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Subject: [M]: Re: Re: Re: 416 XT question
From: Blair MacDonald
Reply To: mapug@shore.net
Date: Tue Apr 04 03:17:43 2000
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This is a multi-part message in MIME format.
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You may be seeing the same bug in IP2000 that I found in an older =
version of the software. It had to do with a mathematical overflow in =
the 16 bit integers used to represent the pixels. During a stretch the =
values would overflow from 65535 (all 16 bits =3D 1) to 0 producing =
black pixels. Send me one of your images that has the problem and I will =
stretch it using MaxIm DL and see if the same problem shows up.
Blair
----- Original Message -----=20
From: amnet_ed=20
Sent: Tuesday, April 04, 2000 12:37 AM
Subject: [M]: Re: Re: 416 XT question
Blair.... Thank you for the reply. I gave the wrong information =
below. In step number three (3) below I said "autofocus" what I meant =
to say was Autoexposure. I had so many problems with Autofocus I gave =
up about a year ago. I learned to do the difraction method and it does =
work 100%. I do stretch the image when I process in IP2000. This is =
where I see the center of the brightest star as a black center. I can =
not see this while I have the image as a raw image. The other stars are =
fine.
Any other ideas????
ED
..Blair wrote
Ed:
Try changing the screen stretch after taking the image and leave =
autofocus off. I had some problems with the display in focus mode and =
just use the normal mode and draw a subframe around the star I want to =
focus on.
Blair
>>>> Ed Registrato originally posted:
Hi everyone....
I have written about this problem before and never got an answer =
on what is going on. Can someone give me some help.
Tonight I took some images of NGC2244.=20
=20
The star group looks ok but.... the brightest star in the field =
has a black dot in the center. The star looks like a de-focused image =
that you want when you are going to colminate. However the camera is in =
focus and all the other stars are perfect.
Here are the steps I took to prepare for the image:
1. focused on nearest star near NGC2244 with difraction focus =
method. This came out perfect. Star was 100 % in focus.
2. moved to NGC2244 and removed strips from scope which I used for =
difraction focus.
3. selected autofocus mode, analog bin on, auto dark frame, =
prescale image on.
4. the camera took about four images. The final one was for about =
13 seconds. This one was good but the brightest star in NGC2244 had a =
black dot in the center of the star. the DN setting showed 0,21333.
5. next I set the antibloom to 6. The camera beeps, the black box =
camera takes the image, I wait for the image to come on the screen and =
when it does the entire screen is white. No stars, no nothing.. the DN =
is 0.
Can anyone help with this problem? Why does the brightest star =
have a black dot (torn center)? If the star is overexposed wouldn't the =
pixel be pure white not pure black? If I cut back my time to 5 seconds =
the black dot goes away but so do all the minor stars in the cluster. =
That is why I think the black dot has something to do with overexposure.
ED REGISTRATO
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<HTML><HEAD>
<META content=3D"text/html; charset=3Diso-8859-1" =
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<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT size=3D2>You may be seeing the same bug in IP2000 that I =
found in an=20
older version of the software. It had to do with a mathematical overflow =
in the=20
16 bit integers used to represent the pixels. During a stretch the =
values would=20
overflow from 65535 (all 16 bits =3D 1) to 0 producing black pixels. =
Send me one=20
of your images that has the problem and I will stretch it using MaxIm DL =
and see=20
if the same problem shows up.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>You can send the image to <A=20
A>.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Blair</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, April 04, 2000 =
12:37=20
AM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> [M]: Re: Re: 416 XT=20
question</DIV>
<DIV><BR></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Blair.... Thank you for the =
reply. I gave=20
the wrong information below. In step number three (3) below I =
said=20
"autofocus" what I meant to say was Autoexposure. I had so =
many=20
problems with Autofocus I gave up about a year ago. I learned to =
do the=20
difraction method and it does work 100%. I do stretch the image =
when I=20
process in IP2000. This is where I see the center of the =
brightest star=20
as a black center. I can not see this while I have the image as =
a raw=20
image. The other stars are fine.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Any other ideas????</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>ED</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; =
MARGIN-RIGHT: 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>..Blair wrote</FONT></DIV>
<DIV><FONT size=3D2>Ed:</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Try changing the screen stretch after taking the =
image and=20
leave autofocus off. I had some problems with the display in focus =
mode and=20
just use the normal mode and draw a subframe around the star I want =
to focus=20
on.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Blair</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; =
MARGIN-RIGHT: 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV><FONT face=3DArial size=3D2>>>>> Ed Registrato =
originally=20
posted:</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Hi everyone....</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>I have written about this problem =
before and=20
never got an answer on what is going on. Can someone give me =
some=20
help.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Tonight I took some images of =
NGC2244.=20
</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>The star group looks ok but.... =
the brightest=20
star in the field has a black dot in the center. The =
star looks=20
like a de-focused image that you want when you are going to =
colminate.=20
However the camera is in focus and all the other stars are=20
perfect.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Here are the steps I took to =
prepare for=20
the image:</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>1. focused on nearest star near =
NGC2244 with=20
difraction focus method. This came out perfect. Star was 100 =
% in=20
focus.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>2. moved to NGC2244 and removed =
strips from=20
scope which I used for difraction focus.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>3. selected autofocus mode, =
analog bin on,=20
auto dark frame, prescale image on.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>4. the camera took about four =
images. The=20
final one was for about 13 seconds. This one was good but =
the=20
brightest star in NGC2244 had a black dot in the center of the =
star. =20
the DN setting showed 0,21333.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>5. next I set the antibloom to =
6. The=20
camera beeps, the black box changes its readout. I next take =
the=20
for the=20
image to come on the screen and when it does the entire screen is=20
white. No stars, no nothing.. the DN is 0.</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Can anyone help =
with this=20
problem? Why does the brightest star have a black dot (torn=20
center)? If the star is overexposed wouldn't the pixel be =
pure white=20
not pure black? If I cut back my time to 5 seconds the black =
dot=20
goes away but so do all the minor stars in the cluster. That is =
why I=20
think the black dot has something to do with =
overexposure.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>ED REGISTRATO</FONT></DIV>
<DIV><FONT face=3DArial size=3D2><A=20
=
<DIV> </DIV></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>
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