#69 The Poetry of Galaxies

Imagine you are standing in a fog so dense that you cannot see any objects around you.  There is fog, and nothing else.  You know there is a landscape surrounding you--trees, buildings, a lake, perhaps.  But none of it can be seen.  You take a few hesitant steps, hoping to glimpse a familiar landmark.  Then, suddenly the outline of something appears before you.  It is very indistinct.  Nothing definite can be perceived, just the hint of something.  For an instant it becomes slightly less mysterious, but then the fog enshrouds it again and it is gone.  This little game continues for a few moments, until you are almost sure that what you are seeing is a building or a village, but you cannot be 100 % certain....

 Old Amersham, Buckinghamshire, England
Author's photo.

And now imagine it is a dark and very clear night.  The humidity is low, there are no lights nearby, and you are away from any cities and towns.  In the eyepiece of your 12" reflecting telescope you are seeking a galaxy of magnitude 15, at the very limit of what you are able to see on the best of nights.  The sky background in your eyepiece view is black, though a few very faint stars are sprinkled across it.  You have been searching for several minutes, with no luck.  Suddenly, out of the corner of your eye, there is a slight flaring.  Is it a faint star, near the limit of visibility?  No, it's larger than a star.  A moment later and it is seen again, this time as a  nearly undetectable oval haze that increases in brightness when you do not stare right at it.  It is probably the galaxy, but you cannot be 100% certain.  You try a different eyepiece, likely a higher magnification.  If it is the galaxy, it should appear again....

http://www.asod.info/?p=1920

Both cases, the foggy scene and the very faint galaxy, are extreme.  Seldom is it so foggy that nothing can be seen nearby, but it does happen.  And out of all the galaxies that I hunt in the darkest skies, only a very small percentage of them are at the limit of what I can expect to see.  Yet just as the foggiest day seems to have more poetry in it than most average days, sometimes recognizing these really faint, difficult galaxies can be the biggest thrill of a whole night's observing.

Galaxies, being what they are, are often the most studied and most photographed objects in the deep sky (deep sky being beyond the moon and the planets in our solar system).  There is no such thing as a typical galaxy, though they all have things in common.  Plenty of stars, for one.  However, from the largest earth-based telescopes used for observing with the human eye, even the brightest and closest northern hemisphere galaxies all look like haze.  Without photography we would still not know what these island universes are, nor have seen their immense beauty.  In fact, it wasn't until 1925 that the debate was settled, when Edwin Hubble, using photographs taken with the 100" Hook Telescope, was able to distinguish variable stars in another galaxy and compute their distance from earth.  Since the stars were hundreds of thousands of light years beyond our galaxy, then other galaxies like ours had to exist.  All of that haze we had been seeing were stars; billions of stars.  We now know that there are more galaxies out there then there are stars in our Milky Way galaxy!  If that isn't mathematical poetry, then I don't know what is.

Galaxies are grouped by scientists into classes, depending on their shape and their light output.  The many different types need not overly concern us in this discussion, but they are important when observing.  Some galaxies that do not fit neatly into any class are referred to as peculiar.  More poetry!  For me, the galaxies that provide the most poetry when observed are called "edge-on."  That is, we are seeing them along their equatorial line.  They appear long and thin, with a central bulge.  Though only haze to the eye, to the imaginative mind we are seeing billions of stars shining together to produce a grayish haze coming from hundreds of millions of miles away.  The bulge is the center of the galaxy, always its busiest, most populated and most active place.  As an extra bonus, some of these edge on galaxies have dust lanes, material within the galaxy that has not yet been converted into stars.  Our own galaxy is filled with such dust, as are many other galaxies.

