DBE with no background

[rdryfoos]

The attached image is a 6 hour of Ha.  There is no background in the image.  I was not able to use DBE since there is no background.  In this situation, how is one to use DBE?
Thanks,
Rodd

[pfile]

just try putting a few sample points in the darkest places and see what you get.

rob

[Geoff]

Sometimes ABE works in these cases. Try it and see if the background it generates looks sensible.

[bob_franke]

Hi Rodd,

This is one of those images were you are probably better off to just leave it alone. I messed with the attached image a bit and only got two background models that made sense. Unfortunately, they were essentially the opposite of each other. ABE completely failed in making a usable model.

Sometimes you just have to go with what you have.

Cheers,
Bob
http://bf-astro.com/

[rdryfoos]

Sometimes ABE works in these cases. Try it and see if the background it generates looks sensible.

  But the dark areas are not background.  Is it ok to put points there?
Rodd

[rdryfoos]

Hi Rodd,

This is one of those images were you are probably better off to just leave it alone. I messed with the attached image a bit and only got two background models that made sense. Unfortunately, they were essentially the opposite of each other. ABE completely failed in making a usable model.

Sometimes you just have to go with what you have.

Cheers,
Bob
http://bf-astro.com/

  Yes but when I add the OIII and SII I am sure I ill need to use DBE.  For the Ha alone I can probably get away without using it--but not on the SHO image.
Rodd

[bob_franke]

Yes but when I add the OIII and SII I am sure I ill need to use DBE.  For the Ha alone I can probably get away without using it--but not on the SHO image.
Rodd

I really don't think you have a problem, unless you shot the OIII with a very bright moon.

I took a look at my data, and you are going to have the same problem with the SII and OIII images. The OIII will be dark in the lower left-hand corner with the rest of the image filled with nebula. The SII image will be dark at the top with small dark areas on the right and bottom. Your Ha image looks just like mine.

All three color channels will be problematic for creating a valid background model. With my image, I did not flatten any of the channels and everything came out fine.

This is color mapped narrowband imaging and no one will be able to say one way or the other that your image is not correct. :-)

–Bob

[rdryfoos]

Yes but when I add the OIII and SII I am sure I ill need to use DBE.  For the Ha alone I can probably get away without using it--but not on the SHO image.
Rodd

I really don't think you have a problem, unless you shot the OIII with a very bright moon.

I took a look at my data, and you are going to have the same problem with the SII and OIII images. The OIII will be dark in the lower left-hand corner with the rest of the image filled with nebula. The SII image will be dark at the top with small dark areas on the right and bottom. Your Ha image looks just like mine.

All three color channels will be problematic for creating a valid background model. With my image, I did not flatten any of the channels and everything came out fine.

This is color mapped narrowband imaging and no one will be able to say one way or the other that your image is not correct. :-)

–Bob

  Well--that just begs the question of what to do under similar situations with RGB data.  I run into this problem for the same reason  there as well.
Rodd

[pfile]

i think vicent once suggested, if you are really invested in this, to wait a month or two and then image the exact same part of the sky, (from an alt-az perspective), during the same moon age, so that you can build a background model of your light pollution for the original image. it's not perfect, and it is difficult, but it's the closest you might get...

rob