Seeing & Transparency

[+Streetbob]

Can anyone enlighten me about the definition of these and how to quantify them?  They are used in Astro Planner.  Thanks 

[Perkil8r]

Transparency is how clear the sky is.

Seeing is how steady the atmosphere is.

 

Transparency can be affected by such things as dust, moisture etc.

 

Seeing is affected by turbulence caused by thermal currents, wind etc.

 

How to quantify them....... no idea.

 

To think of them another way: Foggy day you can't see through it so it's got poor transparency, on a hot sunny day when the road lets off heat and you see heat haze, it's clear but the picture looks wobbly so the seeing is bad.

 

Hope that helps.

[xanthic]

Further reading on Seeing here : -

http://en.m.wikipedia.org/wiki/Airy_disk

[Brantuk]

I always think of it this way - if there's poor transparency then the seeing isn't going to be up to much. It can be a clear night suggesting good seeing - but in fact poor transparency caused by the reasons Mike gives above will result in poor seeing - but at least you have 'some' seeing.

 

If there's fog or cloud cloud cover - then you haven't really got any seeing at all.

[philjay]

Agreed Kim, reminds me of the other year when that Icelandic volcano was churning stuff into the atmosphere. Transparency wasn't great due to dust but the seeing was superb due to steady atmosphere. The lack of planes also had something to do with it

[Brantuk]

Yes - I had to clean my dob mirror cos of all that volcanic dust. It probably didn't need it but I couldn't bear it and cleaned it anyway. At Kelling the whole atmosphere had a red'ish tinge to it as I remember.

[+Ibbo]

Mikes got it right

 

some of my best views of Jupiter were when it was almost foggy , the atmosphere was so steady

 

extended objects, planet,moon,sun are best when seeing is steady

 

transparency is good for deep sky objects

[+Streetbob]

Thanks Guys.  I was out on Monday & I think it was steady seeing & good transparency.  

[Daz Type-R]

Yeah I agree, Monday night was good for me too. A good indicator of how good the seeing is to look at stars, if the stars appear to twinkle then the atmosphere is turbulent, hence the seeing can be poor.

If you live near a town/city and the sky is a orange colour then there is loads of moisture in the air reflecting the street lights and the transparency is rubbish.

Edited November 6, 2013 by Daz Type-R