M92 – In the Shadow of a Giant 

When we point our telescopes toward the constellation Hercules, our eyes almost automatically drift to M13. However, just a few degrees away lies M92 (NGC 6341)—an object that in many ways surpasses its famous neighbor. It is brighter at its center and significantly older.

A Cosmic Senior: 14 Billion Years Old

M92 is one of the oldest known globular clusters in the Milky Way. Its age is estimated at approximately 14.2 billion years (with an error margin of $\pm 1.2$ billion). This means M92 formed almost at the same time as the Universe itself.

• Mass: Approximately 3.3×105M⊙​ (solar masses).

• Metallicity: It is extremely poor in “metals” (elements heavier than helium), confirming its archaic origin.

Astrophotography Challenge: Resolving the Core

Unlike M13, M92 is an Oosterhoff II type cluster, which translates to a very dense and bright core.

1. Dynamic Range: The main issue is avoiding “blowing out” the center of the cluster. Instead of one long exposure, consider using an HDR technique or simply shortening exposure times while increasing the number of frames.

2. Image Scale: To resolve individual stars in the center, you need a long focal length (above 1000 mm) and excellent seeing.

3. Star Colors: Pay attention to the colors—old, yellow, and red giants dominate, but a keen eye will also spot “blue stragglers.”

 

Source: https://en.wikipedia.org/wiki/Messier_92

Photographs taken on March 2019.

• Stack: APP (7 best frames),
• Processing: GIMP v2.10.14 + add-ons (Linux),
• Lights: 7 x 88[s], ISO-1000; 30.3.2019,
• Flats: 22 ISO-1000; 02.8.2019,
• Bias: 20 ISO-1000; 02.8.2019