I have just posted my 2500th image to Astrobin.  In that time, I have imagined hundreds of fantastic objects.  But I have also imaged quite a few clunkers.

This poster was the inspiration of @Charles Bracken, author of many wonderful astrophotography books such as the Astrophotography Sky Atlas and the Deep Sky Imaging Primer, who said that I should create a poster of “objects Gary imaged so you don’t have to”.

So what does it take for an object to make this list, to be named a “Worst DSO”?  It takes more than simply being a dim object - there are millions of those in the sky.  To be a “Worst DSO”, it has to be a named or classified object which you might be tempted to image, as I was, and if you do image it, the result is well below expectations.  You could also call this list 25 of my most frustrating DSOs to image and process.

These 25 are not in any specific order.  The links below take you to my Astrobin image post for that object:

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1. Dwingeloo 2 - The name of this galaxy sounds so enticing - I anticipated finding a magical object with twisting star streams and fanciful arms.  Alas, even after processing, all I found was a blank star field.  This galaxy, located only 11 million light years away, was just discovered recently in 1994 because it is located in the Zone of Avoidance (that part of our sky where distant objects are heavily obscured by the Milky Way itself).  It was discovered not visually but by using the Dwingeloo Radio Observatory, which searched for neutral hydrogen radio emissions. The observatory is located in the town of Dwingeloo, which is in the Dutch province of Drenthe.  Dwingeloo 2 was discovered at the same time as Dwingeloo 1 and is believed to be a companion galaxy.  My faint image of Dwingeloo 1 is here.  These 2 galaxies are both members of the Maffei group of galaxies.  As far as I know, a visual image of Dwingeloo 2 has still never been captured.

2. Hickson 50 - In my opinion, this is the worst object in the Hickson galaxy group catalogue.  This group of 5 galaxies is the dimmest object in the Hickson catalogue, with each galaxy almost 2 billion light years away.

3. M40- Clearly the worst object in the Messier catalogue  - a double star.  Is it really possible to mistake a pair of stars for a comet?  And if so, what is so special about this pair? By the way, strictly speaking, individual stars are not DSOs, so this object (and the next one) should not be on this list of worst DSOs.  But they get special inclusion on this poster because they were included in the most famous DSO catalogue in the world.

4.  M73- Clearly the 2nd worst Messier object!  I guess if you can mistake 2 stars for a comet like M40, 4 stars is even more comet-like.  This is nothing more boring than imaging individual, stand-alone white stars

5. Arp 51 - In my opinion, this is the worst object in the entire 338 member Arp peculiar galaxy catalogue.  How did this tiny, stellar-like galaxy get selected as a peculiar galaxy by Dr. Arp when so many more magnificent peculiar galaxies were left out?

6. Abell 16 - In my opinion, this is the worst object in the Abell PN catalogue.  A very dim PN.

7. BoBn 1- This object looks like a star, but it actually is a stellar-like PN.  In fact, this object is a rare extragalactic PN, believed to have originated outside of the Milky Way galaxy in the Sagittarius Dwarf Spheroidal Galaxy.  The object is now within our Milky Way, in the former galaxy’s stellar stream.  This magnitude 16.4 object spans only 3 arc-seconds in our apparent view, which corresponds to a diameter of 1 light year.  

8. Hubble Deep Field- This is the famous Hubble Deep Field image area.  Guess what - if you try to image an object which took the Hubble 342 separate exposures over ten consecutive days and is one of the deepest space images of all time, you probably won't capture anything from your backyard in a few hours besides an empty star field.  Who would have guessed?

9. Arp 338 - A pair of galaxies which is one of the smallest and faintest entries in the Arp peculiar galaxy catalogue.  This appear to me to be 2 superimposed galaxies at different distances (edge-on and face-on spirals), so not only is this object small and faint, it is also not even a peculiar (interacting) galaxy object.

10.  Cheshire Cat Lensing - This is one of the most visible examples of gravitational lensing, defined as the bending of light from a distant light source by a massive foreground object. This Cheshire Cat galaxy cluster is lensing four separate background galaxies with redshifts ranging from 0.80 to 2.78, which corresponds to light travel distances which range from 7 to 11 billion light years from us. The lensed galaxies appear as extremely faint, barely visible arcs of light near the center of this image, which was my 4th frustrating attempt at imaging and capturing it. 

