Rosette no stars (very few anyway)

[DJScotty]

Thought I would have a crack at removing the stars in Ha in preparation for RGB imaging during Xmas break.

Advice and assistance welcomed!

http://www.astrobin.com/140918/

Thanks for looking
DJ Scotty

[dvj]

Hi Scott,

There are some very large dust motes visible in your image. Did you apply flats to your calibration? Just could not help but notice them.

j

[DJScotty]

No I haven't. That big one in the right corner is gone now. It was on the glass of the camera.

[Garbz]

No advice on removing stars since I'm a novice at that, good work by the way.

However that vertical line, is that a satellite passing through? How are you stacking the images and how many subs do you have? If you have a couple of subs then maybe tweaking the rejection settings while stacking (lower the Sigma High value I think) may be able to completely eliminate the satellite.

[DJScotty]

Thanks Chris
Unfortunately not a satellite. Column of dead pixels on the sensor. Have had several suggestions by various IIS members. They work to some extent. When the final image is finished will have to remove them by hand in Photoshop...

[Garbz]

Drizzling (small movements between frames) may be your only solution for sensor defects

[DJScotty]

Yes. I do dither when using Nebulosity in conjunction with PHD. Alas, the columns still persist. Thank you for the suggestion though...

[Garbz]

Yes dither is what I meant. Interesting. Have you had a look at the subs to see if the dead pixels overlap between any subsequent subs? If you dither enough that the row of dead pixels is different on each sub then I'm back to suggesting modifying the sigma high value doing image integration.

Removing defects like this is exactly what that algorithm is designed for. It should only fail if there are multiple subs with the same defect, then then defect becomes closer to the average and a lower sigma value is needed to average it out.

[DJScotty]

Ok. Without sounding silly, is this a Deep Sky Stacker only thing or can Nebulosity do it as well?