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Observing Jupiter's GRS, in daylight

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#1 Tom and Beth

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Posted 02 February 2012 - 10:29 PM

On the 30th, I was out observing the Lunar X. The bigger scope (10 inch) was still cooling so a short hop over to Jupiter, local time 4:30 ish PM. I noticed the GRS was rotating into view. Eventually the scope equalized and Jupiter could be observed at 231X! Frankly, I was amazed at how much detail was evident. Not only the GRS but the preceding barge, details in the belts...heck, it sure was "downright purty".

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.

#2 Asbytec

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Posted 02 February 2012 - 11:22 PM

Some say observing Jupiter with some light in the sky is great. Maybe there is something to that, never done it during broad daylight. Interesting.

#3 Dean Norris

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Posted 03 February 2012 - 03:13 PM

I have had excellent views of Jupiter in early twilight and great views as early as 4:30 pm local time in January. I have seen Jupiter even earlier when the sky is lighter but found the image to be washed out a bit. Often the seeing is very good at this time of day.

Dean

#4 Rutilus

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Posted 04 February 2012 - 02:18 PM

Below is a drawing I made a couple of years ago of Jupiter at 2 o'clock in the afternoon. Telescope used was my 76mm f/16 refractor.
Also a photo I took in daylight, showing the moons and even picked-up Uranus.

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#5 Eddgie

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Posted 04 February 2012 - 06:52 PM

I have wondered about this from time to time.

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.

#6 Asbytec

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Posted 04 February 2012 - 08:04 PM

Mike argues the same, Eddgie. There is probably some truth to that. One might, and I do, believe the eye can reach photopic state observing planets at night. Always, when observing in cyclops mode, my observing eye is never dark adapted after a bought with Jupiter or Mars. It's easy to tell when you glance at the night sky.

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.

#7 Tom and Beth

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Posted 10 February 2012 - 08:45 PM

I've done a few more observations, and added Venus to the list. While having acclimated optics, steady air and no clouds ( :lol: ) would be common to Night observations, I'm finding a shroud or cloth over the head is important, much as with Solar Observations. I'm not sure how much my pupil expands with this, if any, but I'm still intrigued by the ability to see quite a bit of detail in daylight. And surprisingly, GRS transits as early as 2:45 ish PM were successful. Now bear in mind that all of these to date are when Jupiter and Venus are close to transit, and thus well positioned for observation. Venus observations in particular are much better.

Anyway, another unexpected bonus is that the scope is ready for night time observations earlier.

#8 Dean Norris

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Posted 10 February 2012 - 10:09 PM

Rutilus,

Excellent sketch of Jupiter. The image of Jupiter with the moons and Uranus is a great catch.

Norme,

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.

Tom,

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.

Dean

#9 Tom and Beth

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Posted 10 February 2012 - 11:55 PM

Tom,

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.

Dean


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.

#10 Dean Norris

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Posted 11 February 2012 - 01:06 AM

Tom,

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.

Dean

#11 Tom and Beth

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Posted 11 February 2012 - 11:43 AM

It's difficult to tell in the written word the "feelings" sometimes. No offense was taken, and if anything hope that others will give a shot at daytime observing.

#12 gymnatrix

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Posted 29 September 2013 - 01:01 AM

Hi, I wonder if the shadows of jovian moons are visible on Jupiter during the day?

#13 Astrojensen

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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.


Clear skies!
Thomas, Denmark

#14 charles genovese

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Posted 04 October 2013 - 11:32 PM

I've been viewing Venus and Jupiter in daylight since the 1960's - in the old days with my trusty RV6. The easiest way the first time is to wait until th moon is nearby as a reference. In a clear sky Venus is an easy naked eye object once u know about where to look and learn how to focus your eyes on blank sky. The easiest way is to wait for high flying birds to pass nearby. Sometimes your looking right st it but don't see it then it just pops in and you wonder how you missed it. You can put markes on your observing site to easily reproduce a polar allignment in daytime, then set the dec and just scan in RA. jupiter can't be seen with the naked eye in daylight but pops right out in a 50mm finder. Same for mercury. Position yourself in the shadow of a building or tree and catch it near the Moon for the first observation. Then set Dec and scan a little and it's no effort to find it from night to night.

#15 ericj

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Posted 16 October 2013 - 11:27 AM

Hi Tom & Beth,

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.

Best,

Eric Jamison






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