#90-Small Telescope Adventures, Part 8

The Olcott Project:  Adventures with a 2" Telescope--Nights 9, 10, 11, 12

The small telescope project is alive and well, and I have now completed 2/3rds of my first goal of observing 60 objects.  Space Eye is a 2" refractor from Vixen.  It is quite a splendid little instrument, and it's helping me relive my early days as an amateur astronomer.  However, I always used reflectors when growing up, first having a toy 3", then a Tasco 4.5", then an Edmund 8", and finally an Orion 12" Dob.  There was one tiny refractor in my lineup.  I purchased a 40 mm refractor from K-mart back in 1971, using it for two months until my Tasco scope arrived.  However, Space Eye is my first true astronomical observing refractor, and I always enjoy using it when time permits.  Here are two observations from March 11th.

Object #32:  Messier 41:  Mag. 4.5; 39'; 80 *s; Br. * mag. 8:  From Olcott:  "Also observe M 41.  It is a superb group in a 3" telescope, and the red star near the center shows very clearly."  It is also a pretty fine sight in a 2" scope, with a nice concentration of bright stars in the center, and others somewhat further out.  30x shows some haze behind the resolved stars, but 60x resolves most stars.  About 40 members were counted, not including more distant stragglers.  I spent a long time here enjoying the view.

http://www.perezmedia.net/beltofvenus/archives/images/2005/img2005011502_M41lgrev1.jpg


Object #33:  Jupiter:  This is the first planet I have observed with Space Eye, and probably the one best suited for it.  This Spring, Jupiter is the planetary highlight.  On my first visit I was looking through a fogged over objective lens.  However, the planet was still sharp and bright.  Two equatorial cloud belts were very dark and dramatic; quite spectacular, actually.  The moons were easily seen, and provide beginners and experts alike a never-ending moving tableau.  On a second night (with no fogging) I observed the north hemisphere to be darker.  Two moons were nearly touching, but the scope resolved things well.  I have not used more than 60x so far (it's been very cold, and switching eyepieces requires refocusing), but will go much higher as weather permits.  Jupiter is a real showpiece for Space Eye.

http://en.es-static.us/upl/2013/04/Jupiter-and-moons-io-europa-ganymede-callisto.jpg

 Here are four objects seen on March 25th.

Object #34:  Beta Monoceros:  4.6-5.0/07":  Olcott class this a beautiful object.  While a lovely
                                                          -5.3/10":  double star at 30x, splitting B & C is a challenge, as they are only 3" apart!  I was pretty certain of a split at 60x, but I had to confirm it with Deb's 6" scope.  Lovely double, but a very challenging triple star.

http://web.utah.edu/astro/pics/paul/beta%20mon%20color%20352.jpg

Object #35:  Messier 50:  Mag. 5.9; 15'; 80 *s; Br. * Mag. 9:  Olcott places the object on his maps of Monoceros and Canis Major, though does not discuss it.  Smaller and dimmer than M 41, it nonetheless is a beautiful though faint cloud at 30x.  It is compact and compressed, with perhaps a half dozen stars easily resolving over the haze.  60x resolves the cluster nicely, showing about 25 stars.  Some haze is still evident in the background.  It is tricky to locate, but ultimately worth it.  A minor gem in Space Eye.

http://www.pictorobservatory.ca/images/m50-L_thumb.jpg

Object #36:  Epsilon Monoceros:  4.5-6.5/13":  Split at 30x, though seen beautifully at at 60x.  It seems white and bluish to me.  Olcott says Gold-Blue.  The 6.5 mag. companion was like a tiny pinprick next to the brighter star.

http://www.gabrielevanin.it/Eps%20Mon.jpg

Object #37:  NGC 2244:  Mag. 4.8; 30'; 100 *s; Br. * Mag. 7:  Olcott says:  "Note the cluster NGC 2244, visible to the unaided eye, and a fine sight in a field glass."  This is the famous Rosette Nebula, though no nebula was seen tonight.  This is one of the most easily identifiable clusters, nd it is lovely in a 2" scope.  It resembles a number "6" on a die.  The south two stars point north following to NGC oc 2252, barely discernible in the 2", though lovely in Deb's 6".  Continue further on to Cr. 106, with its central dense knot of faint stars appearing like fine silver dust in Space Eye.  A fun area to explore.

http://www.celestronimages.com/data/media/5/NGC2244a.jpg

A single object was observed on the night of March 26th.