12. Einstein's Cross- This is a gravitationally lensed quasar that is located exactly behind a closer galaxy.  This image also took 4 frustrating imaging attempts.  The quasar is being lensed into four images (the “cross”) plus a dim one in the center.   The cross, with a dimension of 1.6 × 1.6 arcseconds, is named after Einstein in honor of his prediction of this light bending effect in his theory of General Relativity. I think I see the cross here in the bright core of the galaxy.  Like the lensing image above, I am calling this one done and moving on.

13. Sh2-122- One of the worst of several dim molecular clouds included in the otherwise wonderful Sharpless catalogue of bright emission objects.  

14.  Abell 2197 and Abell 2199- These are 2 of the least interesting objects in the Abell galaxy cluster catalogue.  Each of the 2 clusters contains about 80 galaxies and is located about 420 million light years away.  But they hardly stand out from the background

15. Kohoutek 2-7 - An extremely dim PN from the Kohoutek catalogue.  So dim and boring that nobody else on Astrobin has imaged this one yet.

16. LEDA 36252 -  A tiny tadpole galaxy, just slightly larger than the adjacent stars.

17.  vdB 121- In my opinion, this is the worst object in the vdB reflection nebula catalogue.   Barely discernable against the background.  

18. Minkowski 3-55 - A tiny red square PN, the same size as the adjacent star.  

19. Cygnus Fairy Ring - Well, this asterism sounded pretty cool.  A "fairy ring" is a circular area of grass that is a darker color than the surrounding grass due to the growth of fungi, although some would like to believe that they are caused by dancing fairies.  Whoever thought this object looked similar was also seeing too many dancing fairies.

20. Barnard 201 - Is this the worst candidate in the Barnard catalogue?  All of the dark nebulae are tough, but this one is near invisible despite the fact that it is in clear sight, located just west of the famous Double Cluster.

21. Stargate - So, Wikipedia says that this asterism resembles "a portal device featured in the Buck Rogers science fiction TV series".  Now, even if that is true, it wouldn't be enough to justify imaging this lame small grouping of 6 bright stars.  But I can't find any image from Buck Rodgers which resembles this configuration.  All I can find from Buck Rogers is a pattern of an equilateral diamond formed by four points linked by thin "energy beams", which was used as a portal.  That pattern does not look remotely close to this.   How can that be?  How can such a lame asterism be so famous based upon incorrect information, such that I spent a few hours imaging it?  Someone, please help me understand this!  

22. LEDA 67860 - This one of 20 small galaxies that has been associated with a nearby voorwerp gas object.  Voorwerps, which have been described as the ghosts of quasars. are the only DSOs which have a greenish glow.   For most of these 20 voorwerp objects, the voorwerps are too dim to image from our backyard. The green filaments barely show up in this image.

23. IC 342- In my opinion, the worst object in the otherwise wonderful Caldwell catalogue.  I should have anticipated trouble when I saw that this object is nicknamed both the “Hidden Galaxy” and the “Star Veiled Galaxy”.  Like the slightly better Fireworks Galaxy, the location of this object close to our galactic equator obscures the galaxy with Milky Way dust and stars. In fact, the bright and colorful Milky Way star field is one of the brightest and dense that I can recall in the foreground of a galaxy image.

24. Kohoutek 3-93 - This faint magnitude 18 planetary nebula spans only 10 arc-seconds in our apparent view.    

25. UGC 9749 - This dim object, the Ursa Minor Dwarf galaxy, is a satellite of our Milky Way galaxy and is located 200,000 light years away. It spans 2000 light years and has the same apparent size in the sky as our full moon. This galaxy is a dwarf spheroidal galaxy, which is even more diffuse and poorly defined than a typical dwarf.  It is the faintest known galaxy of our local group, with a surface brightness of 25.5.

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That concludes the list of 25. I am sure that you have your own "Worst DSOs".  Please let me know your "favorite" worst ones in the comments below - I would be interested to hear about (and see) them.

If you are looking for better targets to image than these, please see my Imm Deep Sky Compendium, a free planning resource to help astrophotographers find interesting targets in their night sky.  Foreign language translations in Spanish, German, French, Italian, Polish, and Chinese are now available at the link above.

For other offbeat posters, please see my Just Having Fun poster collection here on Astrobin.