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What DSO catalogue do you use, and why?

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#1 Lipperhey


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Posted 09 September 2023 - 03:32 AM

Hi everyone! I'm new here.


These days I'm learning a lot about deep sky objects, so I checked all the catalogues about galaxies, nebulas and clusters. Why? Because I'm writing astronomy articles so I need good sources of information. I use Linux, so I try to find access to this information through a unix-like terminal.


The first interesting thing I'm seeing is that there are two main catalogues for software: SAC and OpenNGC. For this second one I have a CSV file with all the data, and even exists a script (PyOngc) to access this data using Python. That's cool. However, when I use SkyChart (Cartes-du-ciel), for example, I can choose SAC or NGC/IC; the first one shows more objects, while the second one needs to be complemented with other catalogues.


For example, if I want to see the Barnard 33 object I can separately check the dark nebulae catalogue. If I want to see the object LBN 954 it shows the number of the NGC catalogue (NGC 2023): that's because some objects are in both catalogues (LBN and NGC). That's not a problem but a bit confusing.


I wanted to classify DSO images by folders, however due to this "duplicity" I think I'm gonna use the same folder, indicating in the filename the main designations.


I also created som scripts using astroquery and SkyView to download FITS images in DSS and convert them to JPG. For most of the cases I can use the NGC or Messier designations. However I'm seeing that a combination of the Blue and Red bands is more close the color that we can see, so I should generate a CDS image in the R-B band; then I discovered how great is Aladin Sky Atlas. Oh well, this is another topic... Into Aladin I can search objects by most of the names, and it converts to coordinates in RA and Dec.


* I don't talk about the reviewed NGC in purpose. The same with Messier and Caldwell.

#2 therealdmt



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Posted 10 September 2023 - 11:22 AM

Hi, Lipperhey, and welcome!


No one else has replied, so I’ll try and give you some kind of an answer.


First, I can guess that the reason you’ve gotten no replies yet is that your question doesn’t fit so well in this forum, and following from that, that few if any who spend time here know the answers to most of your questions. The Beginners forum of Cloudy Nights is, per the forum description, "A place for new astronomers to ask visual observing or basic equipment questions and report their findings." In practice, that means questions like "What telescope should I buy?", "What next eyepiece should I get?", "Help, I can’t find M13", "Wow, I just saw Jupiter’s moons!", etc. You don’t indicate doing any visual observing but rather seem to be doing research.

There is an additional complication that you are asking questions related to Linux, which is somewhat of a non-standard operating system for general consumers. I’m not saying that nobody uses Linux or that there is anything wrong with Linux, but just that there’s less chance of bumping into someone here that uses it as opposed to Windows, the various Apple OSes or Android. 

Okay, moving on, I could look it up, but off the top of my head I have no idea what SAC is, and while the name OpenNGC is relatively self explanatory, I’d never heard of it until reading your post.


The first interesting thing I'm seeing is that there are two main catalogues for software: SAC and OpenNGC. For this second one I have a CSV file with all the data, and even exists a script (PyOngc) to access this data using Python. That's cool.

Huh? lol.gif


Sorry, we’re speaking different languages here smile.gif You’re not saying anything wrong, and I’ve heard of Python and know what a script is, and also there are certainly IT professionals among the forum members, but this isn’t stuff most people are casually familiar with nor is it within the typical issues encountered in visual observeration.


Moving on again, so you mention how one object might be identified under multiple catalogues. This can indeed be cornfusin. As you spend time reading, you’ll typically see that one identifier gets mentioned more than others, and that’s the one to go for. There’s no absolute rule on this but the general idea is that if the object is within the Messier catalogue, then the "M number" is used. For example, I see that the Andromeda Galaxy is NGC 224, but I don’t think I’ve ever heard or read it described that way — it’s always M31 (or, ‘the Andromeda Galaxy’). And if an object isn’t in the Messier catalogue but it has an NGC number, then the NGC is generally the designation used in preference to all others. For example, NGC 253 doesn’t have a Messier designation so it is typically referred to as I just did by its NGC designation in preference to various other possibilities like, for example, it’s PGC 2789 designation. Meanwhile, many popular objects like this will also have a common name or nickname, such as, in this case of NGC 253, the Sculptor Galaxy. Perhaps unfortunately, it also has another nickname, the Silver Dollar Galaxy, and even yet another(!), the Silver Coin Galaxy, so yeah, this can get confusing. But even NASA will often use these nicknames/common names in their outreach material. And finally, for amateur astronomy purposes, some like to use a Caldwell designation if there is one in preference to the longer strings of numbers in the NGC catalogue (there are well over seven thousand NGCs but only 109 Caldwell objects, so it’s easier to remember which Caldwell number refers to which object in the sky). The popular astronomy "planetarium" software Stellarium seems to use ‘Caldwell 65’ as its main reference for the Sculptor Galaxy (NGC 253), for example.


Regarding Barnard 33, this is a very difficult visual target (though certainly not impossible with dark skies and the right equipment), not a beginner’s target. It is easier as an astrophotography target, but this forum is for visual beginners.


