Need some quick PixelMath help : Subbing one image from another

[Catanonia]

I have a particulary bad problem with flats at the moment and the only way I can solve it is to manually remove a % of the flat directly from the image whilst I work out what is going on.

Can someone help me with the PixelMath or give me an idiots guide on how to achieve the following

Subtract   10 % of FLAT001 image from IMAGE1

I have worked out that if I have IMAGE1 and FLAT001 open in PI and use the following in PixelMath     - FLAT001   then it processes but leaves me with a black image.

I can do it in MaximDL as it has a nice little button for % removal in it rather simple PixelMath Dialog, but I want to use PI to achieve this.

Also is there anyway of doing this across multiple images in either a directory or open in PI ?

Many thanks

[oldwexi]

Hi CATANONIA!

IMAGE1-(Flat001*0.1)

But you can subtract the 10% of the flat of this IMAGE1 only if
IMAGE1  is brighter than the 10 % of the flat,
otherwise you get a black image in some or all parts of the IMAGE1.

In that case you could create a new flat with Pixelmath (click create new Image) with the expression
(Flat001*0.1)
And in the next step you could use ImageCalibration and use the new 10% Flat as Flat...


Gerald

[Catanonia]

Hi CATANONIA!

IMAGE1-(Flat001*0.1)

But you can subtract the 10% of the flat of this IMAGE1 only if
IMAGE1  is brighter than the 10 % of the flat,
otherwise you get a black image in some or all parts of the IMAGE1.

In that case you could create a new flat with Pixelmath (click create new Image) with the expression
(Flat001*0.1)
And in the next step you could use ImageCalibration and use the new 10% Flat as Flat...


Gerald

Excellent help and many thanks.

Thinking of it, of course, save the flat and apply to all the other files with calibration dialog

Thanks again.

[Catanonia]

here is the thread with the problem I am experiencing, just resurrected it.

http://pixinsight.com/forum/index.php?topic=5285.msg46611#msg46611

I am having to manually find my own flat scaling factor and applying that with the above SUB PixelMath to get my flats to work as PI, Maxim and DSS cannot work it out.

Very frustrating and everything is in order with the flats, exposure, well depth, orientations, focus, method of flat, sky conditions everything.

Thanks again for the help, at least I can now automate my manual process a bit more in PI rather than messing with Maxim