Just for fun, Satellite watching

My late wife and I did this many times before at our country property. It is thrilling.

What do you use to view them?

A friend has a 3rd Generation image intensifier system and it's quite impressive all the 'stuff' you can see up there with just a bit of enhancement.

Just eyes will work. You see what looks like an airplane, but it is moving a bit unusual and does not have a repeating flash.

Tell them to find and look at the Hercules cluster. Breathtaking. When I had a 3G device, the Andromeda galaxy was not visible at the time. Tell them to try that one, too.

Just my eyes, not sure binoculars would give any detail, but I'll try next time. Would be difficult to follow with a telescope, but that would be cool. I have decent passes of both the ISS and HST tonight, about 40 minutes apart, here in the panhandle of Florida. I just found this page that says I have about 40 visible* satellites tonight within a 2hr 20min period.

You can only see satellites shortly after sunset and just before sunrise. It needs to be dark to see them, but sunlight needs to hit the satellite and reflect so you can see it. Mikek

*Visible, on a clear night, in a dark area with dark adjusted eyes.

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If you can see small sats with a pair of 50mm binoculars. You just have to wait a little bit and watch for dimmer objects.

Cheers

For this comment to make sense, you should to put the 50 mm in perspective (no pun intended). For dim objects, the exit pupil size is what really matt ers, not the size of the objective lens.

on

The larger the exit pupil, the better - especially for the (usually) weaker eyesight of older people.

An 8x50 would give you 8x magnification with a 50 mm objective lens. The exit pupil would be: 6.25 mm

A 10x50 would give you 10x magnification with a 50 mm objective lens. The exit pupil would be: 5.0 mm

A 12x50 would have an exit pupil of 4.2 mm. And the Nikon "zoom binoculars" at a whopping 22x50 would be only 2.3 mm These last two binoculars have exit pupils that are probably too small to " fill" your eye with light, so you might not be able to pick out the satelli tes, even though the magnification would seem to suggest otherwise.

For a given objective lens size, the higher the magnification, the darker t he image will be.

10 x 50 works for me.

Cheers

Iridium flares can be seen in the daylight.

It helps to have a GPS or "atomic" clock since the satellites aren't visible for very long.

My favorite experience was watching Skylab, and trying to manually point a NASA dish to try and lock on the craft. It didn't work. 1 degree beam width. We tried anyway. We also tried using two dishes, 85 and 30 foot. If one got close, we could use it as a slave. until NASA got accurate data from NORAD, nobody could lock onto it. The lab was falling, and it was a last effort to try and do something with it, since it was shutdown for sometime.

Greg

It is done fairly routinely these days with amateur tracking scope and precomputed trajectory predictions with a webcam. You are likely to get your eye poked out trying to do it visually. And a webcam can stack the video images afterwards in post processing with astonishing results. One of the leading exponents of this has some brilliant images online:

Both are amazingly bright and a surprising number of people have never seen them. But they are as nothing compared to a transient Iridium communications satellite flare which can be a hundred times brighter but over a very narrow path. You have to feed your exact location into the program and maybe move a few miles to be on exact track centre.

Anything brighter than -5 is well worth a look -8 is stunning. Predictions are only reliable for the next few days.

Actually the limiting magnitude for most of their predictions should be visible from a moderately light polluted sky. It is just a question of getting your eye in for a faint moving star.

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Absolutely wrong at least in terms of night vision. Older peoples pupils will no longer dilate past about 5-6mm whereas younger folk can get to around 7mm when fully dark adapted. The main increase in sensitivity comes from being in the pitch dark for about half an hour.

The initial adjustment to see something on the milky way is a couple of minutes in most people but it will get gradually brighter with time. You can boost sensitivity further by breathing pure oxygen (especially at altitude).

You have it entirely backwards for an *unresolved* object like a star or a satellite. Their appearance stays the same. Extended objects including the sky background get dimmer - so improving contrast.

The effect of magnification is to spread the sky brightness out whilst the unresolved pointlike stars stay the same (until the magnification is so great that the Airy disk becomes visible). The net effect is that contrast for faint stars is improved by higher magnification but you have a smaller field of view. There is a new Xmas toy this year for astronomers in the form of wide field milkyway viewers from Vixen:

They turn on its head the usual heuristics of good binocular design.

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Martin Brown

On a sunny day (Fri, 31 Oct 2014 03:09:22 +0000 (UTC)) it happened gregz wrote in :

I threw together some ISS tracker on 2.4 Ghz:

This uses the 'predict' program, added some interface to RC servos, found the ISS orbital parameters online and added it to predict. Have not done anything with it yet, they are supposed to transmit on that band but not that interested in some clowns floating in a tin can doing zero graffiti tricks, seen enough of that, but basicaly its easy. I have seen the ISS naked eye too here, shining in the sun. Of course the beam with of this setup is MUCH wider, hard to miss.

Of course old peoples' hands shake more, which probably eliminates the advantage. ;)

It really is much nicer using 10x80s vs 10x50s for observing comets.

Cheers

Phil Hobbs

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I forgot, the system also had a camera. Had the camera had a zoom, it may have been easy to get acquisition. The only time we used th camera was looking at the moon, when tracking it, and the coll tower.

Greg

ive (no pun intended). For dim objects, the exit pupil size is what really matters, not the size of the objective lens.

cation

aker eyesight of older people.

m

to "fill" your eye with light, so you might not be able to pick out the sat ellites, even though the magnification would seem to suggest otherwise.

er the image will be.

I was primarily discussing brightness, not contrast. If the object is too dim to see, the contrast probably does not matter.

My apologies if I stated it backwards. (Thanks for the correction.) The point I was making is the original 50 mm spec, by itself, isn't saying anything. You need to know the exit pupil size, and how that stacks up aga inst the viewer's eyesight. I also agree with Hobbs' comment below that 10 x80 work better than 10x50's for all the viewing scenarios that I can think of using such a pair for. Well, maybe not better on your neck & back sinc e 10x80's are sure to be bigger and heavier.

How is a smaller pupil an advantage?

10x50s are about the largest useful "general purpose" binoculars. Even they're too bright for full sunlight. 10x80s are good for astronomy but that's about all. 7x35s are good for carrying to the ball park. ;-)

For bright light conditions.

Cheers

"Night vision" and "dilated pupils" in bright light conditions?

No...

Small exit pupil for bright light conditions. When your pupils are not dialated. Large exit pupil for low light conditions. When your pupils are dialated in low light)

Cheers