Congratulations on the new camera and lens.
As a newcomer to DSLR cameras, you might benefit from these 10 tips:
1. The first thing to do is to read the camera manual and Yvon Bourque's e-book for the K-70 thoroughly. You'll be amazed at how capable it is.
2. Work with the 18-135 for a while before jumping in and getting more lenses. When you are new to DSLR photography, there's a lot to learn and it takes a little time to find out where your preferences lie. You have already expressed a preference for night shooting and astrophotography, but try other things too (landscapes, portraits, close-ups, street, architecture, abstracts, flowers, insects, cars, whatever) and you might be surprised. Once you've tried different things, you'll have a better idea of what other more specialized lenses to look for next (e.g. ultra-wide, long telephoto, portrait, street, macro, etc). For me, when I had a wide-ranging zoom I found myself shooting disproportionately at one end or the other, so I went for an ultrawide and a telephoto lens. For others, it might be a wide-aperture lens for low-light and short depth of field (DOF), or a fisheye, or a macro, or a pancake lens.
3. Good gear helps you make the most of your skills, but
skills matter far more than gear. Learning about photography is like any other skill. Read widely (there's a huge body of information on this site alone) and practise, practise, practise. The more you put into it, the more you get out of it.
4. Try to understand the exposure triangle (the interaction of exposure time, aperture and ISO and the effects of changing each variable). It is the basis for all photography. A good intro here:
Stops, Shutter Speed, Aperture, ISO Sensitivity - PentaxForums.com A book by Bryan Peterson, "Understanding exposure", is highly recommended by PF members.
5. Learn to hold the camera and how to steady yourself for handheld shots. It sounds really basic, but most of us keep coming back to it. Great article here:
Making the Most of Long Exposure Handhelds - Introduction - In-Depth Articles
6. Use a tripod whenever you can. If you haven't got a remote shutter release, user the self-timer. (It will switch off shake reduction automatically, by default.) You can even use this with bracketing. If the subject isn't moving, try pixel shift.
7. Learn how to get focus right for the subject. Scrutinize all your shots for accuracy of focus and learn from the mistakes. (There will be plenty.) If you are seeing back-focus or front-focus, calibrate the autofocus for the particular lens:
Fixing front and back focus
8. Learn about hyperfocal distance and about DOF. Use a DOF calculator until you can do it from sight.
9. Shoot RAW+jpg. Post-processing RAW files with good software makes a big difference. If you have information overload, just go with the jpgs and defer learning about software for a while, but save the RAW files for processing later. (My biggest photographic regret is not shooting RAW sooner.)
10. Flash can be a great tool, but if you are already overloaded I'd suggest putting that off for a while too. (When you are ready, follow the course at
Strobist 101. And look at Niel van Niekerk's videos on YouTube. Also see this excellent guide by one of our members:
Comprehensive Pentax Flash Guide - Articles and Tips | PentaxForums.com)