A useful guide to "Seeing"

[aries]

Found this site this evening, and thought it may answer a few questions

about it............

http://homepage.ntlworld.com/dpeach78/seeing2002.htm

:shock:

rather interesting, eh?

[jgs001]

Nice link, and a definite help in understanding it better, thanks

[phillc]

Thanks aries as a newbie found very informative.

phillc :wave:

[PaulG]

That was a good read, thanks for the link

Paul

[philsail1]

Very sobering reading "Aries."

I'll look "through" my 8" Newt with a different perspective now.

Regards,

philsail1

[Sparrow]

Fascinating read - I had to laugh at the bit where it said that viewing is best when mist or fog forms :shock: - haven't seen it like that before

Nevertheless, very informative and explains why it's like looking through a bowl of soup here in Chester

[Talitha]

Here's something I've had bookmarked forever: The Pickering Seeing Scale

It's an animated page which illustrates the Pickering Scale mentioned by Damian Peach.

[AlphaTau]

Aries thanks for this it is very useful.

And Talitha that just tops it off nicely. After reading the article the animation shows clearly what its all about.

Both added to Fav's

Cheers

Andrew

[ringz]

At what sort of magnification does one need to be using to view these seeing artifacts?

--

Martyn

[Talitha]

Martyn, I use my scope's 'usable' magnification limit.

It's about 50x per inch of aperture (400x for my 8" SCT)

or about 2x per mm of aperture (240x for my 120 achro).

[lunator]

Hi Martyn

Most scopes are used upto x25 per inch as an average magnification. To really see what is going on then as Carol says you needto be pushing higher than that.

At the Hanwell observatory in Oxfordshire Chris Taylor frequently pushes his scope to x825 which is x66 the aperture.

Sparrow In the UK there is usually a fairly obvious trad-off between seeing and transparancy and if it is fine detail you want to see then you want stable air that usually means mist.

If it is faint fuzzies you want then you want the air to stay clear but this probably means that it is more active (wobbley) so the fine detail is harder to see.

Just occasionally the seeing and transparancy are both good and it never ceases to amaze me how much the scope can show.

Cheers

Ian

[ringz]

Thanks both for the info. My shortest FL eyepiece is a 9mm ortho so I'm not getting anywhere near the magnification needed to see the Airy disc especially considering that my most used scope is only F5

I guess I'm going to have to dust off my Ultima Barlow and give that a workout or, God forbid, try and get my C8 mounted up. I've kind of gone mad in my small back yard and my viewing area is full with potted plants

--

Martyn

[Talitha]

Thanks for the clarification on the formula, Ian.

The 'usable' magnification I'd read about probably assumes perfect conditions.

..my viewing area is full with potted plants

Sounds absolutely lovely, Martyn!

[Sparrow]

Thanks Ian (Lunator) - I do understand it. It just sounds so funny and conjours up images of standing outside with my scope in thick fog

[AllanJ]

Thanks for useful links for a newcomer starting to get into understanding seeing.

Allan

[aries]

YVW Allan.............. :wave:

Nick...............

[Sam]

Thanks for the link Nick - the two Jupiter shots show the effect of turbulence quite nicely.

[kd001]

'Nights of high humidity were often good (as many observers say) but not all. Seeing was always good when any fog/mist was present.'

How can that be true?

[acey]

'Nights of high humidity were often good (as many observers say) but not all. Seeing was always good when any fog/mist was present.'

How can that be true?

Because seeing is not the same as transparency. Good seeing means still air, good transparency means clear air - and when it's misty the air is still, even if it isn't clear.