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Main
Date: 08 Jul 2007 07:14:33
From: Michael Gorelick
Subject: webcam photography
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hi,
i just made an astro cam using the instructions from http://www.astrocam.org/
and took my first images tonight of jupiter. the problem is that
jupiter just looks like one giant white blob with no detail what so
ever. the image does, however, contain other white blobs for the
moons. does anyone have any tips for an amature trying to get started
started with astrophotography?
-mike
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Date: 09 Jul 2007 19:46:35
From: Michael Gorelick
Subject: Re: webcam photography
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On Jul 8, 2:17 pm, Chris L Peterson <c...@alumni.caltech.edu > wrote:
> On Sun, 08 Jul 2007 18:08:55 GMT, "Roger Hamlett"
>
> <rogerspamigno...@ttelmah.demon.co.uk> wrote:
> >The big problem is first that on auto exposure, the camera will tend to
> >assume the brightest thing is 'white', and will then overexpose the
> >planet.
>
> If that's what it did, it wouldn't be so bad (with astronomical images
> it's generally appropriate to treat the brightest thing as white). What
> autoexposure actually does is look at the average brightness of the
> entire image, and assume it's supposed to be a certain luminosity
> (traditionally, 18%). It then adjusts the gain to try and achieve that.
> In the case of a planet against lots of black sky, that means the gain
> will be set to its maximum- not only will the brightest pixel be white,
> but so will a lot of pixels that are dimmer. Basically, every pixel
> covering the planet or its moons will be set to the maximum value.
> Nearly all information is lost.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatoryhttp://www.cloudbait.com
Thanks for all the tips! Over exposure does indeed seem like it's the
problem and thanks Carsten for the tip on wxAstroCapture (good to see
they have a linux client!) i've been playing around with the tracking
feature of my telescope (just got a celestron nexstar 8) and i think
i've gotten the hang of it. if anyone is curious, one of the images i
took is hosted at http://img102.imageshack.us/img102/9978/webcam1183867424
.
Also, rod, you mentioned an IR filter. When i took the lens off of
the webcam i noticed an IR filter attached to it. do you think it'd
be beneficial to suspend it in front of the CCD even though if it's
not perfectly parallel to it? (i thought up of a way to put the lens
there on a rotating platform so i can take IR/non-IR pictures).
thanks a lot!
-mike
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Date: 09 Jul 2007 22:49:16
From: Carsten A. Arnholm
Subject: Re: webcam photography
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Michael Gorelick wrote:
> Thanks for all the tips! Over exposure does indeed seem like it's the
> problem and thanks Carsten for the tip on wxAstroCapture (good to see
> they have a linux client!) i've been playing around with the tracking
> feature of my telescope (just got a celestron nexstar 8) and i think
> i've gotten the hang of it. if anyone is curious, one of the images i
> took is hosted at
> http://img102.imageshack.us/img102/9978/webcam1183867424 .
>
> Also, rod, you mentioned an IR filter. When i took the lens off of
> the webcam i noticed an IR filter attached to it. do you think it'd
> be beneficial to suspend it in front of the CCD even though if it's
> not perfectly parallel to it? (i thought up of a way to put the lens
> there on a rotating platform so i can take IR/non-IR pictures).
>
> thanks a lot!
>
> -mike
Hi Mike,
You need an IR-blocker, either the original one or even better a 1.25" IRB
filter that screws into a webcam adapter. IR and visible light does not come
to the same focus, so without such a filter you are bound to get fuzzy
images.
Unfortunately, I cannot get your image link to work (I see only a frog
there)
Glad to see you noticed wxAstroCapture. An idea with it is to make linux
webcam imaging easier by providing both a Windows and a Linux version :-)
And the latest version can do long exposures using modified cameras now.
Clear skies
Carsten A. Arnholm
http://arnholm.org/
N59.776 E10.457
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Date: 08 Jul 2007 18:08:55
From: Roger Hamlett
Subject: Re: webcam photography
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"Michael Gorelick" <mynameisfiber@gmail.com > wrote in message
news:1183878873.087050.164760@w3g2000hsg.googlegroups.com...
> hi,
>
> i just made an astro cam using the instructions from
> http://www.astrocam.org/
> and took my first images tonight of jupiter. the problem is that
> jupiter just looks like one giant white blob with no detail what so
> ever. the image does, however, contain other white blobs for the
> moons. does anyone have any tips for an amature trying to get started
> started with astrophotography?
>
> -mike
Rod, has made the important points.
