Colour of Jupiter's Great Red Spot (GRS)

[starfinder]

Am starting another thread here on Jupiter's Great Red Spot (GRS). Junwei earlier wrote:
"by antares2063 » Sun 18 Aug, 2013 10:37 pm
Correct me if im wrong, but it seems that the GRS of Jupiter seems to have faded (in terms of the redness) in recent years.? back in JC years and 2005 i remember seeing it quite often as Jupiter has a very fast rotation..

regards,
Junwei"


Junwei: that's something I have sensed too. Jupiter's Great Red Spot seems to be lighter in colour now than I recall it to have been in around 1998-2000. Not that it was dark red then, and I would refer to it in my mind as the Great Pale-Pink Spot, but it does seem to be a lighter shade of red now and perhaps also smaller than it was back then.

[antares2063]

Thanks Gavin...maybe can rename it (jokingly) as GPS {great (pale..pink?) spot} ...haha...anyway guess the colour has become a similar shade of beige making it a challenge to see now. Jupiter only takes 12hrs approx to rotate one full round on its axis..cant be missing it that often..

Regards,
Junwei

[Gary]

When Jupiter is near enough and sky is clear enough, GRS transits can be easily seen in a 5-inch/6-inch newt/sct/mct. For quality refactors of slightly smaller aperture, should not be a problem too.

[Gary]

According to Damian Peach, GRS seems to be getting "darker and visually more apparent"!

http://astrobob.areavoices.com/2013/08/ ... is-season/

[starfinder]

It seems to be a new development this season. That's good news.

In the same article, Bob King says: "Over at least the past decade the GRS’s color has been closer to pale pink than red. ...
That might be changing. ... News of the spot’s darkening is most welcome. When I was a teen, the GRS stood out a bold red-orange; anyone looking through my little 6-inch reflector could see it."

[starfinder]

According to Sky & Telescope's Java applet, there will be a Great Red Spot transit at 6.18am Singapore time tomrw (Tues 27 Aug):
http://www.skyandtelescope.com/observin ... 04091.html

The GRS is visible about 50 mins before and after it crosses (transits) the planet's central meridian.

That would be good timing for us as it happens just at the crack of dawn when Jupiter is highest these days in the ENE for the day.

I wonder if the GRS's level of redness is measured from year to year using a colour index?

Incidentally, at 6:20am, Europa's shadow will begin to cross Jupiter.
http://www.skyandtelescope.com/observin ... pt/jupiter#

[antares2063]

Thanks for the info, hope can get to catch it , dark clouds looming now at 3pm (did someone buy a new scope?....LOL)

regards,
Junwei

[starfinder]

I managed to haul myself up at 5:30 this morning (Tues 27 Aug 2013) and observed Jupiter for nearly an hour with my newly acquired 12.5" Obsession dobsonian (with an f/5 OMI primary). Jupiter was rising in the ENE, in Gemini, bewteen 28-39 degrees above the horizon. According to SkySafari, it was then at mag -2.0 and 34.4 arcsec size-wise.

A few days ago, the seeing was unusually very poor at around the same time - Jupiter was uncharacteristically awash in fast air currents then -, but this morning the seeing was quite good, with just a few moments of excellent clarity. Sky transparency was good too, but not excellent.

It was a very satisfactory observing session. I viewed the Great Red Spot as it steadily progressed towards and then just beyond the meridian. Whilst I could see a bit more detail and a larger scale at 358x (4.5mm Delos), I found that, this morning anyway, the most pleasing views were at lower power, when using eyepieces for 161x (10mm Delos) and for 230x (14mm XL, with a Celestron 2x Ultima apo barlow which I acquired from Acc years ago at the Singastro fair - time to hold another one!).

At those lower powers, the planet and its features were sharper and more contrasty, very similar to a sharp mid-sized apo refractor, but of course I'm sure with more detail and resolution due to the larger aperture.

A few swirls and festoons were seen within and at the outer fringes of the two main belts, though perhaps if the seeing was better, I should have seen them in better detail. As for the Great Red Spot, yes it does indeed appear to be redder this year than in recent years, and within the spot, it seemed to be a deeper red at the lower (far southern) half of the spot than near the northern end. Its shade of 'red' was more red than pale-pink or orange-brown, but not red like a traffic light red of course. The GRS was fringed at its upper/northern end by a broad cream-white border between it and the southern equatorial belt (the GRS was situated partly within and partly outside the belt).

At 160x, with the 4 main moons as tiny discs framing the planet, Callisto on the lower right, and Europa, Io and Ganymede on the upper left from inner to outer, it seemed as if Jupiter with its two main belts beaming across the globe, was smiling at Earth. Really!

Incidentally, of the 4, Ganymede appeared to be larger than the other 3. I wonder if that's correct.

Just as the sky was beginning to brighten, I managed to see the tiny shadow of Europa infringe on the planet's left (eastern?) edge at 6.30am.

There, not too bad for one set of objects in the sky for an observing session. And the season has just begun!

[Gary]

@Mystiq - Congrats on catching the GRS! Plenty of time from now till its opposition (Jan 2014) to get the correct planetary imaging gear and skills.

@Starfinder - Congrats and nice visual report! Another proof that Dobsonians should be included in the conversation when discussing about what telescopes are good for planetary observing. Can't wait to see/hear how your dob perform on Jupiter during its opposition!

[Canopus Lim]

Hi Gavin,

Jupiter is pretty low that is why you won't be able to use higher power. Typically there is at least a difference of 100x useable magnification of Jupiter from low to high (close to Zenith). For my 12.5" my most used eyepiece is 5mm Pentax XO at 320x. It gives a pleasing 1mm exit pupil and high detail of Jupiter (probably 99% of all details available). Guess when Jupiter rises earlier and you can observe it closer to Zenith, you will get to use your 4.5 Delos more.

Anyway, I am interested to see what my new ZOC mirror can do. However, I will have to wait few months later. Tough waking up so early in the morning to observe! 25th August morning thanks to my daughter waking me up, I brought out my Televue 60 APO with zero setup time, to catch Jupiter at 6 plus am. Managed to catch the GRS. The scope has pretty sharp images at more than 50x/inch. However, 60mm is still far from 12.5". Haa.