RE: [guide-user] Fw: 7observing

Antonio Alves Jan 27, 2002

Seeing is in many cases the main reason.
But there are still other good reasons, for instance, in a light polluted or
luminous sky the CCD or other sensor device could be saturated before the
stop time.
In the case you have an almost perfect: drive; lined mounting; tracking;
seeing (stable or no atmosphere at all ); an appropriated sensor, and the
right processing, the unique 30s exposure will became a better choice to
work. All this perfection is very hard to obtain in the real world.

>> Georgiana,
>> What is the advantage of stacking 10 3-second images over 1 30-second
>> image?
>
> "Guiding" is the simple answer. Even the poorest of drive motors will
> generally produce a satisfactory 3 second exposure, but you need a good
> sturdy mount and a decent drive system to get a good 30 second image.

Another reason is graininess: by stacking 10 images of 3 seconds you
also average out the graininess of each image, compared to using just
one image of 30 seconds.

And seeing is a third reason: if yoiu have, say, 100 images, you
can choose those 10 images which had the best seeing during exposure.