Monday, April 12, 2010

Portal, AZ ~ Observing report

This past weekend I headed down to Portal, AZ to observe with my good friend Jerry Farrar.  As I drove down Interstate 10 east of Willcox, AZ on Friday, I was very surprised to see great fields of  golden flowers covering the desert.  I am not sure what kind of flowers these were, but I have never seen this much color, so widespread in the area.   From the "don't try this at home" category, these pictures were taken with me holding the camera out the window and randomly shooting images while flying down the highway at 75 mph.  At least I was not looking through the shutter!

Portal is a beautiful spot tucked into the southeastern corner of Arizona, and the little town sits nestled at the mouth of Cave Creek canyon at the base of the Chiricauhua Mountain Range.  Cave Creek Canyon is world famous for birdwatching, and most weekends find the campgrounds full by early Friday.  The image to the left is the mouth of the canyon as seen from Rancho del Farrar.   I went for a quick walk in the desert just before dark and saw that there were many yellow flowers (of a variety different that those on the roadsides) growing mainly under creosote bushes.  These flowers were quite pretty.  The upper right picture happened as I was goofing around with the camera and discovered a setting that maintains only a selected color and images the rest of the subject in black and white.

Portal hosts some of the darkest skies anywhere, with an overhead naked eye limiting magnitude around 7 - 7.5 in the absence of moonlight.  In addition to the darkness, the air is typically dry and with an elevation of 5000 ft. the observing is unmatched!  We were joined by another friend and skilled observer, Bill Gates, for what would be two wonderful nights observing at Rancho del Farrar. I had brought my Celestron 9.25 inch Schmidt Cassegrain (SCT), as well as a Stellarvue 90mm triplet (90T) refractor.  My plan was to use the 9.25 SCT to observe some galaxies and star clusters, and to spend some time pushing the limits of the SV 90T to see what it would be capable of under dark and steady skies. 

We observed several objects over the two nights, and following are some of the highlights....some commonly observed objects, and some obscure ones.  If you have had a chance to look west over the past week or so, you will undoubtedly have noticed Venus, shining like a beacon shortly after sunset.  To the lower right of Venus this week, is the elusive planet Mercury.  As Mercury never strays far from the Sun in its orbit, it never appears far above the horizon.  To the naked eye Mercury appears as a fairly bright star, yet through the telescope Mercury currently appears as a crescent (as it orbits the Sun inside the Earth's orbit, it displays phases).  The pictures show both Venus and Mercury during twilight.  The picture on the right also shows the curvature of the Earths shadow as it descends towards the horizon.  Tucson Amateur Dean Ketelson imaged Mercury this week with his 14 inch SCT and his photo is an excellent representation of how Mercury looks in the telescope.

While I observed many objects through the 9.25 SCT, a few stand out and are worth mentioning here.  First, Jerry's ranch has a southern horizon that is wide open.  From the Lost Pleiad observatory much of the southern horizon is blocked by a hill, so when I am in Portal I try and observe objects that are difficult from home.  One of these is the famous globular cluster Omega Centauri  (NGC 5139).  In the 9.25 SCT this cluster is absolutely stunning.  There is no other globular cluster that approaches the grandeur of Omega Centauri.  Viewing it from the dark skies of Portal defies description and leaves even me speechless (its true!).  Astronomers estimate that this cluster has over 1.1 million stars and has a diameter of approximately 300 light years.  Further it is estimated that the average distance between stars in the cluster's central region is a mere .1 light year.

Bill Gates has a vast amount of observing experience, and enjoys searching for objects that are at the limit of perception.  He was using his 5 inch Intes Maksutov Cassegrain to study NGC 5128, the Centaurus A galaxy.  This galaxy is rewarding in most scopes, and the 9.25 inch SCT resolved its "hamburger shape" quite well.  This galaxy is well known as a strong source of radio radiation, and is the nearest radio galaxy.  It also contains a jet, visible in x-ray images, from the Chandra X-ray observatory as displayed in the image to the left.  With Bill coaching me, I was able to detect a very low contrast stream of light perpendicular to the galaxy on the south.  Bill was able to detect this both north and south of the galaxy.  I do not believe it was the jet, but it was interesting to see this feature as I do not recall seeing it in pictures of this galaxy.

Another interesting object I observed was NGC 3201 a globular cluster in the southern constellation Vela.  This object is also object number 79 in the Caldwell Catalog, from which I have been working on observing all of the objects visible from the latitude of the Lost Pleiad Observatory ~ 32 degrees north.  (I have only 5 objects left to observe).  The cluster is very beautiful, being very large and quite bright.  In the 9.25 inch SCT, it is well resolved and is irregular in shape.  As globular clusters go, this one has a weak central condensation of stars.  The beautiful  image to the right is courtesy of the Hubble Space Telescope.

While I was spending some time observing Mars, Bill and Jerry were off hunting objects down from the Arp Catalog of Peculiar Galaxies.  I decided to have a go at one of them myself, ARP 244 the antenna galaxies.  These galaxies are NGC 4038 and 4039. The image to the left reveals how these galaxies came to be known as the antennae galaxies.   The image to the right is again courtesy of the Hubble Space Telescope.  The larger galaxy at the top of the image is NGC 4038.  It is estimated that these galaxies first began their merger a few hundred million years ago, and that they will not completely merge nuclei for another few hundred million years.  These galaxies are approximately 63 million light years away...which means that the light hitting my eyes on Saturday night left these galaxies 63 million years ago, or about the time of the last great dinosaur extinction!  So, how insignificant does the span of human history seem now?  I decided to make a sketch of these galaxies which you can see is not quite as exciting as the Hubble photo.  The sketch was done at a magnification of 180x, and reveals quite a bit of the galaxies, including the bright cores.  No evidence of the antennae extensions was seen however.

