The Story of the Arp Peculiar Galaxies Page

Cartoon of Dennis with some galaxiesHi, I'm Dennis Webb and these are my friends Stephan's Quintet, also known as Arp 319. I met them on the pleasant internet adventure that produced the Arp Peculiar Galaxies Page. I offer the story for the benefit of astronomical hobbyists and beginning web publishers. It is an expanded and updated version of Sky and Telescope's July 1996 Astronomical Computing feature, An Arp-Inspired Adventure. Send me comments or thoughts at

One evening in the middle of the Arp quest: The thing was out of control. It was the third phone call in as many days. Mike had finished loading the galaxy size information into the spreadsheet and was asking what he could do next. I said I would think about it and get back to him. Lara was sending her diameter research on paper. Her crisp, informed penciled numbers would add another dimension to the story of some of Arp's peculiar galaxies. She wanted more work too. Al asked if I had seen the CCD shots he E-Mailed, particularly the one of Arp 188 (UGC 10214), the fourteenth magnitude flea shot. He had caught the galaxy, its faint wisp, and a nearby anonymous spiral with his Cookbook CCD and 32-inch f/4 telescope. That image confirmed that large amateur instruments with CCD's can grasp the peculiarity of many of the 338 views of peculiar galaxies. This was big news in our little project. I guess I have to get on-line to see Mike and Al's handiwork. "Where is this leading?" I asked myself as I clicked the little triangular icon, waiting for the modem to whistle its hello and howl my logon to the net.


Dr. Halton Arp honored the 1995 Texas Star Party with a rare appearance. He would speak on "Quasars Viewed from an X-ray Perspective" but many sought to study his "Atlas of Peculiar Galaxies." Astronomers know this landmark 1966 selection of exotic sights. I hoped to observe a few but could not easily locate the list. Perhaps if I could find it, others would benefit. This was a real astronomy adventure in cyberspace that started with on-line astronomical catalogs and led through CD-ROM's, spreadsheets, downloads and uploads, paper and disk publishing, e-mail among new friends and old, on-line chats, CCD images from across the country, image processing, building and maintaining a web page, publishing an article in Sky and Telescope, and formatting of the work for NASA's Astronomical Data Center.

April 1995: Hunting down the list

It took quite a bit of digging to find even a fragment of the Arp's list of Peculiar Galaxies. The usual amateur astronomy references held only a passing mention of the catalog. Halton Arp's writings have been controversial so perhaps the list has been suppressed! I am not normally drawn to conspiracy theories but my mind raced. I drafted the screenplay in my head... Oliver Stone will cast Kevin Costner as Halton Arp... Who would play Sandage? I will insist that Dennis Hopper play me in the lead!

Uranometria 2000.0's Deep Sky Field Guide ignored the list. Burnham's Celestial Handbook added nothing. My growing library on cosmology had lots of two paragraph mentions of Arp and his work, but no lists. None of my various PC databases had Arp numbers. Friends checked stacks of CD ROM catalogs with no luck. The conspiracy seemed proved! My first success was locating about 140 Arp objects in Emil Bonanno's fine MegaStar database utility. I hoped that they were the brighter objects. I called Emil. He said that they were a sort of random sample, a product of keeping only the three most prominent names for galaxies in this earlier version of his fine product. This meant that his list would omit some of the more famous objects. He also mentioned that I was not the first to ask this question. Adrenaline pumping, I visualized rogue CIA astrospooks converging on me. I coolly asked "Oh, who?". "Do you know Barbara Wilson?" he said. I relaxed, casting Meg Ryan as Barbara and penciling in a James Bond-type subadventure in Aruba. If Barbara Wilson is trying to find the Arp list in a database, I am on an interesting trail. I called Barbara, certain that my phone was bugged.

Barbara was researching the Arp list in honor of Arp's appearance at the 1995 Texas Star Party, an appearance she managed to secure. She had been browbeating Emil to get a comprehensive Arp list into MegaStar and was going to start manually entering the list to shame him into adding it to the next edition. She had studied Arp's original paper in the Astrophysical Journal, at Rice University's Fondren Library. Did I dare tell her of the imminent danger to secret Arp collectors?

