My Quest to Observe the Entire Herschel Catalog: By “Guest Host Larry McHenry” From Pittsburgh

It is Done!

As of May 13th, 2020, I have now completed observing all 2,482 identifiable objects of the Herschel 2500 Catalog.

My last catch was ‘H II-840’ a pretty little one-arm galaxy – NGC3978 in the Great Bear – Ursa Major.

The idea for this ‘Herschel Objects’ project started back at the end of 2012, as I was wrapping up a Constellation survey based on the “Night Sky Observers Handbook“. I realized that my observations would already include a large number of the Herschel-400 objects. So after identifying all the ‘400’ objects that I had previously observed, it only took me less than a year to finish the ‘Herschel 400’ list. For this phase of the project, I utilized the Astronomical League’s “Herschel 400 by Constellation” list and their “Observe the Herschel Objects” booklet. I then downloaded the AL’s “Herschel-II” list of the next 400 objects and began hunting those. 

By the fall of 2016, I was down to the last 60 objects and was wondering what my next project should be. Flipping thru some old “Sky & Telescope” magazines, I ran across an article from the August 2012 issue by Rod Mollise on observing the entire Herschel Catalog of 2500 objects using a deep-sky video camera. This was the inspiration (and project), that I needed, as I was already a videoastronomer, so I began a multi-year effort to observe the entire Herschel Catalog.

So today, we’ll discuss what I’ve learned during that journey among the Herschel Objects. Hopefully, when we are done, you will find them as interesting to hunt as I do.

First, a little background on the Herschel’s:

After the Messier List, the Herschel Object’s are the next most observed deep-sky objects. 
Most amateur astronomers know them by their NGC numbers, but they started out as a list created by British amateur astronomer William Herschel and his sister Caroline, two of the greatest astronomers from the ‘Age of Enlightenment’, which marked the birth of modern science.  

From 1782 to 1790, the Herschel’s conducted systematic surveys of the night sky, in search of “deep sky” objects, and discovered over 2500. Herschel used two telescopes for his survey, a “20-foot Reflector”, which had an 18.5” speculum-metal mirror, and later the great “40-foot Reflector” with a 48” mirror.  Most of Herschel’s recorded observations were made using the ’20-foot’ telescope, as the larger ’40-foot’ was cumbersome to use and suffered from tube current distortions.

Herschel’s telescopes didn’t have clock drives to track the stars, so instead, he would point the telescope to the meridian and let the Earth’s rotation carry objects across his field of view while he was up on a ladder observing. William would then call down to Caroline, at the bottom of the telescope, whenever he saw anything interesting, and she would write down his descriptions and time and where the telescope was pointing. Caroline would then quickly read this back to William and he would confirm the observation while the object was still in the eyepiece. This method allowed them to observe and record a nightly east-west strip of sky. The next day, the two of them would use their recorded observation to calculate the objects position on a star atlas. They would then move the telescope’s elevation up or down, in preparation of the next nights survey run.  Using this method, they were eventually able to observe all of the sky visible from England.

The Herschel’s observing technique of surveying, cataloguing, and classifying what they found, and then using that data to try and understand the structure of the universe, has become one of the most important tools of modern astronomy.

How I accomplished the project:

So back in 2016, as I began a multi-year effort to observe the entire Herschel 2500 Catalog, the first thing I needed to do was come up with a list of the Herschel Objects! While during the process of William and Caroline Herschel’s original recording and publishing of their observations from 1786 thru 1802, along with subsequent reprints and revisions over the 19th century, there have been a number of discrepancies over misidentified or non-existent objects. Depending on the source, of the Herschel’s 2500 objects cataloged, there are anywhere from the low 2400’s to over 2500 actual objects. Mark Bratton, in his book “The Complete Guide to the Herschel Objects“, gives a good review of the issues and historical attempts to rectify Herschel’s list of objects. He eventually settles on there being only 2,435 identifiable Herschel Objects. (I utilize his book’s visual descriptions and DSS images to help in comparing and confirming my personal observations). In addition to the above book, I also utilized George Kepple & Glen Sanner’s “Night Sky Observers Guide Handbook” and internet resources ‘WIKISKY‘ and ‘The NGC/IC Project’ to validate my observations. 

To help tackle this project, I downloaded several lists from various websites, and after combining, distilling, and sorting, I generated a personal spreadsheet/logbook to help in my tracking & logging. The core data for my logbook comes from a list of 2,482 Herschel Objects by Steve Gottlieb. 


All of my Herschel Object observations can be found in their individual constellations in my website under my ‘Constellation Tour’ page. To see the entire list together, I’ve created a specific page for the Herschel Project: “Herschel Tour”  

http://www.stellar-journeys.org/herschel-tour.htm


Over the course of this project, I have spent a total of 239 nights working my way thru observing all of the Herschel Objects. 

Even though I really didn’t get serious about completing the list until 2012, my observations stretch all the way back to 1984. 

All of the early observations are visual sketches, (78 objects), made at the telescope eyepiece, with everything after 2001 using videoastronomy (EAA) short-exposure lucky imaging technique. I eventually used a total of ten different telescopes for this project. Six visually – 80mm f3.2 refractor, 8″ f4.5 dob, 10″ f5.6 dob, 13.1″ f4.5 dob, and a 8″ & 12″ SCT at f10. The dobs and small refractor were manual telescopes, with the two SCT’s being motorized, but all required using star-charts and star-hopping techniques to locate the objects. 

For the videoastronomy observations, I used four telescopes – 50mm f3 refractor, 80mm f6 refractor, 6″ RC at f9, f6.3 & f5, and a 8″ SCT at f10, f6.3 & f3.3.  All these telescopes were on either SCT or CGEM mounts that could track and later utilize GOTO.

The cameras used were a StellaCam-EX (2.5 seconds exposure), StellaCam-II (8 seconds exp), a Samsung SDC435 (8 seconds exp), a peltier cooled, wireless controlled StellaCam-3 (unlimited exp), and finally a ZWO ASI294MC Pro camera used in EAA mode (generally for around 120 second exposure). 

While I prefer going to dark sky locations, such as Pennsylvania’s Cherry Springs State Park, for my observing, utilizing near-realtime deep-sky videoastronomy cameras has allowed me to pull in faint 14th magnitude plus galaxies not visually possible from my backyard observatory located within 10 miles of downtown Pittsburgh, PA. This greatly expanded the number of clear evenings available for working on this project. 

Having spent time over the past several years following in the Herschel’s tracks, you could begin to pick-up on how they were doing their observing run for that particular night back in the 1780’s, slowly letting the Earth’s rotation bring each object into their sweep. Using today’s modern equipment, there’s no need to wait; all you had to do was hop down the sweep path to the next observable object. When you think about that, it’s sort of inspiring to think that in your own way you are following in their footsteps!

In retrospect, I have learned a lot about the lives of William and Caroline Herschel, along with the objects that they discovered. While there are a number of nice large, bright objects including galaxies, star clusters, and nebula, the majority of Herschel’s objects are small, faint, dim smudges of galaxies. It gives you an appreciation for the brighter Messier Objects. Still, there is a wide variety of shapes and sizes of interesting deep sky objects for any type of telescope. I now have a much greater respect for all those faint fuzzies and the work of the Herschel’s! So I encourage everyone to get out tonight and try your hand at finding and observing the deep-sky objects of William and Caroline Herschel!!

An examples of my many sketches:

My equipment used for this project: Telescopes, observatory and camper : Larry McHenry, Pittsburgh, Pa


Hope you enjoyed my story: Larry McHenry

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