As for the most obscure object I observed, it was undoubtedly Markarian 421.  Steve Gottleib has an article in the April issue of Sky and Telescope magazine discussing Blazars.  Essentially, Blazars are galaxies that vary in brightness due to active galactic nuclei that are directing energy in our direction.  These are very faint objects, and using the 9.25 inch SCT along with the finder chart from the magazine I was able to locate Markarian 421.  It appears as a fuzzy star, and this blazar varies in brightness between magnitude 12 and 14.4.  I would estimate its current brightness between magnitude 12 and 12.5.  It is approximately 400 million light years away!
As I mentioned earlier, I had brought a Stellarvue 90mm triplet along to put through its paces under dark and steady skies.  I'll start with my conclusions and then get to the details.  For those of you interested in this scope, my overall impression is extremely positive.  The optics are first rate and the views that the scope delivered across a range of magnifications and targets were essentially perfect.  What I mean by this is that, as a visual observer, there was nothing that I could find fault with in the image at the eyepiece.  This is the the sixth refractor I have spent quality time with (owned), and aside from my TEC 140 APO, it is the best I have looked through.  While it goes without saying, I will remind the reader that what I am reporting is my subjective experience at the eyepiece, not the result of any formal optical testing or evaluation.  There was no false color detected, and contrast was excellent.  I am not an experienced star tester, so I will only comment that when focused at high power the scope produced a well defined airy disc, and the scope had that nice "snap to focus" characteristic.  One of the things that I always look for in a scope is how well it renders star colors, and the Stellarvue provided gorgeous color in stars.

Mechanically, the scope comes with a two speed import focuser that provides for coarse focus and an 11:1 fine focus.  This new import focuser is far superior to the run of the mill import focusers that exist on many scopes, including older Stellarvue scopes.  With stainless steel bearings and a refractor brake, this focuser is just a notch below the feather touch line of focusers.  For visual use, nothing is lost with this new standard focuser, and an upgrade to a feather touch seems unnecessary.  The sliding dew shield, however, was the weak point of the design.  When pointed at zenith, dew shield would slip down.  Stellarvue provides a few strips of extra self-adhesive velvet to deal with this scenario, so during the day I decided I would perform this harmless procedure.  I disassembled the dew shield and discovered that a piece of the original velvet had come off and was crumpled up between the dew shield and tube.  I removed this, and placed a new piece on the lens cell.  I reinstalled the dew shield and unfortunately, it was now so tight it would not move!  With some effort, I removed it again and made another attempt to get it right.  In the end, after three tries, I was unable to achieve a decent fit, as the velvet was worn in some places and not others.  I will be ordering some new velvet and starting from scratch.  In addition, I will likely have a hole drilled and tapped for a nylon tipped thumb screw to hold the dew shield in place.  Despite this issue, I am very happy with the, what about the observing highlights!?!?

First off, before it set, was the great Orion Nebula.  I never tire of observing this object and the view throught the Stellarvue was awesome.  With a 20mm Nagler eyepiece (about 31x) the nebular complex was so large and detailed that I had to pan the scope to take it all in.  While the "wings" of the nebula are obvious in any scope, I wa able to trace a loop of nebulosity extending from the "wings" down below the nebula...a complete ring is the best way to describe this.  I spent some time observing both Mars and Saturn with the scope and a Pentax XW 3.5mm eyepiece.  The views were rock steady at 180x.  Mars was sporting a small north polar cap and hints of albedo features.  Saturn was glorious as well.  The rings, nearly edge on, were razor sharp.  Subtle banding on the planet was obvious, as was polar shading.  The moons Rhea and Tethys (each approximately magnitude 10) were sitting on either side of Saturn just outside the rings. Planetary observing is the domain of refractors, and the Stellarvue did not disappoint. 

For a good test of contrast, I decided to see how many galaxies I could observe in the area of Markarian's chain in the Virgo galaxy cluster.  Basically, I quit after an even dozen as I was getting tired.  While I observed a dozen galaxies in the immediate area, the photo to the left shows the 8 galaxies that are actual members of the chain.  To the right is the rough sketch I made as I went, to keep track of galaxies I saw.  It is not to scale and was simply a way that I could then compare and verify my observations in the 9.25 inch SCT.  The upper circle contains the sketch, and the lower circle contains the Messier (M) and NGC numbers of the galaxies.  What does it all mean?  It means that this scope has excellent contrast and that under dark and steady skies, the Stellarvue 90mm triplet performs at the limit of a 90mm scope.  As always, your mileage may vary!  In closing I provide the size and magnitude for the galaxies that I observed in the area of the chain, from left to right in my sketch:
Object             Size               Magnitude
M84                5 x 4.4'           9.3
M86                7.4 x 5.5'        9.2
NGC 4377      1.7 x 1.3'       11.9
NGC 4388      5.1 x 1.4        11
NGC 4413      2.3 x 1.4'       12.2
NGC 4425      2.9 x 1.0'       11.8
NGC 4435      3.0 x 2.1'       10.8
NGC 4438      9.3 x 3.9'       10.2
NGC 4458      1.6 x 1.5'       12.1
NGC 4461      3.4 x 1.4'       11.2
NGC 4473      4.1 x 2.5'       10.2
NGC 4477      3.6 x 3.3'       10.4

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