect produced
by brush tools in Corel PHOTO-PAINT. As you press down on a drawing tablet with the
pen, the effect produced by such tools changes. Several attributes can be changed at
the same time by pressure, like size, brightness, opacity etc. Like a common pencil,
a line can be drawn thicker by applying more pressure with the pen. I’m still in an
experimental phase with the settings. I hope you like the sketch.

Date : March 12, 2007
Time : 21.14UT
Scope : Skywatcher 102/500
EP : Vixen LV Zoom at 8mm
Power : 63x
FOV: 50′
Filter : none
Seeing : 3/5
Transp. : 2.5/5
Sketch Orientation : N up, W right.
Digital sketch made with a wireless digital tablet and a pressure sensitive pen in
PhotoPaint, based on a raw pencil sketch.
Rony De Laet

http://www.geocities.com/rodelaet, my personal website.

Extragalactic Twins

The interacting galaxy pair consisting of NGC 3166 and NGC 3169 is one of the unsung extragalactic showpieces of the spring sky. They may be located in the north-central region of Sextans, 8.5° south of Regulus. Separated by 6.3′, these two galaxies look like nearly identical twins in my 6-inch scope; they give the strong impression of a ghostly pair of eyes peering from beneath a star-studded hood. NGC 3166 is slightly smaller and dimmer than its companion but it has a more conspicuous central region with a sharp stellar nucleus. NGC 3169 also has a bright core but it is not as well concentrated as its neighbor’s. A 12th magnitude star is superimposed on NGC 3169’s diffuse outer halo, just east of the central core. With a magnification of 60x and placing NGC 3169 near the northeastern edge of the field of view I can just squeeze in the faint galaxy NGC 3156 just west of a trio of 7th, 8th, and 9th magnitude stars (it lies just 2′ from the faintest of the three stars). This little galaxy is elongated northeast to southwest and has a slightly brighter center. A much fainter galaxy, NGC 3165, glimmers intermittently with averted vision 5.4′ southwest of NGC 3166.

William Herschel discovered NGC 3166 and NGC 3169 on December 19, 1783 with his 18.7-inch reflector. He designated them as the 3rd and 4th entries (respectively) in his catalog of “Bright Nebulae”. Both of these galaxies are included in the popular “Herschel 400″ observing list. Each of these galaxies shows evidence of tidal interaction and distortion on photographs. NGC 3169 has a highly distorted spiral arm, while the dust lanes of NGC 3166 have been fragmented and twisted as if
the entire disk has been warped by the interaction with its neighbor. It is estimated that these galaxies lie 52 million light-years away.

Subject: NGC 3166 and NGC 3169
Object Type: Interacting Galaxy Pair
Constellation: Sextans

NGC 3166 (H.I.3)
Right Ascension (2000.0): 10h 13m 45.8s
Declination (2000.0): +03° 25′ 30″
Magnitude: 10.4
Diameter: 4.6′ x 2.6′
Classification: SAB(rs)0/a

NGC 3169 (H.I.4)
Right Ascension (2000.0): 10h 14m 15.0s
Declination (2000.0): +03° 27′ 58″
Magnitude: 10.2
Diameter: 5.0′ x 2.8′
Classification: SA(s)a pec

Observer: Eric Graff
Location: Cuyamaca Mts., San Diego Co., California (4,000 ft. elevation) Date &
Time: 12 March 2007 at 07:35UT
Transparency: NELM 6.7, TLM ~14.1
Seeing: Pickering 5-6/10
Telescope: Parks Astrolight EQ6 (6” f/6 Newtonian Reflector)
Eyepiece: 15mm Parks Gold Series Plössl (60x, 52′ TFoV)
Filter: None
Sketching Materials: #2 pencil, black ink, blending stump, 24# copy paper

Galactic swing dance

Object: Messier 51, The Whirlpool Galaxy
Classification: Galaxy
Position: RA 13h 29.9 min, DEC 47° 12′
Distance: ~23 million light years
Visual Brightness: 8m4
Apparent Dimension: 11′ x 7′
Constellation: Canes venatici
Observing Location: Erbendorf, Steinwald, Bavaria, Germany (800 meters
above sea level)
NELM: 6m2
Seeing: II / VI
Transparency: I-II / VI
Date: March 15, 2007
Instrument: Dobsonian 8″ f/6
Eyepiece: Reese 9mm Super Wide Angle
Magnification: 133x
Sketching Materials: black cardboard, white pastels, white ink, blending stump

A lot of work and patience went into the above drawing of M 51 to bring out as much detail and structure as possible: after one hour of dark adaption, another hour of pure observing and one more hour of sketching was invested, to get a glimpse of the subtle dark and light structures inside the diffuse nebulosity, which is generated by the object. At a first look, two blurry, bright smudges appear in the eyepiece, which can each be separated into a bright, almost stellar core surrounded by a diffuse, somewhat less brighter halo. It becomes apparent that the two objects are not located directly next to each other, but that there is a somewhat darker area in between, which is suddenly “cut off” by a brighter region in the east: the “bridge” of matter connecting the two galaxies! Inside M 51 A two slightly brighter regions start to appear, which bend away from the core and “dissolve” in the galactic disc: a hint of the spiral structure! Finally, two faint stars can be observed, which are apparently located East and West of the core, they are supposedly stars in the foreground. It may be noted here that the detail depicted in the drawing is the result of many hours of observation and patient use of averted vision, resulting in some sort of “sum picture”, which is surely not visible at a first glance. The beginner may be completely satisfied, if he can recognize the two discs and their cores – all the other details will appear with constant and regular observing.

Sebastian Lehner