October 2006

Vale da Lama VIII

Vale da Lama - Alpiarça

Swan and M13
Swan and M13

Another trip to Vale da Lama ("Valley of the Mud"), that despite the recent floodings in the region was still passable. The SQM marked an average of 20.70, consequence of a not very dark night , somewhat milky white sky and also the treacherous high clouds always waiting to ruin an exposure, but served anyway as pauses to simply look at the sky. The moistness accentuated until the beginning of the dawn, but later the night remained calm and pleasant. As always, the traditional snack and grill in good company. The resultant images of this night can be seen here.

Comet C/2006 M4 (SWAN)
Comet C/2006 M4 (SWAN)

I love when comets do this! (clique na imagem - click on the image)

I had followed this comet with the 7x50 binoculars on previous days here at the Patio since it entered in " outburst ", didn't give it more than a 5 magnitude mark. It seemed that was already done before it's way-around the Sun, a then suddenly it appears fulgurant as never. The image was registed along one hour, being this the position of the comet at 20:07 TUC.

A lapse that was almost fatal. I forgot to adjust the date and site on the spreadsheet that I use to do the sidereal hour calculation to polar align the mount. The parameters that I gave were of the Atalaia two weeks ago… (to see the entrance more below). Excused to be said that the images suffered a bit field rotation. Field rotation is almost impossible to detect from photograph to photograph, just only when the images are registered for stacking that the effect is notorious, but that was not nothing that IRIS couldn't handle.

The image shows an impressive size dust tail , extendend by almost 3 degrees (6 moon or sun diameters ), even so very little of it was visible with the 7x50 binoculars, and very light traces with the 90mm at 21x, perhaps due to moonlight and also some luminosity in that area. The coma brightness was slightly similar to the M13 cluster some degrees higher up. I tried to see it naked eye several times without success.

As a curiosity, the comet was at 1,07153668 AU (160,299,606 km) that is little more than in the distance between the Earth and Sun. Knowing that the Sun has 1,39 millions kilometers and has an apparent size diameter of about 32 ' we can easily estimate with simple 3 rule the tail's real size as seen in this image from our perspective: about 5 million kilometers (little more than 3 millions miles), even so the tail probably has the double of the size when photographed with bigger telescopes. An interesting detail is that although all this apparatus that seems that it is disintegranting (which sometimes happens), typically a comet only loses between 0.1 and 1% of it's mass in each orbit.

The widefield image at the top shows the comet's relative brightness when compared with Hercules globular cluster M13, that was situated higher at 1 o'clock, and curiously presents a very similar color. The conditions at this time weren't very favorable, with the comet and Hercules starting to disappear on the horizon, but with good will still traces of the of the extensive tail can be noticed.

Open Clusters M35, NGC 2158, IC 2157 e IC 2156

In the Gemini constellation, at 2800, 13000, 6120 and ???? light years respectively. The two first cluster have the same dimension but 10000 years separate their light. It is easily detectable with naked eye and an impressive sight with thebinoculars or telescopes at low magnification, even so the color difference is only notourious with bigger appertures - NGC 2158 is a good example of “reddening” caused by the interstelar dust becase it is not a very old cluster.
The IC 2157 and IC 2156 are practically imperceptible with the 90mm. The IC 2156 are an illustrious unknown, probably only a asterism that is that small concentration about 11 o'clock of IC 2157. The bright star that composes the image and gives an aid to balance the colors the K0 giant 5 Gem shinning at almost 6 magnitude.

M25, NGC 2158, IC 2157
M25, NGC 2158, IC 2157

Barnard 33, IC 431, IC 432, NGC 2024, IC 435, IC 434, NGC 2023 and NGC 1990

I decided to only include this passable image of one of the most astrophotographic popular regions because it cost me more tha two hours to photograph it. This was the result 30 2 minutes exposures manually chronometered with the consequent camera power recycling (RAW Nikon RAW "curse"), these were what ha lefted after had lost 10 exposures to the sneaky clouds. One hour of exposure simply isn't enough, much less with a practically h-alpha blind camera. Anyway it is the result of the moment.

Rare were the occasions where I've observed visually the Horsehead (Barnard 33) or better said the dark nebula at emission nebula IC 434, but the “Flame” (NGC 2024) is readily seen with the 20cm and 90mm. The IC 431, 432, 435 are reflection nebulas with its color typically from the star that illuminates them. The two great beacons are Orion's belt two young blue supergiants : the Alnitak (zeta at 800 light years) and the Alnilam (epsilon 1300 light years) whose the bluish flash will be the beginning of NGC 1990 that spreads around the star.

M25, NGC 2158, IC 2157
M25, NGC 2158, IC 2157

• elaborated with the music of String Quartets "Haydn" K.387,K.421, K.428, K.458 K.464 e K.465 by W.A.Mozart (Hagen Quartet,Deutsche Grammophon)

Atalaia XXVII

Atalaia (Montijo 38º44N 8º48W)

Comet C/2006 M4 (SWAN)The SQM measured about 20,30 average, lots of humidity, with the Moon to be up at 01:00. Tea and cakes were courtesy of João Gregório.