April 1995: Finding Arp's List

The World Wide Web does have galaxy catalogs. Browsing the astronomical section to the NCSA WWW pages, I noticed an entry regarding NED, the NASA-IPAC Extragalactic Database, a telnet site at Caltech. I am not sure what telnet is but I recalled an icon that had the word telnet in its title. I clicked it and eventually got on-line with NED. The conspiracy visions evaporated. I was in Heaven, or rather the VT-100 text terminal version of Heaven. It seemed to recognize Arp numbers and cross-referenced more galaxy catalogs than I imagined possible.

I initiated a search on Arp and in a few minutes viewed an 810-line listing of galaxies. Barbara Wilson confirmed these to be individual galaxies in the 338 Arp views. After eliminating duplicates, the list reduced to almost 600 individual named galaxies. NED also includes a comprehensive literature index and this first download included the number of references to each galaxy in the scientific literature, ranging from Sky and Telescope to the Astrophysical Journal. For example, 572 articles discuss Messier 82 (Arp 337). Mysterious UGC 06073 (Arp 198) appears but once. NED's listings for Halton Arp included 99 articles, including the 1966 "Atlas of Peculiar Galaxies." NED also supports X-Window protocol, E-mail batch requests and can E-mail you a text file containing the results of your inquiries.

Adding Information

The raw NED file of Arps listed minimum information: common galaxy name, 1950.0 Right Ascension and Declination, count of literature references and several less useful fields. It turns out that if I had just requested the data be sent to me via Email, I would have gotten all of the data I sought, but then I would have missed part of the adventure. For amateurs to enjoy the list we would need to know whether they are visible in amateur telescopes. The file imported nicely into a Microsoft Excel spreadsheet. PC-based spreadsheets were designed for financial modeling, but they are great for developing tables. I added columns for galaxy type and magnitude and started cross-referencing into other sources. While it does not recognize Arp numbers, Uranometria's Deep Sky Field Guide provided considerable information on over half of the galaxies involved. NASA's National Space Science Data Center, CD ROM "Selected Astronomical Catalogs, Volume 1" provided information on many of the more obscure objects. A few tedious late nights at the computer got the additional data into the spreadsheet for searching and sorting.

The sorts revealed much about the Arp list. Forty galaxies are brighter than magnitude 11, including eleven Messier objects (M32, M49, M51, M60, M65, M66, M77, M82, M87, M90, and M101). The brightest at magnitude 6.8 is NGC 5128, Centaurus A. Most are between magnitude 12.0 and 16.0. The twenty-two most mysterious galaxies have no catalogued magnitude in any reference. Arps 312 and 338 are so mysterious that none of the catalogs list anything but the Arp name and coordinates. While most of the list is very faint, informed amateurs can see a lot of these interesting objects.

After assembling the complex data, I sorted it in Right Ascension order to answer the questions "what can I see tonight, where would I find it and is it bright enough for me to see?" I also edited and resorted the list in Arp sequence (from Arp 1 to Arp 339) to answer the question "What and where is Arp 122?" To this second table, I added information generated by Al Kelly necessary to plan CCD imaging. The basic data was complete.

May 1995: Publishing as Sharing

A spreadsheet is a good way to communicate with other fiscal analysts but the format excludes many amateurs. Microsoft Excel and Word cooperated with an inexpensive ink jet printer to produce polished and readable printed material. I printed several sorts and some explanatory text to create a copied and stapled 20-page pamphlet. The key tables converted to text files on floppy disks for those that would want to import the list into a favorite data manipulation program. I had a huge inventory of 5.25-inch DOS disks from the previous decade and felt like they would do fine. Formatting of a list of the 338 objects with common galaxy name and coordinates into a single double-sided legal page was tough. The 8-point Courier New font just barely fits the huge table in and remains readable after copying. This format is inexpensively copied for free distribution.