 An edge-on galaxy, photographed through a large telescope.  Note the central bulge

and the very distinct dust lane running the length of the galaxy.

http://mgio.arizona.edu/older-mgio-journal-entries

In the eyepiece, sometimes only the central bulge of such galaxies can be seen.  However, other galaxies clearly display their full length, and these can send shivers up one's spine when viewed.  With fainter galaxies the full length sometimes comes through only like our foggy day analogy--a glimpse now and then of the full extent of the object.  Patience, and looking indirectly at them (called averted vision) often show faint objects more readily than staring at them.  More poetry!

A second type of galaxy that telescope observers love to view is called "face on."  Now we are situated above the galaxy, looking directly down at it (or it is "above" us--it's all relative in deep space).  With some of the brighter and closer galaxies, we can see the haze shaping itself into spirals, called arms.  Sometimes, these arms show tiny clumps of brighter areas.  These are not commonly seen in smaller amateur scopes, but they are star forming regions, places where stars are either being born or are newly born.  Realizing that one is actually looking at star birth in another galaxy can be an overwhelming experience.  Galaxies where such regions can be viewed in larger amateur instruments are not hard to track down.

Nice comparison of a sketch from the eyepiece

and a photograph.  This is Messier 101, a face-on

spiral galaxy, displaying arms and bright knots, 

which are actual star-forming regions.

http://www.perezmedia.net/beltofvenus/archives/001416.html

Galaxies abound in the skies of Summer, Autumn and Winter.  However, the best time to see them is Spring.  At this time of year, we are in the part of our orbit around the Sun when our night sky faces away from our own galaxy.  The Milky Way, with all of its stars and dust, can make it difficult to see beyond, into really deep space.  But when we look up at the sky in Spring, it can seem a barren field to the naked eye.  There are fewer stars, no Milky Way; just plenty of dark space.  We are looking directly opposite the center of our galaxy, our view now extending out into deepest intergalactic space.  This part of the sky is simply swimming in galaxies; bright ones, faint ones, large ones and small ones, and everything in between.  They are often so crowded together that more than one of them can be seen at a time in the eyepiece.  Sometimes they are physically close to one another, and even interacting, but just as often they happen to be in a line of sight, from our vantage point.  A closer galaxy may appear larger and brighter, with a further and fainter one seemingly right beside it.  

It is a wonderful experience to see and contemplate one galaxy on a fine night, but to see two, three, four or more all at once can really test the limits of one's ability to comprehend.  Just what are we really seeing?  How many stars?  How many possible planets?  It is beyond mind boggling. These experiences are relatively common for amateur astronomers, though I never find anything common about them.  It is always such a thrill and a privilege that sometimes after such an experience I simply stop observing for the night!  Such treats are thus best reserved for the end of an observing session, rather than at the beginning.

 Several galaxies can be viewed at once sometimes.

http://cseligman.com/text/atlas/ngc7436wide.jpg 

Just as intensely foggy days can reteach us the essence of what is, so can observing faint galaxies through a telescope.  By stretching our imagination we can fill in some of the details that the eye cannot fully grasp.  By combining what we know and what we can imagine, there is a meeting of science and poetry; between the universe and humankind.  It is so true that we and our planet are insignificant when compared to objects that are on a cosmic scale, such as galaxies.  However, this fact in itself is significant.  And poetic.

Clear skies.

Mapman Mike

#50 Summer Observing Plans, 2014

With spring galaxy season officially ended (for me it finally ended last night, when I logged a tiny, faint one in Bootes), it is time to bring on the summer milky way and all of the awesome areas of sky contained within. Last summer I enjoyed quite a lot of clear skies, and was able to begin and finish detailed deep sky observations of Lyra and Cygnus, as well as nearly finish Cassiopeia.  The summer constellations are "up there" a lot longer than those of any other season, thanks to the increasing level of darkness creeping back into our lives.  Combined with generally nicer weather, many of us spend entire nights observing in July, August, and September.  I have already observed most of the summer sky with my previous 8" scope, and I am now having another go with my 12".

