Measuring the Sky

Above is a sketch showing approximately what's seen when one looks through a Celestron Micro Guide eyepiece. The linear scale has a real length of 6 millimeters. Adjacent scale divisions are 1/10 of a millimeter apart. I'll be using the Micro Guide eyepiece to make a variety of measurements while using Excalibur - my 13cm refractor.

The separation distance between scale divisions will of course vary depending upon the magnification that the eyepiece provides with a given telescope. My measurements indicate that the divisions are about 24.80 seconds of arc apart when the eyepiece is used with Excalibur without a barlow. With my three barlows the divisions become 11.06, 10.36, and 7.84 arc-seconds apart.

The linear scale will be used to measure linear distances such as the separation of double stars. The outermost circular scales will be used to measure position angles.

I was stricken be a sore throat on the 5th of October. Some congestion and an occassional cough remains. Hopefully it's not progressed to bronchitus or pneumonia. Currently I'm not sure if this situation is getting better or worse, but at the moment I'm feeling healthier than I was earlier. I might be feeling up to at least a brief observing session tonight. I stepped outside this morning in time to catch sight of Saturn in the east-southeast with the unaided eye.

RA 20h 40m to 21h 00m, Dec -09 to -15

Last night I observed and sketched two double stars as well as M72, M73, and an un-named (as far as I know) small asterism similar to M73.

The session actually began with a sighting of the International Space Station gliding across the sky. The ISS appeared to be somewhat brighter than Jupiter -- a rather brilliant, white, moving light in the sky. Of course, as the ISS entered the earth's shadow it rapidly dimmed.

The seeing was 'good' -- a '6' on the modified Pickering Scale. I used 477x for the seeing check.

My NELM was 6.5.

Observations and sketches were all made at 135x, though other magnifications were used at times.

RA 20h 20m to 20h 40m, Dec -09 to -15

The mushroom cloud shown above was visible in the west this afternoon, but fortunately the smoke drifted south of me and the fire may have been successfully supressed by nightfall. The photo is an enlarged (and somewhat enhanced) portion of the original telephoto. The fire was not as close it may appear above. My sky appeared to be 'crystal clear' by the time I had begun my observing session.

In this region of sky (see title) I observed, split, and sketched seven double stars in the course of a little over an hour with the 13cm refractor. One was particularly nice, showing some color at low power. Another was a particularly close 'split'.

Seeing was much better on this evening (Tuesday evening, September 30th locally or October 1st UT) than it was on the previous evening. I rated it as being "Excellent" -- an "8" on the modified (for a 5-inch scope) Pickering Scale.

RA 20h 00m to 20h 20m, Dec -09 to -15

Four double stars were observed, split, and sketched in this region of sky last night. Seeing was 'good' (a '6' on the modified Pickering Scale). Temperature was +52 degrees F (+11 C). The 13cm refractor was used on an equatorial mount with clock-drive engaged.

My long-term goal: to cover the entire sky visible from my location - recording all visible objects of interest using my 13cm refractor. This isn't a new goal. Instead it's a revision of an earlier goal with a bit of modification. Time will tell if this 'new' program can stay alive.

Polar Doubles Revisited

Last night I re-observed the double stars listed in my previous blog entry. The seeing was a bit better this time around. Sketches, with north carefully noted, were made of all five double stars. A magnification of 135x was used for all of the double star sketches.

Prior to the double star observations I trained the scope on Jupiter -- as an object to focus on prior to adjusting the scope in its cradle. Balance is more sensitive for my home-made alt-az mount than it is for my equatorial.

As the bright twilight gradually faded, more stars popped out in the vicinity of Jupiter. A sketch was made at 43x of Jupiter, its moons, and some of the background stars. The seeing varied from poor to extremely poor at this point in time, but it had improved noticeably by the time I trained the 13cm refractor on the double stars.

My work schedule prevents me from making a more detailed post or refining and uploading sketches at this point in time.

Starting at the North Pole

Date: 27 September 2008
Time: 3:15 - 5:30 UT
Telescope: 13cm refractor
Mount: home-made alt-az
Diagonal: 1.25-inch 90-degree erect-image prism
Magnifications: 43x, 80x, 111x, 302x
NELM: 6.5
Seeing: very poor ('3' on Pickering Scale) - at session end
Temperature: +50 F (+10 C) - at session end

Using the Millennium Atlas as my guide I sought out objects within about 3-degrees of the north celestial pole.

