Jump to content

  •  

- - - - -

Cosmic Challenge: Horsehead Nebula (Barnard 33)


Discuss this article in our forums

Cosmic Challenge: Horsehead Nebula (Barnard 33)

 

January 2022

Phil Harrington

This month's suggested aperture range:

Giant binoculars and 3- to 5-inch (7.6- to 13-cm) telescopes

 

 

 

 

Target

Type

RA

DEC

Const

Mag

Size

Horsehead
Nebula (B33)

Dark
nebula

05h 41.0m

-02° 27.7'

Orion

--

4'

 

Let's kick off the new year with what many consider to be one of the most difficult visual challenges in the sky. If you listen carefully, you might even hear the strains of the "Mission: Impossible" theme song playing in the background. Of all the deep-sky objects in the winter sky, none carries the mystique of the dark nebula Barnard 33, better known as the Horsehead Nebula.

 

Lying 1,375 light-years from Earth, the Horsehead is part of the huge Orion Molecular Cloud Complex, which engulfs much of the constellation. It was discovered in 1888 by Williamina Fleming, not visually, but on a photographic plate taken at the Harvard College Observatory.  Later, Edward Emerson Barnard added it as entry 33 in his burgeoning Barnard Catalogue of Dark Markings in the Sky, describing it as a "dark mass, diameter 4', on nebulous strip extending south from Delta Orionis."

 

The Horsehead is located 1° due south of Orion's easternmost belt star, Alnitak [Delta (δ) Orionis], making it very easy to pinpoint.  But as easy as it is to locate, this "night-mare" is a nightmare to see.

 

Above: Evening star map showing the location of this month's Cosmic Challenge.

 

Credit: Map adapted from Star Watch by Phil Harrington

 

Above: Finder chart for this month's Cosmic Challenge.

 

Credit: Chart adapted from Cosmic Challenge by Phil Harrington
Click on the chart to open a printable PDF version in a new window

 

 

The problem is not the object, but rather our eyes.  The human eye is a marvelous tool with an incredible range.  We can adapt to almost any lighting condition, from very bright to very dark and still find our way around.  But when it comes to dim, red deep-sky objects, it's almost worthless.  That's the problem here. The Horsehead is visible only because it is situated in front of the red emission nebula, IC 434.  And IC 434 is, for all intents and purposes, invisible unless viewed under very dark skies or by using nebula filters, or both.

 

In my book Touring the Universe through Binoculars (1990: John Wiley and Sons), I stated that "the Horsehead Nebulais too small and faint to be visible in binoculars."  I reasoned that it's tough enough to find it through large backyard telescopes, let alone binoculars.  But 31 years ago, at the 1991 Winter Star Party in the Florida Keys, after spending some time observing alongside the late, great Tomm Lorenzin, the talented astronomy author and observer from North Carolina, I found out that I was wrong.  Tomm (short for Theurgically Organic Mankind Module) showed me that the Horsehead is indeed visible in giant binoculars!

 

Here's how we did it.  First, we were in an ideal observing site.  The Keys' crystal-clear skies and Orion's height above the horizon certainly made a big difference.  Next, he taped a pair of hydrogen-beta line filters to the eyepieces of his 10x70 Fujinon binoculars.  Finally, we made sure that Alnitak was just outside the northern edge of the field, while nearby Sigma (σ) Orionis was toward the western edge.  Then, with a detailed chart of the area at our side, we looked for a close-set pair of 8th-and 9th-magnitude stars near the center of the field.  These coincide with the leading edge of IC 434 and are just west of the Horsehead.  With Tomm's help, it took me only a few minutes to pick out both nebulae.  Of course, the Horsehead was very small, looking like a thumb viewed from a few dozen feet away, but it was unmistakably there.  I repeated the observation in my own 11x80 Unitron binoculars after retaping his filters onto my eyepieces. More recently, and under less ideal conditions, I spotted the Horsehead through my 4-inch (10.2-cm) refractor, as captured in the rendering below.

Above: The Horsehead Nebula (Barnard 33) and IC 434 through the author's 4-inch (10.2-cm) f/9.8 refractor.

 

Below: Steve Bellavia (CN member StevenBellavia) took this image of the Horsehead and IC 434 using a Borg 90FL refractor and a ZWO ASI 183MM Pro camera. Be sure to visit his Astrobin page for full information on this as well as his other spectacular images.