My summer plans include observing all of the NGC and IC objects in Aquila, Delphinus, and Sagitta, and also getting a start in Sagittarius.  Hundreds of deep sky objects await, many of them completely new to me.  I have also included all of the open clusters from other catalogs shown on Uranometria 2000, as well as the occasional globular cluster and planetary nebula.  My main goal, however, is the NGC list.  Double stars are not forgotten, as I will go back and review some of the best ones seen previously, along with several I could not split with the 8", or could not find back in the day.  Refer to my earliest blogs for exactly how I go about setting up my observing lists. It's an old-fashioned way, but keeps me entertained for hours on cloudy nights and weekends.

I've already had a good start in Aquila, logging four open clusters last night, including 6709.  There are also three (less impressive) clusters in the immediate vicinity.  However, by star hopping to them from 6709 I got to see a lot of lovely star fields, and got to know another small part of the sky very well.  On previous nights I viewed oc 6755 and 6756, along with other open clusters, a few globulars and planetaries, a variable star and a double.  Since I spent April, May and June hunting down (mostly) faint galaxies, it is pure joy to behold the wonders of the Milky Way once again.  I especially like viewing open clusters, and the 12" has revealed them to me in ways only that level of aperture could.  6709, for example, is a minor treasure in my scope, and I spent a very long time last night enjoying the sight.  I began at 43x, and slowly worked my way up to 200x, stopping off for lengthy views at 60x, 83x, 100x, 125x, 150x, and 187x.  Each view gave a new perspective, and it was like arriving amidst the cluster in a spaceship, having begun some distance away. Once deep inside the cluster, I pulled away again and enjoyed low power views.  Believe me, this is a fun way to spend a night!  Afterwards, once the notes are in the logbook, I go back and compare what I saw now with what I saw years ago with the 8".

My wife and observing partner, Deb, has her own method of tracking down deep sky objects.  Deb now has about a year of solo observing under her belt, after assisting me with sketches at the eyepiece for decades.  She started with our Astroscan 4 1/4" RFT, locating all of the Messier objects to boost her driving and hunting skills. Once she had completed that project, she upgraded to an Orion Starblast 6".  That is one fine little telescope, with some of the sharpest views of stars and deep sky objects I have ever seen.  It more than holds its own against all the super expensive 5" refractors that come out to the observatory to observe. It's only drawback is that it does not accept 2" eyepieces. 

Right now Deb is completing her NGC globular cluster project.  Previous to this she took on Spring galaxies. Her next project, just currently getting underway, is finding open clusters within a specific size and magnitude. Basically she observes a large selection of objects in one category (galaxy, open, or globular cluster) and does a comparative study.  She observes each object with the same three eyepieces, comparing size, brightness and ease of finding and seeing the object.  So she is now an expert observer of galaxies and globular clusters using a 6" reflector.

Because we travel to the observatory in one vehicle, and because my 12" scope takes up a lot of the cargo room, Deb is limited to a 6" aperture, though she is often more than happy to take a peek through the 12". Sometimes we have fun by observing the same object at the same time in both scopes, comparing the views.

As always, I am interested in hearing about other observing methods.  Just remember to have a peek at what else may lie around that deep sky object you are looking at, especially if it lies in the Milky Way.  Star chains, small but colourful double stars, tiny asterisms... it's fun to be surprised by uncateloged, undiscovered wonders, too. Happy summer observing!

Mapman Mike

#28: Monthly Update #5: July/August 2013

     At last!  Some clear summer nights with terrific conditions.  We even had a few such nights between last quarter and new moon, something that has been rare.  As a result, a large number of new objects were logged, and a few old classics.  During the observing month I managed to conclude my in-depth studies of Lyra.  I have now moved on to Cygnus and Cassiopeia.  While all three constellations have been examined in detail in past years with the 8", it is a whole new world up there with a 12".  Most of the fainter, previously invisible NGC objects are now available to me, expanding my viewing options significantly.  My earlier studies in Lyra saw me observe 4 NGC/IC objects.  This time around I went after 32 of them, plus one non-NGC open cluster!  Only two objects proved too faint or small.

