Unusual spot on Saturn

[neil phillips]

This is one i posted from the 8th march 01:28 UT

if you look at my rather crude arrow there is a dark spot, its been bugging me, so i wondered what you guys think it is ? processing artifact ? might be but dont think it is. dust on my chip possibly but i havent noticed any recently would need to check that, but looks different to me. too circular. moon shadow ? the only moon i can see listed is Tethys, its faint but its just above the rings on the right. too far from the spot.So im at a loss ? Any way heres a blown up version to see easier

[CKemu]

Could be a new feature as it seems to have the same overall blur/focus as the image. However to my eyes it looks like it extends slighty beyond the edge of Saturn and into the rings, which suggests dirt to me, but either way, cracking image compared to anything I've ever managed to get!

[neil phillips]

Hi i just checked my camera there are a few faint very translucent dust bunnys on the chip, not the sort of dirt that shows up like this ( too dark and distinct ) i could be wrong but i really dont think its Dirt, i wondered about a feature too but im not sure ? seems very dark

[Space Cowboy]

Weird! Have you got any images just after or before this to compare?

[brianb]

Ummm ... somehow I doubt a feature so close to the limb would appear to be quite so well defined. I'm also confused by it appearing to cross over from the disc onto the rings.

[neil phillips]

Exactly Brian it almost seems to be slightly OFF THE DISC, that can not be, and has to be a optical illussion of some kind.

Stuart i did look at a image after, footage wasnt great, and i thought i could see a small rather stretched out fainter, less contrasty dark patch. but im not certain as it was much more indistinct than this. I will check again, possibly post one up. K3 has just run out, i need Peter K to contact me so i have k3 running again. at the moment im locked out. will be doing reg stacks untill i hear from him, i also colour align on k3 so thats it for colour untill i get k3 running again. wondering about tonight, it might be clear, but a little windy, its a weird feature if its not a illusion, very weird infact

[frewi808]

Wish the weather was better so I could look at it...

Will try to find out the CM position.

Freddy

[riklaunim]

To judge if there is something there you would have to take few avis - to check if it will be on all of them and if it will rotate with the planet. There is some activity around the storm, but it may also be a shadow of a moon, which can be checked in software like Starry Nights.

To limit chance for noise/artifacts use slightly lower scale and much higher histogram fill (80-90%).

[johnh]

I have had similar darkening at limb ring intersection but it is not a feature as rotation showed. This may be similar to yours but you need rotation to show really but I am doubtful - although its at a similar level to the storm, there is a storm in the South which I thought you were refering to before I looked. It would not be sensor dust as this always averaged out.

John.

[brianb]

much higher histogram fill (80-90%).

Actually that's asking for artifacts due to non-linearity of response as the CCD wells approach fullness, as well as the effect of sharpening which always increases the contrast & can easily turn bright pixels into saturated ones.

I don't know what mounts you guys are using but, with "normal" mounts being used without autoguiding, erratic drift of the image across the chip prevents even quite serious dust motes from being visible in finished image stacks. My dodgy polar alignment helps, too. With a really good mount you could always try setting the "wrong" tracking rate, solar tracking would probably work quite well with planets.

[beamish]

sounds like a good idea to me Brian

[riklaunim]

Actually that's asking for artifacts due to non-linearity of response as the CCD wells approach fullness, as well as the effect of sharpening which always increases the contrast & can easily turn bright pixels into saturated ones.

I don't know what mounts you guys are using but, with "normal" mounts being used without autoguiding, erratic drift of the image across the chip prevents even quite serious dust motes from being visible in finished image stacks. My dodgy polar alignment helps, too. With a really good mount you could always try setting the "wrong" tracking rate, solar tracking would probably work quite well with planets.

80-90% histogram fill (for the brightest part by the ring) for ICX618 is around 20 FPS at f/20 with infrared filter (Pro Planet 742), which is quite dark for Saturn. Didn't had any problems with saturation after processing the stack. However on lower histogram fills even with greater number of frames there was much more grainy noise after sharpening/processing. It's just that catching dim Saturn doesn't work that good (with this camera).

[neil phillips]

Thanks for all the feedback, If John is right its likely a artifact of somekind then.

The law of diminishing returns Rik ive been experimenting endlessly with scale, from tiny to massive, i think ive sussed whats working best with my system. BTW this was heavily resized, you make it almost sound like it was only resampled a bit ?

LOL Rik i knew how to check if features are real on saturn by creating movies, probably before you ever started imaging, Just a point

The problems on pushing equipment to its limit with the uk altitude and seeing confounding the problems. on the one hand no noise, less chance of artifacts, BUT SUCH POOR RESOLVING POWER I THINK I WOULD GET A BIT DEPRESSED lol. Or slightly dim images that can be processed to bring out the detail. with far better resolving power, but good noise control needed.. I have roughly sussed a power that is optimum i think, with my dirty optics and DMK. Just havent as yet been able to exploit that to its fullest, if i ever get that chance, hopefully you will agree, im shooting at the correct focal length, that has performance in mind, infact i thought some of my recent postings were starting to show signs that im slowly getting there. Not there yet. but theres time hopefully to improve. I appreciate the suggestion, but you said as much to me on jupiter, which i thought was a bit odd, as most people were saying to me, that i was pushing my equipment to its limits. Dont confuse resampling with too high a focal length Rik, i dont think its a problem i often fall into. Maybe you dissagree, But im sure my current focal lengths ( the lower one in particular ) is actually spot on, for the problems mentioned. Hopefully if i can get good seeing i can show thats the case. Heres hoping

Btw John i just love those reds, a C14 beater

[riklaunim]

The law of diminishing returns Rik ive been experimenting endlessly with scale, from tiny to massive, i think ive sussed whats working best with my system. BTW this was heavily resized, you make it almost sound like it was only resampled a bit ?

I've seen lately an Saturn image made with some odd Mintron camera with C8 at f/100 So everything is possible now.

So we just need clear skies, and a comet or two to hit Saturn while imaging

[neil phillips]

I am a bit of a resample Freak Rik, sometimes i go to far, other times, im being told that im doing good. resampling is art, just as much as capturing is, theres good and bad resampling i think. its not as simple as just pressing 150%. I heavily resized this image for benefit of seeing the dark spot, i wouldnt normally resample to this level. If i did i reckon freud might have a theory why ???

Im actually flattered that you think i could take a image that large. with the lack of seriouse seriouse, blur it would create at 34 degrees at that crazy size, thats without the fact my dirty optics ( soon to be clean ) and DMK would just fade away to a signal that was so weak i would need a bull worker, to bring it back to strength. I think i take that as a compliment. i can often push things. at low altitude with the equipment i posses, but thats crazy.

Surely that f100 image was in a different country to the uk, with superb seeing. at my location and equipment it wouldnt look very nice, thats for sure.

A Comet on Saturn would be everyones dream Rik, that would be something.

[riklaunim]

It was made in Poland, so the same low alt. The camera must have very big pixels, as that image was smaller than that resized in the first post:

But IMHO this is even better than from Cassini:

In this false color image you can see the storm in red...