Polaris – Double Star – Seeing the Companion With a Small Telescope, Maybe Even As Small As 60 mm’s?

Polaris has never gained much attention as a double star.  However, If you’ve had an interest in double stars, but never seemed to get started:  Polaris, also known as the “North Star” would be a great double to start with, especially with a smaller telescope.  

For this project, lets call a small refractor, anything 80 mm’s or less. 

Using the “Cambridge Double Star Atlas” by James Mullaney and Wil Tirion, as a reference:

Polaris has a magnitude of 2.1 and the secondary or companion at a much fainter 9.0 magnitude with a wide separation of 19 arc seconds.  The extreme difference in magnitudes can make this double more difficult to separate than you might think, especially if seeing is less than good. 

Sometimes I check this star frequently, when setting up, to gauge seeing.  Normally I don’t make a sketch or notes due to having looked at this double so many times over the years. 

However, I do have some notes and sketches from years past using some small telescopes.   

July 1996:  4-inch Meade Schmidt-Cassegrain f/10, model 2045d:  Seeing only fair, companion was not visible.  Roger Ivester – North Carolina 

September 1996:  4-inch Meade Schmidt-Cassegrain f/10, model 2045d: Seeing very good, could easily see the companion at 50x.  RI

September 1996:  5-inch C5 Schmidt-Cassegrain, white-tube with the single arm fork. Made in USA.  Easy, beautiful and clean.  RI

February 1997:  4-inch Meade Schmidt-Cassegrain f/10, model 2045d: Seeing only fair.  The companion was visible only intermittently.  RI 

October 1997:  90 mm Meade ETX Astro-Scope, Maksutov-Cassegrain: Seeing was good and the companion was very easy at 52x.  RI 

December 1998:  102 mm Vixen/Orion f/9.8 achromatic refractor: Very easy to see the companion at all magnifications.  Roger Ivester 

I was unsuccessful during the week of April 8th 2018, using my latest small economy Orion CT80 f/5 refractor.  Seeing was only fair, so I’ll try it again in the next night or so.   Roger Ivester 

April 17th 2018:  102 mm Vixen/Orion f/9.8 achromatic refractor:  Seeing was very poor, could still see the companion, but only intermittently, using full 102 mm aperture.  Did not even attempt with an effective aperture of 60 mm’s.  RI 

Mike McCabe of Massachusetts was able to see the companion last summer on a night of excellent seeing, using a vintage and classic Sears 60 mm f/15 refractor.   

Observing notes by Mike McCabe as following, for the night of April 18th 2018:

Well, you really got my interest with your lobbying everyone to try and go see the secondary to Polaris with a small scope.  I got lucky here last night – totally unexpected it was – with a clear and stable sky sometime around 9pm local time. 

At first I turned my interest to the 10% waxing crescent moon, and I brought out my SV80ED to have a quick look.  It was spectacular, with incredible earthshine on the moon and a dark, clear sky around it.  There were nearly as many stars in the view as you’d see during an eclipse!  I watched the moon occult a star (don’t know which one) and then toured the Haydes, the Pleiades and then Polaris.  The 80mm brought out the secondary with no trouble.

I decided to bring out the Sears 60mm f/15.  That was a good decision!  I put Polaris in the eyepiece and ramped the power up to 112x.  In short order I had the secondary in view at ~5:00 in the field of view.   

I’ve assembled a 0.965 eyepiece kit, which includes a 40mm, 25mm, 15mm, 12mm, 10mm, 8mm and a 2x Barlow.  I tried many eyepiece combinations, and must’ve looked at Polaris for an hour, and I could see the secondary from 60x all the way up to 180x.  The best magnification occurred at 90x, with 75x being a close second.  At 112x and higher it was still there, but more intermittently.

After last night I’m going with “it’s not only possible to see the secondary to Polaris in a 60 mm telescope, but very, very doable”.  

I have another 60 mm f/15 OTA (a 1980’s era Celestron FirstScope) which I am currently setting up.  I’m wanting to complete the Astronomical League’s Double Star list to receive my certificate which I started working on quite a few years ago, but have never finished.     Mike McCabe – Massachusetts 

April 19th 2018:  102 mm Orion/Vixen f/9.8 achromatic refractor with an effective aperture of 60 mm’s.  Seeing excellent: 12.5 mm eyepiece plus 2.8x Barlow for a magnification of 80x.  The companion was clearly visible as a tiny bluish dot.  Roger Ivester – North Carolina 

April 19th 2018:  Orion 80 mm (CT80) f/5 achromatic refractor.  Seeing excellent: 12.5 mm eyepiece plus 2.8x University Optics Klee Barlow for a magnification of 90x.  The companion was visible as a tiny bluish dot.  Very similar to the view using the 102 mm reduced to 60 mm’s.  A beautiful sight in both telescopes.   Roger Ivester  

When observing with my CT80, I use a 1.25-inch correct image diagonal.  For me it’s essential when I’m sketching a deep-sky object, to have the correct cardinal points in the eyepiece view.  I share a bit more in depth in the following link, and go to “Article.”

https://www.telescope.com/Orion/Accessories/Telescope-Diagonals/Orion-125-Correct-Image-Star-Telescope-Diagonal/rc/2160/pc/-1/c/3/sc/45/p/8787.uts

April 20th 2018:  Orion 80 mm (CT80) f/5 achromatic refractor.  Similar conditions to my observation on the 19th. Using the same eyepiece combinations (90x) and was able to easily see the companion as a tiny bluish dot.  RI 

The following is a photo of my 102 mm refractor with a stop-down mask for an effective aperture of 60 mm’s.  

IMG_0023

My Orion (CT80) 80 mm f/5 refractor.  Yes….I can see the companion to Polaris with this small short focal length achromatic refractor!  My son bought this telescope for my birthday, and it will always be a prized possession of mine….

IMG_2497

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