For the past few months while watching T Corona Borealis, I didn’t realize there was a potential “observable galaxy” using a 10-inch telescope” and fairly close to the novae star:  But, what about a 10-inch from a magnitude ~4.7 NELM location. (?)  However, due to the “high-surface brightness” it just might be possible, but very doubtful.  

The following information from the “Observing Handbook and Catalog of Deep-Sky Objects” by Christian Luginbuhl and Brian Skiff:  

“…galaxy is very small and unconcentrated, but of high surface brightness.  In 25 cm it is circular, about 35 arc second diameter, with a faintly granular texture.” L&S

Interesting to note: This galaxy is not listed in either the Herschel-400 or the H-2 lists.  I’m wondering if it would be more difficult than galaxy NGC 6118: Which is considered by “most all” amateurs to be the most difficult object in the Herschel-400 list. This galaxy (NGC 6118) was “very, very difficult” for me from my suburban backyard, taking me several observing sessions over a couple years.

Note: For those with a 12-inch telescope, galaxy NGC 5961 can be observed using a 12-inch telescope. This is the second of only two deep-sky objects listed in the Luginbuhl and Skiff Observing Handbook.

Galaxy NGC 5961: “Though it is a small moderately faint object for 30 cm, this galaxy has a high surface brightness.” L&S

If I have a very clear night with excellent transparency, I might give NGC 5958 a try with my 10-inch f/4.5 EQ Newtonian. A clear and transparent night during the summer months is very rare for me, observing from the foothills of North Carolina. Due to increasing light pollution and glow on my best nights I can hardly achieve ~4.7 in a winter sky!

What is a magnitude ~4.7 NELM (naked eye limiting magnitude) and how was it derived?

This is the longtime system used by many “mostly” visual observers, using the stars of the little dipper to determine the faintest star that can be seen naked eye.

I learned this from an Edmund Scientific (Sam Brown books) many years ago, and have been using the NELM system for more than 40 years. However, since the sky glow from the horizons is growing from light pollution, I sometimes (on nights) for reasons might add 1/2 magnitude to my NELM near the zenith.

Bortle scale chart:

https://rogerivester.com/2023/10/19/light-pollution-is-increasing-everywhere-what-is-the-bortle-scale-how-to-use-the-following-chart-to-determine-how-bright-your-site-is-without-all-of-the-science-and-calculations/

My backyard Bortle scale number is ~6.5-7.0 which has increased over the past 40 years, as most all backyards in America.

The Bortle scale puts my (NELM) naked eye limiting magnitude at about 4.7-4.8 on a good night, which corresponds pretty close to the Bortle scale.

However, during the summer months, with high-humidity, heat and haze, my NELM sometimes will hover around 4.0 or even less! Defintely not good nights to attempt faint galaxies or nebulae, but can be excellent nights for viewing double and multiple stars.

I’ll never forget the days of growing up in the country and seeing the Milky Way glowing overhead, and extending “seemingly” almost to the southern horizon.

Galaxy NGC 5958 in Corona Borealis:  Wikisky.org snapshot as following: