Presumably the difference isnt as obvious when using narrow band filters like H-alpha. So for nebulosity rather than stars the cheaper option may be as good - or am I misunderstanding?

My main field of observations are lunar, and to a lesser extent asteroidal occultations. I also follow current phenomena but have not delved deeply into filters, nor deep sky imaging. I am a bit of an instrument tragic as my profile on this website will attest, owning a variety of instruments. So, though not strictly a dilettante, I am not in a position to comment upon the finer points.

What did amaze me with the previous achromat was the extent of chromatic aberration and the blue violet excess, though at F8 this is what theory predicted. Why make a 150mm telescope no longer than F8? The simple answer is commercial reality in the sheer size and mounting and the prospect of insufficient sales. So the visual and photographic images, whether solar system or stellar suffered. The difference in price between the achromat, ED, and triplet is about one magnitude jump (2.5 times) with each step.  The ED is still reasonably affordable and I was astounded by the difference it made as demonstrated in the images I posted. (I will post more on lunar/planetary as they are obtained.)

I suppose my purpose was to show the obvious differences and improvements. Much more subtle, and possibly caused by the lenses and coatings etc. is the subtle shift in colour balance if you compare the images. 

Thank you for your suggestions, but this was merely an exercise to compare. I have prepared a powerpoint presentation where I align the images in following slides and it is fun to toggle back and forth. I am happy to share this.