And, of course, there's a huge difference between TL8 and TL15, but Traveller rules really don't seem to cover deep space detection, so I think it's natural to take cues from real world astronomy.
It all depends on what you are trying to detect in deep space. I have found that many Traveller fans way overestimate how much we will detect with shipboard sensors. Frequently confusing what is theoretically possible when one reads the science by what is possible when the real world engineering constraints are applied. Especially with the time frames that are often quoted. Don't get me wrong we can see and figure out some amazing things with the instruments we have if we are allowed to the requisite number of computer cycles to throw at the problem. And, and this part is important these thing require a great deal of Luck as well.