AP question need help

[AshleyRoberts]

hiya 

i just ordered the book everyone raves about im soo excited to get it, but there is a question that is bugging me and i really dont know what it means 

i hear people talking about dark and light images please can someone explain this to me 

kind regards

Ash 

[Tinker1947]

There is a help file in DSS, explains it all.......

http://deepskystacker.free.fr/english/index.html

[astrodam]

Lights are the images of the object and darks are calibration frames to take out noise/hot pixels from your camera.  I've bought a couple of books on AP and it is all explained.  Lots to learn but great fun getting there.  Good luck

[lensman57]

hiya 

i just ordered the book everyone raves about im soo excited to get it, but there is a question that is bugging me and i really dont know what it means 

i hear people talking about dark and light images please can someone explain this to me 

kind regards

Ash 

Hi Ash,

Read the book and it all to make sense but for now just read the simple explanation.

Ligths, Light Subs, Light frames or ( frames, subs, lights in short ) are all the same and just refer to an exposure of a certaing length that was taken using either your DSLR or a Cooled CCD device or webcam from your intended target such as Orion nebula or Jupiter for example.

Darks or Dark frames or Dark subs are exposures of exactly  the same length as your Ligth Frame that you took from your intended target but thiis taken with the lenscap on so no light will enter the telescope, hence the name Dark Frame.

Bias is Dark Frame exposure taken at the shortest possible exposure that your capture device can manage, 1/8000s or 1/4000s in case of a DSLR or 1/1000 in case of most of the CCDs or webcams. No light is allowed to enter the device during Bias Capture.

Flats are light frames taken at a certain exposure length ( to be determined by yourself and is specific to your set up at the time of the main capture ) using a flat and uniform light source, this could be the twilight sky or an artificial light source such as an electroluminescent panel. Flat have to be taken with all your imaging rig in place , at excatly the same focus position and orientation of the imaging rig. Flats as you have gathered by now  are the most troublesome of your  calibration frames ( Darks , Bias Flats ) to do correctly and most people including myself can not consistently do them well. Correctly taken flats will help to eliminate vigneting, uneven field illumination and dust particles or dirt marks your lens and filter surfaces for example.

Dark Flats are exposures taken at exactly the same length as your Flat frames but with no light enetring the capture device, hence Dark Flat Frame. You only need to do these if the exposure length fo your Flats happen to be long enough as to introduce dark current noise in your capture device or for correction of possible light leaks durring the Flat Frame capture and people mostly do not bother with them.

These are very simple explanations and if you really want to understand what you are doing then a lot more reading  is required to understand the science behind all these confusing jargons.

A.G