Imaging.... UFO! :)

[Astr0Kaz]

Hi,  I was taking 3 minute exposures of the Pleiades last week and I noticed a small fuzzy dot moving amongst the stars. I initially thought I had caught an asteroid until I realised the fuzzy thing changed direction randomly!  Please see attached Gif which is showing a crop of each exposure in the order taken.  

I was using my ZWO ASI533mc camera (not the cooled version), William Optics Zenithstar 61 with field flattener 61a, Optolong l-pro filter, Skywatcher Star Adventurer pro 2i and guided with ZWO ASI120 & mini scope.  I was also drizzling.  The guiding was working well. 

The only thing that I can think of, is that it is light reflecting back onto the sensor somehow, maybe from one of the brightest over exposed stars or from external light pollution somewhere?

When I switched to the L-eXtreme filter,  the fuzzy thing disappeared.  The same night, I also imaged the Orion Nebula with both filters and there were no issues.  However, the following night, I tried the Pleiades again with the L-pro filter, and the fuzzy thing reappeared.  This is why I believe It must have something to do with the over exposed stars or maybe the angle of my scope and external light pollution.  

Has anyone seen this before and if so, can you please explain this odd effect? I have been imaging with this OTA for over a year now and I've not noticed anything like this before.  

Thank you 😃 

 

[paul mc c]

Could it be a small spider or small insect.....

[Astr0Kaz]

9 hours ago, paul mc c said:

Could it be a small spider or small insect.....

Hi Paul, thanks for the idea 🙂, but I don't think so. Any dust in the optical train shows as a large circle, so the insect would have to have been hovering a meter or so above my scope to appear so small.  It also disappeared when capturing the Orion Nebula and reappeared the following night when I went back to the Pleiades.  It also stayed still for each 3 minute exposure, but then moved location as my mount dithered.  I really think it must be a reflection of light from somewhere, I'm just not sure where 🤔

I think my stacking software will remove it, but it's just weird! Lol

[Yawning Angel]

37 minutes ago, Astr0Kaz said:

stayed still for each 3 minute exposure, but then moved location as my mount dithered

That would suggest lens flare to me, the way it moves only if the scope moves

[Astr0Kaz]

10 hours ago, Yawning Angel said:

That would suggest lens flare to me, the way it moves only if the scope moves

Thank you 😃  That is the kind of thing I was expecting it to be, however I've been unable to find any lens flare effect quite like it

[GalaxyGael]

23 hours ago, Astr0Kaz said:

Hi Paul, thanks for the idea 🙂, but I don't think so. Any dust in the optical train shows as a large circle, so the insect would have to have been hovering a meter or so above my scope to appear so small.  It also disappeared when capturing the Orion Nebula and reappeared the following night when I went back to the Pleiades.  It also stayed still for each 3 minute exposure, but then moved location as my mount dithered.  I really think it must be a reflection of light from somewhere, I'm just not sure where 🤔

I think my stacking software will remove it, but it's just weird! Lol

Would be the other way round. A very tiny dust mite moving around on the sensor is better resolved, and would be bigger and more diffuse further from the sensor. No idea what it is though....is that movie a collection of subs and what's the length of the sub, the length of the movie overall and the plate scale? We could work our roughly the speed in pixels per second and get a rough size estimate just for fun.

It does look like something imaged in the sky, spooky!