The Texas Star Party was a great audience for the Arp material. Dr. Arp presented a challenging crop of discordant red shift oddities using false color visual images overprinted with X-ray isophotes. These dazzling images hint at physical links between distant quasars and closer active galaxies. Fan and skeptic alike gave the legend a standing ovation and we crowded around for handshakes and autographs. Pamphlets, disks in plastic zipper bags to beat the west Texas dust, and legal size freebies all went quickly with a few simple posters as promotion. The major complaint was about the quaint 5.25-inch disks. My Arp journey seemed at an end with the happy sharing of my information among fellow amateurs.

June 1995: New Friends from the Net

The dispersal of disks restarted the journey. A mysterious "GALAXIES" E-mailed to ask if I would take part in an on-line forum to discuss the Arp catalog. He assumed I was an expert based on the disk a friend had picked up TSP. GALAXIES is actually Toney Burkhart on the faraway west coast. He sent me a another disk to become a temporary member of Delphi. I got it running and logged on the night before the chat to verify it would all work. Browsing the file offerings, I found my Arp data available next to a picture of GALAXIES himself. The chat went off without a hitch and we had a great time. It is a challenge to squeeze intricate paragraphs of complex knowledge and opinion into chunks of one line of text. It is worthwhile when you are squeezing something interesting and making new friends. They invited me back for a second chat.

New friend and fellow Houstonian Mike Brown E-mailed admiration for the Arp disk he got at TSP and offered help in the second edition. Mike manually loaded the galaxy dimensions for hundreds of galaxies from the MegaStar Deep Sky Atlas' database utility and audited the earlier magnitude and Hubble type data. He also convinced Emil Bonanno (MegaStar's author) to precess Right Ascension and Declination coordinates from epoch 1950 to 2000. Leonard Patillo, another Houstonian with a TSP disk had entered constellation names for each galaxy which later became my first image map. Mike delivered everything via E-Mail and we finally met in person after most of the work was done. As his last task, he coordinated his friends in developing a list of the best visual Arp objects for 10-inch telescopes. While there are many bright galaxies involved in the Arp catalog, only 15 reveal peculiarity visually in amateur instruments.

CCD Pictures and Simple Image Processing

People are not interested in what they can't see and most of the Arp list is too faint for visual observation. The availability of CCD cameras and image processing software, married with the increase in aperture of amateur instruments deepens space for the amateur, deep enough for the Arp catalog. As I finished my Arp list research, friend and teacher Al Kelly finished his CB245 Cookbook CCD camera. Al is not keen on Dr. Arp's work but he recognized some interesting familiar objects among the galaxies in the list and he said he would photograph a few. Such an offer is a bonanza because Al's large telescope is a 32-inch Newtonian on an equatorial platform (Reference Sky and Telescope, December 1991, page 661); these would be remarkable photos. Arp 188, a funny looking galaxyThe most remarkable image is of Arp 188, UGC 10214, a fourteenth magnitude galaxy too faint for Uranometria. His image caught the twisted galaxy, its faint wisp, and a nearby anonymous spindle we estimate to be magnitude 19. That image confirmed that large amateur instruments with CCD's can grasp the peculiarity of almost all of the 338 views of peculiar galaxies. Al also photographed Messier 51, The Whirlpool Galaxy (Arp 85).

Messier 51/Arp 85 in natural black and whiteM51 is a popular CCD target, bright enough to show a lot of detail and peculiar enough to raise eyebrows. Arp's 30-year old image from the 200-inch Palomar telescope reveals galaxy stuff way out beyond the spirals in a shape unfamiliar to this familiar view. I dragged the poor GIF through every shareware graphics package I could download trying to pull these faint wisps out through my low-end VGA monitor and card. Messier 51/Arp 85 in cool false colorsThe key tool was popular shareware image processor, WINGIF. WINGIF has a great false color display (LTE GRAY DISPLAY) and convenient contrast and brightness controls. I can save the false color image as a 4-bit GIF, most images being smaller than 8Kbytes. I am almost ashamed to admit it now but I selected this 4-bit false color format because I had not yet figured out how to get 256 color out of my low end 486 PC so the raw images looked pretty bad.

