Has anyone actually done a side-by-side comparison of the STC 17-40x56 and the Dialyt 18-45x65?
Had them both, the Dialyt for 13 years, the STC for one year and I have used them extensively.
The Dialyt is the most robust scope ever, just slide it in your backpack, attach it to the side, sling it over your shoulder. You can use it everywhere, the focus ring in the front makes it very easy to lay it down on poles, rocks, walls or push it against trees. It is the ideal scope for active birders, especially in difficult terrain, you never have to worry about your scope. And don't forget the unique vintage design. Personally I love it.
The STC is also easy to pack because of its size but I kept it always in my backpack, it's less sturdy than the Dialyt.
The TX glass of the STC is extremely sharp and close to perfect, the Dialyt doesn't have HD elements so the image quality is less good. For the STC you need a tripod or monopod, the shell Swarovski delivers is an afterthought. That said, the STC is perfect with a monopod and usable with 35x magnification.
In short, that's the choice, are you hiking, climbing, mountain biking, playing pirate in a canoe, without a tripod or monopod and you want an almost indestructible scope with a unique look? Take the Dialyt.
If you need a small lightweight scope with very good image quality and you are willing to pack a monopod or tripod, use the STC.
There is a difference in image quality but there is also a huge difference in price. They are both worth what you pay for.
[For the record, still I'm not happy with selling them, after multiple eye surgeries my eyes have problems with most scopes, that was the reason]