Far Ranging Thoughts

Last night was my best night with Jupiter this season. My third and fourth sketches of the planet for this year were completed. Excalibur was used at 218x.

For the first sketch (started at 6:45 UT) I employed a Moon-SkyGlow filter which had perhaps a subtle effect. I feel that my 'Jupiter Observing Eye' has returned now. I was able to sit down and make my most carefully rendered Jupiter sketches of this season. Callisto's shadow showed up as a small, round, pitch black spot below the trailing edge of the Great Red Spot. It looked really nice in such close proximity to Jupiter's most famous feature.

The GRS was very pale. It's leading edge was darker than it's following edge. Nevertheless, even the leading edge was very pale. Some structure within the planet's two primary belts (as well as a little zonal detail) was also recorded.

The second Jupiter sketch of the night was started at 8:50 UT. The GRS had moved to the preceding limb of the planet and was no longer visible, but the disrupted end of the South Equatorial Belt following the GRS remained visible. Callisto's shadow remained on the planet, but it now lagged a little behind the GRS.

In the second sketch the impact scar was visible near the planet's south limb. It hadn't quite reached the planet's central meridian at the time of the sketch. The scar seemed to be a little smaller than Callisto's shadow and clearly elongated in the east-west direction. It was considerably less dark than Callisto's inky, black shadow. The scar was about as dark as the matter making up Jupiter's major belts. In other words, it was far less obvious to the eye than was Callisto's shadow.

I'm hesitant to upload these latest sketches, preferring to keep them for my selfish self. Both would provide good material for future paintings -- if I ever get around to it . . .

I've recently become quite discouraged with an astronomy forum that I've been frequenting lately. Forum content has had little to offer me despite my own attempts to increase its faltering signal to noise ratio. Of course, my own lack of a full night's sleep might be adding to the feeling. Time will tell . . .

Anyway, I've been rethinking my Internet presence in general. Eventually re-working my website is a possibility. Also being considered is a limitation on my blogging -- perhaps making one entry at the beginning of each month describing one night's observing session (with sketches if applicable) from the just ending month.

I find it discouraging that there appears to be so little (relatively speaking) Internet discussion and sharing of observations relating to the recent impact on Jupiter. This is only the second time in recorded history that a Jovian impact event has been positively identified and observable with backyard telescopes.

Then there's imaging. It seems that more and more amateurs are becoming interested in setting their eyes aside and letting their cameras do the looking. With visual observing and sketching I feel that I'm in a minority special interest group within a minority hobby. I get the impression that few care to see sketches when digital cameras can show more detail and more color with less work under worse conditions. Such are a few of my thoughts in the early twenty-first century.

Venus - 19 June 2007

Date: 19 June 2007 U.T.
Time: 22:40 - 22:50 U.T.
Telescope: 102mm SCT
Magnification: 72x
Seeing: Poor - Fair
Transparency: Partly Cloudy (thin clouds)
NELM: Daytime observation
Temperature: +86 F (+30 C)

The above is my rough, at-the-telescope sketch. North is up. Preceding is toward the left. Disk details are questionable under the seeing conditions; but the south cusp was suspected to be somewhat brighter than the north. The limb was brighter than the terminator. The planet appeared white against the blue daytime sky.

I went outside around 4:00 pm local time, looked up, saw the Moon, looked a few degrees west of the Moon and spotted Venus with the unaided eye. Afterwards I set up the telescope and made the above observation.

Observational Slow-Down:
Lately a combination of factors have slowed down the frequency of my astronomical observations. Among those factors is increased activity in my other (long neglected) hobby - chess. If my renewed interest in chess continues long enough I may start an additional blog devoted to that interest.

Thoughts on Observing Venus

Despite my involvement in amateur astronomy since the late 1960's, I still consider myself a beginning, visual observer. There is much that I still do not know; and I'm continually learning more. Take Venus for instance:

Back in the late 60's I made observations of Venus using an inexpensive, 60 to 65mm refractor. My observations showed the changing phases of the planet. I was able to see how the apparent size of the planet varied as Venus travelled around the Sun. The planet appeared noticeably smaller when near full, on the far side of the Sun than it did when near new, on the near side of the Sun. Venus was a brilliant, white, featureless planet - excepting only its changing apparent size and phase.

Only rarely since those early observations have I re-visited Venus. I had rarely, if ever, heard other amateurs mention observations of albedo variations on Venus. There seemed little point in observing a planet on which one cannot see surface nor atmospheric features.

This year my attitude toward Venus has changed. The change had its origins in a thread pertaining to the visual observation of Venus in the Usenet group: sci.astro.amateur. Apparently, some people could see a sharply defined (yet, pretty much featureless) planet when they observed Venus through their telescopes, while others could see little more than a bright, boiling blob of ever-changing color.

In the saa discussion, mention was made of the visibility of subtle, atmospheric details that some have claimed to see. So, I decided to start observing the planet on a more or less regular basis with my current arsenal of telescopes and filters - to see what I could see . . .

After experimenting with filters, I found that a green filter (with or without a Moon-SkyGlow filter) seemed to work best on Venus for my eyes. As a result, most of my subsequent Venus work has involved the use of a green filter.

I soon found myself "suspecting" subtle detail in the Venusian clouds; but it took a while before I felt confident enough to attempt sketches of those details. Within this blog I often prefaced references to Venusian details with the qualifier: "suspected". This was because I was not fully convinced that the subtle details that I saw were truly details within the Venusian clouds. When observing near one's limits, other factors can enter the equation. The human eye, for instance, is a far from perfect optical instrument.

