Do I need Bias Frames ?

[johnb]

Hi

I use DSS to stack my images

Using my Modded Cannon I take Lights, Darks and Flats but never bother with Bias ?, do I need to and if I do what difference will I notice ?

Regards

John B

[Psychobilly]

I take lights flats and bias and dont bother with darks with my canons.. it's a funny old world..

What do your results look like?

Peer....

[johnb]

err they look ok ie:

http://stargazerslounge.com/imaging-deep-sky/149946-m27-getting-better-better.html

http://stargazerslounge.com/imaging-deep-sky/145627-ng7000-5-out-10-a.html

John B

[Earl]

As bias are so easy to take there is no reason why not to.

Try with and see if it makes any difference.

[Psychobilly]

They look fine....

Bias frames are quick to take and can be taken at anytime (no light entering camera shortes possible shutter speed same ISO as the lights) ... they can help if you have a noise banding.. some peole find they make matters worse...

I used to use various combinations of the callibration frames until I found something that worked well for me...

Peter...

[roundycat]

Every exposure you ever make contains Bias.

If you subtract a master dark from each light Bias is taken care of.

There is no point in taking Bias just because it is easy to do so. Take them if you need them.

Flats need to be dark subtracted to work properly. That takes out thermal pixels and the Bias. If you do not take the Bias out of the Flat (each flat frame exposure) with dark subtraction you must take it out with Bias subtraction.

That should leave you with a Master Dark containing the Bias and a set of Master Flats not containing Bias.

Hint: take a set of twenty bias frames and combine them using Average. Stretch the master bias as you would a finished picture. Study it, it will help to diagnose camera/processing problems when you get them.

Dennis

[johnb]

Thanks for the advice. John b