A bit boring but my first play with deep sky stacker

[Simon E]

VEGA

A bit boring I know. But my first effort with deep sky stacker.

Made up 8 x 30 sec frames taken at iso 1600 with 10 darks,10 flat and a couple of bias frames.

Taken on the 11th between 23:00-01:00am.

Can't wait to get my new tracking scope, roll on long exposure.

Si

[Mac]

nice first play,

you only need one flat normally, as this is just an image of all the dust ect.

Mac

[Daniel]

Nice Image, some nice colour in the stars and a very smooth result especially considering you used ISO 1600.

I tend to take quite a few flats (about 50-100) stacking them gets rid of any noise artifacts that may be in the flat images and stops it being subtracted from the image when the flat is applied.

Daniel
:O)

[Simon E]

I am slowly building up flats and darks in folders named by iso and temp. I could copy the flats about 50 times and see what happens. But thanks for the words of wizdom.

si

[Daniel]

The problem with copying the flats (or darks for that matter) is that the noise pattern wouldn't change from image to image and would then not be subtracted from the final master flat.

Daniel
:O)

[RobertM]

If you had one ff frame then you can apply copious amounts of gaussian blur (in PS).  The only issue with this is that you would have to apply the flat field frame after Bayer conversion.  Ideally the flat field frame should not have any noise anyway which is why this approach will work.  Alternatively you can remove the stars from an image and do the same thing, it only works where there are only stars in the image.  I've successfully used that method on star clusters.

You could also try Gradient Exterminator or Pixinsight Dynamic Background Extraction (bit of a learning curve on the last one!)

Hope that helps.
Robert

[Simon E]

Robert all I can once again say is



It's great when the pros totally confuse you!!!!!

si

[Fay]

I always do 20 flats & 20 flat darks. They should be done every time as the dust will move position as the camera position is moved.

[Mac]

Just a thought.
why do you take flat darks

the point of a flat is to image the dust for removal from the image?
The flat image will be taken at a speed where there is almost no noise from the sensor.
You already have the bias frames which is for the readout noise,

and the signal to noise of the flat should be huge, compared to the normal light frames we take,

Mark, it might be worth trying to measure if a flat frame of say 1/250 sec, is improved with a dark frame of 1/250.

[RobertM]

The main proviso with what I have said is that the level of dust is insignificant.  If it is a significant factor then you will have to do many flats to define the dust shadows.   Professional astronomers always calibrate their images meticulously with flats, dark and bias and ideally that is what you would want to do with each imaging setup.  20 flats is reasonable number to take.

Fay, what do you mean by flat-darks?  It's a confusing term!  I assume you're doing that for each filter when you could do one set of darks (which take the majority of the time) then a set of flats for each filter.  With your Atik, like my SX, you shouldn't really need darks unless you're doing photometry.

Mac, you posted a simalar query about the flat-darks but I'd already typed my response.

Robert

[Fay]

I match the flats exposure with the cap on scope & do darks, as well as the darks done as same exposure time as Luminance. 

It should be done for each filter. I had so many dust bunnies on my last image I thought I would not get rid of them. Thank God for flats. They do seem to smooth the image as well.