[kkara4 (Krishan)]

wasnt sure where was best to post this in the forum, mods please move if needed.

I was out imaging Saturn, Mars and Jupiter on 8/6/16. I wanted to test the ASI290mm's capabilities on Saturn's moons, so i cranked the gain to max and increased shutter to 35ms, which showed rhea, tethys and dione no problem. Enceladus and mimas were revealed after stacking and stretching levels in photoshop.

but as i did this, an unexpected object presented itself. it can be seen in the two attached images 12 oclock of Dione. anyone know what it is? i have inserted a stacked and lightly sharpened image of Saturn through red filter taken just afterwards to give scale to the whole image. i believe i am at around 0.077 arcsec/pixel here. I put the motion at around 1arcsecond?

It cant be a moon since its motion is retrograde to the others, and i certainly didnt discover a new moon that bright (you can see it is a bit fainter than mimas). Cant be Phoebe, since too close. i dont think its a star but stellarium is all i know in terms of checking this, i know there are much more advanced ways of checking. i dont think its a satellite (too bright/slow?). Asteroid would be too faint? comet would be too faint?

Image details as follows:

Telescope: Celestron EdgeHD 925
Mount: Losmandy G11, polar alignment happened to be excellent.
Camera: ASI290mm, red filter, max gain @ 35ms, stack of ~430 frames.
image times: Filenames contain times, center of recordings 8/6/16 (11:39:43UT and 11:41:06UT). Times are accurate to +/- few seconds i believe, since i time synced to UT the computer clock about 5 hours prior.
IMage stacking: autostakkert, Alignpoints placed on Rhea, Tethys, Dione, Enceladus, best 50% using COG method (hence the apparent difference in blown out disk since i didnt align on it).
My location: western suburbs of brisbane

i have exhausted every resource i know of up to my ability, but my knowledge of the more advanced sky charts and other utilities is limited, so hopefully the much more knowledgeable folks on here can help identify the object!

Please let me know if more details are required. happy to provide. unfortunately these two images represent the first and last sequences i captured, because i was really only testing and i only just got a chance to process the videos.