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My Main Telescope - C14 and Paramount ME

My new Paramount MyT and 8-inch Ritchey-Chretien Telescope

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My Meade 12 inch SCT on a CGEM (Classic) Mount

My 4 inch Meade Refractor with Sky Watcher Guidescope and ZWO camera on a CGEM (Classic) Mount

Skywatcher Star Adventurer Mount with Canon 40D

 

My Solar setup using a DSLR and Mylar Filter on my ETX90

DSLR attached to ETX90. LiveView image of 2015 partial eclipse on Canon 40D

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About the Site

 I try to log my observing and related activities in a regular blog - sometimes there will be a delay but I usually catch up. An index of all my blogs is on the main menu at the top of the page with daily, weekly or monthly views. My Twitter feed is below. I am also interested in photograping wildlife when I can and there is a menu option above to look at some of my images. I try to keep the news feeds from relevant astronomical sources up to date and you will need to scroll down to find these.

The Celestron 14 is mounted on a Paramount ME that I have been using for about 10 years now - you can see that it is mounted on a tripod so is a portable set up. I still manage to transport it on my own and set it all up even though I have just turned 70! It will run for hours centering galaxies in the 12 minute field even when tripod mounted.

 

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Main | The Dumbbell Nebula »
Tuesday
Oct082019

Messier 13 Globular cluster in Hercules

Surely M13 has to be one of the most spectacular globular clusters on Messier’s List. With an approximate diameter of 20 minutes of arc it appears as a massive ball of stars. M13 had originally been discovered in 1714 by Edmund Halley of Halley’s Comet fame, but was catalogued by Messier 50 years later on June 1st 1764.

Messier commented about M13:  “Nebula without star, discovered in the belt of Hercules; it is round & brilliant, the center [is] more brilliant than the edges, one perceives it with a telescope of one foot; it is near two stars, the one & the other of 8th magnitude, the one above and the other below it: the nebula ['s position] was determined by comparing it with Epsilon Herculis.” (SEDS).  M13 can be visible to the naked eye in dark skies as pointed out by Halley himself.  Reverend Webb regarded it as being “ spangled with glittering points in a 5 ½ foot achromat, becoming a superb object in large telescopes”. 

Messier 13 lies at a distance of 25,100 Light Years from us. (SEDS) This is roughly one quarter of the distance of the major axis of our Galaxy. The negative image shows foreground star Tycho 2588:1662, which has a magnitude of 10.99 and lies at a distance of only 72 Light Years. The cluster members appear fainter than this star in the region of 12th magnitude. There have been many calculations over the years as to the number of stars in this globular cluster  - perhaps you could try your own estimate from the photograph! The cluster subtends an angle of 20 minutes of arc at a distance of 25,100 Light Years. My rough calculations based on these figures give an approximate diameter of about 150 Light Years.