Hi Rolf,
I did some imaging over the last two nights in very good seeing
and wanted to show you how I went.
Firstly, I did a few rough calcs of what I was up against and
some comparisons of your imaging setup to mine.
Beta Pic is 63.4 LY away or 4,009,484 AU.
WFPC results on Hubble state the disk is roughly 1500AU edge to edge.
From that I worked out how much of the sky the protoplanetary disk would take up.
Trig gives me approx 1.286 arc mins or 77.16 arc sec.
On your f/5 rig and webcam the disk should take up approx 83 pixels.
Thats quite a substantial chunk of your FOV. All good.
On my f/5 rig and DSI II the disk should take up 66 pixels.
Sounds promising so far...with a sensitive enough chip, a big enough
mirror and a mountaintop we might have a chance.
Here is the BUT......
My camera is 16 bit approx, it has a bigger well depth and is mono
as well, meaning it doesn't have a Bayer matrix of RGB filters.
It is peltier cooled also.
Here are my results:
I stacked 150 frames of Beta and did a difference layer mask blend
over a 150 stack of Alpha.
My exposures were adjusted to compensate for the mag difference
method that you mention.
This method, btw, worked incredibly well as the two stellar disks in
the blend were an exact size match.
A curve adjustment of my image result shows no noticeable disk
that I could confidently say
might be the PP disk.
Notice that I can, (I think due to the sensitivity of my 16 bit setup)
resolve much more fainter detail very close to the star.
I've noted on your image how much 83 pixels extends and
on mine (a 2x upsample), shown how much 66 pixels is (132 pixels on
a 2x upsize)
I hope this doesn't sound like a dig at you Rolf, but I can honestly say
I really think trying to image what is essentially faint zodiacal IR
glow with a 12 bit webcam, albeit SC1.5 modded is a bit optomistic.
I sincerely hope I am wrong, I have admired your extreme imaging for years.
regards,
Steve