okay here we go with the deep sky
stacker this program is Windows only but
it is free and what it does is it
registers your light frames it
calibrates them
we have darks flax and bias files and it
stacks all of that together and can do
things like Sigma clipping to get rid of
things that are abnormal like hot pixels
and and just airplane streaks and all
that kind of stuff and it's a very easy
to use program once you get the hang of
it it does this one thing very well
which is stacking and doesn't do much
else so let's look at it we're just
gonna use the basic features of it here
we start over here in the upper
left-hand corner by clicking open
picture files I'm gonna click on that
and find the light frames for the object
that I'm working with so if you've
already organized like I have here it's
pretty easy you just go into the m42
folder click on the lights folder and
there's all the files if on your
computer you are not seeing your files
for some reason just make sure that down
here it's not set to something weird
like JPEG only or picture files it's set
to just all files and then you should
see all of your RAW files I'm just gonna
click on one and then press ctrl a to
select them all and then click open okay
what I can do here in deep sky stacker
is click on one I'm just gonna click on
the first one and it gives me a nice
little preview here of the file we're
not seeing much other than the really
bright stars here if we zoom in we can
see that there are dimmer stars as well
but if I wanted to brighten this picture
up a bit
this is just for preview purposes I can
go up here to the upper right and drag
this middle slider in a bit to the left
and it brightens up the picture some and
I can see some of the dimmer
stars now which is helpful for
evaluating focus and also how much
elongation of the stars there are and in
every frame deep-sky stacker can do some
stuff with evaluating the Stars for you
but if you want this more manual control
it's here for you you can zoom in you
can look at the pictures you can go
through them one by one it takes a
second for it to load each picture you
can zoom in on this one and I can decide
is this a frame that I want to keep or
do I want to get rid of it and I'm not
going to show that whole process but
I'll just show you an example of a frame
that you would not want to include let
me go all the way down to the bottom
here and I remember at the end of the
night my last frame I must have hit the
tripod because there's like a little
jitter in it
so let me zoom in on this okay and you
see that that's on all the stars that
little jitter on all the stars that's
from knocking something or stepping too
hard or whatever and it can also happen
from wind but basically we wouldn't want
to include that frame so how do we not
include this frame what we want to do is
we first want to check all so I'm going
to go over here and click check all and
then I'm going to just uncheck that last
one that one I don't want to include
just by clicking its little checkbox
here to uncheck it okay so we have 71 of
72 light frames checked now we're gonna
go ahead and add our dark frames click
on dark files over here I'm going to hit
control a to select all my darks have
those
if we look at one of those I'm just
gonna click on one here it doesn't look
like much if we really stretch it still
doesn't look like much
but that's what darks are they're
basically just correcting for hot pixels
and thermal noise things like that let's
go ahead and add our flat files control
a to select all of these click open
brings in our flats let me stretch this
a little bit so he can see what it looks
like too much there we go so you can see
that it gets a little bit darker towards
the corners here that's representing the
vignetting I don't know how clearly you
can see that but that's our flat frames
and last our bias frames let's add these
control a to select them and we have 100
bias frames in here let's see if we can
see anything in the bias it's sort of
hard to see anything but basically that
represents the fixed pattern noise on
the sensor and it can get rid of
horizontal and vertical banding problems
that it is common with DSLRs ok so we
have all of this added now and remember
with that last light frame I unchecked
it looks good
if we want we can look at the raw
settings which are down here under
options raw settings and these are the
same as the last time I set them up I
just use this default Bayer matrix
interpolation I've always used camera
white balance because I'm always careful
to set that if you didn't just uncheck
that to not use it at all I always set
the black point to zero which helps with
calibration I believe and if you change
any of these just remember to click
apply before you click ok next thing I'm
going to do is over here on the left
hand side under register
cheering and stacking click on register
checked pictures it brings up your
register settings these will be whatever
you last set them at so if you want it
to automatically detect and remove hot
pixels make sure just to check that I'm
going to do that if you've already
registered the pictures you can use this
option right above there but I haven't
registered these together yet I mean
putting them all on the same place so
the Stars match up so I'm going to leave
that unchecked I want to check stack
after registering cuz I do want that to
happen and right here it says select the
best percentage pictures and stack them
you can change this to whatever you want
basically it just assigns a score to
each picture based on how round the
stars are and if you only wanted to
include like the best 50% or 80% you can
set that right here if you want to
include everything just put in a hundred
percent I'm gonna put in 97 percent
because maybe there's one that I didn't
catch that it could throw out next thing
I do is I go over here to the Advanced
tab and by default it sets this star
detection threshold to 10 percent you
may not need to change this though to
get a good number of stars if you're
below let's say 50 stars you probably
want to change the detection if you're
above a thousand stars you might also
want to change that detection because
they might be picking up hot pixels and
things like that so I'm gonna go ahead
and click on compute the number of
detected stars it looks at the first
light frame and sees how many stars it
can find looks like I have plenty here
it found almost three hundred so that's
fine I could just leave this alone at
ten percent but if I wanted to speed
this up a little bit I might take this
down to 20 percent I'll compute again
and now it's down to 177 stars so it's
just fewer stars to match against
usually works a little bit faster and
better so I'm gonna leave it at that
I'm gonna go ahead and click on this
reduce the noise by using a median
filter and then I'm gonna click on
recommended settings and basically you
can just step through this and anytime
where it's highlighted in blue here you
can read what it says if you were using
a modded DSLR while I'm not so I'm going
to ignore that if you are processing
narrowband images I'm not so I'm going
to ignore that one and then you just go
through each one and if it's something
that you haven't done you can just click
on that and it will put that into your
recommended settings I'm using Sigma
clipping I'm using bilinear d bearing
and blah blah blah so you can go through
there make sure you have all the
recommended settings click OK if you
want to go into stacking parameters and
look at these this has much more detail
I'm not going to go into all this right
now because this isn't a video about
deep sky stacker it's sort of an
overview of all the processing so this
would take too long but there are other
videos online so if you're interested
you can learn about all these different
settings in here this is good enough
though we're going to go ahead and click
OK and it gives us a nice summary here
of everything we're gonna be stacking 72
light frames with offset or bias
darkened flats
specifically a hundred bias 25 darks and
29 flats the total exposure is 38
minutes 24 seconds all looks good I'm
gonna go ahead and click OK to start the
process and off it goes it starts by
stacking together all your bias or
offset frames into a mess
your bias it then does the same thing
for darks flats it then calibrates all
your individual light frames with those
master calibration frames and then
registers and stacks your light frames
into your final single integrated image
which you can then preview here in deep
sky stacker but usually you just save it
off and we move on to Photoshop or GIMP
so I'm gonna speed up this part of the
video because it's going to take at
least ten minutes probably more like
fifteen or twenty and then we'll I'll
show you saving out of deep sky stacker
when this is all done
okay so what it's doing right now is
it's saving the autosave dot TIFF file
to my lights folder this is important
this is a 32-bit TIFF file that you can
consider your master stack Photoshop can
actually read a 32-bit TIFF file so you
could bring it right into the autosave
dot TIFF right into Photoshop not all
features in Photoshop are 32-bit so you
might have to eventually convert it to a
16-bit file if you're going to be
working with GIMP it probably can't even
open that 32-bit file so we're gonna
have to first save the picture to file
which is over here on the left hand side
under processing and save it as an
uncompressed 16-bit TIFF one thing
that's a little bit confusing here about
deepskystacker is it's making the final
picture right here on screen and there's
a bunch of settings we could change
right here and deep-sky stacker but it's
not really meant as a processing program
it's just a stacking program so really
there's not much point in doing much
here because we're not going to save
these changes anyways so I'm just going
to leave all that alone and go over here
to where it says save picture to file
and I'll just save it here to my desktop
to my m42 folder and I'll call it stack
dot TIFF and I mean to say compression
none and I want to just leave this
option that says embed adjustments in
the saved image but do not apply them
checked so basically just exactly how it
was and click Save okay now that we've
stacked in deep sky stacker we are going
to look at gimp which is a free
open-source program sort of like a
photoshop clone but it's been a long
around for a very long time and I am
using the latest stable release at the
time of this recording which is two
point ten point eight for a long time
GIMP did not support 16-bit image files
and processing but it now does with 2.10
and so we're gonna use that 16 bit
stacked if that we generated out of deep
sky stacker and do just some stretching
and color and things like that in GIMP
and I will admit that I do not know I'm