     Searching for faint galaxies in Lyra (and now Cygnus) has the advantage of observing in overhead skies.  However, the disadvantage is the rich and bright star field surrounding many of them, making galaxy viewing quite challenging.  Of the 32 new NGC/IC objects observed this month, only 5 were non-galaxies.  Those consisted of a globular (M56), two open clusters and two planetaries (one being M57).  This entry will only deal with objects seen in the past month.  For the full Lyra details, see my two previous blog entries.

     For Cygnus and Cassiopeia, I have decided to not only search for NGC/IC objects not previously seen with the 8", but also to undertake a full but quick review of objects already logged with that instrument.  In some cases it's been 20-30 years since I have observed most of these objects, so it's likely time for a revisit.  While more time will be spent on the unfamiliar objects, I will try to spend some time with every cluster, nebula and other deep sky object in these constellations.  My to-do list is extensive, and it will take many sessions to complete.

     This past observing month I observed 25 new NGC/IC objects, as well as reviewed 8 others previously seen.  Most were faint galaxies, and most were in Lyra, but a few were also logged in Cygnus.  While none of the galaxies were outstanding, a few were well worth the hunt, and recommended objects.  The finest objects this past month were all ones I had seen years before.  I will list them in order of interest, beginning with the best and brightest objects newly seen and continuing on to the faintest of the faint fuzzies.  Then I will discuss previously seen objects.

NEW OBJECTS

eg 6764:  The brightest galaxy in Cygnus, and brighter than any of the ones in Lyra except for 6703 (see previous blog entry, below).  Worth seeking, likely making you one of the rare amateurs who know there is a pretty bright galaxy in Cygnus and have seen it!

eg 6702:  2nd brightest galaxy in Lyra, and a nearby companion to the brighter 6703.  Two for one.

pn 6765:  Lyra's "other" planetary.  10" or 12" recommended.  Unusual elongated shape.

eg 6688:  Involved with at least 3 very faint stars.

eg 6692:  Nothing special.

eg 6745:  Check out the Hubble Heritage photo of this object!  Easy with a 12"!

eg 6671:  An easy object, likely doable with an 8".

eg *I 4867:  Small, but bright and easy at moderate magnification.  Near two bright variable stars.
oc 6743:  Called non-existent in some sources, including my push-to computer.  It does exist, and exactly where Uranometria places it.  A bright star is surrounded by a faint cloud of very dim stars.  I counted 18 at 150x.

eg 6662; eg 6665; I 1289; eg 6710; eg 6743; eg 6740; eg 6700; eg6692; eg 6713; eg 6685; eg 6612; eg 6696; eg 6672; eg 6606; eg I 1289; eg 6783 (Cygnus); eg *I 1301 ( Cygnus).  All tricky.  Happy hunting!

*  A note about I 4867 (bright and easy for a 12") and I 1301 (very dim and extremely difficult, just south).  Some sources say they are the same object!  Not!!  Refer to Uranometria.

There you have it--25 new NGC and IC objects.  The only non-NGC object viewed this month was also new to me.  Ste 1 is a very large open cluster centered around Delta Lyra.  Bright and suitable for almost any aperture.  Lovely in the 4 1/4" Astroscan.  About two dozen stars with a 12".

PREVIOUSLY VIEWED OBJECTS

pn 6720--M 57:  Arguably the finest amateur object out there, except perhaps for M 42!  One of two objects I was unable to locate was a faint IC galaxy very close to M 57.

gc 6779--M 56:  Often overlooked in favour of more popular summer globulars, this one is not to be missed in a 12"!

oc 6791:  Resolving this open cluster is more difficult than many globulars.  A real beauty!

oc 6811:  A rich and lovely cluster, with a very fine field just preceeding.  Repays close viewing.  Plenty of brighter stars, and some very dim ones back there, too.  A 4" mirror just begins to resolve it!

