Note - the 4th edition of the Compendium was released on November 6, 2023, including both Mac and Windows versions.   Please go to this link for the latest edition.  
Also,  on Sunday, Dec. 3, 2023, at 8:30 pm CST, I will be giving an overview of the new edition of the Compendium on the free Youtube Astro Imaging Channel.

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The 2023 edition (3rd edition) of the Compendium is now finished and available for free download.   

What is the Compendium?
The Compendium provides the astrophotographer with useful tools for finding interesting deep sky targets to image.  The Compendium consists of 2 parts, a pdf eBook and an Excel spreadsheet, and is available at these links:

eBook download link (45 MB size) - The eBook has over 100 compilation posters of deep sky objects, including complete catalogues such as Messier, Caldwell, Abell, Arp and Hickson, to give you examples of imaging targets. 

Spreadsheet download link (30 MB size) - The spreadsheet helps you to find these targets in your night sky, using the current date and time, your location, a database of over 3100 deep sky objects, and 26 cross-referenced catalogues.  Each object has an image, a description, an imaging rating, a SIMBAD link, an ALADIN link, and 20 pieces of technical data.

3rd Edition Changes
The 3rd edition of the spreadsheet contains the following major changes, most of which were suggested by users of the 2nd edition:

• The entire sky (northern & southern hemispheres) is now included (over 3100 objects).
• Every object has been rated for its imaging potential, from 0 to 5.
• Each of the 3100+ objects has a mouseover object image for your quick review.
• All objects now have hyperlinks to their SIMBAD and ALADIN web sites, in addition to a hyperlink to a high resolution image and complete Astrobin entry for most objects.
• A brief description has been added for every object.
• For many emission nebulae, a relative comparison of narrowband signal strength for each channel (SII/HII/OIII) is shown.
• A mouseover quick start guide has been added to the top row of the spreadsheet.
• Subtype and class categorizations have been added for each object.
• Distance, diameter, and magnitude have been added for each object (when available).
• For galaxies, surface brightness and inclination have been added (when available).
• The transit altitude for each object, based on the user’s location, has been added.
• 70 buttons are provided for convenient filtering and sorting of objects.
• Many other minor additions have also been implemented.

Before You Begin

• Once you download the spreadsheet you must enable the macros, which are disabled by default in all downloaded Excel documents.  To enable the macros, simply right click on the downloaded file in Windows File Explorer, select Properties, and select the Unblock checkbox on the bottom of the General tab.
• Depending upon your computer settings, you may see formula warnings (green triangles in cells) throughout the sheet which are visually annoying and which slow down the refresh time.  Disable these warnings by clicking on one of those cells, then clicking on the exclamation point which appears, then clicking on Error Checking Options, then (under Error Checking Rules) deselecting the boxes for "Unlocked cells containing formulas" and "Formulas referring to empty cells".

Caveats

• Excel is the only program which can completely run the spreadsheet in Windows.  Free Windows spreadsheet programs will not work.
• At this time, a native Mac Excel version is not available, although it should work on a Mac by using Parallels, installing Microsoft Office, and then running Excel.  I have just purchased a Mac and I hope to have a native Mac Excel version available soon.
• The spreadsheet requires decent computer horsepower.  Tablets and small laptops may be challenged to run it in a timely manner.
• This edition has significant changes from the prior edition.  Unfortunately, this may make porting difficult for those of you who added your own content to the past versions of the spreadsheet.
• For numerous reasons, I have not protected the spreadsheet from editing.  Please be careful not to delete any of the columns, or the top 9 header rows (which contain formulas).

Astronomy Scholarship Fund
The Compendium is provided free for your use.  If you find it useful, I would appreciate a small donation to the Imm Astronomy Scholarship Fund, a tax-deductible donation account established to provide financial assistance to college students with an interest in astronomy.  The scholarship will be open for applications in January and will be awarded in June, hopefully on an annual basis if funding allows.  All U.S. and international students attending college in the United States may apply for the scholarship.  For those of us who love astronomy as a hobby, this is a small way for us to encourage and reward students who take up this challenging career.

Acknowledgements
Thanks to Jeff Coldrey, Rick Veregin, Corey Rueckheim, Alan Brunelle, Bruce Donzanti, Uwe Deutermann, Riedl Rudolf, Kurt Zeppetello, Tom Gray, and many others for their input into this edition.

Feel free to ask me any questions and to provide feedback in term of error corrections and additional feature requests.

Best regards and clear skies!
Gary