From: Milton Aupperle <milton@outcastsoft.com>
Date: March 22, 2012 2:47:44 PM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] Help needed with some newbie questions
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