 

This is not to say that seeing the Horsehead is a simple task in larger instruments.  Nothing could be farther from the truth.  Indeed, I can rarely see it from my own backyard observatory using my 18-inch (45.7-cm) reflector with a hydrogen-beta filter in place.  So, regardless of the telescope you're using, the Horsehead Nebula is a difficult challenge, one that will test your instrument's quality, the clarity and darkness of your night sky, as well as your skills as an observer.

Before I close, just a postscript about Tomm Lorenzin. Those who have been into observing for any length of time have undoubtedly heard of Tomm's self-published atlas/handbook 1000+: The Amateur Astronomer's Field Guide to Deep Sky. It's still available on the used book marketplace, such as from addall.com and others, as well as on occasion in the CN Classifieds under Software/Books/Magazines/Etc.

 

Tomm also created a sequel, bigger and better than the first that he generously released on his web site for free entitled, appropriately, 2000+: The Advanced Amateur Astronomer's Field Guide to Deep Sky Observing Database & Sky Atlas.  Tomm passed away unexpectedly in 2014, but his family has maintained his online legacy for all to enjoy to this day. If you haven't already, head over there and take a look.

Have a favorite challenge object of your own?  I'd love to hear about it, as well as how you did with this month's challenge.  Contact me through my website or post to this month's discussion forum.

 

Until next month, remember that half of the fun is the thrill of the chase.  Game on!



About the Author:

Phil Harrington writes the monthly Binocular Universe column in Astronomy magazine and is the author of 9 books on astronomy.  Visit his web site at www.philharrington.net to learn more.

Phil Harrington's Cosmic Challenge is copyright 2022 by Philip S. Harrington.  All rights reserved.  No reproduction, in whole or in part, beyond single copies for use by an individual, is permitted without written permission of the copyright holder.

 


  • okiestarman56, John O'Hara, Sasa and 4 others like this


31 Comments

Thanks for the challenge Phil! Indeed the binocular advantage and emission line filtration. I've enjoyed it successfully that way. My most unusual sighting was at a magnification of 1x using two "double-fisted" Gen 3 Night Vision monoscopes hand-held with 12nm Ha filters screwed on over the objectives. I know that may be considered cheating --- but the experience is real time and most certainly feels presence. With that boost, the Horsehead appears as a miniscule bent notch in edge of the emission veil that "hangs down" below Alnitak. At 1x the tininess becomes the challenge. One eye is marginally invisible... but two is a definite yes! For me, true binoscopic improves both brightness and contrast perception on challenging deep sky targets.

 

PS: I just now found and ordered  Tomm Lorenzin's book, used, second printing.   Tom

    • Dave Mitsky, PhilH, John O'Hara and 3 others like this

Tom, I don't know if I'd call that "cheating." Makes me wonder if there were those back in the 17th century who said using a telescope was cheating. lol.gif

    • John O'Hara and dvmweb like this

Tom, I don't know if I'd call that "cheating." Makes me wonder if there were those back in the 17th century who said using a telescope was cheating. lol.gif

Yeah... technologies and the ways we look at things morph and expand over time. Indeed, Galileo's peeking ~through the looking-glass~ came across as downright sinful back in the day... night?! And By Jove the wonderous things he discovered!    Tom

    • PhilH and John O'Hara like this
Photo
Dave Mitsky
Jan 01 2022 02:05 PM

I've only had a couple of opportunities to give B33 a go from an excellent dark site with my 101mm f/5.4 Tele Vue refractor.  So far I haven't been successful.
 

The smallest aperture that I have been able to log the Horsehead Nebula has been my 8" f/6 Starsplitter Tube Dob, which has a Zambuto primary mirror.  I was at one of the better "local" dark sites but it was still a very difficult observation even with the aid of an H-beta filter.

    • Jon Isaacs, PhilH, John O'Hara and 1 other like this
Photo
Dave Mitsky
Jan 01 2022 02:06 PM

The best view of B33 that I've ever had was with Tom Clark's 42" Dob from the Chiefland Astronomy Village in Florida.  The Horsehead Nebula was an easy target with that telescope.

    • PhilH likes this
Photo
John O'Hara
Jan 01 2022 03:17 PM

Not so sure about this one, Phil.  While I have access to dark desert skies this winter, and I meet the suggested aperture range, I don't own an H-beta filter.  I have OIII and narrow band, I can try, but...

