Archive for February 2022

Medusa Nebula – Abell 21 – Planetary Nebula in Gemini: March 2022 Observer’s Challenge Report #158

February 27, 2022

The following Information taken from “Deep-Sky Wonders” by Sue French:

Sweeping 2 1/2º eastward brings us to the cluster NGC 2395. My little refractor at 87x reveals 20 stars loosely scattered across 15′. At 28x, it merely shows a granular-looking patch with two faint stars, but something remarkable happens when I add an oxygen III filter. Although completely invisible before, Abell 21, the Medusa Nebula, joins the scene 1/2º southeast of the cluster! I can see it with direct vision, but it shows up better with averted vision. This unusual planetary nebula is about 8′ across, dented in its northwest side, and brightest toward the northeast and southwest. With my 10-inch scope at 68x, I prefer viewing Abell 21 with a narrowband nebula filter (rather than the oxygen III filter) which shows this large, impressive detailed planetary to be very uneven in brightness. SF

MONTHLY OBSERVER’S CHALLENGE

Compiled by:

Roger Ivester, North Carolina

&

Sue French, New York

March 2022

Report #158

The Medusa Nebula, (Abell 21, PK 205+14 1, PN G205.1+14.2) 

Planetary Nebula in Gemini

Sharing Observations and Bringing Amateur Astronomers Together

Introduction:

This month’s target:

Abell 21 was discovered during the course of the Yerkes-McDonald survey of  symmetric galactic nebulae. The ensuing catalog was published by Hugh M. Johnson in the May 1955 issue of the Astrophysical Journal, in which it was given the designation YM 29. https://ui.adsabs.harvard.edu/#abs/1955ApJ…121..604J/abstract

The nebula was independently discovered by George O. Abell among globular clusters and planetary nebulae newly found on the National Geographic Society-Palomar Observatory Sky Survey. His paper was published in the August 1955 issue of the Publications of the Astronomical Society of the Pacific, which listed 13 globular clusters and 37 planetary nebulae.

https://ui.adsabs.harvard.edu/#abs/1955PASP…67..258A/abstract

Although the nebula is number 16 in Abell’s list of planetaries, it’s now commonly known as Abell 21. His well-known, updated list of  86 planetary nebulae was published in the Astrophysical Journal  in 1966, and since the nebulae are given in order of right ascension their numbers were changed accordingly.

https://ui.adsabs.harvard.edu/#abs/1966ApJ…144..259A/abstract

In his 1961 “A Description of Fifty Planetary Nebulae”  https://ui.adsabs.harvard.edu/#abs/1961AZh….38…75V/abstract, B. A.Vorontsov-Vel’Yaminov, credits the name Medusa Nebula to a 1961 entry in Astronomicheskij Tsirkulyar No.221 (1960), which unfortunately or mercifully, depending on your point of view, I do not have access to. Sue French

Bertrand Laville: Observer from France (pencil sketch)

Roger Ivester: Observer from North Carolina

Pencil sketch using a 10-inch f/4.5 equatorially mounted reflector

Abell 21 also known as the Medusa Nebula:  

After spending four nights and ten hours, with two different telescopes, and multiple eyepieces and filters:  I was finally able to “visually” see the Medusa Nebula.  For me…the euphoria of seeing an extremely faint deep-sky object after many nights and hours, can “or might be similar” to something physical, such as running a marathon, which I’ve never done, but I have competed in bicycle races.  

To be able to locate and “visually” see the Medusa Nebula, a very dark sky is most desirable, but which is something I don’t have from my suburban backyard. My best NELM seldom exceeds 5.0-5.2 on a superb winter night. But I’ve always tried to make-do, and thus far, been successful in seeing all of the challenge objects for the past almost 14 years, and now exceeds more than 200 deep-sky objects.  

The Medusa Nebula is the most difficult (visual) object featured to-date in the Observer’s Challenge report for the past almost fourteen years.  This might be proof that a dark site with a 6.0-7.0 NELM is not necessary to enjoy the wonders of the night sky. 