Object #38:  Messier 48:  Mag. 5.8; 30'; 80 *s; Br. * Mag 8:  Olcott places the cluster on his Monoceros chart, but says nothing about it.  It turns out to be a nice object for the 2" refractor.  While there is lots of haze at 30x, several stars do resolve.  60x shows the full richness of M 48, which can take your breth away in a 6".  A few dozen stars are resolved in Space Eye, many seen using averted vision and a perfect focus.  This is a true wonder of the late winter sky!

http://scienceblogs.com/startswithabang/2013/02/11/messier-monday-a-lost-and-found-star-cluster-m48/ 

The final pair of objects for this blog entry were seen on April 1st.


Object #39:  Algieba (Gamma Leonis):  2.6-3.8/4":  Olcott quotes Struve in his Field Book:  "Finest double in the northern sky."  Olcott himself calls it the telescopic feature of leo.  It certainly is beautiful in the 6" and 12", and most likely in a 3", too.  It is a challenge to resolve in the 2", and takes a practiced eye, steady seeing, perfect focus, and some patience.  Comfortable seating helps, too.  One star is deeper gold that the other, and one is noticeably bigger.  A beautiful pair in Space Eye, but not a showpiece for the masses.  I only used up to 60x, and will try a higher power next time.

http://zimmer.csufresno.edu/~fringwal/Gamma-Leonis-2006-01-27-120s-f20.png

Object #40a and 40b:  Messier 65 and Messier 66:  65= 9'.8 x 2'.9; Vis. 9.3/SB 12.8.  66= 9'.1 x 4'.2; Vis. 8.9/SB 12.7:  I easily located and saw two of the three members of the Leo Triplet.  While I could not see the third member (NGC 3628), I did get a good glimpse of nearby eg 3593, which appeared round, faint and hazy, though not small.  Both Messier galaxies were seen at 30x, and indeed they were not that good at 60x.  I should have tried 40x.  Next time.  M 66 was noticeably rounder and brighter than M 65, which appeared very long and thin by comparison.  They both were bright and conspicuous, with very bright middles.  A nice catch for Space Eye, and worth showing to others!

http://www.astrofoto.ca/john/files/m065-66.jpg

(edited to crop out eg 3628)

 

Although there are a few more Spring objects I wish to view, I an anxiously awaiting summer, when I can dig into Sagittarius.  I will likely expand my project up to 100 objects.  Also, Saturn and Mars on on their way, and I have hopes of seeing a polar cap on Mars.  So stay tuned.

Meanwhile, work continues in Leo with the 12".  With over 350 NGC objects, this is a multi-year project.  However, I am going to begin reporting on progress so far, so stay tuned for that.  As ever, clear skies!

Mapman Mike 

#12: Visual Magnitude versus Surface Brightness

     Any discussion about observing galaxies must inevitably come round to the subject of the galaxy's brightness or lack of it in the eyepiece.  Galaxies that I could barely see in my previous 8" scope are now much easier to locate, identify and discuss using my 12" mirror.  However, an entire new spectrum of much fainter galaxies is now available, going well beyond what the 8" might have seen.  If I suddenly started using a 16" scope, then the faintest ones now seen with the 12" would appear brighter, and a whole slew of new and fainter galaxies would be available to challenge my view.  This process would literally go on and on with each larger mirror.  There is no end to the faintness of distant galaxies, as evidenced by Hubble's deep field explorations.

     I am still trying to determine the faintest galaxy that I can view in my nearby dark sky with the 12" scope.  So far it has to be NGC 2873 in Leo, with a visual magnitude of 15.4 and a surface brightness of mag. 13.6.  While there are several fine explanations on the web as to exactly what visual mag. is, and surface brightness, I will give my own version here without equations, based on my current understanding and experience.