    • PhilH likes this

“Seeing it” is almost a misnomer. My distinct memory of looking at it the first time (with an H-Beta filter) was that its presence was like an absence of “space.” It was as if the whole area of the Horsehead was a hole in space, slightly darker than the surrounding field, but at the same time almost imperceptible! A friend was looking through the eyepiece after I thought I was on the correct field. I didn’t know the size of B33 in relation to my field of view, and I told him I saw “a dark thumbprint of black” at one side of the eyepiece field. He took a look and instantly said, “that’s it!” It was a somewhat strange observation and I’ve only seen it one other time since. Each time, we had excellent viewing conditions. Definitely something I try for when conditions are just right and when Orion is well placed. Thanks for the article - it brought back some good memories.

    • PhilH, John O'Hara, Sasa and 2 others like this

Great article Phil!

 

Bagged the HH when I received my 100mm binocular telescope.  Even at low power, it appeared as a notch in IC434, which was luminous under pristine skies. Dark Skies AND transparency AND binocular vision are key here.  No filters required.  I'll  never go back to Cyclops viewing.

 

As an aside, 2023 was strongly condensed, 2024 was quite bright and starkly jagged bifurcation noted.  The outer loop of M42 was plainly visible and detailed.  The whole complex was better than photographs in its subtleties and impressions.  Reminds you why we observe! 

    • PhilH and John O'Hara like this
Photo
Arcticpaddler
Jan 02 2022 08:32 PM

I finally bagged the Horsehead two winters ago through my 8-inch SCT on an excellent, dark transparent night here in northern Minnesota. I worked the field for a full half-hour, and it was at the edge of visibility--a void in the already dim IC434.

 

Funny thing is, when I finally was sure I could see it, I realized that I had actually seen it a couple years earlier without a filter on a crystalline night, but just didn't believe it lol.

    • PhilH, John O'Hara and dvmweb like this

For what it's worth:

 

I observe the horse head on a regular basis with my 16 inch and 22 inch scopes. The skies at desert transparent and range from 21.1-21.3 mpsas with times it's darker..  I see it occasionally in my 12.5 inch but it's more difficult and I use the other scopes more frequently.

 

I use an H-Beta filter and near maximum exit pupils. I'm 73 and I'm sure I've lost sensitivity but my dark adapted pupil is unusually large for someone my age so it seems I get the best view with an exit pupil around 7.8 mm.

 

Under these conditions, the nebulosity is quite bright, a white haze with the dark shadow that's the horse head quite apparent.

 

For me, I looked for it for a number of years. The key for me was spending the time to figure out exactly where it was. It's not an object that lends itself to "star hope-ing". Precise star hopping in the main eyepiece is what did it. I'm sure Phil's chart is a good one, I modified this sketch by another CN member to show what I use.

 

HorseHead Alex 1.jpg
 
The double point almost at the horse head and the single star provides the range.
 
Jon

 

    • PhilH, John O'Hara, Sasa and 4 others like this

Horsehead is on the list to see this year.

    • Jon Isaacs, PhilH, John O'Hara and 1 other like this
Photo
Larry Carlino
Jan 03 2022 05:59 PM

The Horsehead is indeed a difficult object.  I've found that it requires VERY dark sky to be seen.  I've been able to glimpse it from a country location with 12 and 17-inch reflectors with an H-beta filter.  Still, not very impressive.   A much better solution is using a Collins I3 image intensifier with a narrow-band H-alpha filter.  This shows the object clearly even from a semi-rural location.  It's very large and well-defined with my 28-inch Dob, and a Vixen 114mm ED reveals it as well at an effective power of 40x, though it's very small.  A 66mm ED refractor revealed just a tiny dark spot in the surrounding nebulosity but a 135mm telephoto failed to show it.

 

Larry Carlino

    • PhilH, John O'Hara and rugby like this

Shot this 10-31-21 with a 420mm ED and a qhy8lc with h-alpha. 2 frames 900s and 600s max gain.

Indeed a faint object, even at these settings little data to process. 


Attached Thumbnails

  • Attached Image: 944BCFE5-019F-4E00-B624-E5EEEB7A808B.jpeg
    • PhilH and John O'Hara like this

I don't have an access to excellent dark skies, I usually observe from our light polluted backyard. On those few occasions under darker skies, I made several attempts to see Horsehead nebula. The best view was so far with 100mm refractor and UHC filter. I did not see the shape of the nebula though. The nebula revealed itself only as an interruption on the eastern edge of IC434.

