Using Maxim Dl to align and stack fits files and perform initial digital development and stretch


for most deep sky images use the settings shown above, auto -star matching for align mode and output as sigma clip.

there are options for planetary images, or you can choose to pick the alignment stars on each image yourself, but stick with the settings above for now

you will see that the “set as reference” box is clicked, this means that the image you can see is the one that all of the other images will be stacked onto.

if this image is poor then use the “next image” box to scroll through the images to find a really sharp one to use as reference and click the “set as reference” button.

using the next and previous image buttons you can now scroll through and reject any images that have serious movement or were ruined by cloud or other things by using the “reject image” button, any rejected images will have a large red cross  on them(don’t worry about satellite trails, sigma clip output tends to remove this for you.)

when you are happy with the images you click on  <overlay all images> this then combines and aligns the images and then gives you a preview of the basic image

(dont worry as long as it looks ok there is much work to be done to tease out all of the little detail later)

if you are happy then click ok and your image should now be on screen, if not unclick the <overlay all images> button and scroll through and reject any other images that are not as sharp or clear as you like.

check the following settings

permanent stretch type  - ****** linear *******

input range - max pixel

output range 16bit

turn off any preview buttons (auto,preview,auto,full screen)

slide the red and green sliders again to the left and right and click ok.

you can then go to file > save and save this file (as a fits file) to be then taken into your choice of image manipulation software (photoshop etc.)

I hope you find this useful.

This is how i do the basic processing and some may pick fault but it works for me.

many thanks to martin t. who taught me how to do this in june 2010 and i have never looked back.

now we need to lock in this stretch.

select the grey rectangular stretch icon in the toolbar as shown below, this should bring up the stretch window setting

ensure kernel - user filter is selected

ensure the full screen and auto are clicked at the bottom of the preview image area

click auto under background and mid-level and the screen stretch histogram will change as you do this.

click auto off on the ddp parameters, and if any mouse options are on turn them off to. (the auto must be turned on whenever you reach this stage at the start of processing) ensure the “full screen” and auto are selected only below the preview image.

once all ddp parameters are de-selected in the lower left the histogram in the screen stretch window should fill up as above.

the above histogram is good but what you are looking for is to be able to see the start of the data on the left hand side which is currently off the left hand side of the screen stretch window.

now, to find that hidden data!

what we need to do now is to decrease the background figure little by little until the start of the histogram can just be seen on the left hand side.

********* n.b. each time you change the figure you must re-select <full screen> before looking at the histogram ********

once you can see the start of the histogram click ok and the ddp window should now disappear

move the red slider to the left of the screen stretch window (picture goes very bright) and move the green slider to the right side of the screen stretch window (picture darkens)

once the settings are as above click close and return to the Digital development (ddp) window

then go to filter > digital development

this opens the digital development window.

click on the <set user filter> box and ensure the settings are as shown

(you only need to do this the first time you use maxim, it will remember the settings for next time)

next ensure the histogram (screen stretch) window is open, click on the little black and white icon in the toolbar as highlighted below.

Open Maxim DL

Go to file>open and select your fits files ( if you have done rgb images just do one colour at once )

go to  process > combine

you are then asked to select the images, because you have already opened the images they will all appear in the left hand column. click <add all> and the list should duplicate on the right hand side, then click ok.

you are then given the combine/align toolbox