#125: Crab Nebula

The following is an article I wrote for our astronomy club newsletter, for January 2020.  I belong to the Windsor branch of the RASC, and write articles five times per year.  To see previous newsletters, link to this address on our homepage.  There are also other fine articles by other members, as well as some outstanding amateur photos.

This time of year very little time is spent at the telescope eyepiece. I did enjoy a fine night on December 21^st, but as of early January that has been it, other than a few naked eye peeks at Betelgeuse. Instead, I will talk briefly about the 2019 highlights and lowlights, and say a bit about 2020.

For me, 2019 will be remembered as the year I had to abandon the club's Hallam site for my observing program. The greenhouse lights to the south have reached a level of insanity I could not have imagined even a few years ago. While in the long term I am optimistic that the stray light problem from Leamington will be addressed, in the short term Hallam is now reserved (for me) for lunar and planetary work. I have had to move my deep sky observing to Chatham Kent County, where I can at least enjoy good skies to the north, east, and south. The success of Detroit’s streetlight program has made the west and northwest sky much more light polluted than several years ago, when nearly half the streetlights in that city did not function.

And yet another big problem lies in the near future, as over six thousand new satellites will be orbiting the Earth within two or three years. These satellites will be used to bring fast internet to the entire planet. They are supposed to be highly reflective, too. In 2020, 1500 of them will be launched. The first few batches of 60 are already up there. Even using remote telescopes for photography will be greatly affected. Needless to say, it isn’t only amateurs who are worried; major observatories will have some serious obstacles to overcome as well. And what happens to these satellites if Earth is struck by a major solar flare? If you think we have a lot of space junk up there now, just wait.

My NGC observing project continued in 2019, as I managed to get out under clear skies with my telescope 34 times, totaling over 100 hours of observing. That is considerably better than 2018, one of the cloudiest years I have ever seen. One of those observations was the total lunar eclipse of January 20^th, possibly the coldest observation I have ever recorded from Essex County. It was a very fine and clear night, however.

And in Spring 2019 I finally managed to complete my viewing of the entire NGC list in the constellation boundaries of Leo! That was a seven year project that took me to some fabulous sights, a few of which I have shared in these pages. My newest Spring observing adventure lies within the border of Coma Berenices, and might take me just as long. Will I ever get to tackle Virgo someday? If I do, you will read about it here.

Winter months are an excellent time to plan a viewing program for the warmer months. I wish you all many happy observing planning sessions, and excellent skies with which to undertake those plans.

Messier of the Month: M 1, “The Crab Nebula”

Approximately 7500 years ago, a star exploded in the direction of the constellationTaurus. Seen and recorded over a thousand years ago by the Chinese in 1054 A.D., the remnant from this supernova was the first astronomical object to be identified as such. The Earl of Rosse drew the object in 1840, observing it with his 36” telescope. His drawing was said to resemble a crab, and thus the nickname. This is one of the most studied objects in the sky, and provides for some fascinating on-line reading. Stunning photos reveal the object in breathtaking detail. What is highly unusual about M 1 is that on very detailed professional photos, significant changes can be noted in less than a month. Even so, I still like to view it in a small scope. In a really dark sky it can be seen with binoculars, though my views have been only through telescopes. And it continues to expand, being significantly larger now in photos than when I first began the hobby.

My first look came in March, 1973, using my 4.5” Tasco reflector. With fresh snow on the ground and an unshielded streetlight only a few meters away, it wasn’t the ideal first look at such an object. A much better view came from my back deck in Anderdon Township in March, 1994. I was using my trusty Edmund 8” reflector. At lower powers it reminded me somewhat of a very large and bright galaxy. The edges appeared smooth, even at 169x. Skip ahead to late November, 2016. I viewed it with the 12” Dob from Hallam, and found it impressively large, very bright, and quite elongated. The large central area is much brighter than the outer areas. Several faint stars appear to me very close, or even touching the outside edges. The south-following end is very patchy, whereas the north end tapers and fades gradually.

My Space Eye view came in October, 2015, from Hallam. I did not have high expectations of seeing M 1 with the 2” refractor, but it was located at 30x! The nebula was really faint, but quite unmistakable. It was oval, and though fairly small, averted vision really helped bring it out.

Messier 1 (NGC gn 1952): 6’ x 4’ emission nebula in Taurus.

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.

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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





#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

#8 My Previous Telescope

      I mention in my intro to this site that I have had considerable experience observing the skies with a telescope.  Most of that was done with my previous telescope, the one with which I have logged the most hours.  Here is the original promo sheet that I got with it.  I was fortunate in that I was able to use the instrument spring, summer and fall in northern Ontario under pristine dark skies for many years.  That scope could pull almost any object out of a dark sky, and served me very well for over 30 years.  I recently sold it to help finance my upgrade to a 12" Dob.  The Edmund 8" was a thing of beauty, and I instantly fell in love with it at the Toronto shop where it was set up.  I was in university in 1978 and barely had a spare nickel to my name.  Student grants and loans saved my life back then, and I didn't mind cutting back drastically on food and beer for awhile to help pay for this.

     To date I have logged 540 formal observations, encountering over 660 NGC/IC objects, hundreds of variable stars, thousands of double and multiple stars, and many objects not listed as NGC.  Quite a few of the observed objects have been sketched, and if I am able to I will soon begin to share some of these remarkable past observations.  Scanning a sheet of black paper containing stars and galaxies drawn and painted on it is a new experience for me, and early results are not promising.

     The first time I got to use the 8" in a dark sky I thought I would lose my mind.  There were stars among stars among stars, and the background just seemed to resolve forever and ever.  My family had a cottage on Lake Penage, west of Sudbury, Ontario.  I had observed there for years with the smaller telescope I had previous to the Edmund.  Naked eye 7th magnitude stars were routine on a good night.  Spring galaxies soon fell one after another to the mighty 8" mirror, as did summer globulars, open clusters, and nebulae.  Star charts for amateurs had just recently graduated from Norton to the more comprehensive ones of  Will Tirion.  I was seeing many faint objects not even plotted on their maps!

     Alas, the 8" had its flaws.  The extreme tension required to hold the mount in place depended on a simple turnbuckle, which frequently stripped suddenly.  The telescope could fall over when that happened, and did on more than one occasion.  Plenty of spare buckles were always on hand.  The 40mm finder-scope was not the greatest, and the main focuser was considerably less than perfect.  Balancing the scope was tricky, and when a large eyepiece was plunked down, things went astray quickly.  The tube had to be loosened and repositioned when changing sky positions (and rebalanced).  But it had a working clock drive for most of its illustrious career, and that really enabled drawing at the eyepiece, as well as meditative viewing.  My wife would sometimes sketch for 30 minutes without ever requiring me to re-center the object.

     It was decently equipped for astrophotography, but other than some lunar and planetary work I was never interested in that aspect of astronomy (another subject for a future blog).  As I have been an avid photographer since the age of 13, this might seem somewhat perplexing.  Parting with the Edmund scope was not as hard as I expected.  I had it up for sale for about a week last fall.  There were no nibbles and I had just made up my mind to upgrade it with a better finder and focuser, and forego purchasing a new 12."  Then along came a buyer, who took it after one look (it is awful pretty).

     I am eager to revisit some objects logged with the 8" scope, now available to me with the 12", but I will mostly go on to different sights with the new one.  In my next post I will talk about those objects and why I gave this blog the name that I did.  Hope you come back.

Mapman Mike