oc 6819:  Smaller and not as rich as 6611, but not to be missed with a large mirror.  Unusual shape, and again in a very bright star field.  Use all magnifications, and then go back to lowest again.  Recommended!

eg 147:  A massive galaxy in Cassiopeia with a very low surface brightness, this one requires a great sky.  One of M 31's nearby cousins.

eg 185:  Very near 147, and also related to M 31.  Brighter, smaller and much easier to view than 147, but it is still huge!

eg 6703:  The brightest galaxy in Lyra and/or Cygnus, and a decent object for an 8" mirror.  6702 appears in the same field.

     It was a most enjoyable month.  I managed 7 observing nights out of the 14 available!!  Happy hunting!

Mapman Mike

#15: Full Moon: Dark Skies Just Ahead

     The time just before and after full moon is perfect for tweaking one's observing plans.  Spring constellations are available to us for such a short period of time compared to summer, autumn and winter ones that careful preparation is even more important than usual.  I have been trying to make a decent start on Leo, and beginning two nights after full moon I hope to resume my work.  Immediate observing projects are to observe and sketch M 66 and eg 3628.  As the moonrise is gradually set back far enough in the evening, I will leave my back deck and set up my scope farther afield in dark sky locations.  I don't know yet whether I'll be able to observe in the 'preceding' area of Leo, where I have a whole collection of faint objects remaining to see, or if I will have to immediately move my observing session more towards the middle and 'following' sections of Leo.  Leo begins at about 9h 22m r.a., and continues until 11h 58m r.a.  No doubt I will still get lots done in Leo if it's clear, but not necessarily from the first pages of my object list, which generally follows r.a. of the constellation I am observing.

     One thing is for certain; Leo will set relatively early during the night.  Though I have notes prepared for Lyra, I decided I needed something to bridge the gap between Leo and Lyra.  Bootes seems to fit the bill nicely, though I have already observed it in some detail with the 8" scope.  Bootes begins at 13h 16m r.a., continuing to 15h 12m r.a.  Bootes is a galaxy-filled constellation of difficult NGC objects, and it contains not a single Messier object or galaxy of real brightness.  Besides galaxies, there is a lone, very faint globular cluster.  Having already viewed and sketched the brightest galaxies and the cluster, there may be little remaining for me to see except the dozens of much fainter galaxies.  While I don't mind reviewing previous brighter galaxies in the newer 12", I also want to add new NGC objects to my life list.  The good news is that right about now where I live, the trees usually begin to leaf.  When this happens, a lot of ground light pollution is blocked and the sky grows a bit darker.  Any slight advantage might make the difference between seeing a faint galaxy or not seeing it.  This year in southern Canada, however, we seem considerably behind in seasonal changes, and I may have to wait one more full moon before the trees are of much help.

     Leo also offers two close-up charts in Uranometria.  Charts A10 and A11 are galaxy-filled playgrounds, and I hope to make a good start on Abell 1367 (Chart A11).  I haven't yet decided on an observing strategy for this remarkable area.  I will first determine which objects and how many are actually available to me by having a quick look there.  If many or most of them are visible, then I will likely enjoy a galaxy-filled observing orgy over several nights.  As I enjoy star hopping so much, I'm certain to love galaxy hopping, too!  If my skies do a poor job of allowing me decent access, then I will likely plan a road trip with my telescope for next spring to somewhere very dark in order to experience this feast properly.  In fact, an upcoming post will likely be about dark site road trips.  Where to go, when to go, why to go and which way to go.  So stay tuned.

     Full moon is also a perfect time to tune up the scope and accessories.  Cleaning eyepieces and the finder-scope is a great idea, and perhaps doing some collimating on the secondary and primary mirrors isn't such a bad idea, either.  And of course it is a perfect time to scour the web and catch up on some blog reading!  Until next time enjoy the full moon, and join me in anticipating the dark-sky nights that will come soon afterwards.