     Visual magnitude refers to how much actual light is coming from the galaxy to the observer's eye.  How it reaches the eye is greatly affected by the object's size.  Some bright galaxies (Messier 66, for example) have a bright visual magnitude, making them seem relatively easy to see in a wide range of small telescopes.  The visual mag. for M 66 is given as 8.9.  If that object was a star, it would be considered somewhat faint but still easily observable in a small telescope.  NGC 2873, by comparison, has a visual mag. of 15.4, making it nearly impossible to see if it was a star, except with a moderately large scope.  If 2873 was as large an object in the eyepiece as M66, it would never be seen in amateur scopes.  And yet the surface brightness levels of the two galaxies are not that far apart.  For M66 it is given as mag. 12.7, and for 2873 it is mag. 13.6.  There is less than a magnitude difference between these two vastly differing objects!  And yet in fact there is more than six magnitudes of difference between them in actual visual light.  A difference of one magnitude is 2 1/2 times, with mag. 10 being 2 1/2 times fainter than mag. 9, for example.  This is most interesting.

     The size of a galaxy, then, is important in determining its brightness, and in making it easier for the eye to see it.  Without getting mathematical (not my strength), let us take 3 hypothetical galaxies as our examples.  Our first galaxy is going to be sized at 1'.1 x 1'.0 (arc minutes).  This is a somewhat small object, and virtually round.  If the visual mag, was, say, 13 (from all the light coming from it), then the surface brightness would be the same mag. as the visual one.  That exact size of object has the same visual mag. as its surface brightness. 

     However, if we now expand the galaxy to 2'.2 x 2'.0, then the surface brightness decreases (there is an easy formula for this).  The same amount of visual light is now spread over an area 4x as large.  A galaxy of mag 13 might now become one with a surface brightness of 14.7 (not an exact answer, just an example, but it will be 4x fainter). 

     If we now shrink the galaxy to something like 0'.55 x 0'.5, then the same amount of light now arrives in a more compact, star-like package.  The surface brightness now increases, so that our imaginary galaxy with a visual mag. of 13 now seems more like a 12 mag. galaxy (again, just a rough answer--the formula is available on-line if you want exact answers).

     The upshot of all this is that a large galaxy that looks bright on paper might actually be very hard to see at the eyepiece, because its light is spread out over a large area (NGC 45 in Cetus is a good example--that one also has a bright star attached that interferes with seeing the fainter haze of the galaxy)).  And a tiny galaxy like 2873  might seem at first to be impossible to see, but is actually a bit easier because of its very small size (its actual size is 0'.8 x 0'.2).  Which magnitude is the one that observers should pay attention to, visual or surface brightness?

     In my experience, neither one should be used apart from the other.  Even taken together, there are still so many other factors to consider when hunting galaxies.  Some of these factors include how high above the horizon it lies, if it is near a bright star, the transparency of the sky and overall seeing conditions, and even how tired you are.  And if the galaxy is the same brightness as the sky background, it will be invisible.  When galaxies get too far west I stop observing them, as that area of sky is very light polluted.  I take both figures with me outside on the clipboard, along with the size.  If the galaxy is very large and bright, then the surface brightness formula only works to a certain degree.  A combination of the two magnitudes is often a better way to go.  M66 lists a visual mag. of 8.9 and a surface brightness of mag. 12.7.  You can't see a 12.7 mag. galaxy in a 4" telescope, but you can see M66.  Halfway between 8.9 and 12.7 is magnitude 10.8, which seems closer to the truth in this case.  A 4" scope can now work very hard and show the galaxy pretty well on a decent night.  My 'split the difference' method is unscientific, but seems to work for me in the field.

M66--is it really only 0.9 magnitude brighter than

 NGC 2873?  M66's vast dimensions (9'.1 x 4'.1) make

its bright magnitude appear dimmer to the eye.

Both photos from

http://www.astrosurf.com/benoit/ngc.html

NGC 2872 on right.  NGC 2874 on left.  Both are easy

to locate in a 12" scope.  Much trickier is tiny NGC 2873,

lying just north of the two larger Leo galaxies,

 in the upper center of the photograph.  The photos

show true relative size of all galaxies depicted, including M 66, above. 

     The same goes for NGC 2873.  I could never hope to see a galaxy of 15.4 magnitude in my skies with a 12" scope, and the galaxy certainly doesn't reach its given surface brightness mag of 13.6 either.  Halfway between the two figures lies mag. 14.5, which gives a more reasonable ballpark estimate as to what my observing companion and I observed a few nights back.

     So for now, I am assuming that I can see a tiny mag. 14.5 galaxy in a good sky with my scope.  This will aid me in knowing which faint galaxies to attempt and which ones to pass up.
Of course the companion volume to Uranometria 2000 is also an awesome source of this information.