Comet C/2006 M4 (SWAN)

The first objectiv was to observe the currently brightest bcomet most in our sky, the C/2006 M4 (SWAN).

The IAU estimates were indicating about magnitude 8 , but it seemed to me quite brighter, almost similar to the near 6.6 mag star that it met there close (the most image's brighter). At 21x the coma was colorless and had oval shape and was very condensed, but without any visible traces of the tail.

This comet look like to have a hyperbolic orbit, that means that probably it is destined to be injected outside of the solar system due perturbations that must have suffered when passing close to the planets (the usual suspects are giant gas planets). Another reason could be that it is an interstellar visitor, but the frequency of visit of these kind of comets is estimated by 1 each 450 years.

At the regist moment it was moving about 2 degrees per day in Righ Ascension, distant more than 160 million kilometers from Earth, having this time the predicted maximum brightness.

More information and better images at the excellent http://cometography.com/lcomets/2006m4.html

The side image shows a tail with two thirds of a degree and the typical color green-emerald (the most important emission mechanism is fluorescence) that despite adverse of observation conditions at such low the altitude (10º), fog, light pollution and eclipses by carbon accumulations (fellow companions). It also doesn't seem that well focused . Made with 5x 2minutes exposures.

Galaxy Cluster Abell 426 (Perseus A)

It takes a considerable portion of good will to consider the image below aesthetic interesting. I had never photographed a clusters of galaxies more than the 200 million light years and for several reasons: excepting the clusters from the Local Supercluster (Virgo), these are typically very faint and their galaxies members smaller than fly shit especially at the resolution scale used (4") with the brighter member having only 7 or 8 pixels in size, it shows well what can be expected from a galaxy cluster. The image has a total exposure of 28 minutes (7x4 minutes), time that is indeed insufficient for this type of object. The North is at the top in both the images.

It is relatively easy to find, being located in the Perseu's constellation at two fingers of Algol (beta Persei).
Unfortunely but as expected , I did not see any, even the brightest member NGC 1275 that starts soon at only magnitude 12,7, and I was in complete insurance that I was looking to them several minutes (MSA cart 98). It is an excellent target for big apertures, as they can read on this amazing observation page.

According to great cataloguer astronomer George Abell who named it it with a number after having lost some eyelashes in the years 1950s by visually examine the photographic plates from the 48" Schmidt at Palomar Mount, this cluster is classified as rich (II-III) on its curious but intelligent classification (neighboring galaxies up to 2 magnitudes less bright than the third brighter) has an average “redshift” of z=0.01790 that according to current age of the Universe places it little at 250 million light-years spreading more than 200 moderately bright galaxies in a 8 degrees diameter of sky !, this number increases and a lot with size of used instrument.

Abell 426
Abell 426

he brightest member is NGC 1275 that it is near the center of the image, also known for Perseus A, is peculiar elliptical giant that dominates the Perseus's Cluster. This galaxy is peculiar for diverse reasons: it has an active nucleus (Seyfert type) with jets, recent star formation, is a powerful source of radio (3C 84), and X rays perhaps being in the middle of a collision/digestion.
There are a lot of galaxies in just 1 squared degree of image, having labelled about forty of them, more faint ones exist and not visible in the image, with the aid of the Guide8 seeing how was the distribution of the cluster most bright members. This subject of Galaxies clusters is of vital importance to understand the organization of the Universe at the great scale, mainly because they show us how the Universe and galaxies were at the beginning of the time.

Pátio 238 - Millennium Star Atlas

Pátio (Leiria 39.75N 8.82W alt:60m)

Millennium Star Atlas and Pocket Sky Atlas
Millennium Star Atlas and Pocket Sky Atlas

The last observation was also the “first bath ” of recently acquired Millennium Star Atlas from the Sky Publishing/ESA.

It is convenient to make a previous warning that I am a big fan and user of stellar carts printed on paper. This type of support little by little was vanishing from the habitual field accessories due larger use of GOTO's or assisted pointing systems. I consider the way how to find the targets so important and fascinating as the target itself, and I appreciate the traditional ways despite being slow, and in special those that are simple, efficient and that never fail, so here are my first impressions.

The Millenium Star Atlases (MSA) is a set of 1548 carts based on the Tycho catalogue which contains about 1 million stars, with additional information of the Hipparcos catalogue covering the totality of both hemispheres. Each cart covers an area of 5.4ºx7.4º, similar area to the field as seen through 7x50 binoculars with a scale of 100 seconds of arc/mm, 16,7 minutes of arc/cm , 1 degree has 3,6 cm. The volumes have 33x23.5x3.2cm and weigh a little more than 2kg each.