The star diagonal used is not of the highest quality, but for an erect-image diagonal it is of reasonable quality. This diagonal was used in order to more easily match the eyepiece view with the detailed atlas charts.

My old alt-az mount was used under the assumption that it would make it easier to navigate around the celestial pole -- easier than using an equatorial mount. At a later date I'll determine whether or not that assumption reflects accurately on reality.

The seeing and temperature were not recorded until the end of the session. A high magnification (302x in this instance) was necessary in order to obtain an accurate value for the astronomical seeing. For all other observations the maximum magnification used was 111x.

Five double stars were 'split' on this evening. Their rough coordinates are given below:

RA 02h 35m, Dec +89.3 degrees (Polaris, Alpha Ursae Majoris) very bright primary with much fainter secondary

RA 08h 20m, Dec +87.25 easily split at all magnifications, not particularly bright

RA 12h 00m, Dec +87.0 a nice double, best at about 80x

RA 12h 30m, Dec +88.7 a close, unequal double, cleanly split at 80x

RA 18h 40m, Dec +88.3 an unequal, easily split double (140 lightyears distant)

Other objects and double stars were looked for, but were either not positively seen or not positively split.

Saturday Evening: Venus in the West

After a cloudy day with intermittent, light precipitation I was greeted by a mostly clear sky after sunset. The tiny point of light near the bottom center of the image is Venus. Clicking on the image will reveal a somewhat enlarged view.

Lunar Limb - Daylight Observation

Date: 24 August 2008

Time: 17:18 - 17:33 U.T.

Telescope: 80mm f/5 achromat

Magnification: 70x

Filter: Polarizing

Seeing: Fair - Good

NELM: Daylight

Temperature: +85F (+29C)

Wind: Calm

Transparency: Very Good (cloud-free sky


The above sketch shows two lunar mountains that were silhouetted against the darker sky background. North is up. Lunar East (preceding) is to the left in this mirror-reversed view. The sketched region is at 90 degrees west longitude and approximately 12 or 14 degrees south latitude. The moon was a fat, waning crescent at the time of the observation.

Not shown in the sketch is Lacus Aestatis which was seen as a dark patch to the left of the lower mountain peak beyond the sketched region. A very rough, larger scale sketch was made to facilitate finding this region on a lunar map. That sketch showed Lacus Aestatis, Cruger, Grimaldi, and Riccioli all as dark patches.

The sun was still spotless today. I used the 80mm refractor at 24x. A glass, white-light solar filter covered the front of the telescope. The filter gave the sun a soft, golden, peachy color. There was something aesthetically pleasing about observing a spotless sun through a telescope with one's own eyes.

Venus and Mercury in Evening Sky

For the past three evenings I've managed to see these two planets low in the western sky shortly after sunset. Brilliant Venus has been the easier planet to spot. Dimmer Mercury has been between one and two degrees to the lower right of Venus.

Binoculars seem to be better suited for catching these two planets than a telescope. The sky has been too bright at prime observing time for Mercury to be seen with the unaided eye.

This evening I set up a small, 80mm f/5 refractor on the porch. Venus was easily visible, but trees blocked Mercury from view. From nearly the same location I managed to see both planets with 20x80 binoculars. This was primarily because my eye level with the binoculars was a little higher than the telescope -- just enough to bring Mercury above the trees.

On the previous two evenings I viewed the two planets with 8x42 binoculars as well as with the 20x80s. Mercury was easier to see with the 20x80s. Venus showed up easily with either pair of binoculars. Once I knew where to look, Venus could also be seen with the unaided eye.

On all three evenings I had to look thru thin clouds when observing Venus and Mercury. The clouds appeared to have formed near the time of sunset low in my western sky. They showed up as horizontal bands of varying thickness, but not thick enough to block the planets from view with binoculars.

Meanwhile, Jupiter shines brightly in the south-southeast. Jupiter and its brightest moons are not difficult to see with either tripod-mounted or steadily held binoculars.

Our Spotless Star

The above photo of the sun was taken today, 12 August 2008. A DSLR camera was used at the prime focus of a 102mm (700mm focal length) Schmidt-Cassegrain telescope. A full-aperture, white-light solar filter covered the front of the telescope.

I knew the sun was without spots today - as it has been for quite some time now. Nevertheless, even a spotless sun can be of interest. Notice that the limb (edge) of the sun is darker than the center of the sun. This is called "limb darkening" and is due to much of the solar radiation originating deep within the interior (rather than the 'surface') of the sun.