not an expert in this program but a lot
of things are at least somewhat similar
to how you would do them in Photoshop so
I know Photoshop very well so it sort of
translates over to GIMP but I don't know
everything about it and so I might do
some things wrong or or just a
roundabout way and if you have any
suggestions you can leave them in the
comments but hopefully this is helpful
for people who do not own or want to own
Photoshop or pix insight for the ones
that I I normally use so anyways let's
get started here I'm going to open up
GIMP 2.10 and I'm going to go up here to
file open and pick I stack dot if
they're from deep sky stacker
okay and the first thing that I like to
do in GIMP is just take this floating
window here holding the image and
stretch it out to fill this space in
between the panels over here and the
panel over here and then I'd like to go
up here to the View menu and turn off
rulers rulers are helpful if you're
working on like a print design but I'm
just processing astrophotography here so
I don't need the rulers on and I also
like to turn off this what do they call
this sorry
show layer boundry it's under view show
layer boundry and it just turns off that
yellow dotted line because I just find
that distracting okay after we have it
open keyboard shortcuts you should know
is - zooms you out + zoom zoom in and
you can see here in this stacked image
we're not seeing much detail there Ryan
Nebula other than in the core here and
it's going to be hard to retain all of
that detail in the core once we stretch
the image but we'll try to do a few
tricks to bring it back in after we've
stretched so I'm going to zoom back out
a bit here okay and the first thing I'm
going to do is over here in the layers
panel
it's the panel is actually called layers
- brushes I'm going to make sure that I
have stacked if selected here and then
I'm going to right-click on it and say
duplicate layer and I'll rename that
duplicate first stretch okay and now
with that first stretch layer selected
I'm going to go to colors the colors
menu at the top sorry colors and then
levels colors then levels and this shows
me the histogram here this is just a
luminance histogram and it's showing me
that there's this very
sharp mountain right they're not it's
not too even a quarter over yet it's
sort of maybe an eighth of the way over
and there's some room over here on this
side showing this is just clipped to
black but there's lots of room for it to
grow this way so I'm gonna take this
middle slider and move that if I can
grab it here come on
there we go move that to the left about
halfway over and you'll see it does sort
of an initial stretch here and I'll go
ahead and click OK on that okay so we
have our first stretch in there but
we're going to continue with these
stretching a little bit resetting that
midway point over to the left and then
resetting the black point a couple times
so we just keep going back here to color
colors levels and we take this middle
slider and again move it over a little
bit what just happened cancel
we take this middle slider and move it
over to brighten the image and then we
take this left-hand slider and move that
over to reset the black point and you
might be thinking oh what is this even
doing anything or what you can always
zoom in on the nebula here just with
plus just Center it on the screen and if
I turn off and on this first stretch you
can see we are bringing or brazing up
the sky background a little bit at this
point but we're also bringing out more
detail in this stretching process you
can see m43 is starting to appear here
in the first stretch right here and in
the stacked image we barely see it but
we have to do this a few times to bring
out enough detail so I'm gonna go again
colors levels and again take this middle
slider move it over take the left-hand
slider move that to the right and again
the middle oops we have to do this a few
times to really see what's going on here
so this time I'm just gonna focus on
bringing that up okay and then I'm gonna
go back in there colors levels and I'm
gonna bring this one over quite a bit
and we're getting close here you can see
the running man Nebula is coming into
focus maybe just one more
colors levels
okay and so you can see there's a
there's a lot of detail in here
but one thing you'll notice here is that
our whole sky background is very red
that's because of light pollution and
the Earth's atmosphere
you know bouncing that light pollution
back down and it gives us this very red
color the other thing you'll notice here
is that there is a gradient if we zoom
out we can see that there is this
gradient where it's darker at the top
and brighter at the bottom that's
because light pollution is coming you
know from the earth so it's usually
going to make this gradient where the
light dumb setting the bottom of your
frame and then it gets darker as it goes
up there's also a little bit of a
gradient left to right here because
probably there was more light pollution
over here on the right side than there
was on the left side so what we want to
do is we want to model this background
and subtract it the way I like to do
that here in GIMP is a little bit
different than how I do it in Photoshop
I'm going to use my color picker tool
which is right here and the second row
of tools for / and I'm going to first
set my foreground color with a value
down here at the bottom it sets it there
and then I'm going to change this to set