Colorful 35mm Slides

Striking visuals can make a talk, but only if projected on a screen in a meeting hall. I needed to translate the GIF's into 35mm slides to take the show on the road. I pasted the Arp GIF's into Microsoft Powerpoint, enlarged them to fill the screen, and added some text labels. Commercial services can convert such a file to film, but I wanted to shoot slides off the computer screen. Trial and error led to the following process: Load ASA 100 slide film in a 35mm camera with a 50mm lens. Mount the camera on a tripod in front of the computer monitor. Set up the image to fill the screen. Attach a cable release and set the camera to automatic exposure. Darken the room to avoid screen glare and stop down the lens to assure that exposures will be at least one second to assure even illumination so that you won't see evidence of the CRT scan pattern. Over expose a stop or two if you have a white background; I still have a problem with underexposure... how do you use a gray card on a CRT monitor? Fortunately the false color images are very forgiving on the exposure and make a knockout impression. Check to see that the cursor is not in the view and trip the shutter. If you do catch a cursor, just call it the "Cursor Nebula" and mumble about it being Hubble's lost planetary. Repeat as necessary. Run to the 1-hour photo processing shop right before you leave to make the presentation. Good slides make an ordinary talk look like a big budget research project. Well, actually, there is no such thing as an ordinary talk.

July 1995: Presentation and Republishing

I proposed the give an informative and entertaining talk on my exploration of the Arp peculiar galaxies at the 1995 Astronomical League (AL) convention in San Antonio, Texas. They were kind enough to allow me to speak, underexposed slides and all. The talk is subtitled, "Observing Challenge for the Next Millenium", perhaps stretching a point but definitely getting the jump on the major millenial obsessing to come. I had updated the booklet and proudly called it the second edition and many attendees were interested in having a copy. Mail me a note if you would like to have a copy. I proposed (to the horror of the AL treasurer) that the AL sponsor an Arp observing program, oriented at both imaging and visual observation. That nice John Wagoner took it under his wing and it may yet come to pass. I also sent a couple copies to the NED folks and they replied with an intent to address some of the some of the naming irregularities.

November 1995: Giving Back to the Web

Slides only go as far as the presenter can travel. To spread Dr. Arp's list faster requires a network, in this case the World Wide Web. I had first met the Web through MOSAIC on a Macintosh on my desk at work in late 1993, although I had read XANADU back in 1987 when we were all trying to grasp the concept of hypermedia. It occurred to me that I could put the Arp data tables and the punchy false color pictures on-line and other amateur astronomers might be interested and entertained.

The remarkable Web and its attractive home pages are mostly written in a language called Hyper-Text Markup Language (HTML), a text based formatting language. Anyone who has done simple programming or old style word processing with "dot" formatting commands can produce HTML documents in a couple weeks, quicker if you are familiar with what Web pages look like. I bought a book about HTML (Teach yourself Web Publishing with HTML in a Week, by Laura Lemay, 1995, Sams Publishing) , downloaded a small HTML 1.0 PC Web browser called CELLO to check the writing and started building the "Arp Catalog of Peculiar Galaxies" page. PAINT, the simple graphics package bundled with Microsoft Windows, can produce colorful banner graphics, limited mostly by the artist's vision. WINGIF can convert PAINT's BMPs to web-able GIFs. America On-Line (AOL, my Internet Service Provider) provides each screen name two megabytes of Web page space through a feature (and keyword) called "My Place". It looked like I had the basic toolset.

