For me it was M57 (ring nebula). I spend a good 20 to 30 minutes trying to find that thing. My first time observing it I didn't realize it was going to be so tiny in the sky. I figured it'd be moderate sized and somewhere along the same magnitude as the orion nebula so I must've passed over it several times. When I finally found it I had my girlfriend come and take a look and she seemed confused and had no idea what I was looking at and then when she spotted it she was just like...ummm, ok...cool, i guess? And went back to doing her thing.

Years ago I observed over half of the objects on the Herschel 400 list using a 17" f/15 classical Cassegrain housed in a dome at the Astronomical Society of Harrisburg's Naylor Observatory.  (I observed the remainder of the list with a number of other telescopes.)  The 17" has a maximum true field of view of only 26 arc minutes.  Going from a 5" f/5 finder scope with a large field of view and no reticle eyepiece to the tiny TFOV of the Cassegrain (and the small dome shutter opening) while star-hopping was a bit of a challenge at times.

I've run into quite a few DSOs over the years where it was not difficult to locate their correct positions but to actually see the objects was very difficult, even with extremely dark skies and very large apertures (up to 32").  These include the gravitationally lensed quasar QSO 2237+0305 (Einstein's Cross), the Haro-Herbig object known as Gyulbudaghian's Nebula (HH215 and GM 1-29), and NGC 1554/5 (Hind's Variable Nebula).  Seeing B33 (the Horsehead Nebula) is child's play compared to Sh2-273 (the Cone Nebula). 

One H400 galaxy, NGC 6118 in Serpens, was completely invisible even with the 17" and a friend's unique 20" f/10 classical Cassegrain at a private observatory with somewhat darker skies.  I was finally able to log NGC 6118, which is often considered to be the most difficult object on the list, using Phil Harrington's venerable 8" Criterion Newtonian under the much darker skies at Stellafane.

Dave Mitsky

Dave,

With all your wide experience in using just about every telescope type there is, do you have one favorite one you used, no matter what you were able to see or not see?

It's very difficult to choose just one due to all the variables involved.  Some of the very best telescopes that I've used include a friend's 7" f/13.4 Questar Titanium Maksutov-Cassegrain, a friend's 206mm f/7.9 Astro-Physics Starfire apochromatic refractor (Roland Christen made only a handful of the 8" Starfires - the OTAs, which originally cost $12,500, fetch incredible sums nowadays on the used market), a 10" APM (?) achromatic refractor with a Chromacor, several Mag 1 Instrument Portaball Newtonians (8, 10, and 12.5"), an 11" D & G Optical achromat, the 20" f/10 classical Cassegrain previously mentioned, the 24" achromatic refractors at the Sproul Observatory and the Lowell Observatory, a friend's 32" f/4 ATM goto Dob, and Tom Clark's original 36" f/5 Yard Scope.  (I once had a look through a 36" Obsession but the conditions weren't too good and the owner was using an eyepiece that produced far too large an exit pupil.)  

Other notable telescopes that I've observed with include a few 6 and 7.1" A-P apochromats, a 6" Takahashi apochromat, an 8" f/15 D & G Optical achromat, an 8" f/9 APM achromat, a number of excellent Starmaster (14.5, 20 and 24") and Obsession (15, 18, 20, and 25") Dobs, a 22" Telekit Dob, two 28" Dobs, and several 30" Dobs (one being a Tectron and the other two ATMs).  I've also used many optically excellent ATM telescopes including Tri-Schieflspiegler reflectors, a Gregorian reflector, Herschelian reflectors, a Ritchey-Chretien Cassegrain, and other oddball designs at Stellafane over the years.

If I had to choose one small rich-field telescope it would be a 127mm f/5.2 Tele Vue-NP127is, one large apochromatic refractor it would be a used 206mm f/7.9 A-P Starfire or perhaps a 229mm f/9 TMB, one small Newtonian it would be a 10" Portaball, one small MNT it would be a used  5.7" f/6.5 HD-145 Peter Ceravolo Maksutov-Newtonian, one large MCT it would be a used 10" f/14.6 Astro-Physics High-Resolution Maksutov-Cassegrain, and one large Dobsonian it would be a 20" f/3.7 Starmaster Sky Tracker Dob. 

Alright, if I had to choose one favorite scope in terms of adequate aperture and ease of use (without imaging in mind) it would be a 12.5" f/5 Portaball.

Dave Mitsky

I appreciate the response and you certainly have viewed through a wide variety of scopes.

It al depends on the scope I was using.

With my 6" dob it was finding IC 289 as part of completing the RASC's 110 Finest NGC list using only a 6" scope. (funny how it's an IC on an NGC list)

With the 25" it is probably Hickson Galaxy Group 50. (the toughest of those groups) It was also because of the man handling required to pointing that big scope on a manual Eq right at the zenith. This means standing at the very top of an 8 foot ladder and leaning.

 With my 12.5" dob it is either the Draco Dwarf Galaxy (for it's dimness) or NGC 6302 (Bug Nebula) due to the fact that from my location (latitude) it is scraping the horizon. I guess NGC 1049 also (a Globular Cluster in the Dwarf Fornax Galaxy) because it is so low to the horizon.

The list is actually long because almost every time I go out I like to pick up as least one challenge object. It can actually be as simple as finding something when at a bright location.

Bill