background color and I'm going to pick
one up here in the upper left corner and
basically that just gives me a
background value and a foreground value
of the sky here then I'm going to make a
new layer so if I go over here to the
layers panel and just click on the
create a new layer button just make it a
normal layer and on that layer I'm going
to pick my gradient tool here which is
one two three four five six rows down in
the tools selection and the gradient
tool should automatically be set to
ooh custom gradient using the foreground
and background color if it's not for
some reason just click on a little
gradient swatch there and you can make
sure to set it custom foreground to
background if you have to do further
editing of the gradient thing just click
into here and you can mess around with
that but this looks good and now I'm
basically just going to try to recreate
the background with my gradient tool
here and so I'm going to click down here
and stretch up to here I don't see how
that looks let go that looks pretty good
I'm just gonna turn the visibility of
this off and on see how that looks
and I think that this sample should
actually go quite a bit higher to make
the bottom half of this brighter look at
that again
and I'm actually going to move this
sample over to the right a little bit
here
maybe a bit too far what's the
difference
okay that looks pretty good we'll see
how it works now I'm going to accept
that gradient and I'm gonna go over here
to this layer with the gradient on it
and change the mode to normal here and
there from normal to subtract sorry
so find subtract here and what that
should do is it should take this
background and subtract it from the
layer right below first stretch that
looks good
and so I'm gonna go ahead and then just
merge that layer down into the first
stretch so you just go to layer merge
down okay
so we've removed the background might
still have some artifacts there when we
stretch it more but it's a good first
step and then let's go ahead and
duplicate that first stretch layer
generally this is the way I work in GIMP
is just to take a few actions on a layer
once you finish those actions just
duplicate it and move on to the next
thing you're doing so I'm gonna call
this one curves and on this new curves
layer
we're gonna go to colors curves and take
this floating window it says curves and
try just putting in a curve like that
okay it looked like looks like our
background removal was a little bit too
aggressive because it killed some of
this odor nebulosity so I'm gonna step
back a few steps here turn this off for
a second and I'm gonna go back here to
this first stretch and I'm gonna stretch
it just a little bit more so I'm gonna
go to colors levels
colors levels and I'm going to bring
this over just a bit more
colors levels and just bring this over a
bit more
trying to make that fete nebulosity out
there show up a bit more and then I'm
gonna look at this again yeah that's
much better even though we're showing a
bit more of this gradient here we can
now see a lot more of that nebulosity
there let me just try I'm gonna go ahead
and merge that down layer merge down and
then I'm just going to subtract the
background one more time so I'm going to
pick two new samples here oops
set foreground color set background
color
make a new layer make a gradient
all right let's try subtracting that
all right we have a little bit of
funkiness still here maybe like a little
bit more blue down here a little bit
more green over there but overall that's
getting pretty good we can desaturate
the sky a little bit in a second here
anyways so I'm just gonna go ahead and
merge that down and I'll duplicate this
first stretch layer and now we're on our
way with doing some curves
sorry for the interruption there but
again I'm sort of new to GIMP so
sometimes it takes me a couple of tries
so we'll go back here at colors curves
let's stretch this out a bit again I
realize we have some funkiness in the
sky down there but we'll desaturate that
in a second I'm really just focusing
here on the nebula so let me zoom in on
that a bit
can't while this is open so I'm just
going to accept that zoom in on the
nebula and that looks really nice pretty
similar to what we were seeing in
Photoshop if you watch that one it's a
nice detail in there we have the outer
nebula of the running man so I'm going
to go ahead and accept that that's good
and I'm gonna go ahead and duplicate
this layer and call it background reset
all right and I'm going to zoom back out
I'm going to select bicolor I'll try to
select sort of both of these colors here
just by clicking and dragging over that
gradient from this blue to green give it
a second here
okay so watch the background pretty well
there you can see it's not selecting the
stars or the bright part of the nebula
and we just want to go and do colors
saturation this little thing that says
scale means when's it when it's at one
that's just no change if we made it
higher than one it would increase the
saturation we want to decrease the
saturation so I'm going to click in
there highlight set it to 0.4 enter wait
for it to show me a preview here
I'm not sure if that worked I'm gonna
click OK and see what it does see how
much that D saturated
oh yeah it was working let me just do it
again so the selection is still on there
it just takes it a second here to
generate that and we'll go back into
