Deep-Sky Objects (DSOs)
The Messier Catalog
Many lists of deep-sky objects have been compiled by experienced observers in the past. Most scope users begin deep sky observing with one of the
very first of such lists - the Messier objects. (Click here for interesting information on Charles Messier and his famous list.) They represent a collection of objects that is a favorite of amateur astronomers because they tend to be the brightest deep-sky objects in the sky (due to the optical limitations of scopes like the ones Messier used in the late 1700s). The Messier objects are present in the databases of all GoTo scopes, and O’Meara’s Messier Objects book is particularly helpful when you’re getting started observing them.
The NGC and IC Catalogs
In the late 1800’s an astronomer named J. L. E. Dreyer compiled a much longer list of deep-sky objects based upon the much-improved capabilities of
telescopes at that time. He called his list the New General Catalog of Nebulae and Clusters of Stars, published in 1888 and commonly referred to as the NGC catalog.
(The NGC does include the Messier objects but those are more commonly referred to by their Messier numbers rather than their NGC numbers.) In 1895 Dreyer subsequently published a follow-on Index Catalog of even more objects, followed by a second Index Catalog in
1908; taken together these two lists are commonly referred to as the IC catalog. Astronomers at the University of Arizona updated the NGC list in the late 1970s and published the Revised New General Catalog of
Nonstellar Astronomical Objects. Most all GoTo scopes include the Messier, Revised NGC, and IC catalogs in their computer databases for automatic go-to capability.
Note that the NGC objects were originally discovered visually (rather than photographically) so you have a good chance of seeing them with your scope, although a galaxy or nebula with a
magnitude of 11 or dimmer can be tough to see with an 8” scope.
The IC catalog objects with numbers lower than IC number 1530 were discovered visually as well, so you also have a good chance of seeing them with your scope, but the IC catalog objects numbered 1530 and above were discovered photographically so they can be difficult to detect in smaller amateur scopes.
Since some of the most beautiful objects in the NGC and IC catalogs were overlooked by Messier or not visible to him, other observer organizations have compiled lists of the “best
non-Messier objects”. I have identified several of these lists lower on this page.
The Caldwell List
(Diatribe follows <grin>:) A non-Messier object list was compiled by the noted British amateur astronomy observer and author Sir Patrick Moore, in
cooperation with the editors of Sky & Telescope magazine in December, 1995. To avoid confusion with the Messier objects (which are referred to by M-numbers) he called this new list the Caldwell Catalog. Despite this lofty pedigree, the Caldwell object list is basically silly. (Click here for an explanation as to why this is so.) When you want to move past the Messier objects with your scope, try the other lists on this page. If you really want to know about the Caldwell list, the Hawiian Astronomical Society has posted a list of the Caldwell objects, and David Ratledge’s Virtual Home also has information on observing the Caldwell Catalog. (Diatribe ends. <grin>)
The Ultima 2000 Non-Stellar List
When Celestron created their first GoTo scope, the U2K, they out-sourced the development of the U2K's computer databases to Tangent Instruments
(Ventura, CA) because they didn’t have an in-house software capability at that time. As part of the database development for the U2K, Tangent created a “Non-Stellar Object List”.
This list comprises a group of 661 DSOs that are not contained in the NGC or IC lists described above, but are within reach of amateur scopes (although you'll be reaching pretty far for a few of them with an 8" scope <grin>). A few of the most famous objects (the Coathanger cluster or the Horsehead nebula) are contained within modern GoTo scope databases but the vast majority of them are not, so the Non-Stellar database is unique, excellent, and highly recommended. I have a copy of that list, which includes some corrections done by me and by Michael Swanson (thanks, Michael!), that you can download as an Excel spreadsheet here:
Other non-NGC object lists are described farther down on this page.
Stars themselves are also lovely objects to observe and double stars, especially those of contrasting colors, are particularly enjoyable. One of the first
lists of double stars was compiled by F. G. Wilhelm Struve in 1827, and more stars were subsequently added by him and by his son, Otto Wilhelm Struve.
