Canopus is the second-brightest star in the sky, but people in the Northern Hemisphere seldom see it, because it is in the southern sky at a declination of -52º 41’ 44”. The simple rule for what you can see in the sky is that the furthest south you can see is your latitude minus 90º. Therefore, the northernmost latitude from which you can see Canopus is 37º 18’ 16” — about the latitude of a line running from San Jose, California to Richmond, Virginia.
But you can still see Canopus from further north, owing to two other factors. The first of these is atmospheric refraction. The atmosphere bends light, allowing you to see stars that, without an atmosphere, would be below the horizon. This allows you to see a further half-degree south, moving the limit line north about 30 miles.
But that’s a limit line; at that latitude, Canopus would just brush along the absolute southern horizon, and in practice you’d never see it, because there’s sure to be a tree, a hill, or a sign for McDonald’s blocking the view that low.
But there is one other way you can extend your range further north: climb a mountain. From a higher altitude, you can see further south. Here’s the geometry of the situation:
Here, “r” is the radius of the earth, “h” is the height of the mountain, µ is the latitude of the mountain, and ß is the additional amount by which you can see below the regular horizon due to the mountain’s height. The trig for this situation is:
cos ß = r/(r + h)
Now, I saw Canopus from my home above San Jose one year. The latitude there is about 37º 25’, and the altitude is 2000’. I also sighted Canopus from the top of Mount Diablo, at a latitude of 37º 52’ 54” and an altitude of 3848 feet. For Mount Diablo, the calculated angular altitude of Canopus (taking into account both the height of Mount Diablo and atmospheric refraction) is 56’, a tad less than one degree of arc. I can assure you that sighting Canopus from that location required a telescope and precise timing.
But there’s one site that might also work: the top of Mount Tamalpais, north of San Francisco. It is at a latitude of 37º 55’ 45”. That’s just three minutes of arc further north than Mount Diablo. But there is a problem: Mount Tamalpais is lower than Mount Diablo: its height is 2571 feet. The calculated altitude for Canopus there is just 41 minutes of arc. That’s REALLY low. Fortunately, the line of sight from Mount Tamalpais due south goes over the Pacific Ocean, so there won’t be any trees to block the view. But you’d have to look for it on a cold, clear night; at any other time, water vapor in the atmosphere would surely block your view of Canopus. Wait for a cold front to pass through.
Are there any other even more northerly locations from which Canopus might be seen? I doubt it; most mountains are part of mountain ranges and have mountains close by. A mountain south of a candidate location would block the view. What we need is a mountain higher than 4,000 feet in elevation that is sticking up all by itself. Mount Diablo is unique; it sticks way up above the rest of the Coast Range. Mount Tamalpais is lucky that the Pacific Ocean is close and directly to its south. However, the Pacific Ocean over which the line of sight must travel is problematic. Here’s what the view to the south often looks like:
You’re not going to see anything through that murk.
There is a promising location in the Canary Islands: Mount Pico on Pico Island. It is at a latitude of 38.458º, and is 7,713 feet high. My calculations show that Canopus will be almost a full degree above the horizon. Unfortunately, the top of Mt. Pico can be reached only by taking a car to Casa de Montanha, at an altitude of 4,000 feet, and then climbing the remaining 3,700 feet to the top of the volcano, which, fortunately, does not appear to be active. Of course, one would have to lug the necessary telescope up as well. Moreover, the only time to see Canopus in the northern hemisphere is in February, so the mountain is likely to be covered in snow. I have looked at other possible sites in Europe and Asia, and none seem likely to me.
So there you have it. I lay claim to having seen Canopus from the most northerly location on the earth; however, somebody else should be able to easily beat my record from Mount Tamalpais. Even though I cannot prove my claim, it should be easy for anybody else to confirm my finding for themselves. The same applies to Mount Tamalpais. I very much doubt that anybody will be able to pull it off from Mount Pico. And perhaps somebody might find a location somewhere else. There are plenty of high mountains in the American west at the right latitude — but finding one that is at the right altitude, has a clear view due south, is accessible by car, and won’t be covered with snow in February is a long shot. Good luck!