Friday, March 18, 2016

M4, Cat’s eyes

In 2012 I saw and sketched the majestic M4 for the first time (click here). I described it as a “faint white-grey spot floating in the sky”. The very dim and weak view of the globular cluster was just a ghosty patch in the binoculars FOV and that was in part thanks to the heavy light pollution from Bogotá. One would think that with a bigger scope the view would improve but even with the 5” reflector telescope M4 looked like a fuzzy round spot among the stars.

Now I am back in the ring with a telescope. We (me and my wife) bought a telescope in US last year and in January of this year I finally got it here in China thanks to my sister-in-law. It has a little more aperture than my first scope (6” or 150mm) and is of another optical design: Smith Cassegrain.
I got the Celestron C6 OTA and complement it with a CG4 equatorial (EQ) mount. The scope has a focal length of 1500mm but because it’s optical design is a very compact tube of less than 50cm long and 10lbs/4.54kg of weight. The mount itself is a bit heavy (30lbs/13.6kg tripod and counterweights included) but it still works well for a very capable portable scope. Another option to reduce the weight would be using an ALT-AZ mount like the Twilight I from Explore Scientific (11lbs/5kg of weight) instead of an EQ.  Then you will have a nice scope to take to a moderately or truly dark sky and make count every centimeter of aperture.

I am very blessed to live in a small city under a clean sky in China. As I told in previous entries, not far from my home I can find blue, grey and black zones that mean moderate dark skies Bortle 4 or 5 where the stars visible to the naked eye make an awesome sight in a clear night. Last 14th I tried my first glob sketch and decided to choose M4 because it looks simpler than others but still with a good detail inside to train new sketching skills.

I use a Celestron Omni 40mm eyepiece with a cheap and unnamed 2x Barlow. The view was acceptable but still lose some brightness in part because the Barlow optics. I could see nice detail inside the cluster and resolved some stars inside but M4 compared with others like M5 and M3 which still look a little loose and also lack brightness.

Some details become evident with averted view like darker and more condensed areas inside the cluster and also some stars inside the core that appeared to be lined up at the equator of the core.

I processed the sketch with Photoshop trying to conserve as much of the original sketch, but I washed out the image a bit to simulate as much as possible the view at the eyepiece.
It is always nice that with a moderately dark sky and good optical equipment, one can see amazing stuff like this among the stars.

Clear and dark skies,


Edited by Jennifer Steinberg (editor in chief)