Pagman wrote in post #18494339
The last shot I showed was the result of 22 stacked frames in DSS they were all 1sec shots from my 300mm on the d7100, all at f4 and split between Iso 1600 and 3200, then after leting DSS do its work I opend the Tiff up in LR5 and moved the sliders around, but nothing was going to show the colourful gases that seven sisters has.
You had 22 seconds of data. While you had 22 exposures, they had such limited exposure time that the signal gained from stacking remains minimal. You'd probably have gotten more signal from a single 22 second exposure (I realize you can't do that with a telephoto lens here without a tracker). M45 is bright, but the nebulosity is feint and to see it, you will need a lot more data. A lot more. I would suggest you actually use a much wider lens, something that will allow 20~25 second exposures without star trails, and practice getting exposure correct and allow you to get a ton more exposures over the night to stack so that your data is measured in several minutes, and not just a few seconds. You'll get a lot more data that is usable that way.IMAGE LINK: https://flic.kr/p/Q3njU5 Pleiades_12262016
Also, your 22 seconds of data, was probably very under-exposed. But I wouldn't know for sure unless I saw the histogram of a single exposure. But you really need to make sure your exposures are correct (the sky is not black) before committing time to lots of exposures.
I realize you're not going to buy a tracker, so, you will always be limited to what you can do with exposure time. So, the alternative is to up the numbers in your favor that you can effect, without buying something. And that's number of exposures to contribute to the stack.
You could get away with 1 second exposures, but you would need a TON of exposures to stack to make it meaningful (literally on the order of 1 second x 2,000 + images to get about 33 minutes of data, or double that for an hour). That's the kind of data acquisition it takes, to really get the details out, especially with short exposures. The only way to get away with few exposures, is with really long exposures.
So, to do that, you may want to get a few thousand 1 second exposures, and do it over a few nights so that your image count is as high as you can tolerate without going mad, and you might just get enough signal to noise to extract significant details.
Also, to process, you will not be using sliders. You need a pixel editor because you will need to learn how to use Curves & Levels primarily. Refer to the tutorial link I posted with the video. It's an hour, but well worth it (and save it). I use those techniques to extract detail from high signal images.
I took 31 minutes of data time captured in 31 exposures x 60 seconds each, at F7.5, ISO 1600 with a Canon T4i. Because of the signal to noise ratio from the longer exposures (even though I only stacked 31 images), I was able to get the feint nebulosity of M45:
by Martin Wise
, on Flickr