As ever, I am curious to hear what you think.
Mapman Mike

#9 NGC Life List

     In my very first post earlier this month I talked about astronomers who work their way methodically through object lists, often to the detriment of the object.  A quick glance, a note or two, maybe a quick sketch and then they are off to the next object.  All well and fine if you are looking at 14th magnitude galaxies, but if your list is packed with the brightest deep sky gems, what is the hurry?  400 top objects could well last your entire life.

     To make certain that I never finish my life list, or run out of options on any given clear night, I chose the NGC list a long time ago as my main deep sky emphasis.  I will not pass a Collinder or Berkeley cluster without a look, but my longest viewing time is spent on the NGC list.  In a lifetime of observing I have only seen about 630 of them, averaging just over one per observing session (last night I logged two new ones).  I really need to ramp that up a wee bit if I want to see all available from my latitude before I die.

     The new edition of Uranometria 2000 claims that more than 30,000 non-stellar objects are on its charts.  That's over 22,000 more than are in the NGC list.  Good grief.  Makes me kind of thankful that I am not overly obsessed.  Of those 30,000 objects, nearly 26,000 of them are galaxies.  Which means that nearly 5 in 6 non-stellar objects viewable in the night sky with amateur scopes are galaxies.  Most of those are pretty faint, too.  Here is the breakdown, as reported on the atlas' back cover:

     25,883 galaxies

     671 galaxy clusters (Abell)

     14 star clouds

     1,613 open clusters, including those in the Magellanic Clouds

     170 globular clusters

     355 bright nebulae

     367 dark nebulae

     1,145 planetary nebulae

     260 radio sources

     35 x-ray sources

     I remember being very surprised when I first learned how many galaxies were available to amateur astronomers (all the ones listed in Uranometria are mag. 15 or brighter).  I mean that I was very surprised.  Growing up loving the Milky Way area and all of its clusters and nebulae, it was easy to conclude that clusters of stars far outnumber galaxies.  That, to say the least, was an erroneous conclusion.  If one decides to choose the NGC for a life list, one must be prepared to see some galaxies.  I don't just mean the ones in the Messier catalogue, either.

     Finding and doing justice to galaxies requires the very finest of dark skies.  I used to be able to pick off 12th mag. galaxies from my back deck with my 8" scope.  Light pollution has increased so much in my area that this is now quite impossible.  I did snag one last night with the 12", but if I want to do a decent job of observing in Leo this spring, I have to be prepared to travel with the scope.  This brings on an interesting conundrum.  I also had a preliminary look last night at M 65 and M 66, bright galaxies in Leo.  Compared to faint little eg 2894 viewed previously, they were pretty darn impressive.  So, do I observe the brighter galaxies from my home, saving the fainter ones for country skies?  Though this is a feasible plan, I try to imagine what eg 2894 might look like from a dark sky.  If I can even see it from home, then it might just be that much more impressive from a dark sky.  Should I save all my faint objects for darker skies?  What about M 65 and M 66?    Of the two, M 65 was less bright but it was really huge after viewing it for a few moments.  M 66 was quite bright, and I could probably have used up to 300x without any loss of brightness.  However, what would these objects look like from a really dark sky site?

     One solution to this problem, which I'm certain many of us face all too often, is to keep notes and report on the brighter ones as seen from home suburban skies, but also return to them in dark skies and enjoy a quick peek.  eg 2894 seemed to have a little cluster of very faint stars superimposed over it, only barely resolvable at high power with averted vision.  Was there a stellar core?  Couldn't really tell.  But the elongated galaxy could be seen in behind the star field, best at 150x in the 12".  I know I want another look in darker skies, resolving those faint stars more easily and perhaps seeing some detail in the galaxy itself.

    Whereas fainter galaxies pose severe problems for suburban viewers, objects such as clusters and nebulae, especially planetary (I also enjoyed good views of pn 2346 in Monoceros last night), do not pose significant problems.  And double star work can carry on quite well, too, often even during full moon nights.  However, I am determined to do as much deep sky work in the darkest skies I can reach.  I've been spoiled by my northern Ontario early years of observing.  Another time I will talk about my nearby observing options, and how they may best be used.  Until then, I hope you enjoy a clear sky night or two.

Mapman Mike