But, is it best to have a small number of long exposures or large number of short exposures, when it comes to demand on computer resources?
Since I'm planning to get an AZEQ6 mount, I am able to go for a shorter number of long exposures, e.g. 5 minutes per exposure.
Hi Mark,
for efficient disk space usage, a smaller number of files is always an advantage. Thus taking long(er) exposures per frame is recommended.
Tip-1: Mind the seeing!
Often overlooked is the fact, though, that for long exposures like 5 min you really
need excellent seeing conditions - because otherwise your stars become bloated due to atmospherical turbulences (scintillation aka "twinkling") while collecting the photons.
I live in the
Alps and we might have Bortle 4 skies on average in our valley, which is useful. But concerning
seeing I abandoned the idea of taking 5 min subs. I take only 3 min subs now, at most. I repeatedly get better stars with 1 min subs ... which of course flood the hard disk and increase processing time.
Tip-2: Siril's /process and /masters folderI am still working with a
13+ years old Linux desktop system exclusively. Siril producess tons of files in the
/process directory and some stacks in /masters. Hundreds or thousands of files have to be written into and accessed from the
/process directory (aka "folder").
Thus I bought a very fast
USB3-SSD (a
SSD stick!, not an external drive that would need a power cable and/or power supply!) and plugged it in the USB3 port.
Then, before starting a huge processing in
Siril, prepare a minimal, temporary working directory for
Siril on that new fast
SSD (=THERE):
Example:# go to the ("traditional") hard disk working directory (=HERE)
cd /home/frank/astro/And-M31
# create real folders on the new, very fast SSD (=THERE)
# the new SSD device needs to be already mounted (e.g.) as
/astroSSD# setup the
"Andromeda M31" working directory THERE
mkdir -p /astroSSD/And-M31/{biases,darks,lights,flats,masters,process}
# being still HERE, link
/process and
/master from THERE to HERE
ln -s /astroSSD/And-M31/{process,masters} .
# check the current directory (HERE) for the twolinks
ls -al
...
...
... ......./masters -> /astroSSD/And-M31/masters
... ......./process -> /astroSSD/And-M31/process
...
Okay!
Note: We still have and
keep the folders and contents of
./biases, ./darks, ./flats and ./lights HERE: These files are only
read once by
Siril. The by far most time consuming part is accessing, reading and
writing all those interim files in the
./process folder!
Thus, when using
Siril manually (without scripts) this would be everything needed - we could star!
When using preprocessing scripts to let it all happen
without interaction, then we need to prepare some more things - simply because
all Siril scripts make use of "cd ..", which is a
relative directory (folder) change to the
"parent" directory of the current directory,
Siril cannot find any files in the subdirs
./biases, ./darks, ./flats and ./lights folders' contents from that
"parent" directory, because we created them before and they are still empty. So we need to
symbolic link all those files from HERE to THERE:
# go THERE (/astroSSD/And-M31) and link (don't copy!) all files within
./biases, ./flats, .darks and
./lights from HERE to THERE
cd /astroSSD/And/M31
for dir in biases flats darks lights; do cd $dir; ln -s /path/to/original/$dir/* .; cd ..; done
Go!Being at the right place now (the former THERE called directory "/astroSSD/And-M31") already, we can now start
Siril and set the current directory THERE (/astroSSD/And-M31) to be Siril's
working directory.Launch an appropriate preprocessing script from the
Scripts menu ... and
get a coffee. But hurry up ... because you'll have much less time than expected for it!
Good success and clear skies,
Frank
