Going . . .

Great composition and subject, trouble is, it's not sharp.

I guess your dining room window doesn't have SMC coating.

You might get some flare-like artefacts if taking images towards the sun, but that can mostly be sorted by putting a hood on it.

A 645D would be no use to Katie if she has problems with image size/angle of view v focal length on APS-C.

If you are ever able to buy a Pentax FF body, which I seriously doubt you will, prepare to be disappointed when you fit your 12-24mm to it.

It's a DA series lens who's image circle suits the APS-C sensor size. It will vignette terribly at the wide end of its focal range.

My personal experience, which has led to my offering for sale the SMCP-K 500mm 1:4.5, is that for situations where I could have made good use of the long focal length, I didn't have the lens with me.

Instead, I now carry the DA* 300mm and the SMCP-F 1.7x T/C which is much more compact, though not as fast a combination as the f4.5 of the 500mm prime.

If I were out in the Australian bush or the plains of Africa, I'd most definitely choose the 500mm for pre-sunrise/post-sunset opportunities.

You'll need a lot of power to run all that. I'm sure there are a few coal mines around that could be reopened. Then you'd need an efficient rail network to deliver it.

Well as long as its got cyclone technology, I'd buy one. Where do I send my blank signed cheque. You fill in the amount, I'm confident of getting my money back.

You could consider getting a second body of the same model. You can then put your two most used lenses on the two bodies to minimize lens changing quite dramatically.

Having two different model bodies can be a nightmare.

The 'blobs' at top left of your photo's is sensor contamination. My recommendation is to get yourself an Arctic Butterfly from Visible Dust. IMHO it's the best sensor cleaner there is. It's all I ever use. I've never wet cleaned my sensors in 2 - 3 years.

Using a blower to clean dust from a sensor can cause damage to the coatings of the high pass filter which covers the sensor, if you were to touch it with the blower's nozzle.

Sensor contamination is not just dust either. Stubborn particles that resist the efforts of a blower are probably pollen, which is slightly sticky.

If I were going to spend much time taking photos by the sea, I would put a UV filter over the lens to protect it from salt spray and sand, which you did.

When changing lenses, hold the body face down to avoid anything falling in to the mirror box. Carry a large bin bag in your kit for windy/dusty environments for lens changing.