Okay thanks. So you want to photograph deep sky with what you have, and as I remember, you had a photo of the Leo triplet of galaxies. The 150mm F5 OTA is potentially a powerful telescope. No need to upgrade the OTA in my opinion. I have a 150mm F5. It's very good for deep sky.
Your EQ3 mount, well that's the weak point. For the 150mm F5 OTA, you can get great pics if you can get at least 15 - 30+ seconds without trailing. I don't think the standard EQ3 has a guide port, so that leaves you with two options. Unguided and manual guiding. For manual guiding you would need a guidescope, mounting brackets and an illuminated reticle eyepiece, oh and your eye.
The idea with manual guiding is to be able to expose longer before the stars trail by making small corrections with your hand controller. You line up your main 150mm scope, then you find a guide star in the guidescope and place the guide star in the middle of the reticle. With practice, careful guiding and good polar alignment, you may be able to expose for several minutes.
Unguided, well you've already seen how quickly the stars can trail. Which ever method you use, very accurate polar alignment is a must for astrophotography. You may have the best mount in the world, but if it's not well polar aligned it's useless.
Head over to the beginners astrophotography forum and see what they are able to achieve with modest equipment.
