okay
Today i'm going to be using Siril on
my mac
to do the stacking and some of the
pre-processing
tasks and then probably finish off with
gimp this is
the second part of
my lagoon no tracker series so if you
haven't watched the first part
where i show how how i captured and
planned for this shot
i recommend watching that first the link
will be in the description
and cyril is a free open source program
that's really cool for
as it says here astronomical image
processing uh
the website is s-i-r-i-l.org
and today i'm uh i think last time i
showed uh
cyril i went to the download tab here
and just used the latest
release uh that wasn't uh a beta release
but uh
um the the full release that they do
um today though i just i'm really
interested in their their beta release
that they talked about here in the news
tab
um it's also available here on the
download tab
under beta testing
and the reason i'm so interested in this
one is it's a it's basically
a uh um
early release of their 1.0 version where
they've updated
the user interface and done a bunch of
other cool things
including 32-bit and all kinds of things
so
um i i'm gonna try this
uh we'll see if we run into any bugs
since it is a beta uh if you're not
comfortable with
it with running beta software then you
can always watch my earlier serial video
to see
um the 0.9 release um okay anyways
i'm i've gone to the news tab here
clicked on
this 1.0 beta testing
article and then if you scroll down to
the bottom of the article there
are pre-packaged downloads for
uh windows mac os and debian so i'm
going to click on
mac os because that's what i'm running
here
and then just go ahead and open the the
dmg file
it's a package file for installing mac
software
and just drag this to my applications
folder
and replace the existing version
okay i can eject this temporary drive
now
close out of chrome
and i'm just going to go here to
my finder and click on go to
applications
and double click on cyril
and if you get this when you first
install serial that it can't be opened
because it's from an unidentified
developer this is a new mac
security setting one way to get around
it is you can just
right click on the application and click
open
from the right-click menu and then
instead of just saying cancel you now
have this open button right here
and that will let you open the
application once you do that once it
will remember that setting and will open
it
every time like that without giving you
the security warning
okay there's a little thing here say
saying that if you that they're going to
show us an introduction that's pretty
cool
i'll say okay okay we've gone through
the little
tutorial i'm going to go ahead
and make cyril full screen here
and the first thing that i'm going to do
is change my working directory
which you do by just clicking this
little home icon right up here
and i'm going to change my working
directory to the desktop
and then this lagoon folder that i
created
and if you're new to serial let me show
you this folder
this has my biases my darks my flats and
my lights just like i showed you
uh in the part one of this video how i
sorted those we did we did all that
by looking at what was on the camera and
then sorting
the raw files um so we're we are all
ready
the to use a script um inside serial
because we have a working directory
and then inside that working directory
we have these four working directories
that have to be named
just like this biases darks flats and
lights
okay i'll open backup serial here
and i'm going to go to
scripts and
i'm going to do one shot color
pre-processing
all right and it
starts you can read about what it's
doing over here in the console
basically it's going to first create
our master bias master flat master dark
then it's going to calibrate the light
frames
and register them and stack them
together
so you can of course do all of this
manually right here just by following
along
with pre-processing meaning calibration
registration
stacking so forth um but we're i'm gonna
do it the easy way today
um just to make this video a little uh
shorter
and um uh use
the script osc for one shot color
pre-processing okay i'll let it do its
thing here and it'll probably take uh
quite a while because we're dealing with
hundreds of frames and then
when it's all done we'll see what it
produces
okay it's done with pre-processing so
now i'm just going to open up the result
which is right here in my lagoon folder
result.fit
and when i open it it's not going to
look like much that's because i'm in the
linear
view mode so if you've used other
programs that do stacking a lot of times
when it's done
it'll just look sort of black like this
with maybe a few little white dots that
are
star cores but this is completely normal
result what we want to do is turn on
the pre image preview that will give us
a stretched view but only as a preview
it's not actually going to apply the
stretch yet
and so we can do some work like
background extraction and color
calibration
when the image is still in this linear
state and then those
processes will work better so to turn on
that preview if you look down here at
the bottom
of the window there's this little
display mode uh option and it says
linear
and i'm just going to change that to
auto stretch
okay and i guess i had the red channel
selected up here so this is the red
channel
there's the green channel there's the
blue channel
so you can see uh for some reason the
green channel
came out quite a bit brighter than the
red and the blue
