I heard somewhere that in a real good 10 inch or larger scope you can see detail on Jupiter's largest moon. Is this true? Has anyone done this? What does Ganymede look like? Just wondering.

I'm going togo out on a limb here and say that on a night of near perfect seeing and transparency, at very high power, you may be able to see Ganymed as a tiny disc, but I don't think you will see any detail.

 Observing detail on Ganymede was reported in the late 80's by Vic Menard and Tippy D'Auria, the guys who wrote the "book" about newtonian collimation.

Using a 20" f6.2. I doubt it could be seen by less than expert observers with perfect seeing and optics. 

I recall having seen sketches of Ganymede in several books. Unfortunatelly I don't have them at hand now but, one of those books, I believe, was the German "Handbuch fuer Planetenbeobachter" or Handbook for Planetary Observers and another book on planets published in former East Germany.

Anyway, I do believe it is possible to see subtle detail on Ganymede with amateur telescopes. Given perfect conditions and equipment, 12 inches+, a magnification of 600+ and maybe the use of an orange or red filter (to enhance contrast) may apply. I will certainly try in future.

I have, on several occasions, already seen Saturn's Encke ring division, and Titan as a tiny disk (approx 0,7" diameter) through my 15 inch.

 There have been a number of articles and papers by professional astronomers from observatories around the world of observation of detail on Ganymede. Back when everything was visual. The earliest I've run across was 1801.

Don't hear much from the amateur community. A difficult target and probably not too many spend the time and effort to do it. 

To do detail on another planets satellite's will require extremely good seeing conditions and magnifications in the realm of 1000 X. These objects are only in the order of our Moon size and even millions of miles further away. I can hardly believe that any detail can be seen through amateur equipment.

JJ 

 You would have to contact those who have reported the observations.

I certainly wouldn't even attempt it, but I'm not much for planetary observations anyway.

One reference in print is in Perspectives on Collimation; Principles and Procedures, 3rd edition. 

Ganymede's diameter near opposition is 1.7", that of Callisto 1.6" - that's tiny but, those two moons appear as disks even in good 4 inch scopes under perfect seeing conditions and 250x (I can confirm that). Some of the historic observations of detail on Ganymede were done with telescopes as "small" as today's larger amateur scopes. When you look at Ganymede below, you will see that the moon is devided up into very wide darker and evenly wide bright areas. An orange filter (often used for Mars) will only enhance the contrast and it should therefore be possible to see those features on Ganymede. I have no clue, though, when exactly that side of Ganymede turns into vision. That is an important factor, too.

The ultimate question mark does not really rest with scope size and magnification only but, seeing conditions... Nights with seeing under 1" are extremely rare in mid-northern/southern latitudes. Seeing usually improves later at night, so try in the early morning hours after 2 am. Another problem right now - Jupiter is fairly low for observers in Europe and northern US. Someone in Florida is definitely advantaged. I still have not bought the 2.5mm ocular - looks like its high time to get it

Ganymede is also the largest of any moon in our Solar System.

Jeese, maybe I better get back at that 12.5" f6 I've been working on. Have been thinking about optimizing that thing just to do planetary work. 

You can find this light/dark blotchiness in images done by amateurs, but I don't know anyone personally who has seen it via direct observation. As was pointed out earlier, you need sub-arc-second seeing to do this visually and that doesn't happen often.

Look at images by Christopher Go and Damian Peach for examples.

Daiman Peach of the ALPO Jupiter group posts some images of Ganymede every once in a while. 

He uses a 14" SCT to pull out details like this: 

http://www.damianpeach.com/barbados06/jupiter/jup2006_04_09gany.jpg

The camera (in the case of planetary cameras) generally shows only slightly more detail then you get with the naked eye, so it is possible with just a 14" scope...great seeing is the real requirement. 

Visit his site to be inspired... and jelous of him for taking trips to places like the Barbados for the purpose of imaging Jupiter ;)

His site:

http://www.damianpeach.com/

Cheers,

Darren

Beautiful pictures!

Hi everyone! 

With very good seeing and clear skies I thought that it would be worth trying to scan Jupiter's biggest moon for details. I had attemped the "impossible" before with magnifications of up to approximately 500x but did not succede. Weather conditions were very favourable today with 28 C and 67% humidity at 2200 local time. No wind. The temperature inside the house was around the same, so the mirror would be in perfect condition for the observation. And, of course, Jupiter very high up in the south (latitude here is 14 N). I first trained my 15" scope towards the moon at 342x magnification, to see how good the seeing was. Ahhh, steady, just a tiny little bit of low frequency wobble. I increased the mag to 732x (7mm Nagler + 3x Powermate). I was amazed to still get sharp views. OK, one more final increase to 1026x (5mm Nagler + 3x Powermate). Craters and shadows still sharp - unbelievable!! Right - Jupiter now. The first glimpse of Jupiter at 732x was disappointing, though. Lack of contrast and by far not as many details as I expected. Well, Jupiter is tricky and contrast is absolutely essential to see a lot of detail. Actually, I saw more at 342x... Now I had no more hope for more. Nevertheless I pointed the scope at Kallisto first. Wow - what a beautiful dark, tiny disk. I was stunned by the color that reminded me of pictures right away. Then Ganymede: Geee, like a tiny Mars! Beautiful orange and already fairly big at 732x. After some 10 minutes and waiting for seconds of very steady seeing, I thought that it had seen hints of shading on Ganymede. Now go for it! 1026x... It almost blew me over when I realized that there are shadings visible on that "not-so-tiny-anymore" disk. What I saw was basically a cone-shaped dark area that ran through the center of the moon. The northeastern and southeastern parts of the disk (scope direction) were distinctly brighter than the area around the equator of ganymede. In moments of perfect seeing I could spot a very dark tiny patch southwest of the disk's center. Ganymede's brightness was at the limit. With those high magnifications, any scope smaller than 13-14" might not deliver a bright enough image of Ganymede. I can say now that 750x magnification is also a lower limit. The whole observing session today reminded me of my 25 years-ago attempts to see detail on a 5 arcsec Mars using my 4.5 inch at 200x.... Now I will have to find out what part of Ganymede I saw and then compare my sketches to maps.The date and time of the observation was 2 hours ago, 14 Aug 08 at 14 - 1500 UT from Kanchanaburi, Thailand. Wow, I am still breathless... Post the observation and go out again for more!

Clear Skies!

Wow, that is cool! What a great report. Thanks for letting us know.

John 

Fantastic! Notice the image by Damian Peach corresponds well with the high resolution image of Ganymede shown above.

Here's an addition to my Ganymede observation yesterday. The image on the right was generated by a German friend using Starry Night Pro 6 program. It shows Ganymede at the time of my observation. The left picture is a sketch I prepared yesterday. My observation do not match 100% but, there is definitely some resemblance.

I tried it again today but, seeing was not as good as yesterday, which was an exceptional evening.

I'm convinced that you've seen some genuine detail.   It still amazes me though!    Well done.