Is it possible to take pictures of bright nebulae with a tripod only? Yes it is! For sure not to the extent that it is with a tracking mount, but still: applying digital image processing techniques to the raw images, you can still capture the nebula and thus get astro pics.
There are three important steps in order to get results like the one below with a tripod only:
1. Good raw images with no star trails in each single frame. Depending on the focal length used this may lead to short exposure times of only 1-2 sec per frame. But still: even in such images there is much more detail included than you see on first glance!
2. Lots of such good raw images. The more the better! Also here, depending on the focal length, there is a limit to the maximum useful number due to the object drifting out of the field of view. Using 200mm though, 5-8 images taken right after another works fine though.
3. Some simple image processing ie stacking those images to improve the signal to noise ratio
Of course, the 'faster' your lens is, meaning ideally f/2.8 or faster, the more light you will capture and the better the results will be.
So how does it work?
Once the pictures are taken, load them into an astronomical image processing software that allows for stacking those images. There are lots of freeware programs available on the internet that can do that (deep sky stacker for example). Make sure to stack the raw images using the "Median" method as this will give the best and smoothest result.
Since you are lacking the tracking mount, there outer edge of the median image will be black and have less quality. This is due to the overall image drift between the start of the first exposure to the end of the last exposure. The center region of the image though is visible on all images / frames. If this total timespan gets longer, the less 'usable' field you have left in the center.
After the median image is created, use this for the final image processing. Stretching the levels and curves, adjusting the sky background color and maybe cropping the image are probably the desired steps.
Canon EOS unmodified with 200mm f/2.8 lens, 5x 2sec, ISO 3200
Canon EOS unmodified with 200mm f/2.8 lens, 2sec, ISO 3200
100% crop from the image center. The level of detail is not too bad.
By the way: those images are taken in the middle of a mid-sized city with lots of light pollution. No filters were used.
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