Regarding LBN numbers, I’d never heard of such until reading your post (and may soon forget it again). I’m not saying that there is no value in it, and looking the LBN Catalog up and reading a bit about it just now, it does sound interesting (so thank you for bringing it up, actually — I just learned something new), but it’s not something most of us talk about every day (so, it’s at least somewhat obscure for general amateur astronomy).


Regarding your last paragraph, I’m back to mostly "Huh?", though I do know what you mean about red and blue bands. Not quite sure what you’re trying to do there though — it sounds like neither visual observing nor astrophotography, but rather a type of research that also might not exactly fit our scientific astronomy forums.


To wrap things up, my suggestion is to go outside and learn the constellations (yep, I wrote that), then get a telescope (perhaps preceded by binoculars, which is a good intermediate step and, like your naked eye constellation viewing, will be a tool you can continue to use the rest of your observing life) and see what kinds of things you can actually see with it. After that you might try some beginning imaging (and, as with your visual observing, take that as far as you wish). Meanwhile continue your reading and other research. Include among your reading the history of the Messier Catalogue (who made it, when, with whom and why) and the NGC Catalogue, among other catalogs and observing lists. As you spend time with the sky, your equipment and your research material, as well as with other amateur astronomers (including us here on Cloudy Nights), all will unfold before you. Eventually you’ll know well for yourself that, for example, Cr 82 is not typically called that, nor is it called NGC 2168, but rather M35, and more than that, you’ll know by heart its location on the western foot of the Castor twin of "The Twins" constellation Gemini, and you’ll know well how you can go from there through a string of wonderful open clusters as well as some smaller more obscure ones, right up into the heart of Auriga, the Charioteer, and the anti-center of our galaxy. You’ll know the famous Eskimo Nebula is nearby to the northeast, and that the bright star Castor above is actually a wonderful double star.

And even more than stuff like that, these things are actually beautiful. Not all views, not always, but on occasion some of these will burn themselves into your soul. And like that, many of these mind numbing alphanumeric designations will over time turn into real things that have become old friends to you smile.gif while others will be hazier memories of brief past encounters, and still others intruiging challenges yet to be tackled.


I hope the above is at least somewhat helpful. Best of luck with your journey

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#3 Jon Isaacs

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Posted 10 September 2023 - 11:44 AM

I will just add a few comments to those of therealdmt:


Visually, color in visible in only a few few deep sky objects. Color images are quite amazing but in a telescope, they will be grayscale and quite dim.


Apps like SkySafari Plus and Pro integrate many of the features you seem to be interested in all into a single package that is easily used in the field on a a tablet and/or phone. There are many images as well as the ability to download DSS images.


For most purposes, the catalogs are extensive, integrated and cross referenced. This is an example DSS downloaded by SkySafari.




There are many features which make it a potent tool out under the night sky.








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#4 Dave Mitsky

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Posted 10 September 2023 - 12:07 PM

Your post would probably get more traction in the Deep Sky Observing forum, Lipperhey.

#5 Gert K A

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Posted 10 September 2023 - 12:14 PM


I wanted to classify DSO images by folders, however due to this "duplicity" I think I'm gonna use the same folder, indicating in the filename the main designations.


And also:
A folder system with filenames is probably not gonna cut it.
A database will be more suited for this task.
The advantage of a database of sorts would be multiple entries on one item, all searchable.




And welcome to you

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#6 BrentKnight


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Posted 10 September 2023 - 01:05 PM

One of the better programs available attempts to solve the designation issue by tracking all the various calalogs and letting you prioritize them.


Screenshot 2023-09-10 125240.png


This is the designation preference window for nebuale in SkyTools 4.  I don't know of a similar program available for Linux.

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#7 DeepSky Di

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Posted 10 September 2023 - 01:15 PM

Welcome to Cloudy Nights, Lipperhey. This topic has been moved to the Deep Sky Observing forum as suggested and I hope you get more replies here.

#8 PeterSurma


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Posted 10 September 2023 - 03:38 PM

It might be better using web resources for data lookups, as basically everything is in the web today. Try this:






Type in any identifier and see what you can get. I do not think you have to re-invent the wheel and code software to sort catalogues...


You could also buy a reasonable chart programs (Guide, Stellarium, Cartes du ciel)  on a PC (one would assume that such a device can basically be found everywhere) and checkout the data in there. Same for an apple/android tablets with the chart app SkySafari being run on it... 

Edited by PeterSurma, 10 September 2023 - 03:45 PM.

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#9 FernandoPrz


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Posted 11 September 2023 - 04:13 PM

In my opinion, catalogs are useful as an 'approximation' to the subject. If you want to 'deep dive' into the subject you start to find errors, overlaps and other problems.


As PeterSurma said, Simbad and NED are the way to go if you want to discover and learn about new objects.


Mother Nature doesn't like 'ordered lists' ... as we like. The good news are that you always are welcome to build new and improved catalogs/lists.



That said, the main (professional) source of catalogs is Vizier:




Currently, 24135 catalogues are available, some are really good, but there is little to none 'order' there. It is a very hard job to extract useful observation lists from there, but sometimes you can find precious gems.

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