Terzan 11 Globular Cluster in Sagittarius
by Vern on Sep.12, 2007, under Astronomy, Globular Cluster
The image below is of a faint globular cluster in Sagittarius called Terzan 11. Dark area surrounding cluster is probably caused by obscurring dust which extinguishes light from an area that is rich with Milky Way stars (compare to star field on the left). The globular is listed as magnitude 16.4 so it is a tough object even for large aperature scopes. Tough to guess the classification as it so faint. Location was confirmed with DSS POSS2 image. I should have posted this before but I mis-filed the images and didn’t come across them until this afternoon.
Images were taken at Fox Park in Wyoming on July 15, 2007 at 03:35 am MDT with a Celestron Nexstar 11 telescope, F3.3 focal reducer, and Stellacam II video Camera. Stellacam set at 14/14 gain, medium gamma, and 256 frame integration (8 sec). Registax4 used to dark subtract, flat field correct, align, stack, end brightness enhance 30 frames.
Sky was mostly clear, some high thin clouds, transparency generally quite good despite the high humidity 70%, dew on everything, temperature about 38°F, and no wind.
March 19th, 2009 on 2:31 pm
Hell Vern, great work! Its nice to see that these super faint globulars can be imaged with medium size scopes. No easy feat!!!
Again, great work.
Tony
August 22nd, 2009 on 8:34 am
By the way Terzan 11 is actually Terzan 5. Terzan 11 was mis identified…it was actually a rediscovery of Terzan 5. Great work with and 11 inch scope!!!
August 25th, 2009 on 6:04 am
By the way, Terzan 12 then became Terzan 11…so be careful with some of the older sky maps out there as they can sometimes be identified incorrectly.
August 25th, 2009 on 12:16 pm
You might take a look at Barbara Wilson’s write up regarding Terzan 11 at http://www.astronomy-mall.com/Adventures.In.Deep.Space/obscure.htm She discusses the confusion regarding this object as well.
I originally searched for Terzan 11 on the DSS – ‘The Digitized Sky Survey’ website and retrieved an image of the region. I used it to confirm that the star field matched with what I was seeing on the monitor when I obtained the image above. I repeated that check this morning using a DSS image of the region. The DSS coordinates for Terzan 11 match those that Barbara quotes. These are also the coordinates for Terzan 11 used in the Astroleague’s Globular cluster book.
Based on this, I still believe the image is correctly labeled as Terzan 11.
As I understand it:
The globular which was named Terzan 11 was found to be the same as Terzan 5, so it was renamed Terzan 5.
Terzan 12 was then renamed to be Terzan 11. IE that is the globular pictured above, if I follow Barbara’s article correctly.