As I made more observations, I became more convinced that I was seeing actual albedo variations on Venus. Nevertheless, due to their subtle nature and the less than perfect seeing conditions it has remained difficult to record those variations with a high degree of confidence and/or accuracy.

I take my own Venus observations with a grain of salt. The main reason for this self-scepticism has to do with the subtleness of the suspected details. Observing detail on Venus is not like looking out a window and seeing a tree. It's more like looking out a window on a very foggy morning and "suspecting" a tree. In the case of Venus, atmospheric turbulence (in Earth's atmosphere) causes subtle planetary detail to be visible sometimes and invisible at other times - during the same observing session. It's necessary to patiently study the planet in the eyepiece, waiting for the detail to show itself. It's very much like catching intermittent glimpses of a tree as the fog thickens and thins.

Atmospheric turbulence was noticeably less problematic during my last Venus observation. The subtle Venusian details could be seen more consistently than ever before. Furthermore, I was using my largest telescope (and a green filter). Also, Venus was nearer to Earth and thus appeared larger than it had for my earlier observations. For that observation, I can remove the qualifier; "suspected". Detail was very definitely being seen, and that detail originated within the Venusian atmosphere.

So what about the boiling, colorful blob that some see when they look at Venus?

When conducting a test, the only time I could see color around Venus when using my Newtonian (a telescope type that does not suffer from chromatic aberration) without filters was either when I viewed the planet using an eyepiece that was poorly corrected for chromatic aberration, or when I waited for Venus to settle lower in my sky -- allowing Earth's atmosphere to bend the different colors by noticeably different amounts.

Of course, the "boiling" aspect that some have mentioned is due entirely to thermal effects in the line of sight between the observer's eye and the planet. More specifically, these thermal effects exist either in the air above the telescope, in the air inside the telescope, or both.

Some telescopes are less susceptible to internal thermal effects than others. Some observers exercise more care in avoiding telescope thermal effects than others. Some observing sites are better than others. Certain times of the year may be better than other times for a given location. Venus is not equally high in the sky near local sunset for observers observing from different latitudes. The list goes on . . .

I'm fully convinced that Venus can be an interesting and rewarding planet to observe for those willing to devote the necessary time and effort.

I.S.P. Disappointment & sci.astro.amateur

Almost one week ago the newsgroup feed from my Internet Service Provider ceased. It took a few phone calls and a few days to learn what little I now know about the situation.

I've participated for several years, under one identity or another, on the unmoderated Internet Usenet group: sci.astro.amateur. My presence in sci.astro.amateur pre-dates the origin of my website. As a matter of fact, it was discussions on saa that led me to create the website.

Initial contact with my ISP indicated that they were unaware of what a newsgroup was and unaware that they had been providing the feed.

After the passage of several days I was informed that my ISP had been under the impression that they had dropped newsgroups last October! When asked if they were going to turn back on the newsgroup feed, their response was; "No."

Unfortunately, options are very limited in my rural area when it comes to ISPs. It's possible to access Usenet in other ways; but so far I've not found an alternative that I'm entirely comfortable with. So, at least for the time being, I can read postings to saa; but I'm unable to make responses.

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.

Omissions from my 17 January Posting

I intentionally made yesterday's posting brief; but I may have made it too brief! I intentionally omitted my full descriptions of all 51 observed objects; but I also omitted the following:

Zodiacal Light: At 2:00 U.T. the Zodiacal Light was visible from my western horizon all the way up through Andromeda -- on or near my south meridian.

Barnard's Loop: I didn't write it down at the time, nor did I consult a chart at the time; but I noted the Milky Way passing along the left (east) side of Orion. Furthermore, I noted a distinct gap to the right of the main body of the Milky Way, followed by a narrower arc of "Milky Way". Only this arc might not have been part of the Milky Way at all. It might have been Barnard's Loop -- a large arc of nebulosity in the same general area of sky. I've been unable to determine for certain (checking atlases and photos today) if the arc I saw was a part of the Milky Way or if it was Barnard's Loop. At the time I didn't bother training the binoculars on the arc. Hopefully a second observation will clear this up for me. My sky might be clear tonight . . .

Enhanced Night Vision? Two nights ago (17 January U.T.) deepsky objects looked unusually good. I saw the California Nebula with ease. Normally one would conclude that this would be due to improved sky transparency; but I specifically checked my NELM on that night. It was no better than on a typical, dark night. Furthermore, there was even an aurora on that night; though it wasn't particularly bright, nor did it cover a large area of sky.

Approximately 36 hours prior to the night observations I had spent a few minutes looking for Comet McNaught (near the Sun, which was blocked from view) in the daytime sky. I had used binoculars for the search. Might this have resulted in sensitized eyes some 36 hours later? I can recall one similar 'coincidence' several years ago. It's enough to raise my suspicions.

Additional observations and/or experimentation may be necessary to get to the bottom of this mystery.

My Final Omission: This one was intentionally omitted; but upon further reflection I see no good reason not to provide at least some details. During my binocular observations, at one point approximately 6 aircraft flew over within a short period of time. It's uncommon to see any aircraft fly over my location, let alone 6 at once! All were headed in the same direction. All were silent (I was wearing a sheepskin hat with earflaps down). All had a bright (one might even say 'brilliant') white strobe light. I trained the 20x80 binoculars on one of the nearer aircraft. Based upon a small number of much dimmer lights, the aircraft proved to be either nearer or larger than I had anticipated. The body of the aircraft was all but invisible -- most likely black. From the rear, the exiting exhaust looked little brighter than a typical nebula, but bright enough to show up as a somewhat faint, blue-white color. It was not noticeable to the unaided eye (I didn't have my corrective glasses on).

One never knows what one might see from the middle of nowhere on a clear, dark night!