All of these photographs were taken with the camera mounted on a tripod, without any compensation of the daily rotation of the sky Earth. This limits my exposures to about 6-8 seconds, any longer times make the images of the stars spread out into little streaks. I'm going to buy some tracking device really soon, this will allow me to enter a whole new level of possibilities 
Without "tracking device", seconds of exposure that U can make (without stars looking like a "little streaks") are limited with the level of magnification that U use. Larger magnification = less secs for exp. With your 300mm U can take 6-8 secs exposures, but with larger magnification (ie. 500mm) U could take exposures of maybe 0,5-1 sec.. And that's all fine for the wide field astro-photo.. But if U wanna "enter the new level of possibilities" and take photos of DSO (Deep Sky Objects) like Galaxies, Nebula's or Star clusters, U would need a telescope and a "tracking device" as U call it.. I use Equatorial mount - to be precise..
This is what I use:
Newtonian reflector SkyWatcher 150/750 and EQ3 mount with built-up motors for tracking. I'm taking photos with the "prime-focus" technique with my Canon EOS 500D. Prime-focus is when U take off the lens from ur camera and connect it directly on the telescope, and the photons of light are "falling" directly on a chip of a camera.
The whole process of taking and processing photos this way is much more complicated and I won't explain it here now, but if U're interested in any of this, don't hesitate to ask for a suggestion cause I'm into this hobby for several years already..
Here's some of my DSO photos, just to get a clue what am I on about:
Whirlpool galaxy or M51, located approx. 25 million light years away. It's a stack of 12 photos, 30sec exp each on ISO1600:
Star cluster M13, that's formed of approx. 300,000 stars, located 25,000 light years away. 20 photos, 30 sec each, ISO400:
Eagle nebula M16, 20x30sec ISO3200 + 20x30sec ISO1600 + 18x30sec ISO800:
Lagoon nebula M8, 9x30sec ISO3200 + 30x30sec ISO1600 + 10x30sec ISO800:
And I have to say that the credits is not only on me, 2 friends and me are doing all of this together.. We have our own amateur-astronomy association and a blog where we present our work to the local astronomers.. The whole technique and the equipment that we use is already obsolete.. It was not too expensive, we've got the whole equipment for smth like 850 euros, 2 yrs ago. Today, there's a lots of new equipment that's much easier to use, like auto-guiders, Go-To, CCD cams and stuff, but for us it's too expensive for a hobby from which U cannot gain any money back..
At least we have the enthusiasm and the results which satisfies us..
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