[APML] Re: Bubble with [SII], Ha and [OIII

["Richard Crisp" <rdcrisp@earthlink.net>]

the red channel in the SII/Ha/OIII is actually SII

The signal is very small in the SII channel and there is secondary
reflection inside the filter. When the signal is boosted up, it will show an
elongation. It will only show up in the brightest stars.

I have spoken with David Marcus of Cust Sci about it and there's not a lot
that can be done to the filters. The SII signal is just not very bright.

The other thing that happens when I boost up the SII data is that the stars
get fat. If you carefully examine the Hubble "Pillars of Creation" image,
you will see fat red haloes around the stars. It is the same mechanism best
I can tell.

If you don't boost up the SII data, then there is hardly any impact on the
image from the SII data. It is just a lot weaker than the Ha or OIII data.
It is just that the intensity of the SII signal is just considerably lower
than for the other channels best I can tell.

I have checked the filter mounting to ensure squareness in the filter wheel
and it is not any different than the rest. I shot at f/12.46 with the C14.

Usually I clean up the elongation on the bright stars with PS but last night
I just didn't take the time.

I will put the components on my web page so you can look at them separately
and maybe will clean up the bright stars a bit with PS. Time time time.....

Thanks for the comments folks: you guys have a better and more critical eye
than I am finding on the ccd groups. I appreciate that.

Best regards
Richard


----- Original Message -----
From: "Scott Hogsten" <scotthogsten@yahoo.com>
To: <rdcrisp@earthlink.net>
Sent: Friday, September 26, 2003 5:50 AM
Subject: Bubble with [SII], Ha and [OIII


> Nice image and I am really impressed with what you are doing with
> these filters. But I have a question - what is causing the oblong
> images in the red channel (h-aplha ?) it almost looks like something
> is not squared up in the Optical Train.
>
>
> Scott Hogsten
>

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