so if we look at the rgb image it's very
green but that's fine because we're
going to do
the first thing we're going to do is a
photometric color calibration which is
going to correct
that color balance issue and so
to bring up that process we go to the
image processing menu up here at the top
and go down to color calibration and
then photometric color calibration
and what we want to do in here is just
type
in the relevant details right here
so uh well actually sorry
so starting at the top uh you're first
going to search for
an object that is in the picture so
that's as close to center as possible so
i'm going to do
m20 which is the triffid nebula because
that's in the picture
and it's a little bit closer to center
than the lagoon which is m8
and click find
then you just uh can click on it and it
will put in the
the r a and deck of that object uh
telling you
that's where this picture is pointed
that's good
and then we're going to put in the focal
distance which was 50 millimeters
and the pixel size in microns so if you
are if you don't know what your pixel
size is
what you can do is just
um type in the name of your camera
so i was using a canon 60d and
pixel size and
if it doesn't pop up right here like in
this case it did 4.3 microns
if you don't see it there like is a
featured snippet from wikipedia it you
usually can find it in
in this website um digicam database
uh and so pixel pitch is the same thing
as pixel size so it's saying
4.2 microns or rounded up 4.3 either is
going to work
so i'll just type that in here i'll use
the more accurate one of 4.29
and then that tells me that i have a
resolution of 17.6
um pixels per arc second um
which is very very what we call under
sampled
meaning uh if we really zoomed in on our
stars they would look sort of blocky but
that's okay because this is a wide field
image
okay and then i'm just going to leave
everything else automatic and
click ok uh that
failed because it said it couldn't plate
solve so i have this hunch that the
reason is is because
of this black border over here so i'm
going to try this again
but first i'm going to crop the image
and the way to crop
in cyril is you just draw out a box of
where you want to crop
so i'm going to try to get as much of
this in here as possible
cropping out this black part at the edge
and then you just right click and choose
crop
okay then i'm gonna try running that uh
photometric color calibration again
and just see if this works any better
okay my hunch was correct
it was able to plate solve that time
after i did the crop
and it did
seem to apply the correction
so i'm going to go ahead and close this
and go back to my rgb
and you can see now it's a much better
color balance um okay so
next up uh what we want to do is um
do a little bit of a background gradient
removal well at least try it i'm not
sure if it's going to work on an image
that has so much
uh it's filled with the milky way so
much but i'm just interested to see
if it can improve the image a little bit
so
let's go up to image processing and go
down to
background extraction and i don't want
to
click generate because that
automatically applies the samples and
it's not very intelligent about placing
them it just places them in a grid
basically
and since there's so much milky way and
nebulae and stuff in this
image i want to place them myself
and i'm going to place them more
strategically
so i'm going to do it just by
left-clicking over here in the image i'm
going to do
oops it says you can't place them on the
rgb
so i'm gonna have to place them here on
the red that's fine um
so i'm gonna place them uh
sort of um on the dark
nebulae rather than
in this place that's really in the
places which are really
bright if you can in your image
you won't actually place it on the
background sky but i've
found that at least with pix insight
that placing
samples on the dark nebulae can work
too at least for an image like this one
so and we just want to try to get as
much coverage as possible
you don't have to place that many
samples usually something like
8 to 10 is enough this this corner might
be an issue because there's not really
anything
super dark down here but i'm just going
to place it there
i'll place one down here okay so
again this is an experiment we'll see
how it works if it looks really wonky
then
we can undo it i'll go ahead and apply
okay it's telling me not enough samples
so okay i'll do some more
and again when i'm when i'm placing
these samples i'm just trying to
at this point just basically trying to
pick darker parts of the image
and avoid big stars okay we'll try that
okay it did it i'm gonna go ahead and
click close
and uh here's before
and here's after
and uh it's a mixed bag
uh you know i don't think it actually i
think it hurt more than it helped
uh because it's just it's just
changed the the color balance and but
there's it it created
different problems uh but didn't really
uh
work how i wanted it to so uh
if someone has better suggestions for
for how to do that
uh please let me know in the comments
but i'm gonna i'm gonna not
apply that background extraction with
this milky way shot because it's just
it's not working and and that's pretty
common even in pics inside i i would
have trouble probably
extracting a clean background out of a
shot that's this filled with
milky way and honestly there wasn't too
much light pollution so it i don't know
if it really even
needs that i'll probably just crop some
of this side in this site a little bit
anyways
