I expect that everybody approaches a night of observing in a slightly different manner; however, I think we all discover that to get the most out of it, it's important to plan ahead. In this article I would like to share my approaches to finding really dim, obscure objects hiding in areas of the sky with no reference stars.

It took me quite a few years, but I worked my way through the Messier list and completed it several years ago using my 41/2" reflector on a Dobsonian mount with a little help from one of the club's 6" reflectors. Many of these object, after I "discovered" them for the first time, have been included in my repertoire so I can point them out to others.

After my 10" Dob became operational, I realized I needed new goals, so I started on the Herschel 400 list. Although most of the objects on this list are more challenging than those in Messier's list, there is a recurring problem-finding the really tough objects.

What makes an object really tough? There are two factors that contribute: The ease of finding the correct location and the ease of actually seeing the object. However, the first, finding the correct location, can be the real challenge. Here are some definitions I invented to describe the difficulty of finding an object:

Very easy: The object's location is easy to find with the unaided eye and the object is visible in the finder scope (or unaided eyes).

Easy: The object's location is easy to find with the unaided eye and the object is readily visible in a low power scan.

Moderately difficult: You need to star hop to the location using the finder scope, but the object is readily visible with low power

Difficult: There isn't an easy star hop to the location, but the object is readily visible with low power.

Really Tough: There isn't an easy star hop to the location, you're not sure you're looking in the right spot, you need moderate power and averted vision to see it, and you're not sure if you are seeing the object or imagining it.

Here are some examples: The Orion Nebula (M42) and the Pleiades (M45) are very easy because you can see them with unaided eyes. The Andromeda Galaxy (M31), once you know where to look, is very easy. It can be seen with unaided eyes from a moderately dark site like Mickie Gordon, but it sure doesn't look like the pictures!

I rate M32, a companion galaxy to M31, as easy. Its proximity to M31 makes it easy to find and it can be seen in 10x50 binoculars from a moderately dark site. However, it looks like a star at low magnification and when conditions are poor.

M110 is moderately difficult. Under very dark skies and with good transparency it can be seen with averted vision in 10x50 binoculars if you know what you're looking for and where to look. However, it's visible from Mickie Gordon in a small scope when the transparency is very good. I often use this object as a transparency test. Some nights at Mickie Gordon it's barely visible in my 10".

M40 is actually a difficult object, not because it's hard to see, but because it's not recognizable. It's a double star, and without accurate and detailed charts, you won't be sure you've found it. In a small scope, M101 is really tough object. It's quite large and has a very low surface brightness. You need to be sure you're looking in the right place and the conditions have to be very good to make it out. Here are some things I do to find the toughies.

I use Sky Atlas 2000 and Uranometria. Sky Atlas shows stars visible in my 10x50 binoculars and 8x50 finder scope. Uranometria shows dimmer stars and is excellent for star hopping with a low power eyepiece.

I prepare for an observing session by developing a list of objects sorted by chart. This works just fine on most objects, but it isn't adequate preparation for the tough ones. If I can't find an object first time out I do some more homework to prepare for the next session.

If I've been unable to find an object, or if I expect one to be difficult (e.g., galaxies in the Virgo cluster), then I use my planetarium program, SkyChart III, to prepare more detailed charts. SkyChart III can show stars to magnitude 14 which is more than I need for my 10".

The Digitized Sky Survey (DSS) is an outstanding internet resource that lets me view an object and see what it looks like. Although the detail in the images aren't visible in my scope, I can see the shape and exact location among the stars. I also use the DSS after a session to look at an object if I was uncertain of my observations. Another excellent online source for object information is "The Interactive NGC Catalogue Online." This source provides information on deep sky objects (not just by NGC number) and will get a DSS for objects of interest.

It turns out there is another reason that an object can be difficult to locate: Sometimes the charts are wrong! In particular, NGC 7023, an emission nebula surrounding a magnitude 7 star in Cepheus, is catalogued as a cluster with different coordinates in some references. I spent a considerable amount of time investigating this object. After my first attempt to view this object I couldn't really be sure I saw it. The star appeared to be flared, but subsequent review of the DSS makes me think it was larger. It is a Dfn, not a cluster. I received a nice note from Brent Archinal clarifying the catalogue problem after I related my efforts to research this object via the NOVAC e-mail list.

On my second attempt I spent a lot of time trying to decide if I could really see this object. My observations were 1) The central star appeared slightly "fatter" than it should - it didn't quite achieve a pinpoint focus, and 2) At 262x (16mm ep with a 2.8x barlow) there was a faint glow (viewable via averted vision) emanating from the central star and slightly elongated in the direction of a barely visible magnitude 14 star to the south. I could detect a dimmer section in the center of the glow. When I checked the DSS, the view matched the image very well. I was very happy. I spent a lot of time on this object and am very pleased to add it to my observed list.

The URL for the DSS is: http://skyview.gsfc.nasa.gov/cgi-bin/skvadvanced.pl.
The URL for The Interactive NGC Catalogue Online is: http://www.seds.org/~spider/ngc/ngc.html.