Mapman Mike

#14: Monthly Summary 1 (mid-March/mid-April 2013)

     With the moon now waxing, and the ten-day weather forecast predicting some form of rain every day for the foreseeable future, it is safe to say that dark sky observations have ended until after full moon on the 25th of this month.  I desperately tried to observe a few objects last night in Leo, but consistent clouds and haze made decent views impossible.  It is now time to summarize achievements during the past lunar cycle.  Despite many overcast nights, there were some remarkable successes since March 15th.  I got outside with the scope 8 times, and a few of those nights were near-perfect skies.  Many, however, ended early with incoming clouds.  Even worse was having clear skies predicted, staying up late only to find no such clear skies appearing.

     Despite some bad luck with weather a total of 19 new NGC objects were officially logged, many of them sketched as well as reported on with good old fashioned words.  One of the objects accounted for 4 of the new NGCs.  The Rosette Nebula in Monoceros has the following designations:  2237, 2238, 2239 and 2246.  The cluster itself, seen last lunar cycle, is 2244.  The nebula is vast and completely encircles the open cluster.  I could see nothing at all without a Skyglow filter, but with it and a low power eyepiece (28 mm) the emission nebula appeared as so much faint cloud interspersed among the rich stellar background.  So score 4 NGC right there!  I had hoped to also have a look at it with my Edmund 4 1/8" rft, but did not have the opportunity (more about this little scope soon).

     So besides the 4 galactic nebulae, I also viewed in detail this past month 5 open clusters, 9 galaxies and 1 planetary nebula.  One of those galaxies was M 65, and though I observed the entire Leo Triplet several times, M 65 was the only one so far to be officially entered into the logbook.  Sketches and verbal descriptions of M 66 and eg 3628 await better skies.  The Leo Triplet was easily the highlight of the observing month, with all three galaxies easily fitting into my 2" eyepiece at 43x, and just barely into my 1 1/4" 25 mm 60x eyepiece.  I now know that area so well that I can close my eyes in bed at night and still see it all clearly.  Two other worthy NGC galaxies lay within an easy star hop of the Triplet and were also seen on a few occasions, though not yet officially reported.  This is one of the great advantages of taking one's time when exploring the deep sky.  Once you have really explored and star hopped through an area over several nights, it will stay in your visual memory for a very long time.

     The Leo Triplet wasn't the only galaxy triplet observed this month.  NGCs 2872, 2873 and 2874, though much fainter and smaller, mark another worthwhile goal for 12" scopes or larger.  On my first attempt, only 72 and 74 were viewed, virtually touching.  72 is brighter than 74, though 74 extends further than its bright counterpart.  On a subsequent night I was able to see the third and very faint member, 2873, and it remains the faintest galaxy yet seen with the new scope.  And finally for Leo galaxies, the duo 2911 and tiny 2914 also make a worthy pair.  A nearby third member (2919) has yet to be found.  All three are an easy star hop from 6 Leo, a colourful double star.

     Monoceros is rich in clusters, though this month there were no real standouts.  oc 2353 was the best of the new ones, though I also liked 2252 (it looks like a Star Trek symbol to me) and 2364.  This last one is interesting because very little is said about it, and some photos show nothing at the site.  I definitely saw a cluster, however, and exactly where Uranometria puts it.  It is very small, and consists of 5 "brighter" stars in a curving line, with a field of very faint stars mixed in.  At lower powers the surrounding field is rich with stars, though the cluster itself is relatively barren.

     Of the non-NGC objects, my favorite was oc Collinder 106, a really huge affair that made for grand, informal sweeping.  Dense knots of stars can be found amidst its very bright and scattered field.  Two double stars also stood out this month.  8 Monoceros and 6 Leo are worth a stop if you appreciate doubles, and can easily be split in any modest telescope.  Other objects of interest are near each.

