Observing Jupiter's GRS, in daylight
Posted 02 February 2012 - 10:29 PM
OK, this might be old news to many of you, but in 40 years I never had the right combination of seeing, equipment and opportunity to observe this feature during the daytime. Sadly it was too windy to catch the GRS today when the GRS would have been at it's best around 3:30 PM MST.
Posted 02 February 2012 - 11:22 PM
Posted 03 February 2012 - 03:13 PM
Posted 04 February 2012 - 02:18 PM
Also a photo I took in daylight, showing the moons and even picked-up Uranus.
Posted 04 February 2012 - 06:52 PM
I have done planets in the late afternoon many times. Sometimes, I think that some detail does show up a bit better.
I have a theory, but I don't know how sound it is.
We often hear that the eye can resolve detail down to about 1 arc minute in angular size. This is true, but only for brightly lit targets when the eye is in photopic mode.
When you observe at night, your eye starts to fall into mesoptic and photopic function. In photopic mode, the eye actually has trouble resolving detail smaller than between 5 and 3 arc minutes in size.
I have had the thought that perhaps because the eye is in full photopic mode, some of the smallest detail might actually be a bit more within reach simply because our eye is working more efficently when the pupil is constricted.
Just a theory. I have also made some good observations during daylight, but the sky can also seem to wash out detail too, so I can't say that observing is better during the day. Only that I have seen some very challanging detail during daylight observing.
Posted 04 February 2012 - 08:04 PM
It does seem to take a minute or so to reach full resolution, even when walking out of a lit room. In a short while at the eyepiece, concentrating on Mars does seem to allow photopic adaption and albedo features to be easily seen.
It's a subject I'd like to know more about. It does seem to indicate daytime viewing is just fine. I might worry about contrast as the sky is generating some photons, too.
Posted 10 February 2012 - 08:45 PM
Anyway, another unexpected bonus is that the scope is ready for night time observations earlier.
Posted 10 February 2012 - 10:09 PM
Excellent sketch of Jupiter. The image of Jupiter with the moons and Uranus is a great catch.
I agree with Mike on this as well. When observing planets at night I leave my studio light on (which is in my backyard near my scope) and go back in every 10min. or so to keep my eyes adjusted to the bright light. I find that contrast and colors are more vivid when doing this.
I have never observed a planet at 2:45ish. It would be difficult finding Jupiter in such a bright sky. The earliest I have seen it is around 4pm. Of course it also depends on what month we are talking about. At 4pm in December the sky is already darkening some. Without goto or setting circles locating Jupiter at 2:45ish would be a challenge for me. When Venus is near elongation I have seen it with the naked eye early in the day around 3pm.
Posted 10 February 2012 - 11:55 PM
I have never observed a planet at 2:45ish.
The beauty of this hobby; to see what few have ever seen, the pursuit to observe objects each of us has never seen before. You'll note in my first post that in 40 years I had never seen this before, yes?
It would be difficult finding Jupiter in such a bright sky.
Thus my desire to see it earlier than my first chance encounter. So?
The earliest I have seen it is around 4pm. Of course it also depends on what month we are talking about. At 4pm in December the sky is already darkening some. Without goto or setting circles locating Jupiter at 2:45ish would be a challenge for me. When Venus is near elongation I have seen it with the naked eye early in the day around 3pm.
Goto or setting circles are fairly common and inexpensive. I can understand the simplicity of NOT having them, as from time to time I do observe with scopes that are on camera tripods or basic AZ/ALT. It's a big hobby and room for both.
It's what I observed. Maybe my writing style stinks. Yet this is a big group and perhaps interesting to some. I hope sometime you try it yourself.
Peace. To me the thrill of this hobby comes on these chance encounters.
Posted 11 February 2012 - 01:06 AM
I am impressed with your observation of Jupiter so early in the day. I have tried a few times to see Jupiter earlier in the day and have failed. Maybe I can catch it when it's close to the moon.
I meant no disrespect to you by my earlier comments. I apologize if you took them that way.
Posted 11 February 2012 - 11:43 AM
Posted 29 September 2013 - 01:01 AM
Posted 29 September 2013 - 03:40 AM
Hi, I wonder if the shadows of jovian moons are visible on Jupiter during the day?
They are. I recall a German observer reporting seeing them with a 4" Vixen achromat, during the day. I have also observed Jupiter in daylight, but it was pretty washed out. The sky must be very clear. Mercury and Venus are easier. Mars should be as well, when it's approaching quadranture, but I've yet to see it.
Posted 04 October 2013 - 11:32 PM
Posted 16 October 2013 - 11:27 AM
Back on August 18th, 1990 I observed an occultation of Jupiter by the Moon. Here are my observing notes.
I got up early around 8:30 UT to observe the occultation of using the AP 7" f/9. The weather was warm and humid, and I noted that mosquitoes do in fact swam at dawn (and dusk as I have found out before during other observing sessions). However long pants, a long sleeve shirt and light jacket, and plenty of Cutters bug spray helps cut down on he number of mosquito bites.
This is probably the "oldest Moon" I have ever observed, and it showed a lot of interesting detail.
I began observing Jupiter and noted that the South Equatorial Belt (SEB) was still faded, but the Great Red Spot was visible in its usual location. It looked odd as I was used to seeing it along the SEB, but now it appeared to be sitting by itself. The North and South Polar regions were visible, as were the North and South Temperate zones and belts.
As the sky grew lighter I noted that the indeed the colors of the belts do tend to change a bit. For example When I first set up the NEB appeared medium to dark brown, but as the sky grew lighter the color changed to more of a natural color, sort of a creamy light brown or light-brownish pink, reminding me somewhat of the Voyager photographs.
As the sky continued to get brighter I could no longer see Io, Europa, Ganymede, or Callisto, and the Jupiter appeared smaller than I recall seeing it before. I realized later that Jupiter was just past conjunction, and so was on the other side of the Sun from Earth. Usually I observe it when it is near opposition.
By 9:50 UT it was no longer possible to see the Moon as the sky grew brighter and the haze reduced transparency, so I would not be able to watch the occultation of Jupiter.