Re: Why .avi format ?


David Nakamoto wrote:
> For even Jupiter (Saturn normally does not present any cloud features that show
> up in amateur imaging) a few minutes of video can acquire a thousand images or
> more, and a few minutes is not long enough to show motion of the cloud features,
> at least at image sizes where Jupiter is perhaps a quarter to a third the width
> of the video, so I don't see this as a major reason to not go video as I think
> you're implying.

First, amateurs have taken images showing small transient features
(w.o. but not only) on Saturn since few years ago, even with "small"
apertures (I did it with a 8" MN/MCT, see
http://www.geocities.com/andreatax/2002-2003_opposition.htm or
http://www.geocities.com/andreatax/2004-2005_opposition.htm).

Secondly, the intrinsic limit of the length of a video on a planet like
Jupiter is much less then you might think of, 120s-160s is about as
good as it gets at its maximum angular diameter with a 10". I'm
assuming a sampling of 4 pixels per airy disc diameter. Saturn can even
be worse than that as it is far dimmer than Jupiter, although the
length of the video recording can be 2.5x that of jupiter. To build a
high resolution, good quality image of saturn you really need thousands
of good images and that only happens when the seeing is extremely good.

>
> It's true that adaptive optics can produce more consistent, sharper images, but
> for those that don't have the equipment to do it, video is a good way to go.
>
> As for the readout noise, are you sure you're not referring to sensor or thermal
> noise?

Thermal noise is irrelevant. We're talking about readout noise.

Andrea T.

.

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