Dark patch on Ha subs?

[oldannie]

Have done a very quick stack and process of 15x300sec Ha exps of NGC6960 taken with Takahashi 106ed and Atik mono 460ex on NEQ6 with MGEN guider.  Can anyone tell me what might be the cause of the dark patch bottom left. It has also appeared on another target.  Can light leakage result in a dark patch?

 

Annie

Edited September 29, 2019 by oldannie
Typing error

[steppenwolf]

I would suspect that this is a dust mote in the light path - did you take matching Flat calibration frames during the same session and apply them before the rest of the processing?

[oldannie]

I haven't added any darks, flats or bias Steve but will now - I never thought of the obvious!!

Annie

[steppenwolf]

Annie, hopefully that's all it is!

[oldannie]

Thanks Steve.

 

Annie