okay um let's keep moving here there's
not much else to do
in cereal before we move on to the new
image manipulation program
for some final touch-ups
there's probably actually a lot more you
could do in here but i just still am
learning the program
so uh sometimes what i like to apply a
little bit of color saturation
in this linear state um
and so i'm just going to apply something
like
0.2 let's see if that made any
difference at the preview
maybe able to do a little more let's try
0.4
okay yeah i think that looks better so
applying a little bit of
saturation uh to the linear image i
think
sometimes helps uh later on in the
processing so i'm gonna apply that
okay and if we go back to linear
you can see this picture is still uh in
its linear state we just have this
auto stretch turned on which is why
we're seeing it like this okay um
before i save this to move into
gimp let's change it to 16
bits converting
it says may lose some precision that's
okay
just click ok there there we go save the
image in a different name
so right next to the save command is
that and i want to save it as
a tiff file there we go so just pick
tiff from this list
and click save
oh and i guess we didn't have to switch
from 32 to 16 up there we could have
just done it
right here in the saving command so you
can
ignore that earlier when i change from
32 to 16 there you can always just do it
i guess when you save the tiff
so this is what we want 16 bit integer
click save
okay and now we're we're done with cyril
we're going to move on to
gimp
okay i'm using gimp 2.10 that's what i
recommend i think it's the latest major
release you can always just download it
straight from
their website and we're going to do file
open
and pick this serial result
dot tiff that says
it contains orientation metadata um
i'm saying i'm gonna say keep original
i'm not sure what that's about
okay so here is uh
gimp the first thing i'm gonna do is i
wanna fit the whole image into the
window here so i'm going to go to view
zoom and do fit image in window
okay and then the next thing i want you
to do is if you see brushes over here
see if you have a tab for histogram if
you do go ahead and switch to that
and make sure that your histogram is in
rgb mode
if you don't see the histogram just go
to dockable dialogs
and pick it from this list right here
and it should come up
i'm just going to go up here to the
colors menu and go down to levels
grab my midtone sliders this little
triangle right here in the middle
and drag it over to the left to start
stretching the image
and click ok and you should see this
this histogram peak come out here and
what we want to start doing we're just
going to keep going back to that colors
levels command is stretch the image so
basically
we're taking something where the dynamic
range is very compressed
all the information is compressed into
this little peak right here and we want
to stretch it out make
it wider and we're going to do that by
taking the shadow slider
and moving it to the right and taking
the mid-tone slider
and moving it to the left
and each time we do that it should it
should make the
the width of this histogram information
wider meaning that we're having we're
getting
more shadows midtones and highlights by
stretching it out
and adding contrast so i'm just going to
do that a few more times
and when you take this
shadow slider you can move it pretty far
over here to the right you never want to
pass the peak though so i always bring
it to just up to the left side
of the peak of the information but never
passed
all right that's a good enough stretch
for now
next thing i'm going to do is the image
somehow i guess that was what that
message was about is that it somehow
got rotated 180 degrees so let's go
ahead and
uh rotate it back to how we had it
before
so i think that's just under view
flip and rotate and we're just going to
rotate 180.
okay there we go and then um there's
still a little bit of issues on the
edges here of the image
this this corner this corner this corner
i'll have little black edges
and there's a little bit of a color
shift from green to magenta across the
image this way so i'm just going to crop
away a little bit of the image here
just with the crop tool
and i'm just going to start up here in
this
corner and
bring it down like this and just crop
away
and you can take these corners and
adjust it
and i'm just trying to adjust it so that
i have the omega
the eagle the trifid and the lagoon all
still in the image
and that i can just get as much of the
image as i can without getting
sort of the weird stuff in the corners
okay that looks good i'm going to go
ahead and press
enter to accept that crop
okay next what i'm going to do is i'm
going to add some saturation to the
image i'm going to go back to the colors
menu and go down to saturation
and just take this scale slider here
and move it over to the right
i'm going to move it to about 1.5
okay i'm just going to zoom in on the
image now a little bit
just doing a shift equals or plus
on my keyboard to zoom in
just check out a few of the details here
oh this is weird it got it also got
flipped
uh horizontal because the trifid should
be on this side of the lagoon okay
so let's let's fix that uh
that's under view
flip and rotate let's flip uh
horizontal horizontally i think
yes okay sorry i don't know what all
these flips and rotations are about but
now it's now it's right so this is
looking really nice
i can see a lot of detail in here i
think we can add
even a bit more saturation though so i'm
