Saturn: 25 February 2007

Date: 25 February 2007 U.T.
Time: 5:55 - 6:48 U.T.
Telescope: 30cm Newtonian
Magnifications: 250x and 300x
Filter: #80A and unfiltered
Seeing: Fair to Good
NELM: 5.3 (Moon in sky)
Temperature: +17 F (-8 C)

The above sketch shows the basic appearance of Saturn on this night. South is up. Preceding is to the left.

After initial collimation of the truss-tube telescope I pointed the scope at Polaris, increased the magnification to 400x, and used the de-focused star's Fresnel pattern for a final 'tweak' of the collimation.

The scope had been outside for a few hours prior to the session. At the beginning of the observation the seeing was Fair. The sketch was initially made at 250x with the #80A filter.

As the session progressed the seeing improved. I removed the filter and increased the magnification to 300x. At times of steadier seeing the image was quite sharp. Tethys, one of Saturn's moons is shown just south of (above) the preceding (left) portion of the ring system.

Initially, Cassini's Division was not visible all the way to the limb of the planet, but that changed after the seeing improved. Both the preceding and following limbs of the planet were darkened a little. The C-Ring was visible against the background sky as well as against the ball of the planet. The filter may have darkened (increased contrast) of the planet's southern hemisphere belts as well as the C-Ring against the planet. The outer portion of the A-Ring was darkened somewhat and some structure was hinted at. The inner portion of the B-Ring was darkened somewhat.

Some clouds came and went during the observation. The outside of the telescope had attracted a fair amount of frost during the session.

This was my first high magnification planetary observation with the 30cm Newtonian. It's not likely to be the last!

The Great Orion Nebula

Date: 20 February 2007 U.T.
Time: 4:20 - 4:50 U.T.
Telescope: 30cm Newtonian
Magnifications: 61x and 155x
NELM: 6.5
Seeing: Poor
Temperature: +24 F (-4 C)

The Great Orion Nebula, also known as M42 is one of the brightest and most beautiful nebulae in the night sky! This large nebula practically fills the field of view at 61x. In its brightest regions it's possible for some people to see color. I noted a weak greenish glow in the brightest parts of the nebula and a hint of red in some of the other areas.

Within the brightest part of M42 is a tight group of four stars known as the Trapezium. At 155x I was able to see a fifth star in the Trapezium without much difficulty. A sixth star was more difficult due to the poor seeing conditions; but it was occasionally suspected near the glow of the brightest member of the 'big four.' On a good night I've seen all six stars with ease while using a considerably smaller (13cm) telescope.

M42 is a very irregularly shaped nebula. It has many curves and regions of widely varying brightness. I used the low magnification of 61x in order to be able to see the entire nebula at once; but it's well worth the time to study individual parts under higher magnification.

M43 shares the field with M42. It's much smaller in size, has a semi-bright star within it, and has the shape of a fat comma. While having separate entrees in the Messier Catalog, M42 and M43 are parts of the same nebula complex.

Before ending the session I swung the scope around to Saturn for a quick look at one of our solar system's real show-pieces. Saturn is always a joy to behold!

Even if I weren't too tired to continue observing I would have had to quite soon due to increasing clouds. As I was bringing the scope, etc. back inside more and more stars were disappearing behind the thickening clouds.

Horsehead Nebula, etc.

Date: 20 February 2007 U.T.
Time: 4:10 U.T.
Telescope: 30cm Newtonian
Magnification: 61x
Filter: UltraBlock
NELM: 6.5
Seeing: Poor
Temperature: +25 F (-4 C)

I started out without using the above mentioned filter. NGC 2024 (also known as the Flame Nebula and Tank Track Nebula) was visible near Zeta Orionis. This nebula has a prominent dark lane running through it.

After shifting the telescope slightly to the south, Zeta Orionis left the field of view. The small, bright nebula NGC 2023 was now easily visible surrounding a star.

The next logical step was to look for IC 434 (a faint 'bright' nebula) and the dark notch within it known as B33 -- the Horsehead Nebula. These objects were visible with difficulty. IC 434 was only slightly brighter than the background sky. The Horsehead Nebula has a reputation for being a particularly difficult object to see visually without the use of a specialized (H-Beta) filter. In order to successfully see this object without a filter one must observe from a dark location that's free from the glow of city lights.

I don't have an H-Beta filter; but I do have an UltraBlock filter. The UltraBlock is a multi-layered, interference filter that selectively blocks the wavelengths of some of the more common man-made light sources (as well as some of the natural sky glow) while allowing other wavelengths to freely pass through. I screwed the UltraBlock filter into the eyepiece and took another look.

