Hi this is Graham from Jenham's Astro today we're going to try and produce an
image of Messier 45 otherwise known as the Pleiades or the Seven Sisters star
cluster, so we're aiming to produce an image perhaps that's something like this
okay so we're going to do that using a William Optics GT81 refractor and it's
going to sit on top of an equatorial mount but in keeping with the spirit of
this website we're not going to use all the bells and whistles so we're not
going to auto guide we're not going to use bias frames or flat frames we are
going to take a series of light frames dark frames I'm going to stack them together
in deep space stacker and then we're going to enhance them using Paint Shop
Pro so that's the kind of basic process you can follow, absolutely there are ways
of getting a better result a more sophisticated approach than the one I'm
going to show you but this is what we're going to do today and we'll see what we can
produce if we try to keep things simple
so here's the setup we've got a
telescope on an equatorial mount we're pointing at a bright star that is near to
the target and we've got the Canon digital SLR with live view connected to
a laptop so the first thing to do is to focus a telescope I'm using a Bahtinov
mask so this allows you to get a really good focus on a nearby bright star and
then after that you take the mask away and do the light frames so what I do is
I use the timer function to set up a series of light frames all of the same
duration I'm using 60 second light frames and with a little bit of a gap in
between each one to allow the sensor in the camera to cool down, and as we're
running these light frames I'd periodically open one of them up and
using the digital photo professional software and have a look just to make
sure that nothing's gone wrong and that the tracking is still working well and the
focus hasn't shifted because these are all problems you can have and
waste a lot of time. Finally we put the lens cap on the telescope and take
some dark frames
moving on to post-processing so I'm using the deep sky stacker program so
you open up the program and you select the light frames that you've captured in
this case I think in the end I've got just over an hour's worth and put those
into the tool and then do the same with the dark frames so I've only got nine or
ten files here but again they're taken with the same exposure settings as the
light frames so they're all inside deep sky stacker and I choose to check all
the files you can check files that are above a certain number of stars but this
is doing it a simple way and then finally you register the check pictures
and I usually set a percentage here to say I want to use the best 95 percent
you notice that it's got a little bit of amber text there that's telling me I
should I should use bias or flat frames and then
finally off it goes so we're now registering the pictures and this is a
pretty lengthy process so after it's completed that it'll move on to stacking
the frames on top of each other and then finally after you've maybe had a couple
of cups of tea or coffee then you'll get an image produced out of the end which
slowly builds up you can see it slowly populating it looks like a black and
white image that's normal and you wait for it to be fully populated and then
you save the file
okay and then the important thing here is to not use compression and to select
that you should embed the adjustments any adjustments that are made but you
should not apply them that way that any changes will be stored within the file
but they won't change the file itself you want to do that in another software
application so store away the file and then you can close deepskystacker
now I'm using PaintShop Pro basically because it's affordable image processing
software and you open up the frame that we've just generated from deep sky
stacker and edit that frame and really what we do here is a bit of trial and
error but basically we'll repeat a process where we use a function called
levels which generally darkens the frame a little bit and removes a bit of noise
you see I'm setting this lower boundary and then you use
a curves which is a function which you can set up a curve like this stored away
and it effectively amplifies certain sections of the image and you repeat
this over and over again levels and curves levels and curves and the
thing really is to just trial and error with this doesn't appear to be making any
difference but if you persist then eventually if you look at the stars you
start to see a bit of definition around them there we go we starting to see a
little bit of nebulosity which is obviously one of the things we're
looking to see in this particular target so carrying on it's looking better each
time we repeat the cycle and there he goes that's looking looking really good
and now there's lots of similar functions I won't profess to be an
expert you can use other methods of adjusting the the brightness the
intensity of the different parts of the image so for example here you can use
the histogram adjustment and have somebody use the sliders and see what
what it does it's your picture totally up to you how what you like is your
preference and then let's just have another go one more set of curves and
see what that does and then wow that's a big difference so yeah I like that I'm
basically going to take that as my final image and then I'm just gonna add a
little text note here so that I can remember the target and when when I took
the took the image just generally I put that in the corner of the frame again
it's up to you personal preference whether you choose to label label your
image
okay so what else?
so while we're here we can have a bit of a look at the detail of the image and a
few points to note so we can zoom in clearly the stars in the centre of the
frame are nice and round but if you look in the corners you'll notice that
there's a general elongation of all of the stars at the extremes of the field
this is because I haven't used a thing called a field flattener and a fast
scope like this GT81 one will get this you'll get this effect on the outside of
the frame because it's not flat it's not a problem here I'm looking to do a
review of a flattener in the future so we can come back to this and compare before
and after images but overall I'm happy with that and then just if we go
back to compare what we have from deep sky stacker you can see it's almost like
magic the the image processing has gone from just a black and white series of
dots to quite a nice image showing the nebulosity
okay I hope that's been useful thanks for watching