The sun goes through a roughly 11-year sunspot cycle. Approximately 11 years pass between sunspot maximums. Sunspot minimums occur roughly midway between the maximums.

Shooting the Moon

Shown above is a 'snapshot' of this evening's gibbous moon. It was taken under poor seeing conditions with a DSLR camera attached to a 102mm Schmidt-Cassegrain telescope (about 700mm focal length). This was one of two experimental images I took of the moon. The telescope's tripod was set up on my south porch - not the most stable of platforms, but sufficient for experimental purposes.

The Perseid Meteor Shower should be near its peak after the moon sets later tonight. If you read this early enough (Monday night - very early Sunday morning), have adequate sky conditions, and can affort to lose the sleep (a lot of 'ifs') you might want to spend some time lying back, staring at the sky, and counting meteors.

What is a planet?

What is a planet? In my opinion any astronomical body that's essentially massive enough to maintain a spherical shape, but not massive enough to trigger a self-sustaining fusion reaction (becoming a star) should be considered a planet.

Looking over the known bodies in our solar system, it seems that a reasonable cut-off at the low end would be 10e20 (one with twenty zeros) kilograms. Some solar system bodies with a mass in the 10e19 range are reasonably spherical, others are not. Since it's desirable to have an unambiguous definition (based solely on mass - which is one of the most easily determined properties of solar system bodies) it seems reasonable to fix 10e20 kilograms as the lower limit for planetary status.

The upper limit would be more flexible (as far as mass goes). The primary criteria here is that the body in question is not a star - that is, it does not generate a self-sustaining fusion reaction. For objects otherwise similar to those in our solar system, this limit would likely lie within the 10e28 kilogram mass range.

Planet Classes can now be designated as:

Class 0 -- with masses in the 10e20 kilogram range

Class 1 -- with masses in the 10e21 kilogram range

Class 2

Class 3

Class 4

Class 5

Class 6

Class 7 -- with masses in the 10e27 kilogram range

Class 8 -- with masses in the 10e28 kilogram range

Jupiter would be a Class 7 planet. Earth would be a Class 4 planet. Pluto would be a Class 2 planet. Tethys (one of Saturn's moons) would be a Class 0 planet.

Bodies with masses less than 10e20 kilograms could be referred to as "subplanetary" and designated as lying within Subplanetary Class -1, Subplanetary Class -2, etc. for masses in the 10e19 and 10e18 kilogram ranges respectively.

Note that the location of an object is not relevant in this system. The object is classified the same regardless of whether it orbits a star or a planet. A Class 5 planet, for example, could even be adrift in interstellar space.

Jupiter's Family via 25x100 Binoculars

Shown above are two sketches of Jupiter and its brightest moons as observed on 1 August 2008 U.T. The uppermost sketch was made at 3:15 U.T. The lower sketch was made at 7:25 U.T. The lower star at the far left is an actual star, not one of Jupiter's moons. Europa was in transit across Jupiter's disk (and not visible in the large binoculars) at the time of the first sketch, but by the time I had started working on the second sketch it had reappeared off Jupiter's preceding (western) limb.

Jupiter's North and South Equatorial Belts (the dark bands running parallel to Jupiter's equator) were visible in the tripod-mount 25x100 binoculars. Seeing conditions were rather poor on this night. Jupiter's moons and the various field stars appeared to twinkle due to earth's unsteady atmosphere. A haze (most likely from forest fire smoke) seemed to fill much of the sky as well.

My First Star Field Photo

This is my first (and so far only) photograph of the night sky taken with my new camera. I attached the camera to a homemade equatorial wedge (built for a 102mm SCT) and set the assembly on my north porch. The "Little Dipper" asterism can be seen offset toward right center. Some nearby tree tops are silhouetted against the brighter night sky at the bottom of the photo.

Digital photography is certainly far more user friendly than film photography! One gets to see the results right away, and PCs make it easy to tweak the images as necessary. The above photo is a 30 second exposure at ISO 800 with an 18mm lens at f/3.5. It was taken at 11:59 pm local time on July 31, 2008.

Comet C/2007 W1 (Boattini)

Date: 13 July 2008 U.T.
Time: 9:40 - 9:50 U.T.
Telescope: 13cm refractor
Magnification: 66x
NELM: dark twilight, growing brighter
Temperature: +41 F (+6 C)

The above sketch shows an approximately 0.54 degree wide portion of the telescopic field centered on Comet Boattini. North is up. West is to the left in this mirror-reversed view.

