What's causing this mark on my images?

[lukebl]

This is a single frame from my Canon 700d, captured with a 75-300mm zoom set at 75mm. 15 seconds, f/5.6, ISO1600.

There's a dark fuzzy blob in all of the images which I assume is some sort of dust mote, although it's quite large and diffuse. Any suggestions as to where it is in the image train and how to get rid of it?

 

[Albir phil]

Looks like a dust moat, your sensor needs a clean you can get a cleaning kit from a camera shop.

[Peter Drew]

+1    🙂

[Elp]

I wouldn't rule it out that it isn't on the external glasses or within the lens. A bulb blower usually works, hold said item upside down so any debris can fall out. More often than not in my experience such things are on other things rather than the sensor (filters, optics etc).

[Elp]

If you take flats and calibrate your images it'll disappear from the image in most cases.

[lukebl]

Thanks folks. I’m sure the sensor is dusty, so I’ve ordered a cleaning kit.

[The Admiral]

When I tried cleaning my conventional camera sensor I used up a lot of the cleaning sticks, but there's still a mote left behind! Turned into an expensive exercise. Have fun 😊.

Ian

Edited March 18 by The Admiral

[Albir phil]

31 minutes ago, lukebl said:

Thanks folks. I’m sure the sensor is dusty, so I’ve ordered a cleaning kit.

Take your time only use cleaning pad for one pass ,then use a second one.As said use blower first before you clean 

[tomato]

3 hours ago, Elp said:

I wouldn't rule it out that it isn't on the external glasses or within the lens. A bulb blower usually works, hold said item upside down so any debris can fall out. More often than not in my experience such things are on other things rather than the sensor (filters, optics etc).

That’s interesting, my experience has been the opposite, ie all the dust motes that show up on the image reside on the sensor window rather than further up the optical train. My evidence for this is that flats taken with LRGB filters all show the same dust pattern.

[Elp]

6 minutes ago, tomato said:

That’s interesting

Do you assemble and disassemble each time? I think that's why mine are this way even if they're cleaned afterward. But even my daytime camera bodies rarely get anything on the sensor, it's always on the optics and filters too.

[tomato]

I don’t take the OTA apart after every session, but I do change cameras from time to time, and take new flats each time I do this. I now don’t bother to take separate flats for the RGB filters as I find the Lum flat corrects for these subs just as well.