     Overall, I would have to say I was somewhat disappointed in how little I was able to accomplish in Leo.  Of the 9 galaxies officially logged, 8 of them are pretty faint, and a few are very faint.  They usually require some time to locate, see and reconfirm.   Early in the season I had hoped to complete about 5 pages from my extensive 32-page object list of the constellation this year.  I have yet to fully complete page 1!  With spring galaxy season nearly half over for Leo lovers, it will have to be very clear in May if I hope to reach my goal.

     With a little vacation approaching, I will be taking some time off from observing and blogging.  I will be back around the 1st of May, hopefully faced with 10-12 days in a row of clear skies.  May you have the same.

Mapman Mike

#13: More About Galaxies

     I said awhile back that 5 of every 6 non-stellar objects plotted in Uranometria 2000 are galaxies.  That only includes objects to 15th mag.  If we dip down to 17th or 18th mag, virtually every object past 15 is a galaxy.  They are difficult to avoid if observing faint objects.  Since this blog is currently concerned with the NGC catalogue (and much of the IC list), I will only discuss the main list at this time.  With over 7800 objects of all types in the NGC list, galaxies still reign numerically supreme.  It might be of interest to look at which constellations have the most NGC objects within their boundaries, and just what type those objects are.  Because I live and mostly observe at latitude 42 degrees north, I will only discuss those constellations which are visible from mid-northern latitudes.

     The constellation (north or south) with the most NGC objects is........Virgo!  Not a huge surprise to seasoned observers, I'm sure.  Virgo has 637 NGC objects.  And guess what?  636 of them are galaxies!  There is one lone globular cluster (gc 5634).

     Number two on the list with the most NGC objects is....Ursa Major.  There are 407 NGC objects.  Only two are non-galaxies!  There is a single very famous planetary nebula and one open cluster.

     Number three constellation is Cetus.  Some of it is a bit low in the sky for me, but it is all there.  Cetus has 383 objects.  There is one lonely and very low surface brightness planetary nebula (NGC 246).  The rest are galaxies.

     Number four on the list and close behind is Leo, with 378 NGC objects.   Every single one is a galaxy!  No relief here, though it is peppered with some lovely double stars and multiples.  I am currently beginning my extensive and hopefully exhaustive exploration of this early spring constellation.  It will take me many years.  To date, I have located 13 of its NGC galaxies, though I've officially logged only 9 so far (it`s been pretty cloudy).

     Number five is Eridanus, a constellation that winds from north to south, meaning that I cannot see all of it from my latitude.  With 315 NGC objects, it has one reflection nebula and one planetary nebula.  All the rest are galaxies.

     So, then, the top five constellations for northern latitude viewers contain a total of 2,120 NGC objects.  That`s about 2/7ths of the entire list.  And a whopping 6 of those objects are non-galaxies!  Let`s continue through the top ten NGC constellations.

Number six is Pegasus.  With 298 NGC objects, only 3 are non-galaxies.

Number seven is Coma Berenices.  293 objects.  It has 3 globulars.

Number eight is Draco.  287 objects.  2 planetary nebula.

Number nine is Pisces.  270 objects.  All galaxies.

Number ten is Bootes.  267 objects.  1 globular.

     We are now up to 3,535 objects, nearly half of the NGC list!  All are galaxies except for 15 objects!  I don't know about you folks, but I find this quite astonishing and somewhat amusing.  "Well," you say, "what about those rich milky way summer constellations?"  OK.  Let's look at Scorpius.  Lots of interesting objects there.  Scorpius has a grand total of 71 NGC objects.  There are some totally amazing ones, too.  However, there just isn't a whole lot of them compared to those galaxy constellations (Sagittarius has 77 NGC objects).

     After the top ten NGC constellations comes Hydra, Canes Venatici, Hercules, Andromeda, Aquarius, Cancer and Lynx.  All are very heavy with galaxies.  I am not trying to prove any point here, but merely stating some interesting (for me) facts.  And no, I did not count the objects myself from the atlas.  This website does it for me.  
http://www.nightskyatlas.com/constellations.jsp

I did, however, scan through each constellation's list to search for non-galaxies, so there is some original research involved.

