calibration frame help

[graham.hobart (Graham stevens)]

Hello, Here is a 80mm refractor wide field of some Virgo galaxies.
Notice the blob in the middle.
I took darks when I did the lights. The next day I did flat frames and flat darks using a light box with the camera,scope etc not having been changed around except to park the scope and cover it.
My first set of flats had different dust bunnies on and when I went back to check there was a spot of dust on the light box screen which was obviously not calibrated with the darks and lights.
So I cleaned it all up and re-shot my flats and dark flats.
I used Exfo's light box at 0.5sec at 100 iso with the same set up as my lights i.e home modded canon, CLS filter, scope , light box.
I then turned the light box off and noticed at that exposure is was very dark so I did my flat darks like that.
I still have a dust bunny or something in the centre of the frame.
?Help
Graham

[rcheshire (Rowland)]

Graham. How does it look without flats of any kind? and/or without the dark flats?

[graham.hobart (Graham stevens)]

Rowland - this is the lights with darks only subtracted- as you can see there is a lot of crap in the imaging train!
Will post a lights/darks-flats no dark flats later
Still unsure what the bloody hell is happening!
Cheers as always
Graz

[rcheshire (Rowland)]

Except for the anomomly, the flats have done a good job.

[graham.hobart (Graham stevens)]

Rowland , that is right, but do you think the middle thing is an artifact or a real thing?
graz

[rcheshire (Rowland)]

EDIT: Dust motes - judging by the size, at a guess on the face of the low pass filter.

I thought you had posted a slide of pond water. Then I saw the stars. A great illustration side-by-side with the corrected image.

If you are not using PS, or something similar can you download GIMPshop, or GIMP for Windows and install? I suggest GIMPshop for Windows users as the interface is more aligned with PS.

Apply an auto equalisation to a flate frame, as in the image attached, which should reveal or accentuate the detail. If the object is in the flat frame then... if not... but I suspect it is.

[irwjager (Ivo)]

Graham, most definitely looks like there's something on the sensor that shouldn't be there.
PS To do the equalisation trick in StarTools (1.2+), launch the Layer module and select 'Equalize Histogram' for 'Layer Mode'.

Cheers,