Over the past year, I’ve discussed observing difficult Messier objects using a small telescope, with a number of amateurs.  Seems that everyone has a list of their most most difficult Messier’s, but most all agree with M74, M76, M97, M101 and M109.  However, we know that the observer, location, and light pollution are all important factors. 

Using a humble 4.5-inch f/8 Newtonian that a friend gave me last year, I observed eight Messier objects from my suburban backyard on Friday night (March 20th.)  The transparency was poor, due to incredible amounts of pollen in the air. The Crab Nebula was easy and bright, but couldn’t see galaxy M109. I decided not to use my 80 mm f/5 refractor due to the poor transparency.

I will “not likely be able to see many of the objects” using the small refractor from my suburban backyard with a Bortle 6.5 sky, and sometimes worse! I’m not even sure about my success with the reflector.

I’ve observed all of the Messier’s many times, but and using a 10-inch f/4.5 Newtonian, from my suburban backyard with ease. And after 15 years (185 consecutive months) of the Observer’s Challenge report, I needed a challenge, but not too difficult, or time consuming. I wanted to have a more relaxed observing project, using two small “economy” telescopes to observe the entire Messier catalog…if possible.

I’ll be taking my time without a completion date, and will observe only when I have the time, or feel like observing. This will not be a priority in my life, as I have so many other things I like to do. The project will not be likely completed this year (2025) but will carryover into 2026.

The fun of this project, or any endeavor in life is the journey, and not the destination.

The two telescopes I plan to use for my Messier quest will be an 80 mm f/5 achromat and a 4.5-inch f/8 Newtonian. It’s interesting to note again….both telescopes were given to me. 🙂

The 80 mm f/5 achromat was a birthday gift from my son…making it a special telescope. I use an amici prism diagonal for a right angle correct image view. I want my pencil sketches to be scientifically correct, as they appear in the sky and not mirror reversed.

I like the thought of using a humble refractor for my Messier quest and not an expensive apochromatic, which can sell for as much as $1,000, or even more!

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.

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.

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