From: "vbertus" <vbertus@yahoo.com>
Date: March 22, 2012 4:04:20 PM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: Help needed with some newbie questions
Thanks for your detailed response Milton. Sorry about my transgression of discussing other software.
--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@...> wrote:
Dear Vince, George and others;
On 22-Mar-12, at 1:51 PM, vbertus wrote:
Hi folks, Astro IIDC newbie here. I read through most of the
manual and it explains the software very well, but I have some even
more basic operational questions so go easy on me. :-)
I am using the software for lunar and planetary imaging with a Mono
PGR Flea3.
1. Camera Settings: Exposure time, gamma, and gain. Previously,
with cheap webcams, I have only worked with exposure time and gain
(called brightness in IIDC?) The gamma setting is new to me, so
what should be my basic thought process in these adjustments prior
to capture? I was thinking adjusting exposure time and gamma first,
then adjust the gain to the minimum amount necessary to get an image
of acceptable brightness on the screen. Would this be correct?
Also, what effects do different amounts of gamma have on the final
image wrt detail, noise, etc?
Gain always increases noise levels, so your choices in order of least
noise effect are exposure, Gamma, Binning and Brightness for noise.
Gamma will generally not affect noise levels - except if you crank it
way up or way down. Generally I would leave it to 1.00 except for
narrowband Solar imaging where your tying to get faint prominences and
the bright disk visible at the same time.
If your shooting LRGB or IRGB (even for planetary), have a look at
using 2x2 binning for your R G B filters. Your Blue and to some extent
Green channels don't carry much detail for planets like Mars and
usually get blurred badly by atmosphere. That's why lots of people
shoot the moon using an IR cut filter, to reduce atmospheric loss.
Here is an example of Saturn I shot L 1x1 RGB 2x2 to keep the
exposure times reasonable:
http://www.outcastsoft.com/AstroImages/Saturn20090502MJA.jpg
Also my software Binning algorithm preserves image scale, so binning
1x1 or 2x2 or 4x4 has the exact same image scale and size.
File size: Man, the 16 bit files are huge, about 1 gb per min @
60fps.
Depending on your target, you can reduce the size by restricting
capture dimensions using Hardware ROI (see page 31 of the Astro IIDC
manual). So if you have a big (i.e. 1300x1300) pixel Flea3 camera and
are capturing Mars, then use Hardware ROI to isolate it and capture a
smaller (say 400x400) pixel area which saves file space.
I was wondering about using a 500 gb external firewire drive for
the capture of the files. Would this preclude me from be able to
get 60 fps in 16 bit mode? I'm running a late 2008 MBP, 2.8 ghz
Intel Core 2 Duo, OSX Lion, so not exactly a cutting edge machine.
That will not work if your expecting to Capture to an external hard
drive. The data is moved into the Mac from the camera over FireWire
800 and then moved out of the Mac over FireWire to the External Drive.
That cuts your available bandwidth in half or less, so you will max
out at about 35 to 40 megabytes per second and reduce the frame rate.
If you use USB 3 or E-Sata or a Thunderbolt Hard drive then you could
do it, but not via FireWire on the same FireWire bus at the same time.
If you have an expandable Mac with an Express or PCI slots, then
adding a second FireWire card will work as long as you keep them on
separate FireWire busses (Camera to the internal FW port - FW 800 Hard
Drive to the Express Card FW port).
Avoid USB 2 as Apple's USB 2 drive support is abysmal and you get
about 2/3 to 1/2 the rate you get with Windows or Linux (using all the
same hardware). It would never keep up with a FireWire 400 camera,
let alone a FireWire 800 camera.
Apple's built in giga ethernet throughput is also mediocre and doesn't
even come close to FireWire 800 speeds either.
2. Guiding: I'm clear on calibration etc. However the manual
seems to imply that I can actually guide on a centroid or limb while
simultaneously using the same camera to capture the image? Would
this be correct? If so, would this lower the useable frame rate for
the image capture?
Yes that's correct. You can guide and capture an object at the same
time. You need to control the Capture (to frames or movies) via an
ApplsScript, which are supplied in the "Other" folder of the .dmg.
Unless your using a really old < 1 gighz single Core Mac, doing both
at the same time it will not have any effect as our Centroid and other
code is all done in SIMD (hand written Altivec and SSE3).
3. Registration and stacking: I have only ever used Registax, but
it of course requires you to convert to an .avi file which I would
rather not do.
You lose 16 bit support too. Apple doesn't support 16 bit Avis
conversions.
How do you find the frame sharpness filters, registration and
stacking algorithms in Astro IIDC as compared to Registax?
I don't use Registax, so I don't know how it compares. I do know that
they still have problems doing MAP, where as we don't. Also Astro IIDC
4.08.00 Alpha is now massively multi threaded for 8 or 16 bit stacking
and has even more SIMD (Altivec and SSE3) optimizations, so the more
CPUs you have the faster it runs - well until the hard drive access
becomes the next bottleneck.
For final sharpening, is there anything on the Mac platform that is
similar and at least as effective as the wavelets function in
Registax? The sharpening algorithms in Pixinsight perhaps?
Astro IIDC does multi spatial Wavelet sharpening in the Image
Processing part and has done so for at least 4+ years now (see page 60
and 73 of the Astro IIDC manual).
4. Further Post Processing: I have migrated completely to
Pixinsight for processing my deep sky astro images and now only use
Photoshop for some final tweaks. Do any of you use Pixinsight for
processing your planetary and lunar stacks, and how do you find the
results?
Just so you know, it's not considered appropriate to discuss other
software on this list. If this was a generic Astronomy list that
would be fine. But this is an Application Specific list to promote and
support Astro IIDC, not other products. I don't want to be an ogre
about it, but that is one of the few rules I do enforce here rather
strictly.
HTH..
Milton Aupperle