tool or sorry colors saturation and I'm
gonna set it to let's try point two this
time enter get a preview nice so it's D
saturated again
and with that selection still active
what's this time go into curves and just
try setting the black point a little bit
to the right here so I'm just going to
drag that point over
and maybe I'll make one more point here
and drag it down a little bit
and I'm specifically going to try to get
rid of this greenish value here by
dragging that down
all right let's try this again so I'm
going to duplicate this layer curves and
we're gonna work on fixing the
background so I'll call this BG reset
and first let's just try doing something
with curves here and I'm gonna first
work on the green there I'm gonna bring
that point over a little bit you can see
that's working pretty well on that
left-hand side there okay and then I'm
gonna go into the blues and do the same
thing yeah that worked pretty well maybe
just bring them down just a little tad
bit more in the brighter parts here
okay actually that worked pretty well
didn't hit the nebula too bad and we
fixed a lot of the sky problems there so
let me go ahead and make a duplicate of
the curves layer here now again I'm
going to put that on top of my
background reset and I'm gonna apply a
screen blending mode
did a pretty good job of bringing of
getting rid of that green and blue but
then it replaced it with some redness
here so I'm going to go ahead and now
just select by color and grab this red
background
and could color saturation bring the
saturation of that down quite a bit so
it starts at one
I'm gonna go ahead and put in point 2
looks good except that
we can get rid of the selection now by
going to select
none
I'm going to duplicate this background
reset layer call it more curves and
we'll go back here to layer now colors
curves and let's bring this curve up
again
okay and at this point I'm trying to
just sort of apply a bit of a bit of an
s-curve to this
so basically keeping these the dark sky
low but bringing out the nebula detail a
bit more but you don't want to bring it
up too high that you're making the stars
really bloated and big so it's sort of a
balance here but that's pretty good go
ahead and click OK at this point rather
than keep fighting with this lower part
that keeps coming up when I stretch I'm
just going to crop that away cuz it's
not really important to the composition
anyways so I'm just going to crop to
this central part here and let's go
ahead and go back here to our first
stretch and duplicate that and I'm going
to call this core I'm going to bring the
core back up here to the top and it has
a lot more core detail in there and I'm
going to go ahead and apply what's
called a layer mask which is right down
here as a little mask icon and fill that
with black so right now we're not seeing
any of that core detail but we're just
going to go back to our default colors
here by pressing D and then I'm gonna
switch white to the top of my foreground
color and I just want to paint in a
little bit of that core detail with a
nice low opacity soft brush so I have
mine set here to 30% opacity it's nice
and big and soft and then I'll just
paint in a little bit at core bring down
the size
okay and then if I went a little bit
overboard
I can always hit X to switch to black
and just sort of paint it back a little
bit
okay I think that looks pretty good I'm
just going to do another layer here but
I want sort of everything that I've
created just like this so I'm gonna do
layer new from visible it makes a new
visible layer right there and I'm going
to go ahead and call this final touches
and I'll start my final touches with
again layer curve or colors curves and
let's just bring up the faint stuff just
a tad yeah that's cool and let's also
now fix our saturation level got a
little bit washed out I'm gonna raise
this up to let's say 1.5 yeah cool
hmmm I know the background just got a
tad raised up a little bit too high so
let me just go back into curves one more
time reset that black point back down
okay zoom in here a bit all right so not
too bad we gets a little bit of the
brownish dust around the objects running
man came out nice
alright nebula came out pretty nice got
a little bit of that odor nebulosity
lots of good detail in here stars are a
little bit bloated and if I did a little
bit more work over here I could probably
fix that a bit but this gives you an
initial idea of how to work with GIMP
after making a stack of your data in
deep sky snacker
so hopefully this made some sense to
review the main points it's just about
duplicating a layer doing an action like
stretching with levels duplicating it
again trying curves trying to neutralize
that background as best you can we did
that through making a gradient and
subtracting it but I'm sure there might
be other good ways to do that in GIMP
and then we just did a little bit of HDR
bringing in this the core just tapping
it down with a first stretch and then
some final touches bringing back in the
saturation and bringing up that outer
nebulosity a little bit so that's it you
can then save it off as all kinds of
different things
TIFF or JPEG or whatever you want let me
know if there's anything that I missed
about astrophotography processing in
GIMP or if you want to see something
different I'd be happy to try to learn
more about it
but again it's not my main processing
tool I mostly use pixinsight and
Photoshop thanks for watching
