Members evening 26th nov

[Simon E]

Hi guys and girls,

What usually happens at a members evening, never actually been to one yet?

Maybe I can pick up my membership card as well as a long black tube

si

[Mac]

What usually happens at a members evening

its exactly the same as a normal evening except instead of having an invited guest to talk about a topic
of interest, one or more of the members provide the entertainment topic for discussion.

Marks one on noise looks like its going to be very interesting, considering the amount of imager's
we have, pity i'm going to miss it.

Mac.

[Carole]

Ask Tom the Treasurer for your membership card.

See you tonight.

Carole

[Tony G]

Maybe I can pick up my membership card as well as a long black tube

si

Well Si,

After carrying that tube 6 miles on foot, with it strapped to my back, and all the heckling from young gangs roaming through the South London streets, I discovered that you were not there. 
Si let me know what you want to do and I'll meet you somewhere if that suits you 

Tony G

[Carole]

I think Tom's going to post your membership card to you.

Carole

[Simon E]

Sorry guys after two 12 hour days working at Heathrow and getting in at about 7 last night, after a blow out of my tyre at 70 on the M25 I couldn't face it, still at home now after having a lay in. Tony maybe we can met up somewhere, or I can pop round and give you some fosters and maybe some new shoes, ideal for hiking.

si

[Tony G]

You managed 70 on the M25 

Tony G

[Simon E]

I had a quick spirt

si

[mickw]

Mark, very interesting talk last night - I even remember one or two of the words 
Which brings me to............................
Any chance of posting the bare bones of your talk somewhere - unless you're writing a book or something.
I'm sure it would help imagers understand why the noise problems occur and what can be done to overcome them.

Who'd have thought I would be asking for more maths 

[Tony G]

I still don't understand why you have to throw marbles at your camera, and to get a better image you have to throw twice as many for twice as long, and then divide it by the Std Dev, which is the square root of........................

Mark,
A very interesting talk, and like Mick, I understood a good deal of what you spoke about, and how you achieved certain results, the problem is how do I now put that into practice and get similar results, when something as simple as removing one frame from another is something that I have never done.

A nice day at a future UDSC or DSC, and I'll pick your brain.

Tony G

[mickw]

I'll pick your brain

You're gonna hit Mark with a pick axe 

[Tony G]

If that's what it takes. 

Tony G.

[MarkS]

Mick, Tony,

I intend to put the contents of my talk, with examples and better explanations on my website sometime.

I'll also create a spreadsheet to make the calculations really easy for you and also to calculate optimum exposure lengths.

The briefest summary of my talk is here:
* Electrons are generated from photons and by temperature effects
* Collecting electrons always creates noise - it's a "Law of Physics".
* Bias frames contain read noise
* Dark frames contain thermal noise + read noise
* Light frames contain skyglow noise + thermal noise + read noise
* Subtracting pairs of bias frames frames and of dark frames and the background areas of light frames allows you to estimate that noise.
* Remember that noise adds together like this:
     total_noise_squared = read_noise_squared +  thermal_noise_squared + skyglow_noise_squared
* If using a DSLR, make sure all your frames are taken at the same ISO setting
* Make sure the lights have the same exposure length as the darks and were taken at the same temperature
* Work with the RAW frames - before they have been converted to colour pictures
* For the light frames you should do the calculations separately for the red pixels, the green pixels and the blue pixels.

There you are - that saves you sitting through a 40min presentation!

Mark

[mickw]

that saves you sitting through a 40min presentation

It was only 40 mins ? it seemed much............................... 

Thanks for that Mark