Kaptain Klevtsov

Every little helps, as they say, maybe if everybody joined up we'd be up there and find the little green men.

Captain Chaos

Have you joined the team? Seems like a silly question but you do need to tell it that you want to join.

Captain Chaos

Here goes with a quick go at the mystical numbers on your telescopes and how to decode them.

I'll start off with some definitions in case some of these are non-obvious, the whys and wherefores of the f/ number will have to wait until I can condense the f/ concept better as I've just tried and messed up.

Aperture

This is the diameter of the hole that the light enters the telescope through. A 100mm refractor will have a front lens of roughly 100mm. A reflector will have a tube slightly larger than the aperture as the actual aperture is the primary mirror (the tube is merely a way of holding all the bits together).

Focal length

This is the distance from the primary (front lens in a refractor or the big mirror at the bottom of the tube in a Newtonian) to the focal point. The focal point is where you put the eyepiece or camera.

f/ ratio

This is the relationship between the aperture and the focal length.

So what does all this malarky mean?

The significance of these three numbers is, in simple terms:-

Aperture

More aperture means that you are collecting more light and more light makes the image appear brighter. Bright things are easier to see and to photograph. More is better.

Focal length

This has a direct bearing on the magnification. No other number is involved as far as the telescope is concerned. The magnification is calculated by dividing this number by the focal length of the eyepiece. Using the above example and a 10mm eyepice gives a magnification of 1000/10 = 100. If you use a 20mm eyepiece the magnification goes down to 1000/20 = 50.

For imagers that doesn't help much so there's another way of looking at it. If you could look through a hole the size of your camera's sensor you would be able, by moving your eye from side to side, to see a section of the sky. Bigger sensor, more sky. To work it out more exactly you need to imagine that all the light comes through a tiny section in the centre of the lens or primary mirror so you can use the focal length of the mirror and the sensor size to work out how much sky you can "see" using that sensor. If you sketch an isosceles triangle with a base dmension equal to your sensor width and a height equal to the focal length of the 'scope, the angle at the pointy end is the angle which also covers the piece of sky that you can image widthwise. Do the same for the height and you get the angle corresponding to the amount of sky you can image in the other direction.

To be continued...

Captain Chaos

I think it uses whatever is left over after your computer has done everything you asked it, kind of like the system idle process does normally. If I set mine doing registax or Deep Sky Stacker then Boinc backs off until the important stuff has finished.

Captain Chaos

One of the best views I have ever seen of Saturn through any small amateur telescope were those produced by a humble 6” f/8 Newtonian. I have no idea what the Strehl ratio is or the wavefront error and nor do I care, because the views of Saturn on one night of perfect seeing will stay with me for a lifetime and that is what amateur astronomy is all about!

So you've finished then, well done.

I'll get my coat.

Captain Chaos

The project URL is http://setiathome.berkeley.edu on its own. Once you're up and running you can join the team (option in Boinc). It should be easy enough once you're connected.

Captain Chaos (Jonathan in the SETI team)

Doctor Who. Last first series, big refractor... *wicked* brass gears and knobs

Arthur

But it wasn't a telescope, it was a doodah to mess up the werevampirie things. I had thought that it wouldn't count bcause of that.

My kids stood back when the castle was revealed and their dad went "kennel, look at that fracking thing" all out of nowhere. He was gagging to fix it up and make it work, I could tell just by watching him.

But really, us adults don't watch these childish things do we.

Captain Chaos

Is there a SETI doctor in the house?

Looking at the stats, I am listed twice! (Jonathan, my mother's way of refering to me).

Is there a way of combining the two for convenience? I just set up the kids' machines to help out and I find that I'm schizophrenic suddenly (and so am I).

Captain Chaos

The team is now in the top 10,000.

Captain Chaos

Thanks Lee, it's doing stuff again this AM, but its not showing the team info. yet. We'll see how it goes when it connects again and gets a result.

Captain Chaos

Has seti stopped needing help? Mines sat idle at the moment, though I might have messed something up trying to attach to SGL. It's saying it's connected to localhost and I've no idea where thats kept.

Captain Chaos

I'd better have another go at it then. Maybe I've got some kind of conflict in there?

Captain Chaos

I used to do the SETI one, but when they swapped over to the boinc server I had no end of problems so gave up on it, and they lost all my completed work units I had over 1000 !

Alan

I had problems too - slowed down the laptop too much and I had to take it off!

I had over a years worth of work logged before they made me change to Boinc, now they forced me off altogether.

Boinc was supposed to be a screensaver, same as SETI@home but it ran all the time, wouldn't give back the 'puter straight away when i wanted it AND it does more fancy pictures rather than just doing the sums like it was meant to. If they want clock cycles for the maths, why do they waste them on over fancy graphics?

I might get the kid's computers involved, they don't have work stuff on theirs, just to see if it works on something faster than my "old" P4 laptop.

Captain Chaos

Is that in radians or degrees?

Captain Chaos

It must have something to do with the lens in the eyepiece. This bends the light so that, although all the light is coming in a narrow cone from the objective lens/mirror, the eyepiece spreads it out so that it "looks like" it's a wide view that you are seeing. Is that the answer to your question?

Captain Chaos