IC 434 and the Horsehead Nebula were suddenly significantly easier to see! The filter significantly darkened the background sky, but not the light from IC 434. As a result, the nebula became easier to see.

I should add that filters such as the UltraBlock do not improve the visibility of all objects in the night sky. Many objects become more difficult to see when such filters are used. Everything depends upon the wavelengths of light and their relative intensities as emitted by the various celestial objects. Furthermore, the effects of many such filters can vary significantly depending upon one's sky conditions and light pollution situation.

For more information on the Horsehead Nebula the curious reader is encouraged to visit Stephen Waldee's excellent Horsehead Nebula Main Page and associated links at:
http://home.earthlink.net/~astro-app/horsehead/index.html

Limiting Magnitudes, Plans, etc.

Date: 15 February 2007 U.T.
Time: 3:00 - 3:40 U.T.
NELM: 6.6
Temperature: -9 F (-23 C)

During the lengthy cloudy spell I revised observing projects, etc. A (new) home-made, square, eyepiece field stop was fabricated that includes a means to more accurately determine angular size as a fraction of the field of view. Refinements were made on a deep-sky project geared toward an all-sky, telescopic survey. Rough plans were drawn up for systematically sketching (mapping) the entire visible portion of Earth's moon.

I'll be as surprised as anyone if I actually manage to succeed in seeing these plans through to their natural conclusions! I'm easily distracted by a bright comet, a well positioned planet, other projects, etc.

I dug up some 'new' limiting magnitude charts that should allow me to make nightly estimates on the limiting magnitudes of my binoculars. I wore red goggles inside a dimly illuminated room for half an hour or so to aid in dark adaptation prior to going outside.

Once outside I used my new charts to determine my Naked-Eye Limiting Magnitude (NELM). Next I repeated the procedure using 8x42 and 20x80 binoculars, both hand-held. I have little doubt that a solid tripod would increase the binocular limiting magnitude. Eventually I'll need to check that out . . .

The limiting magnitude of the 8x42 binoculars was about 10.0. That of the 20x80 binoculars was about 11.4. All values, including the NELM were adjusted for the zenith -- one tenth of a magnitude was added from what was seen in the 45 degree altitude star fields. With practice these values should become more reliable. I hope to eventually correlate the various measurements with one another.

Later I may add telescopic limiting magnitudes figured for a specific exit pupil size (telescopic aperture divided by magnification) to the mix.

I also want to start making better use of filters for the Moon, planets, and deep sky objects; but I think I'm going to need multiple lifetimes in order to accomplish everything!

Happy Birthday Galileo! Galileo Galilei was born on 15 February 1564 in Pisa, Italy. He's known not only for his ground-breaking telescopic observations; but also for his experimental approach that led to the discovery of the pendulum's time-keeping potential, ballistic science, and much more.

The Sun, Mercury & Venus

Date: 26 January 2007 U.T.
Time: 18:02 - 19:00 U.T.
Telescope: 13cm Refractor
Magnifications: 80x and 110x
Seeing: Poor
NELM: Daytime
Temperature: +33 F (+1 C)

The above sketch shows a sunspot that has just rotated onto the Earth-facing side of the Sun. North is up. Preceding (west in the sky) is to the left. Both sketches appearing in this post are mirror-reversed. Notice that the spot's umbra appears off-set toward the center of the Sun. Sunspots near the solar limb often show this "Wison effect."

The brighter patches near the sunspot are faculae. Faculae show up best near the solar limb where limb-darkening darkens the surrounding area.

A safe, white-light, solar filter was placed over the telescope's objective for this observation.


The above sketch shows Mercury (to the left) and Venus. North is up. Preceding is to the left. The thin, unlit portions of the planets were invisible; but in the sketches those areas appear darker than the background sky. I decided to depict the planets in this manner after seeing how difficult it was to notice the phases in my previous Mercury - Venus sketch. Venus was a tad bit closer to being full than the above sketch suggests. There's always something that isn't quite right; but usually I don't say anything!

Hercules & Atlas

Date: 25 January 2007 U.T.
Time: 21:08 - 22:00 U.T.
Telescope: 102mm SCT
Magnification: 72x
Filters: Polarizing
Seeing: Fair to Good
NELM: Daytime
Temperature: +51 F (+11 C)


The above sketch shows the region around Hercules (bottom) and Atlas. North is to the upper right; and west is to the lower right in this mirror-reversed sketch. This sketch is the actual 'at-the-telescope' sketch. A polarizing filter helped to improve contrast for this daytime observation of the first quarter Moon.

Daytime observations have some advantages over night observations. There's no need to use artificial lighting for note taking and sketching. The temperature is more comfortable; and it's often possible to catch the object at a higher altitude in the sky.