    • PhilH and John O'Hara like this

A UHC style filter is not a great choice for the emission nebula surrounding the HH, because the nebula lacks much in the way of OIII emissions.  This matters because UHC filter bandpass is considerably wider in order to reveal H-beta and OIII lines.  Good samples of UHC have a bandpass about twice as wide as good H-beta filters.  

 

On the other hand, a good H-beta filter is considerably narrower (about twice as narrow), reducing the general glow of any light pollution and natural airglow without damaging the emission signal.   The signal to noise ratio of the H-beta on appropriate nebulae can be about 2x as great.

    • Jon Isaacs, PhilH and John O'Hara like this

A UHC style filter is not a great choice for the emission nebula surrounding the HH, because the nebula lacks much in the way of OIII emissions.  This matters because UHC filter bandpass is considerably wider in order to reveal H-beta and OIII lines.  Good samples of UHC have a bandpass about twice as wide as good H-beta filters.  

 

On the other hand, a good H-beta filter is considerably narrower (about twice as narrow), reducing the general glow of any light pollution and natural airglow without damaging the emission signal.   The signal to noise ratio of the H-beta on appropriate nebulae can be about 2x as great.

 

waytogo.gif

 

I make a crude filter transmission test using my SQM meter.  An O-lll filter or H-Beta filter darkens the skyglow about 3.0 magnitudes, a UHC about 2.2-2.3. that's just about the factor of 2 one expects.

 

In moderately dark skies like mine, that's the difference in skyglow between 24.0 mpsas and 24.7 mpsas.

 

Another way to think about it, an H-Beta under magnitude 21.3 skies is like a UHC under pristine magnitude 22.0 skies.

 

I think an H-Beta filter is worth owning. I often use mine just to judge/measure the relative H-Beta content in a nebula.  If there's very little like the Veil or the Helix, that points to the O-lll filter. If I see a nebulosity with the H-Beta, that points to the UHC filter, the assumption being that there is O-lll.

 

Jon

    • Dave Mitsky, PhilH and John O'Hara like this

A UHC style filter is not a great choice for the emission nebula surrounding the HH, because the nebula lacks much in the way of OIII emissions.  This matters because UHC filter bandpass is considerably wider in order to reveal H-beta and OIII lines.  Good samples of UHC have a bandpass about twice as wide as good H-beta filters.  

 

On the other hand, a good H-beta filter is considerably narrower (about twice as narrow), reducing the general glow of any light pollution and natural airglow without damaging the emission signal.   The signal to noise ratio of the H-beta on appropriate nebulae can be about 2x as great.

Yes, I know. But UHC filter was the only one which I had at those times. Later on, I was trying to spot Horsehead nebula using Hbeta filter as well. Even this was from the same place and similar sized telescope (110mm refractor), I had less luck with Hbeta.

    • PhilH and John O'Hara like this

I've tried for 2-3 hours with a 14" sct hoping my eyes would settle in, but to no avail. I tried all the tricks including a heavy blanket over me and my scope.I read somewhere that if you can't see the flame nebula, you won't have a chance at the Horsehead.

    • Jon Isaacs, PhilH and John O'Hara like this

I've tried for 2-3 hours with a 14" sct hoping my eyes would settle in, but to no avail. I tried all the tricks including a heavy blanket over me and my scope.I read somewhere that if you can't see the flame nebula, you won't have a chance at the Horsehead.

 

Yes, the Flame is very bright by comparison and can be easily seen without a filter.

 

For me, the difficulty with a C-14 would be getting a large enough exit pupil though this would not be an issue for many observers.

 

How dark were your skies?

 

Were you using an H-Beta filter?

 

Jon

    • PhilH and John O'Hara like this

I've tried for 2-3 hours with a 14" sct hoping my eyes would settle in, but to no avail. I tried all the tricks including a heavy blanket over me and my scope.I read somewhere that if you can't see the flame nebula, you won't have a chance at the Horsehead.

What tricks specifically?  Because the ones that would apply to a 14" SCT would be:

  • Dark, transparent sky--where are you observing?
  • 2" H-beta filter
  • Large exit pupil, 55 Plossl (or similar, to get a bright exit pupil in an f/11 scope.)   41 Pan might suffice, but 4mm or larger exit pupil is what I prefer for diffuse nebulae.

The flame/tank track is super easy, one that can be seen in town.  If you don't see it all, then the HH is definitely out, but seeing the flame is no indication that the HH will be visible, it is just too bright to be a useful metric for comparison with a much less intense nebula.