Comet Boattini is currently visible with binoculars in the early morning sky, low in the east, prior to the onset of bright twilight. The time of this observation in local time was 3:40am - 3:50am. Earlier the comet would be seen in a darker sky, but it would also have been closer to (or even below) the horizon. Later, morning twilight would have had a more drastic, negative effect on the comet's visibility. This comet will be climbing higher in the morning sky with each passing day, but moonlight will soon add a negative element to this comet's visibility.

Comet Boattini is heading out away from the sun now, so it can be expected to grow smaller and fainter in the upcoming weeks. Currently the comet appears like a round 'fuzzball' with an outer boundary the blends into the background sky. The comet is brighter closer to its center. I noticed no tail and no central condensation (or pseudonucleus). This comet was not visible to my unaided eyes - at least not under the twilight sky in which this observation was made.

This comet looks like a typical, relatively bright, telescopic comet. That is, it's easily visible with a telescope or even binoculars; but it has no (visible) tail and presents nothing out of the ordinary to see - at least not at this time.

Binocular & Small Telescope Session

Date: 13 January 2008
Time: 3:05: 3:25 U.T.
Binoculars: 8x42 & 20x80
Telescope: 80mm f/5 Achromat
NELM: 6.0 to 6.5

Comet Holmes was visible to the unaided eye, but it was significantly better with the binoculars. A crescent moon was above the horizon to the southwest, but appeared to have little if any adverse effect on the evening's viewing. Clouds were approaching from the west.

Mars looked like a tiny, yellow-orange disk in the ST-80 at 105x without filters. Markings on the planet were difficult to see with the small telescope, but they became easier when the planet's brightness was reduced and contrast was increased via the use of a #23A Light Red filter. The #23A filter transformed the color of the planet to a orange-red. Normally I wouldn't consider using such a small telescope on Mars, but I was curious concerning what could be seen with minimal optical aid. Without any filters, the ST-80 is likely to disappoint just about anyone when viewing Mars. With filters, a fair amount of patience, a bit of observer experience (and a good solid mount!) it's possible to conduct some regular study of Mars when the planet is near opposition, but I would strongly suggest that any interested observer use a larger, higher quality telescope.

Surface markings were ill-defined and difficult to pinpoint in location due to the telescope's small aperture, the relatively low (for Mars) magnification, the less than perfect (achromatic) optics, and the somewhat uncooperative, home-made mount (One of these days I should add a friction adjustment to the mount's altitude axis).

After Mars I lowered the magnification to 22x using a wide-angle eyepiece. I took quick looks at the Great Orion Nebula, the Andromeda Galaxy (and its two nearby satellite galaxies), M33, and Comet Holmes. The ST-80 and its home-made, alt-az mount seem to perform at their best when used for such low magnification purposes. All of these objects were very pleasing in the small, short telescope. Comet Holmes looked like a fairly bright, diffuse (amorphous) cloud occupying approximately one-third of the 3.34 degree field of view.

In the course of the evening's short session I never felt any need to uncap the telescope's finder. It was easy enough to point the telescope at Mars, etc. with the 22x eyepiece in place prior to switching to higher power.

I brought the telescope and mount inside, leaving the tripod out in case I decided to try out a 102mm (4-inch) SCT on Mars. Later, when I went back outside, I discovered a cloud covered sky and frost on the tripod. It was clearly time to bring the tripod inside and wait for another clear night.

Two Bright Comets

Date: 2 January 2008
Time: 4:30 - 4:50 U.T.
Instrumentation: Binoculars and Unaided Eye
NELM: 6.5 or better
Temperature: +3 F (-16 C)

Comet 17P/Holmes remains an easily visible naked-eye comet. I was able to immediately spot and recognize this comet with the unaided eye upon stepping outside. The view was improved with 8x42 binoculars, and improved even more with 20x80 binoculars. Comet Holmes has increased in size and become a bit more diffused in appearance since my last blog entry.

Comet 8P/Tuttle was initially spotted near the Aires - Pisces border with the 8x42 binoculars. It was better seen (as a circular haze with a brighter center) with the 20x80 binoculars. At times I suspected Comet Tuttle as being visible to the unaided eye, but I was never 100% convinced.

These observations were made from my south porch after a period of indoor dark adaptation. The floor of the Colosseum (my open-air observatory) has been coated with a layer of ice for the past couple of weeks. Thus it would be ill advised to set up a telescope at that location.

Future Plans: At present I'm inclined to make fewer blog entrees and post even fewer sketches in 2008; but one never knows for certain what the future may hold.