Less is more, and more is less

Less is more and more is less,
But let's go down the wondrous list -
Ignoring the one, so high and near,
And yet the lowest of all, I fear.

The dog's on top, then find your way,
The nearest, and a giant far away.
These are all above what's naught,
And yet in truth they are below.

So many more, some more, some less:
Shining beacons of hope, God bless.
Now you've read this tale bizarre,
Don't you wonder what they are?

I think this riddle describes

Stars

Less is more and more is less, But let's go down the wondrous list -

Less meaning less star magnitude - the lower it is, the brighter they appear.

Ignoring the one, so high and near, And yet the lowest of all, I fear.

The Sun, our nearest star, is the lowest magnitude at -27 and we will ignore it below, especially as the Sun isn't visible in the night sky.

The dog's on top, then find your way, The nearest, and a giant far away.

The dog's on top: The brightest star in the Earth's night sky is the dog star aka Sirius with a magnitude of -1.5

Find your way: The next brightest star visible from Earth is Canopus, with a magnitude of -0.7
Canopus was a navigator in Greek mythology.

The nearest: Then the next brightest is Alpha Centauri (star system) which is the nearest star after the Sun with a magnitude of -0.3

A giant far away: Then Arcturus a red giant is −0.05

These are all above what's naught, And yet in truth they are below.

Star magnitudes - These are the only stars which have magnitudes below zero. The next in the magnitude list is Vega which is positive at +0.4

So many more, some more, some less: Shining beacons of hope, God bless.
Now you've read this tale bizarre, Don't you wonder what they are?

Twinkle, twinkle, little star, How I wonder what you are!

"Shining beacons of hope" - Babylon 5

• Good job! There are a few bits you haven't got though, especially in the second stanza. – Rand al'Thor Jul 19 '17 at 11:41
• Thanks for this puzzle! I've updated and hope I haven't made too many astronomical errors. – Tom Jul 19 '17 at 12:35
• All correct. FTR, "find your way" was meant to refer to Canopus, a navigator in Greek mythology, and "Shining beacons of hope" is a very obscure Babylon 5 reference. – Rand al'Thor Jul 19 '17 at 12:39