Selected excerpts as following from an article by Jay Reynolds, regarding two of the most difficult objects of the Herschel 400 list. The telescope used was a Vixen 55 mm f/8 Fluorite refractor. 

NGC 6118 (Serpens) and open cluster NGC 6540 (Sagittarius).  If you are considering taking on the Herschel-400 list.  If can see these two objects…it’s very likely you will be able to see all of the other 398 objects. This is contingent on having an unobstructed sky, and with a minimum of light pollution 

During the winter of 1994, I began my effort to see as many of the H-400 objects as possible from my suburban backyard.  Due to light pollution, trees and obstructions, I knew it would be impossible for me to see the entire list.  I started in earnest and dedicated “the majority of my observing time” for about two years to the list. Many of the small open clusters gave me a problem and were difficult to identify.  I called many of these clusters “non-existent” in my notes.    

I made notes of all the objects, and sometimes with a pencil sketch of those worthy of a sketch. However, after ~250 Herschel-400 objects and two years, I called it quits.  What a relief, as I could now resume by personal survey of the sky, which would (to-date) be about 2,000 plus deep-sky objects. 

Roger Ivester 

Now some information from the original article by Jay Reynolds Freeman:

     “Seduced by exquisite optics and compact size, I bought a used Vixen 55 mm f/8 refractor, whose objective used the optical material fluorite, in April, 1998. To replace by attitude what it lacked in size, I repainted the tube, and named the telescope Refractor Red, for its new, fluorescent color. I mounted it on an altazimuth mounting from an 80 mm refractor, then set out in pursuit of all the Messier objects. I anticipated the search would not be difficult, for three of my previous Messier surveys had been with less aperture. So I decided to try something harder, too — the Astronomical League’s “Herschel 400″ list. That modern selection from the brighter objects discovered by Sir William Herschel, would be challenging.” 

“…As word of my project got around, curious fellow observers asked whether I had tried their favorite difficult Herschel-400 targets. I kept hearing about NGC 6118 and NGC 6540. The former is an obliquely viewed low surface brightness spiral galaxy in eastern Serpens Caput,the latter a little cluster in Sagittarius. One June night, I looked for both from Fremont Peak State Park, a popular observing site near San Juan Bautista, California.” 

“Uncommonly good transparency and an incomplete fog layer on the coastal plain below made the high sky quite dark. The North American Nebula was easy with the naked eye: I could detect the “Gulf of Mexico”within it. I looked for NGC 6118 with two eyepieces, alternating between my 12 mm Brandon and a 20 mm Meade Research Grade Erfle, which gave 22x and a 2.5 mm exit pupil.” 

“With each eyepiece, I saw a faint, diffuse, and not very centrally concentrated glow, popping in and out at the limit of averted vision, at the charted position. Jiggling the telescope, or moving it slightly with the slow motions, helped a bit. The glow was detectable only ten or twenty percent of the time, but it kept reappearing at the same place. Since I did not see similar fluctuations of intensity at random places in the field, I logged it. That was the toughest object in my Herschel-400 survey with Refractor Red.”

“Its difficulty might stem from not having nearly as large or bright a center as most other galaxies. A bright core seems to draw the eye, and to give the brain a reference point for locating the fainter, outer periphery of the object. Since I had an equally good view at 22x and 37x, I suspect that a magnification between those values might have best suited NGC 6118 that night.” 

“Unfortunately, I had not brought a suitable eyepiece. Herschel described NGC 6540 as a faint, sparse, relatively small open cluster, yet what _Millennium_Star_Atlas_ plots is a ten arc-minute globular. Using the 12 mm Brandon, I saw a six or seven arc-minute unresolved circular glow, just barely brighter than the background of the Sagittarius Milky Way, with a smaller, brighter core superimposed.” 

…NGC 6540, was easier than NGC 6118. 

This entry was posted on March 13, 2026 at 12:22 pm and is filed under Roger's Articles, Virgo Diamond: Faint Five Star Asterism. You can subscribe via RSS 2.0 feed to this post's comments. Responses are currently closed, but you can comment below, or link to this permanent URL from your own site.