Interesting. The image of Orion, showing the Benard Loop, which is one really difficult target, the subs are only like 3 minutes exposure for RGB, 5 minutes for luminescence, and 15 minutes for H-alpha. Definitely doable here in Singapore.
The image of Orion in the video was taken with a Takahashi FSQ, and FSQs are known to be 500mm focal length, F/5. The author used a reducer to bring it down to 380mm at F/3.6. This means he shot parts of the constellation and combined it into a mosiac. Very time consuming and difficult to execute well, but his efforts totally paid off.
The easiest start is to shoot moon and planets. Here focal length wins, but the smart thing to do is ditch your camera lenses and get a cheap telescope instead. A 1500mm, 6" aperture telescope cost $1.3k, which is about same as a good 200-300mm telephoto. A small 5 to 6" aperture cassegrain on a tripod with gear head beats even the most expensive telephotos hands down in this category. All you need is an adaptor to mate your camera to the telescope. There are rigs to hold pns cameras to shoot through the telescope eyepiece, so your camera don't need to be high-end. And of course there are adaptors for slrs. The adaptors are all standard sized and readily available.