going to go back to colors
saturation and add some more
yeah that looks good so i added an
another 1.3
to the scale and i think this is the
is the right amount of saturation now
okay i'm really impressed by this i
think it actually is looking
better than our results in deep sky
stacker and
gimp or deep skystacker in photoshop
it's a little bit more subtle but also
not as noisy
and uh i think
more polished looking okay um
next we're going to remove the stars
from the image and then
add them back in and so this is
for this we're going to use a another
piece of software so we've
started in serial we've moved into gimp
we're now going to bring it out of gimp
use another piece of free software
called star net plus plus
and then we'll finish back in gimp so to
use starnet plus plus we want to
save this as a tiff file again
and so i'm going to do file export as
and i'm just going to save to the
desktop and call it
lagoon for starnet
dot tiff okay so from google i'm just
going to
um search for starnet
plus plus like that
and the first search result here is
this sourceforge.net download site
and that's what you want to go to
and then go over here to files
and if you do have pix insight you can
get the pix insight module
but um assuming you don't have pix
insight we're going to just get the
standalone version
and so you would just go into version
1.1 here
and then pick your operating system so
if you're on windows pick windows
or win if you're on mac pick this mac os
and if you're on linux pick the linux
one
and i'll just click on that
and then it will start downloading here
okay it's finished downloading so i'm
just going to
open up those open up the zip
folder and put it on my desktop
and if you look at the readme this is
where it's going to give us instructions
on how to use it
okay and basically we just have to look
at this little um
shell file here this is a just a little
command that's given and if we open that
up i'm just going to open it
with a text editor but
you can open it with any kind of text
editor it doesn't matter
all we're going to do is just change
this right here
to the name of our file so i'm going to
choose i'm going to say
lagoon for
starnet dot tiff and then i want the
output
to just be lagoon starless
and then the last thing here is i'm just
going to change the stride number to 32
what that means is that it will take a
little bit longer to process
than with a stride of 64. but it will
give us a better result
for removing the stars especially with
wide field images like this one i'm
going to go ahead and save that script
close out of that okay with
that done we've edited the script 32-bit
stride
it has the right file name we can go
ahead and run the script the way we do
that is through
a command line program so i'm just going
to use the built-in
command line program on mac which is
terminal
and to run it we have to do two things
we first have to move to this directory
so i'm just going to type in
cd space to do change directory command
and then
drag this folder over so cd
space and then go to the folder
hit enter we're now inside the folder
and from there i can run
this command just by dragging it over
and hit enter again
okay and then it starts its thing
um it
reads the file it tells me yep it's a
16-bit file
with three channels here's the height
and the width
here's the cpu i'm
using with tensorflow
and then this is the number of tiles
that it's going to break
the file up into and then it's going to
look at each one and remove stars from
those tiles and then
recombine the image and then down here
it tells me how long it's going to take
for that
to happen um a percentage as it's going
and you can see it just went from zero
to one percent
so it does take quite a while probably
at least an hour
maybe two on an image of this
size okay back in gimp here i'm going to
do file open
and open our new starless image
and we're just going to apply a few uh
tweaks to it
make it pop a little bit more so i'm
going to go to colors
curves which curves is basically just
like a more advanced version of levels
where
you have your whole range of shadows to
highlights based on this
line right here and you can place points
wherever you want
and bring things up and down and so what
i'm going to do is i'm going to
bring up the mids and bring
down the shadows with this curves like
this
this is called creating an s curve
because it makes sort of like an s
okay and right now i'm in the value mode
i notice that
in the shadows there's a little bit too
much
green so i'm just going to bring
down the green just a tad
like that just by eye it's a pretty
subtle adjustment
and i think there's a little bit too
much blue
too so i'm just going to bring that down
just a tad
okay that's good
i'm just going to go back to value and
now just bring up the whole
image just a little bit perfect okay
i'll click ok
and then um i'm going to go back here
and increase the saturation just a bit
let's just do
1.15
okay and now that
this image is boosted let's add back in
our stars
we can do that by just doing edit
uh copy visible
and edit
paste
now why did it come in flipped and
flipped again i am
gonna have to figure that one out is
something that i did when i opened this
image for the in the first place out of
cyril it was like
flipped and then i i guess i chose the
wrong thing
sorry about that anyways we can rotate
this layer
okay we want the tools transform tools
and i want to flip
that layer there we go
and i want to rotate it
180 degrees
okay
