From: Jim Chung <jim_chung@sunshine.net>

Date: September 26, 2010 6:05:54 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Sunspot #1109

Thanks Milton,

I believe its a common trait of all PSTs, they exhibit a central sweet spot and flats should indeed fix it.

Jim

Quoting Milton Aupperle <milton@outcastsoft.com>:

Hi Jim;

Very nice image.

If you scale the image down to half size, you can see this somewhat

darker donut / rings around the center, then the outer ring is

brighter again.

Is that some internal reflection?

Some Flats would likely take care of that.

TTYL...

Milton Aupperle

On 26-Sep-10, at 2:09 PM, jimchung2338 wrote:

Well, not the most exciting solar image but I did have to dodge

several hours of clouds this Sunday morning to get it. This was

taken with the improved 80mm PST mod scope that I had put together

this past winter. My AP Traveler is otherwise occupied so I sprang

for a cheap used $60 Celestron 90mm f/11 achromat, cut off 13cm of

it and installed an even cheaper all plastic Meade 2" focuser.

Despite humble origins, it works quite well. The addition of the

BF10 (BF5 is stock with the PST) I get a much larger fov and less of

the troublesome internal reflections. So I get the resolution of an

80mm solar scope with the internals of a PST etalon.

http://dl.dropbox.com/u/4852049/Sunspot1109.jpg

Jim