The Medusa Nebula:   

Easy for the imager, but extremely difficult for the “purist” back yard amateur astronomer, using an eyepiece, an O-III or UHC filters, a pencil, note and sketch pad.  

Amateur astronomy can be anything the amateur wants it to be.  But for me, I want it be “not too distant” from the nights, taking out a 60mm refractor, in what I called the “weedy-field” beside my childhood home.  I wanted to see some of those fabulous spiral galaxies (and in color) that I’d seen in my 6th grade science book.  Of course I never did, but without any support or guidance, I learned what was possible.  

I’ve never been disappointed in those very faint objects that are barely visible in the eyepiece, and requires hours or nights to finally see, but somehow “for me” those are my favorite.  Where in the solitude of the night, I might whisper to myself:  THAT’S IT !  

For those few that choose to carefully, and with patience, observe and sketch a deep-sky object, also supplementing with copious notes, they will never forget what that object looks like, and with instant recall. 

After 50 years of observing, I’m so glad I never lost my EP, my pencil, or my sketchpad, as I never had any desire to become an imager.  I also have a library with hundreds and hundreds of “one of a kind” pencil sketches, to review, and for future reference.   

If you’ve never attempted to make a pencil sketch, with supporting notes, you should consider.  And we need to keep the ancient art of visual observing and “pencil sketching” alive.  A skill or facet of amateur astronomy that fewer and fewer seem to be interested in these days.

After all, this was the original reason or concept for the founding of the Observer’s Challenge back in 2009.     Roger Ivester

Observing Omega Centauri And Centaurus A From North Carolina At +35º North Latitude

February 19, 2022

After years of wondering if I could see globular cluster (NGC 5139) Omega Centauri and galaxy (NGC 5128) Centaurus A from my home at a latitude of +35º 18′ so I gave it a try on April 26th 2009.  

My poor southern view required that I go to a dark-site on the southern rim of the South Mountains, only thirty minutes away.  I also met two other local amateurs at the site, with one bringing a 12-inch Newtonian, which was invaluable in seeing galaxy Centaurus A. The 12-inch also provided an excellent resolve of Omega Centauri, despite the telescope being almost parallel to the ground. 

Theoretical limiting horizon calculation from Western North Carolina at +35º North Latitude:

(90º-35º) = -55º theoretical limiting South Latitude. 

Omega Centauri South Latitude:  -47º 28′  

My limiting southern horizon @ -55º (-) -47º = Only 8º above my theoretical southern horizon, and again…which puts my telescope tube almost parallel to the ground!   I share the following of that night:

I made the following sketch on 4-26-09, using a 102mm f/10 refractor. The NELM was ~6.5 at the zenith and with a good view of the southern horizon. However, the excellent seeing overhead did not transfer to the extremely low southern view as expected, at only 8º’s about my limiting horizon. 

The sketch of Omega Centauri with the 102mm was made “during the observation” at the eyepiece, at a magnification of 42x, using a white charcoal pencil on black card stock. The globular appeared fairly dim, mostly round, well-defined edges, granular with some brighter members sparkling in the interior with averted vision.  I also noted many faint outliers enveloping the cluster. When observing with the 12-inch f/5 reflector, the cluster was “surprisingly” well resolved. 

Observing Centaurus A using a 12-inch Newtonian:

Despite observing at a dark-site, I was looking over many distant lights, and many layers of atmosphere which diminished the view significantly.  I “could not” see the galaxy with my 102mm refractor.

Observing Centaurus A with the 12-inch f/5 reflector…it was extremely difficult.  My notes read: Difficult! Appearing only as a small smudge with a stellar nucleus.  Regardless, of the poor view of Centaurus A, I was very happy to have been able to observe and sketch Omega Centauri and at least to be able to see Centaurus A from the foothills of North Carolina.  