all right so now we're back on where we
should be
um i can just call this pasted layer
stars
and to this stars layer what we want to
do is
change the mode from normal to screen
um so right up here in the in the layers
panel you'll see the word mode and then
it says normal just click on that word
normal and change it to screen
and the first thing you'll see is the
image will get a lot brighter
but you'll see a lot more detail in the
image
and that's perfectly normal basically
what it's doing is it's it's uh
it's applying a sort of multiplication
of the two images but but
making the dark parts of this top layer
transparent so that you're seeing
into the image below
and what we have to do now is reset
our values our black point and our white
point on this image
and we can do that with curves but to do
that we first want to just basically
create
a copy of what we see here so to do that
we're going to go to
layer new from visible
so now we have this new visible layer on
top and on that visible layer i'm going
to do
colors curves
and i'm going to reset the black point
just by dragging this
shadow slider over
and then i'm just going to bring down
the shadows just a little bit and bring
up
uh no actually i think just the whole
image should just get a little bit
darker
that looks better um we still have this
sort of green
cast in the middle of the image here
so let me just see here if i can
fix that with a green curves
you know that looks pretty good that
definitely helped a lot um
it maybe is making the top part of the
image a little bit too blue
by removing the green from the middle
if i really go for it you can really see
the top part of the image goes blue
so let's do this let's
click ok
and let's make a copy of this visible
layer
or duplicate it so i'm just going to do
right click
duplicate layer so now we have visible
copy
i'm going to go into this visible copy
layer
and basically
bring down the blues in the top part of
the image here
until it looks right
there we go but of course now that just
just uh now we have the same problem in
the middle of the middle getting too
green
but what we can do is with this visible
copy layer we're going to add a layer
mask
so i'm just going to right click and
choose add layer mask
and you can
leave it on this default initialize
layer mask to white that's fine
and then we're going to add a gradient
to
this layer mask
so let me grab my gradient tool here
and in the default mode it goes from
white to black that's exactly what we
want
and we want the top part of the image
for this visible copy to apply but down
here in the middle
we don't want it to so i'm just going to
drag a gradient
from the top to the middle of the image
and hit enter to accept that gradient so
you can now see there's a gradient
drawn onto the the layer mask on this
visible copy
if i turn that layer off and on you can
see what it's doing is it's correcting
that
really strong blue cast on the top of
the image
okay there's definitely more that we
could do with this but i'm going to call
this
good i really think it looks pretty neat
um
a lot of detail in the milky way and the
lagoon and trifid
let's go ahead and save it so of course
to save in gimp we can just do
file save and save in gimp's
default format of xcf and this way we
could return to this and keep messing
around with the layers here in gimp
so i'll just call that lagoon.xcf
save that to the desktop
and then to save in other formats you do
file export and
you can just put in whatever
ending you want so if you wanted to save
it as a 16-bit tiff you just leave there
that is tiff i'm going to save off a
jpeg so i'm just going to do
jpeg jpeg is good for you know sharing
on social media or online because it
it's compressed so you can
send it more places and it loads faster
i'm going to go ahead and export that
i always exported 100 quality so
as little as compression as gimp will do
go ahead and export
and let's go ahead and take a look at
our final result here
okay um it's maybe a little bit um
over saturated for some people's tastes
maybe i could dial that down a little
bit and then we
still have some color cast issues like a
little bit too red
in this corner two red magenta in this
corner
a little bit too green in the middle and
some other stuff up here
so we could continue working on those
i'm using that same tactic i showed you
where if you apply
a new layer and then apply a gradient
mask you can
fix some of these color casts but for a
first start this is definitely pretty
cool looking
this is under 10 minutes um not tracked
just
on a tripod with my canon 60d
which is a stock uh canon 60d camera and
my 50 millimeter canon lens
let's go ahead and zoom in a little bit
here
just to show you some of the details
another thing we didn't do is any noise
reduction so
it is a little bit noisy because it's
only uh
under 10 minutes of data but it looks
pretty good i think
some nice detail here in the core of the
lagoon
we even have that sort of extension of
the lagoon over here
the trifid looks nice this star cloud
looks nice
we have a little cluster over here i
don't remember i think that's a messier
cluster but i can't remember what it's
called
and then we have the omega and the eagle
up here at the top
and then of course really it's meant to
be seen
in full like this with the whole extent
of these brilliant milky way
stars because this is right into the
core of the milky way
okay till next time this has been Nico
Carver from nebulaphotos.com
and clear skies everyone