I had figured all of this out and got started on normal hobby time, but needed a critical mass of time to actually get it online, between debugging confused formatting, correcting invisible typos, and navigating AOL's web page support areas. You know how it is. Fate intervened and handed me a week off. I was furloughed as a non-essential government employee during the historic U. S. Government Shutdown in November 1995. Fighting my first inclination to sit around drunk and weeping on the sofa in my bathrobe, I burned the midnight oil at the PC. I also did housework had a great long night of weeknight observing with friends. After three long nights, the Arp page was working and I whipped out pages for my artist wife, my astronomical self, and (I am sorry to say) our cat. Fortunately for the Web, I was considered an essential government person for the December shutdown.

I submitted my URL via Submit-It to many of the search engines and was honored with a featured position by Yahoo, an astronomical favorite. Within a month, E-Mails arrived: from a west coast educator who added the Arp page to his index, from an Italian amateur curious about the technical details of the photos, from a thoughtful critic who found the false color images objectionable, and from a Halton Arp relation charmed to see the family name on the internet.

July 1996: Sky and Telescope Article

I had been looking for an opportunity to write this story in print and proposed it to Stuart Goldman of Sky and Telescope and also the facilitator of AOL's astronomy forums. He thought it might be interesting for the Astronomical Computing column, emphasizing the Web aspect. Under his clear guidance, we hammered my self-indulgent writing style into a pretty good feature. Stuart also recognized some problems with my pick and shovel HTML code; it seems that the CELLO browser is terribly forgiving of HTML errors (missing closing tags and quote signs). The message to web publishers is TEST, TEST and MORE TEST on ALL of the current browsers. When it was published in the July 1996 issue (page 92), all hell broke loose on my email. At the peak, I was getting 20 notes a week from all over the world including some real astronomers. The Prodigy folks invited me to chat on their astronomy forum. By the fall, many astronomy club web pages included links to the Arp page. During this time I gave the Arp talk to the Johnson Space Center Astronomical Society, the Astronomical Society of South East Texas, the Austin Astronomical Society, the Texas Star Party (where I got to meet Toney Burkhart in person), and the Fort Bend Astronomical Society. Maybe I need to get out of the state. Hey Hawaii, do you need an Arp talk? New Mexico?

September 1996: NASA's Astronomical Data Center Hosts the Data

The most notable of the notes I received following the publication of the S&T article was one from Nancy Roman of the Astronomical Data Center. The ADC maintains the comprehensive on-line archive of astronomical catalogs and publish those wonderful CD ROM's with astronomical data aplenty. Ms. Roman had seen the S&T feature and asked about the comprehensiveness and quality of the data, and if I could polish the tables into the ADC/CDS standard format. This felt like the astronomical big time (or as close as I am likely to get). I was a little insecure about errors in the listing so I reviewed my accumulation of irregularites and disconnects across catalogs to see if I could address any before going into the serious astronomical reference. I resolved a few including the complex confusion between Arp numbers 296 and 299. Comparing Megastar's PGC/RC3/HSTGSC findercharts with the Digital Sky Survey image of the area, I uneasily settled on the current interpretation, which disagrees with Dr. Arp's labeling in his 1966 paper. The keepers of the archive assigned my data to File Number 7192. What an honor! A mere engineer/bureaucrat astronomical hobbyist can contribute to the great library of human knowledge of the universe. I guess you AAVSO and ALPO folks already knew that feeling.

December 1996: Epilogue

What started with curiosity about a rare galaxy list became a two year adventure. I could not have planned the steps at the start. The internet offered the first information and served as a steady medium for new ideas and connections to interesting people. I am using better browsers to check the work and am cautiously adding HTML 3 features. I wonder what we will be doing next year?

I am less worried about a conspiracy. I do think that it is a shame that amateurs have had to hunt for the Arp listing. Let the cosmological mind police come if they must! The People have a right to know!


What started out as a solitary undertaking quickly became a group effort. This page would not have been possible in its present form without the enthusiastic support of several individuals:

Irrelevant but Interesting Arp Imprinting on the Author

The name "Arp" is a longstanding thread buried in my thought processes:
Return to Arp Page, Page first built December 1996 by Dennis Webb