Rough Field-Sketch as following made on 4-26-09 @ 1:00 AM EDT

Rough field sketch with 12-inch f/5 Newtonian from the same location and night:

James Dire Image from Barking Sands, Kauai, Hawaii

Stellarview 102mm f/6.3 refractor w/Teleview 0.8x focal reducer flattener

James Dire: 100mm Lens Canon DSLR Camera

Omega Centauri reports:

Fred Rayworth of Las Vegas, saw Omega Centauri from Cathedral Gorge, Utah @ +37º 49′ 20″

“I saw Omega Centauri just over the hood of a truck on the horizon. I had a chance to see it at Death Valley, California when we went to the airport, but never caught it.”

+90º North (-) +37º 50′ = (-) 52º 50 mins or limiting southern horizon

So:  -52º 50′ (-) -47º 28′ = ~ 5º 22 mins above the horizon from Cathedral Gorge.    

Larry McHenry: Observing from West Virginia

Globular cluster NGC 5139 – Omega Centauri

Location: Calhoun County Park in central West Virginia. Setup on a ridge of about 1100 ft in elevation. (more about Calhoun at: http://stellar-journ…calhounpark.htm 

At the time of observation, NGC 5139 had an elevation of about 3.5º

First a wide-field “finder” image of NGC 5139 (Omega Centauri) using my Canon 100mm video lens & ASI290MC camera. 

Here’s the main EAA observation of Omega Centauri, again thru the trees, from 4/28/22 at 12:28 AM.

(8-inch SCT @ f/6.3 on an Atlas German equatorial mount , ZWO ASI294MC camera with L-Pro filter, 20 second subs, no dark or flat frames, not guided, live-stacked using Sharpcap for 80 seconds). 

Due to the short exposure time, we were able to see the dark feature called the “Eye of Omega”, which is possibly a dark molecular cloud that is in front of the cluster in our line-of-sight. 
This is generally only seen visually, as most images are longer exposures to pull-out more of the cluster stars. 

The timing was really good for making this observation thru the trees, as the foliage was noticeably thicker a few days later as warm weather really brought on the leaves.

And an observation of galaxy NGC5128 – “Centaurus A” made about 20 minutes prior to the hunt for Omega. (same location as above)

With a higher elevation of 8 degrees, I was able to catch the galaxy sailing thru a clear gap between trees, before it too eventually dived back into the limbs.

(8-inch SCT @ f/6.3, ZWO ASI294MC camera with L-Pro filter, 3 minute subs, dark & flat calibration frames, PHD guided, live-stacked using Sharpcap for 15 minutes).

Overall, It was a successful observing trip!


The park is opening a new observing field on a different ridge that has clear sight-lines to the horizon (one ridge over). Omega should be “in the clear” from there!

Unfortunately, I’ll be at the Cherry Springs Star Party for the next New Moon, and my club’s observatory (ORAS) for June. Next trip to Calhoun wont be until July, so a better observation of Omega will have to wait for one more year.

Larry McHenry

The Deep-Sky From Florida By Guest Host: Mario Motta

February 14, 2022

I was able to get my C-14 up and running in Naples, Florida, and the following are my images to-date.

The above image is my Naples, Florida setup. I work under a Bortle 5.5, which is not ideal and a full magnitude below my 4.5 skies in Gloucester, MA where my 32-inch scope is located.

I have an iOptron CEM 70g mount and pier-tripod, which has a level and a built in polar alignment scope. I find it invaluable for a quick polar alignment, when I set it down on a pre-marked location via a pad.

This mount is center-weighted, which is excellent for southern objects, and much better then a standard German equatorial, due to the weight of the scope “hanging off” the end of the polar axis at +26º North.

On this mount the polar axis is “centered” between two bearings…spreading the weight distribution well for southern locations, and It has excellent tracking.

As shown above:

My C-14 Edge has excellent optics, and I employ a focal reducer, so my work is at f/7 instead of f/11. 

I then have a filter wheel, with a Astrodon Light pollution L2P filter in place of standard Lum filter, which helps cut the LP down a bit. Then standard R,G,B astronomik filters, and finally astrodon 5 nm, Ha, S2 and O-III filters.

