From: Ray Byrne <ray@in4media.co.uk>

Date: December 8, 2010 7:00:16 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] 150mm PST Monster Lives!

Hi Milton,

Thanks for that I was being blinkered in my view of it of course the exposure is the variable which could achieve the desired effect. A bit of experimentation could really solve this, I find it a problem I must admit with my 80mm PST conversion.

Cheers

Ray

On 9 Dec 2010, at 01:43, Milton Aupperle wrote:

Hi Ray;

On 8-Dec-10, at 4:47 PM, Ray Byrne wrote:

>
>
> Hi Milton,
>
> Is this in regard to the use of flat fielding?

Yes.

> I may be wrong here but the problem is inherent to the filter itself
> so a flat field frame would have the same problem and the light
> source would have to be incredibly bright.

> I don't understand!

Flat field corrects for uneven light being collected by the CCD. It
doesn't matter if it's uneven from a Filter, or optical issues or dirt
or even decreasing sensitivity of the CCD. It corrects the CCD image
until it's "flat".

As to exposure, I'm not sure how much one needs using a halogen flood
light, but it should not be too long (<3 seconds?).

People shoot with narrow band DSO filters and 150 m refractors all the
time and those aren't too much different.

> The PST as a filter just has that sweet-spot it seems to me and you
> live with it or get a bigger filter (at $$$$ more cost)

I don't know much about them, so your guess is as good as mine.

>
> just my two-pen-north
>
> Ray

TTYL..

Milton Aupperle