There are now much larger catalogs of double/multiple stars but the Struve doubles tend to be the ones most observed by amateurs because they are the brightest (again due to the more limited optical capabilities of Struve’s time). Struve’s double stars are commonly designated by the notation STF (Struve The Father) followed by a number up to four digits. (In pre-computer days the designation was usually the greek letter sigma, but since the greek letters are not part of the ASCII character set for computer keyboards, STF ultimately became the designation more convenient for astronomers to use.) Double stars suitable for amateur telescopes are listed in many of the observing books I describe. Or, you can download a list. If you are just starting out observing try the “best of” double star lists from the Astronomy League or the Belmont Society. If you become really interested
in double stars you will want the extensive double star list published by the Saguaro Astronomy Club. It includes almost 12,000 double stars with
their specific data, and cross-references on their names to other designations such as R. G. Aitken's Double Star Catalog (ADS number); in fact, it is the only really complete reference database of double stars for amateur observers, and represents a huge amount of work by SAC members. SAC offers this list as a group of database files. I have converted it into an Excel spreadsheet - to download that spreadsheet, click on the link below:
SAC Double Star Catalog - Excel.zip
If you become interested in observing variable stars, you will eventually want to know more about any specific one (such as the star’s actual period of variability or brightness range
from maximum to minimum) than is typically given in the telescope manufacturers’ databases or other observing lists.
You can download the General Catalog of Variable Stars from the Institute of Astronomy of the Russian Academy of Sciences' Centre for Astronomical Data.
This is an extraordinarily complete variable star database, but it is a huge file and is in a general ASCII data format that you then need to import into a spreadsheet or database to use. I have converted it
into an Excel spreadsheet and eliminated many of the rarely-used data columns - for example, the GCVS includes RA and Dec for each star for both Epoch 1950 and Epoch 2000 and I eliminated the Epoch 1950 data.
My version is a 2 MB zipped Excel spreadsheet - to download that spreadsheet, click on the link below:
General Catalog of Variable Stars - TLKs - Data Reduced.zip
However, note that the GCVS includes almost 39,000 variable stars! Should you not be willing to observe each of them one at a time <grin>, here is my list of 90
interesting variable stars in the northern hemisphere:
TLKs 90 Interesting Northern Hemisphere Variable Stars - xls.zip
Lists of Non-Stellar Objects You Can Download
Aside from the Messier (and Caldwell) lists, the NGC and IC lists contain thousands of
objects, and there are thousands more stars in a GoTo computer’s database as well. Some good places to start to sort through all these possibilities are to download the SAA 100 Best Non-Messier Objects List, and the Saguaro Astronomy Club’s 110 Best of the NGC list, or the RASC's Finest NGC Objects List published by the Royal Astronomy Society of Canada. Some additional non-Messier object lists have been proposed by observers who are members of MAPUG (the Meade Advanced Products Users Group), who use Meade LX scopes. Go to the MAPUG archives site and download their lists, particularly the “105 Finest Objects” list. If you have a U2K instead of an LX200, I took the MAPUG “105 Finest Objects” list and revised it with the U2K’s keypad numbers rather than the LX200’s. It is available as an Excel file for your download here:
105 Finest Objects - MAPUG - U2K.zip
Another set of “finest objects” lists is at Jerry Lodriguss’ Catching the Light web site. Also, The Albuquerque Astronomical Society (TAAS) publishes a good list of 200 deep-sky objects for observing, which they call the TAAS200 list. They have it available as a PDF file, or an Excel spreadsheet which you can also download here:
TAAS 200 xls.zip
Many fine objects are not listed in the NGC catalog. The Saguaro Astronomy Club has created a list of “The Best Deep Sky Objects Not in the NGC”. They post it as a text file on their Web site; you can download it here as a zipped Excel spreadsheet file (note that this list includes deep-sky objects that will be tough to see with an 8” scope depending on your sky conditions - to avoid frustration check the listed magnitude of each object):
SAC Best of the Non-NGC List.zip
One of the more complete observing lists I’ve seen was created by Vic Menard and includes 400 objects. It was published in the Summer, 2001 issue of Amateur Astronomy. Vic
graciously sent me his original digital file, and it is available for download here as an Excel spreadsheet:
Vic Menard 400 List.zip
Be sure to look at the spreadsheet’s second worksheet, called “Notes” for an explanation of some of the columns.
Early in my use of the U2K I created an observing list spreadsheet for myself.
