So I finally figured it out.

I decide to buy a new birdwatching monocular. The one I picked is the same brand with my current 8x42 binocular. And I argued that purchasing a telephoto camera like nikon P950 or Canon SX70 HS is not worth. I generally use phone to take pictures and I'm fine with that. And I don't want to carry extra weight.

Also looks like Nikon and Canon are moving forward from telephoto cameras and now it's too late to go into that line of products. And the performace is relatively similar to my phone. So why don't I just use my phone?

The birdwatching monocular I'm planning to buy has 20x to 60x zoom with 82mm objective lens, combined with 3x telescope lens from my phone, I can get 180x zoom (I hope that's how physics works). And It saves money. That's the main point.

Now I'm looking forward to get my first month of salary 😋
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And when I don't watch bird, I can use it to watch my neighboor. (jsut kidding)