Sky Atlas 2000.0, Uranometria, The Observer's Sky Atlas, Millennium Star Atlas and Pocket Sky Atlas The MSA is divided in 3 volumes, each one of them covering 8 hours of right ascension from pole to pole. Such arrangement can excuse at least one volume from the luggage to carry, which in the case of the 3 volumes and box can reach a somewhat heavy 6,7kg, that curiously at time of its first edition in 1997, was how much some portable computers started to not weight. Nowadays, everything that is printed there and even more suplemental information fits in small shirt pocket.
But no matter how much I appreciate the convenience of my Palm Tungsten or laptop, I simply do not find them adequate to use them at sites of visual observation, not only for the size and scale but also because of the retro-illumination from these devices that ruin the observer's and its neighbors's nocturnal vision.

Although these atlases are typically considered the better and more adequated reference to advanced observers with big aperture telescopes, I consider also that it is an almost faithful representation of the stars up to a to stellar limit magnitude 11 that can be readily observed through telescopes and binoculars around 50-100 mm of aperture, what makes me to remember that observing behind cited they will consider these mere finders … Well anyway it fits like a glove when uses with small instruments. The level of stellar depth has enough stars to allow to place with great precision any visible or invisible object on the center of a eyepice field. Also I consider these atlases very useful on comet observation and bright asteroids, having more than enough comparison stars to make estimates, being also able to draw its position and to note the most similar stars.

The stars with appreciable proper movement in decades are drawn with arrows of different lengths that shows this movement, guaranteeing much longevity to these atlases. The variable stars (8200) also are written down in way to give ideia of the magnitude of variation with style of circle around the stars (solid, point, traces). The double stars (22000) also have a “sui generis” notation , one small trace that shows the orientation and aproximate separation.
I find these star notations quite usefull on the field and when have no availability of written detailed information. I rarely to stop on a cart and not to look for what else also exists there to be seen in that rectangle of sky.

The used projection was the simple conic according to Raisz (1934), that allows to measure angles with less than 0.2º error in all the carts. According to the extensive introduction, the the stars positions accuracy is greater that paper aging or deformation after having get some moistness. I consider decent the used paper (similar to the one used on Uranometria), but doesn't seem very reasonable to expose it to the elements. For that kind of use would have to be plasticized. The paper does not have enough thickness to be absolutely opaque, stars can be seen marked of the page reverse, but me it does not seem to be really annoying.
A first problem appeared when I displayed for the first time the these volumes under wet open sky.
Sooner or later the books will change their volumetry due use and moistness, not fitting the all three in its box which in mine case was made with too tight tolerance. The softbound seems to hang well a layer of water on any physical state, but the golden prints already started to vanish. Initially it had thought to put some plastic layer, but the tight box did not allow me, but now is too late, the time will certainty tell more concerning the durability and quality of construction.

With respect to non-stellar objects, only Messier's list and stellar and non-stellar objects that have a popular common name are tabulated , being these reprinted at the end of each volume, there is no index of deep sky objects catalogued by numbers (i.e NGC). Additionally on vol. I, comes an index for all the stars with Greek letter assigned . Also in this volume there are tables of the brightest stars, the closest, the fastest (including a detailed trajectory of the Barnard's star) and the brighter doubles.
It doesn't have also any detail carts, like the Uranometria has for the areas of dense concentration as in the case very populated areas like the Galaxy plane or galaxies clusters. The apreciadores of the later can consider a comparativily negative aspect.

I didn't found anywhere written the exact number of deep sky ojects, (perhaps too small when comparing to Uranometria), but the introduction that says to have >10000 non-stellar objects distributed like this:

Sky Atlas 2000.0, Uranometria, The Observer's Sky Atlas, Millennium Star Atlas and Pocket Sky Atlas
Sky Atlas 2000.0, Uranometria, The Observer's Sky Atlas, Millennium Star Atlas and Pocket Sky Atlas

To date does ther is any reference (or companion) manual , but Uranometria's volume 3 (Deep-sky Field Guide) is perfect to fulfill that function, listing up to three times the objects that MSA plots.
Some can find too few objects, but for visual observation more than enough for any aperture, with probable exception of special projects, but in that case I think I will have the rare pleasure to draw them.

Before taking it to the field, I practised to find on carts several known objects to get used to it's organization. I found to be very easy to find everything that I had looked up to, even the on'es I had faint notion of its localization. The division by declination strips, with contiguous carts in R-A. is extremely logical and natural. In effective use at the field it really came to prove that these atlases are practical and efficient.
Although it is possible to use only the carts index at the end of each volume, the scale and detail is not very practical to point with unitary finders like QuickFinder or Telrad. For this task I also use the Karkoschka and/or the recent Pocket Sky Atlas, that had always served like excellent finder charts. It's easy to conclude that this is best paper atlas on paper up to magnitude 11, even when currently seems to be the only one in print. The only alternative that can concur to it are carts generated by a planetarium aplication (Guide8, Skymap or others), but if you take the cost of paper, ink and time that takes to make equivalent quality carts , it is probable not so good ideia, or on other words, both the solutions are comlementary and compleat each other. The price, is similar to a good plossl eyepiece, or any another good excuse of similar value.