I’ve continued to refine it, and I’ve posted it here for your use. It represents many hours of work, combines objects from a wide range of sources (including the sources I discussed above) and lists them by constellation, with the NexStar’s SAO numbers as well as the U2K’s digital catalog numbers, as an Excel spreadsheet. It contains over 1200 objects, and along with deep-sky objects it includes colored stars, colored double stars, and variable stars, which are often omitted from observing lists but shouldn’t be. Download it here:
TLK’s 1200 Object Viewing List xls.zip
(Note that with some exceptions this list does not include objects with magnitudes fainter than 11.5 or so; with an 8” scope you need really dark skies and experience in observing to see
those. Also, the list includes objects from the U2K’s Non-Stellar Objects database - NexStar owners won’t be able to readily enter these in the NexStar’s hand controller since Celestron didn’t include that
list for the NexStar, but they can insert the RA and Dec of each object to drive the scope to them.)
The Students for the Exploration and Development of Space (SEDS) has a Deep Sky Collections and Catalogs web page that has a compendium of a lot of the deep-sky object lists that have been published over the years. It’s one of the better “list of lists” I’ve seen on this topic.
The above lists use acronyms and terminology with which you may not be familiar.
If you want to learn about the terminology used in amateur observing and celestial object databases, go to the Glossaries page on this web site.
If you have a NexStar GPS, you can make your own NexStar observing list
If you have a NexStar GPS scope, you can create your own observing list by downloading the NexStar
catalog files from Michael Swanson’s NexStar Resource Site. Or, you can download his excellent NSOL (NexStar Observer List) software, which contains
the NexStar databases, allows you to create customized observing lists, and also drive your scope to them if you connect your NexStar to a computer.
If you have a U2K, you can make your own U2K observing list
Your can create your own observing list from the objects that the U2K has built into its memory.
The databases in the U2K’s memory are available as Excel spreadsheets, although not from Celestron directly (a bit of a sore point with many of us U2K owners). Tom Stamm has many of the U2K databases available in Excel format on his Web sight, The Macintosh/Celestron Ultima 2000 Information Page, but he doesn’t include all of them and because he was specifically interested in programming his
Mac to control the U2K he only presents the bare U2K databases.
I took some of the spreadsheets he has, got the Non-Stellar object database from Celestron (available in hard copy only, which required scanning it in to an OCR application), and took them
one step farther by adding a field that includes the name of the constellation each object is in. This Excel spreadsheet includes the U2K list of Stellar Objects, Non-Stellar Objects (uncorrected - see above for a corrected version), and Messier Objects and is available for your download here:
Download this file, open it in Excel, and sort the objects in each list by constellation. Then you can combine the objects in each list, by constellation, and create a viewing list by
constellation for your use.
This sounds more complicated than (but just as laborious as) it really is, and the end result is a set of pages that you can use over many nights to guide you on where to aim the U2K. (That’s how I created the “TLK’s 1200 Object Viewing List” file above.) I also recommend that you take notes on what you see - one of the real joys of owning a scope is sharing sky objects with your family and friends, and your notes will help you return to those objects (since they may not have as much patience as you do, in wandering around the night sky.)
Here is a file with the rest of Tom Stamm’s original set of Excel files (the ones not included in my file just above), which include Celestron’s Index Catalog (IC), Revised NGC, European
Southern Observatory (E), Uppsala General Catalog (U), Named Objects and Named Star lists for the U2K:
U2KCatXL - TLKs.zip
In general these remaining lists can be sorted by constellation since the constellation name is the first word in the description field.
There are two observing areas that can provide a challenge to beginning telescope users: Sagittarius/ Scorpius and the Horsehead Nebula in Orion. A large number of
Messier Objects are in Sagittarius and Scorpius, which for most northern latitudes are visible only in the summer but are low in the southern sky at that time. Aside from Antares there aren’t many stars in the
U2K’s Alignment Star list near these constellations. However the U2K’s Star catalog (ST) includes most of the stars in these constellations, and as an aid in achieving good alignment I’ve created a JPEG file
showing them with the ST catalog stars identified. Download this file:
Sagittarius & Scorpius - U2K.zip
The Horsehead nebula in Orion can be very difficult to observe. To help you get your bearings for the Horsehead here is a Microsoft Powerpoint slide that shows that region:
Horsehead Area - Powerpoint.zip
Some Notes on the U2K’s Databases
The U2K’s databases contain some idiosyncrasies of which you should be aware if you own a U2K scope. Click here for an explanation of them.
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