tele lens

It's a catadioptric lens Billy, a cassegrain mirror lens: Diagram Reflector ArgunovCassegrain.svg - Wikipedia, the free encyclopedia

I had one years ago, produced reasonable results and had the advantage of being much less bulky than a standard lens.

Not sure how good that one is and whether it will benefit from auto exposure, it doesn't say, but focussing will be manual. It's certainly not very expensive, but not that bright either, so would be a problem on dull days.

The best thing is that you could buy and then re-sell if you didn't like it.