_________________________________________________________________________________

Here are a couple of older sketches each depicting a galaxy I saw with my previous scope, the amazing Edmund 8":

My first attempt to scan some early sketches.

eg 4565, Coma Berenices.  112x.

15'.8 x 2'.1  Vis. Mag. 9.5.  Sur. Br. 13.2.

One of the showpieces of the heavens.

eg 4448, Coma Berenices.  72x.

3'.9 x 1'.4  Vis. Mag. 11.2.  Sur. Br. 12.9

The star field is at least as interesting

as the galaxy.  The scale for this sketch

is obviously not the same as for the one

above--I cropped this one a lot.

Happy galaxy hunting!

 

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

#10 Mirror Size

     I mentioned somewhere in an earlier post that if I had easy access to a truly dark sky, I would not require anything larger than an 8" telescope.  To any readers fortunate enough to have that dark sky on demand, along with an 8" scope, you have an ideal situation.  Or not.  It depends on what you are searching for, and how much you hope to see.  You won't be resolving any galaxies into millions of stars with it (nor with any other instrument).  A 6" scope would be quite nice in a great sky if an observer was after only the best and brightest of deep sky objects.  An 8" would be a big bonus for such a project.  For someone enamoured with the whole NGC list, however, a 12" scope in that beautiful dark sky would be darn near perfect.  A 14" objective would be a bonus. 

     I've owned a 3" reflector, a 4.5" reflector, an 8" reflector, and my current 12" Dob reflector.  Going from a 3" reflector to a 12" is not a bad upgrade.  One might think that going from a 3" to a 6" would double the light, and then double it again from a 6" to a 12".  Thus 4x the light gathering power belongs to the owner of a 12" compared to his neighbour with a 3" (refractor or reflector, makes no difference when merely gathering light).  However, this is not the case.

     In actual fact, even though my math is not exact to seventeen decimal points, upgrading to a 6" mirror from a 3" is already an increase of 4x the light-gathering power, not 2x.  7.1" sq. versus 28.3" sq. is 4x the light-gathering power.  Going from a 6" to a 12" increases it again by 4x, from 28.3" sq. to 113" sq. (pardon my non-metric calculations).  In my lifetime, I have increased my light gathering power by a whopping 16x.   I'm still not going to resolve M31 into individual stars with it, but the galaxy sure looks a lot brighter (and I can now see a few globular clusters in it!).

     When I observed with my 8" reflector, I had pre-cut cardboard circles on hand so that I could cover the top of the tube to see what certain objects looked like from a 4" objective and a 6" one.  With the holes cut away, it was also easy to actually see the difference between areas of different sized objectives.  I recently cut a new cardboard aperture to fit over the 12" tube, being 8" (off-centre).  That 8" hole now seems awfully small, with the huge amount of cardboard left over showing the full 12" circle.  Since upgrading from an 8" mirror to a 12", I have increased my light gathering power from roughly 50" sq. to 113" sq., or by about 125%.  It had not really struck me how much bigger that 12" mirror was until the cardboard cover was finished.

 A very rough 8" diameter hole cut from a 12" piece

of thick cardboard.  Black tape hides the bad cutting,
and keeps the circumference roughly even.  Not only
can I now see how objects compare at 8" and 12"

(roughly speaking), but I can really see how much

larger the 12" mirror is (more than 2x, or about 125%).

     We could push this discussion some more, discovering that a 16" mirror has about 201" sq., and a 22" one has around 383" sq.  These scope sizes and larger ones now regularly appear in amateur astronomers' inventories.  How long until we get one big enough to visually resolve Andromeda galaxy at a local star party?  Hmm, that requires around a 200" mirror.  Or maybe several 25" ones spread out and linked by computer on-site.  Maybe that day isn't really too far off after all.

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