Take a dip with the dolphin in October skies

Face south around 8 o’clock to find the Summer Triangle. Our featured constellation Delphinus lies just to the left or east of Altair in Aquila. Maps created with Stellarium

Without the moon to brighten the evening sky, mid-October’s a fine time for a dip with the celestial dolphin. All you need are your eyes to see one of the most delightful of the 88 constellations: Delphinus.

To get there, we begin around 8 o’clock and look high in the southern sky to find the three bright stars outlining the figure of the Summer Triangle.

The bottom star is first magnitude Altair (all-TARE) in Aquila the Eagle. Thrust your arm out and look one fist to the left of Altair for a small, rather faint group of five stars you can cover up with just a few fingers. That’s Delphinus.

The dolphin Delphinus appears to be leaping away from Altair. It’s highest in the sky around 8 p.m. local time. Another small, dim constellation, Sagitta the Arrow, lies one outstretched fist above or north of Altair.

The exquisite diamond shape is the dolphin’s body; the single star below it, the tail. Small telescope users should be sure to look at Gamma Delphini, a binary star of magnitudes 4 1/2 and 5 separated by 9 arc seconds. 35x will split Gamma into a bright, neat pair of golden stars.

Delphinus is rich in attractive double stars. Besides Gamma and Struve 2725, the bright triple star Struve 2703, located between Beta and Zeta Delphini, is easy to split in small telescopes.

Not far from Gamma in the same low power field of view is a slightly fainter, tighter pair of stars called Struve 2725. You’ll spot them perpendicular to Gamma and a short distance to the southwest. 50x  will easily cleave both pairs.

Two gorgeous doubles in the same view – can it get any better? Well, maybe. That all depends on what you think of triple stars. Tucked between Rotanev and Zeta Delphini, the triple Struve 2703 curls a beckoning finger at the telescopic observer.

I confess that after years of looking at Gamma and Struve 2725, I saw Struve 2703 for the first time only this week. How I avoided it for so long is beyond me. Even 35x will split this overlooked gem into a skinny triangle of three 8th magnitude stars. You’ll love it.

All three multiple stars we’re talking about today are real, physical systems where each star in the pair (or triple) revolves around their common center of gravity. They travel through space together and are married for life.

This mythological depiction of Delphinus, Sagitta and Aquila is a plate from the atlas Urania’s Mirror. The dolphin represents the messenger of the ancient Greek sea god Poseidon.

If you’re feeling a measure of confidence at finding Delphinus, take the next leap to Sagitta the Arrow, a fist above Altair (see map above). It’s smaller and fainter but what it lacks in brightness it makes up in compactness and distinctive shape much like our dolphin.

The man himself – Nicolaus Cacciatore

Before we leave Delphinus, you must know about its two brightest stars – Sualocin (Alpha Delphini) and Rotanev (Beta). Many Westerners assume the star names are traditional Arabic. Not so. Instead they’re the words Nicolaus Venator spelled backwards.

Nicolaus Venator, whose real name was Nicolaus Cacciatore, worked as an assistant to the famous astronomer Giuseppi Piazzi at the Palermo Observatory in Sicily at the turn of the 19th century. It was Piazzi who discovered the very first asteroid Ceres in 1801. Cacciatore helped him compile an important star catalog of the time.

Cacciatore assured his name a measure of immortality during the catalog’s creation by naming two stars in Delphinus after himself. ‘Cacciatore’ means ‘hunter’ in Italian, which translates as ‘venator’ in Latin. So yes, we have Nicolaus Venator to thank for Sualocin and Rotanev! He did this quietly of course, and it was only uncovered later through the detective work of English astronomer Thomas Webb.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

14 thoughts on “Take a dip with the dolphin in October skies

  1. Hi Bob

    This is probably the stupidest thing I’ve asked you :-) but I read on the web about an asteroid but it’s named as 2014 AZ5, so I presume that it doesn’t exist as they are usually named by the year so as we are not in 2014 it can’t be true I presume as it says it will impact us next March 2013 so is this incorrect. Thanks Bob :-)

  2. Hi bob I have sort of a crazy question but I need help in answering my kids questions.. what is ur take on 2012 ? Do you think we have anything to worry about? I try to do research but I remember u told me once becarfull with what u read on the web lol so I thought I’d ask for ur help and wisdom ….. thanks bob take care

    • Milayla,
      Isn’t the world supposed to end this year or something? I think we’ll all do fine. The Mayan thing is one gigantic hoax/wishful thinking based on a misinterpretation of their ancient calendar. Think of the hundreds (thousands?) of times people have predicted the end of the world. Never once has it come true. Politics, wars and economics worry me a lot more than calendars and predictions.

  3. That’s what I was trying to explain to my son but he just asked about leap yrs lol and if their were no leap years wouldn’t it had happens all ready ?? Cause he said the Mayans didn’t have leap yrs? Thanks so much for ur help my son loves ur blog he reads it all the time he thinks ur the smartest man in the world ( won’t argue with that) u def have a fan thanks

  4. I did a little comparing of the ephemeris of Comet Encke and Comet ISON next year. On Oct. 16 , it looks like both will be at the same right ascension and both possibly at about Magnitude 8. Encke will be about 21 degrees in declination, north of ISON.

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