Day observations also have disadvantages: Contrast is lower for lunar features; and care must be taken in regards to the Sun.

Mercury & Venus - Daylight Obs.

Date: 25 January 2007 U.T.
Time: 18:40 - 19:08 U.T.
Telescope: 102mm SCT
Magnification: 120x
Seeing: Fair to Poor
NELM: Daytime
Temperature: +45 F (+7 F)


The above sketches show Mercury to the left and Venus to the right. West is up in these mirror-reversed sketches. The phases of both planets were close to full. The terminators (border between day and night) of both planets are to the East (down in the sketches). The terminators were slightly darker than the rest of the limb region on both planets; but more so for Mercury than for Venus. Some subtle shading was suspected on Mercury -- to the northeast. None was suspected on Venus. Both planets appeared to be white or almost white in color.

Venus was considerably brighter and appeared to be about double the apparent size of Mercury.

Both planets were quite small as viewed in the telescope's eyepiece. Both are currently on the far side of the Sun from Earth; and both are currently east of the Sun in the sky.

A note on "go-to" telescopes: Some people might consider a "go-to" telescope to be a necessity for pointing a telescope at planets in the daytime; but observers made daytime planetary observations long before the invention of electronic computers and self-pointing telescopes. None of my telescopes or mounts have the ability to point themselves at astronomical objects. I've found no need for the technology and have managed to do fine without it. I prefer to point my telescopes myself -- even at planets in the daytime sky. For myself, part of the joy of amateur astronomy is 'driving' the telescope myself.

Theophilus - Revisited

Date: 24 January 2007 U.T.
Time: 21:15 - 22:08 U.T.
Telescope: 102mm SCT
Magnification: 72x
Seeing: Good
NELM: Daytime
Filters: Polarizing
Temperature: +52 F (+11C)

The above sketch Shows the ring mountain Theophilus which is 100km (62 miles) in diameter. Nearby is the 28km (17 mile) diameter crater Madler. North is toward the upper right. West is toward the lower right in this mirror-reversed view. The approximate location on the Moon is 11 degrees south latitude, 28 degrees east longitude.

I'm somewhat more pleased with this sketch than I've been with my other recent lunar sketches. Sometimes it doesn't take much practice to make a difference; but usually it takes more than the few (lunar sketches) that I've made this year!

I was surprised at the temperature! Several years ago I could expect temperatures in the neighborhood of minus 20 degrees F. for a week or two at some point in the December through February time-frame. Temperatures in the 50s at this time of year are kind of scary! Of course, the temperature could still drop like a rock at any time . . .

Lunar Observation - Atlas

Date: 23 January 2007 U.T.
Time: 00:01 - 00:28 U.T.
Telescope: 102mm SCT
Magnification: 94x
Seeing: Fair
NELM: Evening Twilight
Temperature: +37 F (+ 3 C)



The above sketch shows the 87 kilometer (54 mile) diameter lunar crater, Atlas. North is to the upper right. West is to the lower right. The sketch shows the mirror-reversed telescopic view. I'm still not very happy with my lunar sketches; but the only solution is more practice.

My weather this evening was (according to the Clear Sky Clock) supposed to be: Bad Seeing, Poor Transparency, 30% cloud cover, and strong wind; but the sky was clear. So I took out a small telescope for a quick lunar session.

Last night I set up the 30cm Newtonian (or as Ann referred to it: "The Big Gun") shortly before sunset; but the weather worsened and I ended up bringing the frost-covered scope back inside after several hours of waiting. The weather proceeded to improve afterwards; but by that time it was too late. I decided to get some sleep.

Brief Morning Binocular Session

Date: 20 January 2007 U.T.
Time: 12:25 - 12:35 U.T.
Binoculars: 20x80 (hand-held)
Seeing: Good
NELM: 6.5
Temperature: +15 F (-9 C)

Observations were made of three Messier objects in this brief morning session. The first was the globular cluster, M68. Next was the "Sombrero" galaxy, M104; and the last was a rather nice binocular galaxy, M83. All three objects were also visible with 8x42 binoculars; but the 20x80s showed them much better.

Comet McNaught's tail: At the start of astronomical twilight I scanned my eastern horizon for any hint of this comet's tail in the morning sky -- just in case. No hint of tail was evident with either pair of binoculars. On the other hand, parts of my eastern horizon, particularly in the southeast, are cluttered by trees that obscure as much as six degrees from view.

On the more casual side I took quick looks at a few additional Messier objects and scanned parts of the Milky Way before ending the session. For all practical purposes I stopped observing around the beginning of astronomical twilight.