 

Looks like Jon just posted the same sort things while I was composing this.

    • Dave Mitsky, Jon Isaacs, PhilH and 1 other like this

Red:

 

What eyepiece do you use for the horse head in your 20 inch F/5?

 

Jon

    • PhilH and John O'Hara like this

Jon,

 

I typically use the 31T5 for 81x and 6.2mm pupil.  Sometimes I am using the 26T5 for low power at 96x and 5.2mm pupil.  The HH is large enough that I haven't used the 20T5 much for it, but it is my next low power stop in 2".  For some nebulae I will work back and forth between these three eyepieces looking for the optimum balance of scale and apparent brightness of the nebulosity to see something best.  (And of course I have the 41 Pan used at times for its maximum field, but at 61x and huge 8.2mm pupil that effectively stops down the scope somewhat.)

 

And to tie this back to the 14" SCT and why I suggest the 55, I have used a 55 Plossl with the 20" stopped down to ~8" (off axis) to yield f/12.5 for 61x and ~4.4mm pupil.  This allowed me to view the HH with H-beta.  I have also used the 55 for the HH with the 127 f/15 Mak (closer to f/17 in 2" mode).  I put the exit pupil with the Mak at ~3.2mm and 39x.  That was enough with the Mak to see the notch and a bit of the shape, but weak averted vision.

    • Jon Isaacs, PhilH, John O'Hara and 1 other like this
Photo
John O'Hara
Jan 09 2022 12:36 AM

I gave it a try with my 100 mm f/9 refractor on the evening of 1/6.  It was a very good night with 9/10 transparency in the KOFA Wildlife Refuge in southwest Arizona.  I used a 40 Pentax XL yielding a 4.4 mm exit pupil and studied the field with and without an Orion UB filter.  I printed out a chart from Cartes du Ciel to match the field of my eyepiece, so I knew exactly where to look.  I suspected seeing the HH at one point but will not claim victory yet.  Perhaps an HB filter is in my future.  (In my previous post I mentioned an OIII, which was a typo, as I know this filter would not work for the HH.)

 

I have seen the HH on a few occasions at Cherry Springs State Park, but through large Dobs equipped with HB filters.   Still, I'll give it another try with the 100 ED later this month, when the moon is again absent. One interesting note, after packing up my scope later that night (actually on 1/7) at about 4:30 AM, I noted that NGC 5128 and Omega Centauri should be on the meridian.  I managed to snag both with my 8x40 Celestron Ultima binos before leaving.  I picked up the galaxy as a very faint smudge, but it was there for sure.  Omega was obvious and quite large...surprisingly so.  The binos showed a bright core with a faint halo, it was really striking.  Too bad I'd packed the scope!

    • Dave Mitsky, Jon Isaacs, PhilH and 2 others like this
One interesting note, after packing up my scope later that night (actually on 1/7) at about 4:30 AM, I noted that NGC 5128 and Omega Centauri should be on the meridian.  I managed to snag both with my 8x40 Celestron Ultima binos before leaving.

 

 

On the morning of January 6th, not long before astronomical dawn, I realized Centaurus was nearly due south so I was able to catch Omega Centaurus, Centaurus A as well as NGC4945 in the 16 inch. Good views of OC and A, my first of this season.

 

NGC4945 must be an amazing from further south, it's 23.3' x 4.0' at mag 7.9 but it transits at 7.9 degrees so I just see a large, low contrast fuzz. 

 

Jon

    • PhilH and John O'Hara like this

I saw it once, in a 6” newt w/triple bandpass filter, out in the California desert, a couple of hours east of San Diego, and a couple of miles up a wash from the road, back in the mid-90’s. It was a tiny notch in a dark cloud against a dark sky.  To be honest, my ex spotted it first. I had looked for about 15 minutes, trying to follow a path to it. It wasn’t until the flame nebula was out of view that she could discern it. Even then, it took a couple more tries to know that I saw it!

 

it was actually kinda disappointing at the time…. Not like pictures at all! I doubt that I will be able to see it here (Sugar Land TX), but imma gonna try. There are a couple of darker spots about 20 miles from here, but I’m not in great shape, so it’s hard to get out to the country these days…. I’ve got an ES ED APO 127 triplet, along with a few filters (h-a, h-b, OIII, UHC).  Maybe I’ll get really lucky, I do still have good vision, although not as good as 25years ago…

 

-Kealey

    • PhilH and John O'Hara like this


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics