Ganymede sketch + Obs Report 19/11/10

[pgc hunter]

After having surgery on my toe, I thus had no work last night (Friday 19 Nov) so took advantage of the clear skies. 7timer predicted good seeing until midnight and skippy sky was showing 9/10 for the whole night.

Seeing was very good from after sunset until about 12:30-1am, when it deteriorated slightly.

Time: sunset-3am
Scope: 12" F/4.4 truss dob
Seeing: 7/10 dropping to 6/10
Transparency: 0/5 (nearly full moon)

Spent the first half of the night largely on Jupiter and Uranus.

Jupiter
At 267x, I caught the GRS just as it was dissappearing over the planet's eastern limb. The spot is pale and a light pinkish colour. The outer rim appeared slightly darker than the interior. As the evening progressed, seeing continued to improve, and at 334x at 10:52UT (9:52pm local DST) I could see some interesting features coming into view in the SEB. Three white ovals, with the preceeding one the largest and the following two decreasing in size were seen, along with a darkish cloud feature that appeared intertwined between the ovals. The most obvious part of this feature stretched between the large preceeding oval and the second oval, looping over the preceeding oval appearing similar to the classic side-on view drawing of a breaking wave.

Ganymede
Seeing was good enough to view the Galilean moons as disks, each with obvious difference in size. At 534x, in moments of good seeing, I caught some surface markings on Ganymede. In the northern hemisphere a dark wedge shaped feature could be seen, while the northern polar regions appeared lighter and whitish compared to the orange-yellow hue of the rest of the moon. Seeing was still blurring the image, but it also settled enough to get a crisp view of the disk momentarily. I also noted Ganymede's orange-yellow colour contrasting with Callisto's Ice-blue, which was a neat sight.

Uranus
Uranus was the clearest I've ever seen it, even at 534x, the disk was pretty crisp, and at 334x it was text-book perfect! On a typical night at 250x things start to go south. So, at 534x I got a nice pale blue ball, and despite moonlight, Titania was spotted. I attempted to see albedo features that some other observers had noted, and I suspected the polar region to be slightly lighter tone, but could not be certain.


I also moved on to 47 Tuc and NGC 362, I could not believe how crisp and clear they were at 334x, it was amazing. Infact, even at 762x, focus was so good that I had to check the eyepiece and barlow if it really was the combo for this mag. I was getting the image quality I'd normally get at about half that mag. 47 Tuc's core was brilliant, a powdery bowl of suger overlayed with glints of light. A nice semi-circle of stars partially encloses the this central region. NGC 362 was as resolved as I've ever seen it, it's core rather than a haze was more textured and granular.

Then, not long after, I got a real dose of reality. I first hand witnessed the difference between great seeing and average seeing. A couple of hours later I revisited the clusters again, and guess what.... using the same mag of 762x, the resolution was not even remotely as good as what I got just prior. That "snap" focus was gone! It just mushed thru focus, unlike before when I got that satisfying crisp snap into focus effect. From that point on, seeing wasnt as good as earlier in the evening.

I moved on to NGC 1535 which at 534x presented a nice clean annulus surrounding a central star. It appeared brighter along thewestern rim. The E/NE section of the interior appeared brighter than the western portion, which consisted of a darker croissant-shaped region, but it was brighter than the background sky. A faint, ill defined outer fuzz was seen.


IC 418
Gorgeous at 534x, a brilliant egg-shaped, high surface brightness PNe, whitish in colour with a bright central star. The outer rim appeared brighter than the nebula's interior giving a slightly annular effect, with the NW quadrant brighter. The interior ofthe PNe appeared to have slightly undulating surface brightness.

NGC 2022
A planetary in Orion. Visible as a small circular grey soup bubble at 166x, with only a hint of annularity at 381x. The OIII filter provided only modest improvement, with the annularity slightly more obvious.

NGC 2440
This excellent planetary in Puppis clearly shows two bright white knots at 267x, superimposed on a rounded diamond-shaped background haze orientated perpendicular to the long axis of a line drawn thru the centers of the two knots. Suspected another brighter feature W of the knots. The two knots and the background haze give this planetary a creepy alien like appearance with those glowing eyes just staring at you. At 534x, the two knots are joined by a narrow "bridge", and the knots themselves appeared elongated E-W with the northern one brightest. Another much more subtle bright region can be seen W of the main complex, which is elongated and curves from just west of the northern knot down towards the SW.


Sirius
Tried for the Sirius pup, clearly visible at 534x and 762x but didn't try any lower magnification to see how far I can drop it due to the fact that I couldn't be stuffed changing eyepieces :P



A great night that probably won't occur again for a long time!

[Suzy]

Sab, what a fabulous report! Also loved your sketch of Ganymede. It was also great to get that report on the very apparent levels of seeing conditions you experienced. And I see you pulled nearly an all nighter taking advantage of the conditions. :lol: Thank you for sharing. :)

I hope your toe feels better.:) I'm sure that dose of photons you got in all those many hours of observing would have made you feel better. :D

[pgc hunter]

Thanks Suzy! That session was not only one of the best I had, but a real learning experience. I've found that seeing greatly effects globulars at least, so the myth that seeing doesnt matter for DSOs is a bunch of old codgewollop, the difference in sharpness at high magnification as the seeing changed was night and day, ... it gave me an opportunity to see first hand the brutal effects of very good vs average seeing!

The seeing was really only great until about midnight, the rest of the time was waiting for the summer planetaries to rise, and some good views were had there. Last time I had seeing like this was about half a year ago. ANd not everyday seeing is good enough to spot detail on Ganymede that's for sure! Tried for it again tonight, seeing was superb just after sundown with Jupiter showing nice detail at 308x but turned to custard in a hurry so no Ganymede obs. But got to see a transit of Io which was pretty sweet especially as the moon ingressed. Did a sketch of Jupiter aswell which I 'll post later :thumbsup: One thing I regret is not sketching Jupiter last night, because it was a crapload better!

[mental4astro]

Oh, you lucky bugger!

Surface features on Ganymede, to be sure!

And getting to use 500X +, oh you lucky bugger, again!

Fabulous stuff, Sab. Those are the nights we crave for. I'm glad someone was able to take advantage of the special occasion, :thumbsup: .

[michaellxv]

Well i'm guessing your toe is ok then. Either that or it's too far away from your head to interupt what your eye is doing.

Nice report. Fabulous descriptions. And a sketch of Ganymede. Well done.

[astroron]

Nice report Sab, It is good when you can see the Galilaian Moons other than bright points:thumbsup:

[pgc hunter]

Thanks all. The rarity of these nights can be illustrated by the fact that I had only 1 other night like that this year. Even this particular night the real good seeing lasted only half the night. I myself was somewhat skeptical of seeing detail on Ganymede until now but given the right conditions and enough magnification the tiny disk actually appears quite sizeable and the dusky markings manifest themselves. It is also possible to see subtle colour differences between Ganymede and Callisto, it's an interesting contrast between the yellow-orange hue of Ganymede and the pale ice-blue of Callisto when the pair are close to each other.

[Paddy]

Fantastic observations. Seeing detail on Ganymede!:eyepop:I am green, Sab, absolutely green. This is a beautifully written challenge to my ideas of what can be seen. And a great sketch, of course. Of Ganymede. A sketch of Ganymede. I can't get over it.

[pgc hunter]

thansk! It really is possible if seeing cooperates, but it has to be damn steady otherwise you won't see nothing.

Just after sunset last night seeing was excellent again and at 267x Jupiter was fantastic showing a wealth of festoon activity and even the SEB appeared uneven and curdled. I could even hint at a dark marking on Ganymede again. Sadly, the seeing went to absolute soup in the following half hour, bad enough to the point where I just packed up.

[ngcles]

Hi PGC & All,

Great report mate -- loved it. I've suspected some detail on Ganymede with the 18" occasionally and it is a real test of seeng to be able to see such tiny low contrast detail. Well done!

Loved the description of NGC 2440 -- that's almost word-for-word how I'd put it too. I had a fabulous view of it about 10 years ago with my 31cm at x262 and x363 I remember with some fondness -- in the backyard at my old home.

Excellent stuff!


Best,

Les D

[SteveG]

Really enjoyed reading the observations. When the seeing is good, I can often distinguish the various disc sizes of Jupiter's moons, but never thought that surface details on Ganymede were doable. Amazing job!!

Another Jupiter challenge is viewing one of the outer satellites. I have an observing report on another board on viewing Himalia (http://www.cloudynights.com/ubbthreads/showflat.php?Cat=&Board=deep&Number=3352419&Forum=f30&Words=Himalia&Searchpage=0&Limit=25&Main=3352419&Search=true&where=bodysub&Name=&daterange=1&newerval=3&newertype=y&olderval=&oldertype=&bodyprev=#Post3352419) and more goodies.

--Steve

[Lismore Bloke]

Hi Sab, I'm glad you had an exceptional night - you really made the most of it!! I would not not have thought it possible to see detail on any of Jupiter's main 4 moons with amateur sized instruments. It just goes to show that superb conditions and eyesight exceptionally acute and sensitive to detail can record something pretty special. Well done!!

[pgc hunter]

Hey Les, great to hear from you again! This would've been a great opportunity to go after some of the tiny HSB summer PNs, and NGC 3918 in seeing like this, it's fun trying to eek as much detail as possible. Always wanted to go after 3918 in excellent conditions. I later looked up images of 2440 to compare to my own obs and discovered that the outer plumes of the PNe extends about 2x further than the parts I saw, something to try for next time.


Thanks! It's also interesting to note the moon's colours, on this night Callisto and Ganymede were side-by-side providing an interesting juxtaposition of Ganymede's yellowish hue against Callisto's pale ice-blue. Nice report on Himalia, sounds like it's within my reach at it's brightest.



Hey Paul, seeing's gotta be near perfect in order to get the required magnification to blow up Ganymede's disk to a reasonable size, it's certainly difficult as even in great seeing, at very high power the tiny disk is still bouncing around and blurring quite a lot so you'd want to spend at least 15 minutes studying it.

On a related note, someone on CN claimed to see detail on Neptune (with an 11" scope IIRC) under what he describes as *perfect* seeing, it seems a little far fetched but would it really be possible :question:

cheers!

[ngcles]

Ganymede and Neptune are approximately similar sizes with Neptune a little bigger, but Ganymede has a brighter colour which presents as better surface brightness and the contrast on detail would, I'd think, be markedly better though neither would be described as a "walk in the park" basically due to size. I'd be sceptical too, though it's not outside the realms of possibility to see limited detail on Neptune in 28cm. BTW, what's an "IIRC" ?? :question:

Have seen Himalia -- tracked it down some time ago now it is by some distance the next easiest Jovian moon after the four big ones and not hard to see in 46cm in good conditions. The trick is finding the correct location/field and distinguishing it from a 14th-odd magnitude star. There is an ephemris here:

http://ssd.jpl.nasa.gov/horizons.cgi#results

if anyone is interested.

It is obviously easiest at greatest elongation from Jupiter. If you can find Pluto, Himalia won't present many issues. It orbits well outside Callisto meaning you can exclude Jupiter from the field with ease during most of its orbit. Jupiter is heading north over the next few years which will make it harder as it is closer to the horizon and the air-mass you are looking through is greater. On the other hand, Sagittarius also presents problems of its own because of the blizzard of 14th mag stars it will be hiding among. Now could be a good time ...



Best,

Les D

[pgc hunter]

Neptune is not only dimmer, but the changes in surface albedo would be very slight so to see that, if possible at all, would require very, very high power which would dim the planet too much, render it fuzzy (unless seeing is a 1 in a million - even then the limitations of the scope would apply) all of which works to further reduce one's ability to detect very slight difference of shading at such a small scale.

IIRC = If I remember correctly :)




cheers Les looks like an exotic challenge as few people ever seem to attempt to hunt Himalia down. Might try for it sometime.

[ngcles]

Hi PGC & All,



Well don't I feel a fool!

I stupidly imagined "IIRC" must have been some new, exotic brand of Ritchey–Chrétien or some-such telescope with ion-milled focus knobs etc.

I also imagined the observer in question making this claim would similarly boast that it was at least the equal of any other sort of 'scope twice it's aperture in resolution or contrast and with whom I was likely to have a de-facto fundamental disagrement over the physical laws as they relate to optics in a visual-use telescope.

Hanging my head in shame ...


Best,

Les D

[pgc hunter]

lol don't worry, didn't have a flamin clue myself when I saw it on another forum recently, had to google it to see what the heck they were on about :lol:


:rofl:



I wouldn't have a problem believing his claim, it's the fact that he say he did it with an 11" scope. Can't see an 11" resolving detail on Neptune, the mag required to get it large enough in angular size to attempt it would likely render the planet too fuzzy and dim to attempt to differentiate between the very subtle markings you'd find on the planet.