The big problem is first that on auto exposure, the camera will tend to
assume the brightest thing is 'white', and will then overexpose the
planet. Focussing will be a b*&*tard to get really good, with movements of
a tiny amount needed, and until the exposure and focus is right, the
result will be a white blob...
Best Wishes
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Date: 08 Jul 2007 18:17:54
From: Chris L Peterson
Subject: Re: webcam photography
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On Sun, 08 Jul 2007 18:08:55 GMT, "Roger Hamlett"
<rogerspamignored@ttelmah.demon.co.uk > wrote:
>The big problem is first that on auto exposure, the camera will tend to
>assume the brightest thing is 'white', and will then overexpose the
>planet.
If that's what it did, it wouldn't be so bad (with astronomical images
it's generally appropriate to treat the brightest thing as white). What
autoexposure actually does is look at the average brightness of the
entire image, and assume it's supposed to be a certain luminosity
(traditionally, 18%). It then adjusts the gain to try and achieve that.
In the case of a planet against lots of black sky, that means the gain
will be set to its maximum- not only will the brightest pixel be white,
but so will a lot of pixels that are dimmer. Basically, every pixel
covering the planet or its moons will be set to the maximum value.
Nearly all information is lost.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 08 Jul 2007 05:35:36
From: RMOLLISE
Subject: Re: webcam photography
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On Jul 8, 2:14 am, Michael Gorelick <mynameisfi...@gmail.com > wrote:
> hi,
>
> i just made an astro cam using the instructions fromhttp://www.astrocam.org/
> and took my first images tonight of jupiter. the problem is that
> jupiter just looks like one giant white blob with no detail what so
> ever. the image does, however, contain other white blobs for the
> moons. does anyone have any tips for an amature trying to get started
> started with astrophotography?
>
> -mike
Hi;
1. Turn off autoexposure if it's on. Set frame rate for 5 fps (no
higher), and adjust shutter and brightness sliders for a good image.
Keep the gain slider as low as possible.
2. Focus obsessively. I often spend a half hour getting focus correct.
3. If you can't see any detail on the planet despite the above, seeing
is probably not what it should be. Wait for a better night.
4. An IR block filter can help with image sharpness depending on your
scope, and will definitely help with color balance.
You might also look into a program like K3CCD Tools for image capture.
For processing, get Registax.
Unk Rod
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Date: 08 Jul 2007 13:54:33
From: Carsten A. Arnholm
Subject: Re: webcam photography
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Michael Gorelick wrote:
> hi,
>
> i just made an astro cam using the instructions from
> http://www.astrocam.org/ and took my first images tonight of jupiter.
> the problem is that
> jupiter just looks like one giant white blob with no detail what so
> ever. the image does, however, contain other white blobs for the
> moons. does anyone have any tips for an amature trying to get started
> started with astrophotography?
>
> -mike
Hello Michael,
It sounds as if you are using auto exposure feature in your camera. The fact
that you see the moons is in fact proof that this is what is going on.
Such auto-exposure features are worthless when there is a lot of black sky
in the image, because it measures the average level. When there is a lot of
black sky, the planet becomes overexposed ane featureless.
The cure is to swith off auto exposure (using the camera driver dialog) and
then adjust the exposure time/gain/gamma manually until you see maximum
surface details. It takes a bit of practice but you will quickly figure it
out.
Btw. you can get more help in the QCUIAG Yahoo group
http://groups.yahoo.com/group/QCUIAG/
That is where webcam astrophoto is discussed
You may even be interested in this
http://arnholm.org/astro/software/wxAstroCapture/
Clear skies
Carsten A. Arnholm
http://arnholm.org/
N59.776 E10.457
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Date: 08 Jul 2007 09:07:47
From: David Nakamoto
Subject: Re: webcam photography
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Michael Gorelick wrote:
> hi,
>
> i just made an astro cam using the instructions from http://www.astrocam.org/
> and took my first images tonight of jupiter. the problem is that
> jupiter just looks like one giant white blob with no detail what so
> ever. the image does, however, contain other white blobs for the
> moons. does anyone have any tips for an amature trying to get started
> started with astrophotography?
>
> -mike
>
Yes, taking photographs, especially astrophotographs, is a lot more
involved than "point and click".
You need to learn how to change exposure time, contrast, brightness, et
al, in order to get the right exposure. If you can see some details on
a planet you know has some, then you'll be able to process them into
clarity later. If you can't see it in the original, you'll never
recover it.
And learn how to use stacking software.
And prepare to spend a lot of time learning. Experiment and keep track
of what works and what does not. Those that do this a rewarded with
good results.
--- Dave
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