Observing Double and Multiple Stars

There have been occasional clear nights when I was inspired to do some serious visual observing, however, whatever chance I had of getting a decent night of observing was going to be hindered by the brightness of the full moon. Back a few years ago, on one particular crystal clear night during a full moon, I dragged out my Edmund Scientific Astroscan 4.25" reflecting telescope and determined exactly what I could observe.

As I looked up and pondered at what I could view on such a bright night, a thought suddenly struck me. I realized I have never taken the time to seriously observe double and multiple-star systems. Being that deep-sky observing was not an option, I figured why not take a shot at splitting some of the well-known double and multiple stars? A small telescope like my 4.5" reflector can resolve many double and multiple-star systems. These star systems are interesting to observe because they offer different orientations from one another; star colors, various magnitudes as well as separations between component stars.

Artist's Rendition of Double Star System Albireo in Cygnus.

The almost endless selections of these star systems and the fact that the availability of these specimens can be seen on almost any night of the year make this type of observation possible on a bright night with small telescopes. Some double stars are known as "fixed" double stars meaning their components have not moved since their discovery. However, the majority of these star systems do show orbital motion over periods of time. The explanation is that the secondary star appears at a different position as it orbits the primary star. Some stars show orbital motion over a span of years while others may take decades to change their relative positions.

Double star observers use a unit of measurement called a position angle. Determining the position angles of double stars is a project that any amateur astronomer or student could undertake with any size telescope. The position angle measured between the two stars is from 0 to 360 degrees in an easterly direction from the north. The difficult part of determining position angles is knowing exactly what orientation your telescope's field is. For example, a reflecting telescope has a field of view south at the top and east to the right. An easy way to remember position angles for this field is to picture an imaginary clock face with the primary star at the center...

North (0°) is at 6 o'clock, East (90°) at 3 o'clock, South (180°) at 12 O'clock, and West (270°) at 9 o'clock. For example, the position angle for the double Albireo, a double star in the constellation Cygnus the swan is 55° with a separation of 34.6".

An article posted on Sky and Telescope Magazine's website has a list of the best double stars to observe as well as more information on observing double stars.

Read More

Featured Deep-Sky Object - NGC 6334 The Cat's Paw Nebula

The night sky offers many wonderful deep-sky objects to observe and image. As the staff of Insight Observatory started compiling a small catalog of deep-sky wonders for demonstration purposes to present to a local public school district, they figured it would be essential to include some of the less-known deep-sky objects as well as the more popular ones. Browsing through the night skies at Siding Spring, Australia via the planetarium software, Stellarium, we came across NGC 6334 also known as the "Cat's Paw Nebula" in the constellation Scorpius. 

NGC 6334 - "Cat's Paw Nebula" - Imaged by Insight Observatory.

The image was acquired remotely from our offices in Massachusetts at a remote telescope network Insight Observatory utilizes located in Siding Spring, Australia. The 10-minute exposure was taken using a Takahashi Sky90 (90 mm) telescope with an SBIG Wide-Field Color CCD camera attached. The image was then processed with PixInsight and Adobe Photoshop.

NGC 6334 (also known as the Bear Claw Nebula and Gum 64, besides the Cat's Paw Nebula) is what's known as an emission nebula and star-forming region located in the constellation Scorpius. The nebula was discovered by astronomer John Herschel in 1837, who observed it from the Cape of Good Hope in South Africa. The nebula is about 50 light-years across and covers an area in the sky slightly larger than the full Moon. The emission nebula lies at an approximate distance of 5,500 light-years from Earth. It is one of the nearest H II regions to the solar system. The large glowing cloud earned the nickname "Cat’s Paw" because it resembles a huge paw print of a cat. The nebula is a perfect example of an active stellar nursery (similar to M42, the "Great Orion Nebula). A study conducted by researchers from the Harvard-Smithsonian Center for Astrophysics and released in 2013 suggests that the Cat’s Paw Nebula may be undergoing a stellar “baby boom,” a period of rapid star formation.

Stellarium Planetarium Software

NGC 6334 is a realm of extremes. The object contains about 200,000 suns' worth of material that is coalescing to form new stars, some with up to 30 to 40 times as much mass as our Sun. It harbors tens of thousands of newly formed stars, more than 2,000 of which are very young and still trapped inside their dusty cocoons. Most of these stars are forming in clusters where the stars are spaced up to a thousand times closer than the stars in the Sun's neighborhood.

In the future, NGC 6334 will resemble multiple Pleiades star clusters, each filled with up to several thousand stars. Unfortunately, it won't look as impressive as the Pleiades (Messier 45) to Earthbound telescopes because it is more than ten times farther away, at a distance of 5,500 light-years, and its location in the galactic plane obscures the region behind a lot of dust.

Sources: Harvard-Smithsonian Center for Astrophysics, Constellation Guide, Wikipedia

Read More