m51 from Bromley...

[Fay]

So, Chris, you put whatever white over the end, & the readout will be around 20-30 thousand. Do you then alter the exposure length to bring that number  down to what you want?

I am confused because I was running the mouse over my image but the number at the bottom changes all the time depending on if the mouse is on a white part or black.

[JohnP]

I am confused because I was running the mouse over my image but the number at the bottom changes all the time depending on if the mouse is on a white part or black.

Fay - yes of course it will the mouse is effectively measuring the intensity of light at the different positions on the image - if you put it on something black it is going to be a lot lower number then if you put it on something bright.... When you do the flats most of the image will be white just ensure that the value of the white is around 20-30,000 by adjusting the exposure length... It's really very easy to do...!!!!

John.

[Fay]

Ok, so put the mouse just on the white part of the image

[MarkS]

Fay,

Yes, I'm saying that pointing at a computer screen will work to create flats. 

You may need to do it for each filter you intend to use.  Is that right John?

And stop calling me Robert!!!!

Mark

[Fay]

Sorry Mark.............................they're coming to take me away ha ha ha ha to the funny farm!!!!!!!!!!!!!!

[JohnP]

Mark - Yes - You need to do for each filter as it's a different optical path... Also don't forget to take flat-darks as well....

Thks for the computer screen tip - I'll give it a go - only thing is to make sure screen is perpendicular to end of scope - do you literally put screen right up against opening of tube?

John

[MarkS]

Yes, bring the screen right up to the scope (and perpendicular!).

[Fay]

MARK,

I have just set up the scope indoors & had a practice at taking a flat fom the computer screen.

Not sure but it seems Astroart sorts out the exposure, could be wrong.

[Fay]

Will have to have another go getting image on screen

[Fay]

I am thinking I should not  have enabled FlatField Correction in AstroArt, am I right?

I have never used 2x2 binning, but the image was taken  in 2x2 as per AA.
When you have taken flat fields, do you have to process them  as you do a normal image?