Finally, my standard camera is a ZWO ASI6200MM pro. I like this camera due to its very low dark current and excellent sensitivity, and wide field.

Piggybacked on this set-up is a Night Hawk 85mm f/6.5 refractor, which I primarily use in auto-guiding with a starlight express Ultrastar. On occasion I use this for a super-wide field image, such as the Vela supernova remnant image, as shown in the images below.

Finally…I have a Celestron dew control system, which is a necessity here in Florida. The humidity and dew-point can and most often is somewhat high.

After spending a night with a hairdryer removing dew every half hour, I recognized immediately that a dew-control system was not just a necessity, but a must!

Set-up time is about 50 minutes, with about 10 minutes to polar align after placing on the preset location.

A nice dark-sky would be great, but not…which indicates we need good light-pollution laws in every state.

In addition to my “Florida images” as posted by Roger Ivester, you can see a large set of my images (~700) at www.mariomottamd.com

So click on the top ribbon pane under astronomy to view my total images.

Enjoy….Mario Motta,

I plan on catching those deep south gems that are not available to me from my home, back in Massachusetts, and will be adding my latest and newest Florida images as following, as they occur.

If you can’t remember this link: Whatever search engine you are using, just type in “The Deep-Sky From Florida Mario Motta”

For the benefit of those that might want to follow Mario in his quest to observe deep-sky objects from Florida, I’ve included the following calculation for your use. Or you might just want to determine the deep-south objects that are available to you, which you might not thought were possible.

Calculation for Naples, Florida as following:

Theoretical limiting southern horizon calculation from Naples Florida at ~ +26º North Latitude:

(90º-26º) = -64º limiting south latitude, which opens up a vast number of deep-sky objects not available in the NE!

From my (+35º 15′ ) in North Carolina, my theoretical south latitude 90º (-) 35º = ~ -55º. Of course the terrain and light pollution can most often be the limiting factor for many in their limiting theoretical southern latitude. I can see the star Canopus, at a south declination of (-52º 42′) but in a distant tree-line. However, it shines brightly! Roger

Vela supernova with 90mm f/5.5 scope, use this scope only for piggyback guiding. ASI 071MC pro camera, and with optalon L-extreme filter. Two hours of 5 min subs, this is low in the sky, but with the filter able to image nearly to the horizon.

NGC 1097, in Fornax, 45 MLY away…a beautiful barred spiral

NGC 2467, in Puppis, the “skull and crossbones nebula.” This is NB imaging, mostly H alpha

NGC 4536, barred spiral in Virgo

NGC 5068, open spiral in Virgo

SH2-302 nebula, the “snowman nebula in Puppis. This is all H-alpha

Faint section of the Vela nebula…a supernova remnant

NGC 1365: Known as the Great Barred Spiral in the constellation of Fornax (Feb. 2022)

NGC 2736: The Pencil Nebula (a supernova remnant) in the constellation of Vela (Feb. 2022)

Sh2-301, a small diffuse nebula in Canis Major, can be imaged from Gloucester, but easier from down south. (Feb. 2022)

Globular Cluster NGC 1851 in the constellation of Columba (February 2022)

Centaurus A NGC 5128 in B&W (March 2022)

Centaurus A – NGC 5128 in color (March 2022)

The Famous Globular Cluster…Omega Centauri (March 2022)

Galaxy NGC 2997 in Antilla (March 2022)

Globular Cluster NGC 3201 in Vela (February 2022)

Galaxy NGC 4945 in Centaurus (March 2022)

NGC 6357 in Scorpio, an H alpha region of intense star formation. Taken with the C-14, and the ZWO ASI6200 camera, with H alpha, O3, and S2 filters, combined in PixInsight and processed. The star cluster embedded within the nebula contains some very massive stars, 10-100 solar masses among them. This nebula is also nicknamed the “lobster nebula” (Posted April 26th 2022)