Best image of Ganymede?

[markclaire50]

Please could you show me your best image of Ganymede and the equipment you used. I will award a 'cup' to the one I am most impressed by. 

[Pete Presland]

I have seen a few with hints of surface detail captured over the years.

[markclaire50]

2 hours ago, Pete Presland said:

I have seen a few with hints of surface detail captured over the years.

Hi Pete 

Which scope did you use? 

Thanks 

Mark

[Pete Presland]

I have not managed it with my c9.25, but it's possible . 

I say surface details,  its more albedo markings than actual detail

[Stu]

I suspect this guy might win ??

http://www.damianpeach.com/jup_misc.htm

[markclaire50]

1 hour ago, Stu said:

I suspect this guy might win ??

http://www.damianpeach.com/jup_misc.htm

Yes, I've seen his images also Saturn. Best advert for getting a C9.25!!

[markclaire50]

3 hours ago, Pete Presland said:

I have not managed it with my c9.25, but it's possible . 

I say surface details,  its more albedo markings than actual detail

Please tell me nice things about your scope! It's on my short list of scopes. ?

[chiltonstar]

I've picked up a little visible albedo detail and managed to capture it once or twice. Taken with a Mak 180 plus AS1224 camera.

Nothing like Damian's brilliant images though! Need a bigger scope, better location and seeing, and a lot more skill.

Chris

[Pete Presland]

On ‎21‎/‎02‎/‎2019 at 16:39, markclaire50 said:

Please tell me nice things about your scope! It's on my short list of scopes. ?

I upgraded from a Mak180 to the C9.25. Its a nice balance between aperture size and still reasonably light.

I have no negatives to say really other than the usual SCT comments. 

 Dew shield is essential,  crayford focuser desirable, cooling downtime very important as well.  

[markclaire50]

1 hour ago, Pete Presland said:

I upgraded from a Mak180 to the C9.25. Its a nice balance between aperture size and still reasonably light.

I have no negatives to say really other than the SCT comments. 

 Dew shield is essential,  crayford focuser desirable, cooling downtime very important as well.  

Hi

Maybe a silly question but do you see more than the mak? I know aperture says yes, but on their areas of strength which I believe are similar, does the sct show that extra aperture in real world? 

Thanks 

Mark

[Stub Mandrel]

It may not be brilliant, but it's the best one (two!) so far ?

 

 

[Pete Presland]

6 hours ago, markclaire50 said:

Hi

Maybe a silly question but do you see more than the mak? I know aperture says yes, but on their areas of strength which I believe are similar, does the sct show that extra aperture in real world? 

Thanks 

Mark

Difficult question for me to answer really, the Mak isn't referred to as a planet killer for no reason though.  A Focal Length: 2700mm (f/15) makes it perfect for planets.

[markclaire50]

18 minutes ago, Pete Presland said:

Difficult question for me to answer really, the Mak isn't referred to as a planet killer for no reason though.  A Focal Length: 2700mm (f/15) makes it perfect for planets.

Hi. I'm mulling over both. I've seen fantastic images by Damien Peach using a C 9.25. I've also seen photos on flickr also showing linear markings on ganymede with a 180mm mak. Based on you having used both, which would you instinctively choose for planets and doubles? 

Thanks 

Mark 

[Stu]

I think alot comes down to conditions, and collimation and cooling. Mr Peach images from the best sites in the world with the planets high in the sky, with steady seeing, or at least the knowledge to pick the best times to image. Properly collimated and thermally stabilised scopes make as much difference as the exact scope type I would think.

[Pete Presland]

I wouldn't switch back to the Mak, I think the C9.25 is a more versatile scope. 

[chiltonstar]

Worth adding perhaps that the angular diameter of Ganymede is such that with an amateur scope the Airy disk is a significant fraction of this, in other words resolution of fine detail is not really possible. Any fine structure actually seen is likely to be imaging or processing artefacts.

Chris

[markclaire50]

18 minutes ago, chiltonstar said:

Worth adding perhaps that the angular diameter of Ganymede is such that with an amateur scope the Airy disk is a significant fraction of this, in other words resolution of fine detail is not really possible. Any fine structure actually seen is likely to be imaging or processing artefacts.

Chris

Hi. I always think Damian Peach's images show actual detail, with his C9.25. Detail in the sense of actual shaped darkened feature. At opposition, ganymede can be as big as 1.8" so a sct scope like the C9.25 with a Rayleigh limit of about 0.6" using high magnification and with good optics could theoretically resolve larger surface features? 

Mark

[chiltonstar]

7 minutes ago, markclaire50 said:

Hi. I always think Damian Peach's images show actual detail, with his C9.25. Detail in the sense of actual shaped darkened feature. At opposition, ganymede can be as big as 1.8" so a sct scope like the C9.25 with a Rayleigh limit of about 0.6" using high magnification and with good optics could theoretically resolve larger surface features? 

Mark

30% of the actual diameter? Hmm..... C14 maybe.

Chris

[markclaire50]

11 minutes ago, chiltonstar said:

30% of the actual diameter? Hmm..... C14 maybe.

Chris

I thought that the rayleigh limit was a good indication of resolution certainly for extended objects. The rayleigh limit is 138/D, so a C9.25 would have a rayleigh limit of 0.6", which is one third of 1.8. Hence, in theory a C9.25 could see large surface features, albeit as darkened shape. This is supported by Damian Peaches photos. 

Now, whether you could see this visually is perhaps a tougher challenge, but the numbers in theory don't rule it out under optimum conditions and high magnification. 

[chiltonstar]

Major features yes, I agree. Not fine detail though.

In the past, I have carried out convolutions of NASA images with different Airy disk sizes, and the results closely match the detail in some of the brilliant images by Astrovani on this site.

Chris

[markclaire50]

1 hour ago, chiltonstar said:

Major features yes, I agree. Not fine detail though.

In the past, I have carried out convolutions of NASA images with different Airy disk sizes, and the results closely match the detail in some of the brilliant images by Astrovani on this site.

Chris

Yes, sorry if I wasn't clear on that. I meant large 'shapes'. In a C9.25, visually I'd be happy with seeing an albedo difference on ganymede, even more so if it had some shape to it! ? 

I assumed such albedo 'shapes' would be large enough to be resolvable by a C9.25, given its capabilities.

Cheers

Mark