Deep-Sky Observing And Other

Over the past year, I’ve discussed observing difficult Messier objects using a small telescope, with a number of amateurs.  It would seem that everyone has a list of their most difficult Messier’s, but all agree with M74, M76, M97, M101 and M109. However, we know that the observer, location, and light pollution are all important factors. I rate my backyard with a Bortle Scale of ~6.5 on an average.

The two telescopes I plan to use for my Messier quest (of only the most difficult objects) will be an economy 80 mm f/5 achromat and a 4.5-inch f/8 Newtonian. My son gave me the refractor telescope for a birthday present…so this is and will always be a special telescope.

The 4.5-inch Newtonian was given to me by a friend. If the telescope had not been in new condition, I wouldn’t have taken it. However, the original mount was so flimsy, and weak…I discarded it, almost immediately.

My largest telescope after the sale of my 10-inch f/4.5 EQ (earlier this year February 2026) is a 6-inch f/6 Newtonian. The 10-inch had just became too heavy and difficult to take out and bring back in…especially for short observing sessions.

I purchased the 10-inch in February 1992, and logged over 2,000 hours at the eyepiece, but it was just time for another serious amateur to have this telescope.

Expert visual observers, Tony Flanders and Jay Reynolds Freeman share some interesting information regarding the more difficult Messier objects, as following. Remember, Jay saw all of the Herschel 400 objects using a 55 mm Vixen f/8 Fluorite refractor! 

Roger invited me to post my own personal list of the five hardest, and on the whole I find it’s really impossible to say. All the Messier objects are bright and obvious to an experienced observer with a 90-mm scope under dark skies. Once you start to increase the level of light pollution and decrease the aperture, they become harder in varying degrees depending on the precise level of skyglow, the particular instrument, and my own mood and inclination. Tony Flanders

For what it’s worth, I looked over my Urban/Suburban Messier Guide, and here are the objects I was unable to see through my 70-mm refractor from my local city park, with skyglow probably a tad worse than 18.0 mpsas:

M20, M26, M59, M61, M68, M73, M74, M76, M83, M90, M91, M95, M98, M99, M100, M101, M107, M108, M109

I was able to see M97 with a filter, but not without one. A filter makes a huge difference for this object, and somewhat less so for M20.

Of these, I’m sure M20, M68, and M83 were hard only because they’re far south, and therefore very low from my latitude of 42N. I’m a little surprised that the open cluster M26 is on my can’t-see list; maybe I should have tried harder.

Of the listed galaxies, I’d say that M74 and M91 are almost certainly intrinsically hardest, ignoring issues with latitude. I’ve also always had problems with M109, due to the combination of small size and fairly low surface brightness, and likely also proximity to bright Gamma UMa (Phecda).

M101 is challenging under bright skies due to its extremely faint core, but even a slight improvement in skyglow makes it relatively easy due to its huge size. M76 is challenging in very small instruments and in conventional binoculars due to its tiny size, but becomes quite easy as I use larger apertures even under very bright skies.

Tony Flanders 

M74 and M76 have given me trouble occasionally. Jay Reynolds Freeman

My problem with M74 is that it has low surface brightness — I have found it with a 7×50 binocular in dark sky, but it becomes more difficult in brighter conditions. More aperture helps — it was no problem in a 12.5 inch Newtonian when observing from a location in the peninsular suburbs of San Francisco.

M76 is simply small in angular size, which makes it difficult for me to verify as non-stellar with low magnification, such as when observed with binoculars. Yet I have found it in a 50 mm refractor with a little more magnification, I think I recall using 24x.

Jay Reynolds Freeman

This entry was posted on March 24, 2026 at 2:36 pm and is filed under Observing The Messier's With A Small Telescope. You can subscribe via RSS 2.0 feed to this post's comments. Both comments and pings are currently closed.