SXV H16

One question, I notice that some of the bright stars have a trail in one direction. Is this something from the optical system, the camera or the processing?

Those are fabulous images Kieran. The SXVH9 is really doing the biz for you.

I'd say the streaks on the bright stars is caused by blooming. That is a residue left when the image is read off the CCD chip. Software such as Maxim DL has filters to help remove this.

That's what I was thinking too initally, but it's only in one direction. Usually it would act in two directions, would it not?

That's what I was thinking too initally, but it's only in one direction. Usually it would act in two directions, would it not?

No blooming only shows in one direction. The reason for it is that some ccds read off the data by shunting each line towards the read buffer as each line falls off the edge it goes into the read buffer and is then read off. However as highly saturated pixels are shifted they wells don't fully recover before the next line is shunted. The result is a remnant of the bright star being left over and beuing added to the next line, resulting in a little streak like the one that shows in Kierans images. Progressive scan ccd's commonly used in DSLRs dont suffer from this due the frame being broken into odd and even lines which are read off independently of each other.

At least thats how I understand it!

[later edit] another type of blooming can occur because of highly saturaded pixels bleeding into the ones adjacent. That type of blooming doesn't occur much in modern ccds. That would show in two directions.

ah, understand now. thanks for the explanation.

cheers,

The H16 has an interline ABG chip which is the same one as used in the SBIG STL-4020M which is just over a grand more expensive. Must of the images were stacked 10 second or 30 second exposures so I am surprised that the stars have bloomed. I could use the deblooming routine in astroart or I may stick some cross hairs over the front lens and go for diffraction spikes (not very realistic but looks very nice). Ian King had this camera on trial from Starlight Express. He took some images of the Gamma Cygni region with longer exposures and no obvious blooming. I might contact a guy on the Yahoo Starlight Express group who has the camera and ask what his images are like.

additional: Spoke to Charlie Warren who has had no blooming with his H16. So its either an internal reflection problem or a potentiometer needs adjusting to control the pixel bleed. My next clear night I will test the system for relection with a different camera.


Kieran

Quick update,

Apparently after speaking with Terry Platt at Starlight Express the camera needs to have a higher rated capacitor put in so its going back to them next week. I suppose that I will have clear skies and perfect seeing over Co. Down the moment its on its way.

Kieran