Rick Lyons wrote:> > On 28 Aug 2003 13:17:36 +1000, p.kootsookos@remove.ieee.org (Peter J. > Kootsookos) wrote: > > >Jerry Avins <jya@ieee.org> writes: > > > >> It's obviously a disk with binoculars, but the seeing hasn't beem good > >> enough for me to see the polar caps with my 5" scope. Not likely > >> tonight, either, but maybe tomorrow. > > > >Here in Brisbane last night it was glorious astronomy weather. The > >city lights are a little bright for "serious" astronomy, but for > >seeing Mars it was great. > > > >Ciao, > > > >Peter K. > > Hi Dr. K, > > Northern California had good viewing last night. > > When I first saw Mars I thought it was an > airplane, so I looked in another direction. > Then I noticed the 'airplane' wasn't moving. > Wow! > > Now I wished I hadn't donated my home-built > 6-inch reflector to the local high school. > I wonder if I could have seen Mars' > polar caps with a 6" reflector and my old eyepieces. > > See Ya, > [-Rick-]You probably can, just. If you want to see it on your monitor, look up http://home.houston.rr.com/klarson/mars2.jpg Keith took that picture less than a week ago. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
linear phase iir filters
Started by ●August 26, 2003
Reply by ●August 28, 20032003-08-28
Reply by ●August 28, 20032003-08-28
Andor wrote:>...> > My astronomy program tells me that seeing should be better in early > September, when Mars will rise higher into the sky.And the moon will be brightening. BTW, I use Skyglobe. Nice shareware.> > Perhaps you will even be able to see the canali with the binoculars > then :). > > Regards, > AndorJerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 28, 20032003-08-28
Jerry Avins wrote...> > And the moon will be brightening. BTW, I use Skyglobe. Nice shareware. >Hi Jerry For my screen saver I use the public domain 'Sky Screen Saver for Windows' by John Walker the founder of Autodesk, Inc. and co-author of AutoCAD. http://www.fourmilab.com/skyscrsv/ Another more serious program for astronomy that I can recommend is MegaStar. This is a 'depth of information' kind of program that is a little less glitzy than something like RealSky, but thats not what I need! If you want to see what mars probably wont look like, but never the less was derived from data through my telescope, have look here. This is a simple stacking of a number of video frames with a little bit of contrast and color push. I am still working on a filter that best matches the data. http://home.houston.rr.com/klarson/mars2.jpg At least this way I get to have some fun from getting no sleep Best regards, Keith Larson
Reply by ●August 28, 20032003-08-28
In article ce45f9ed.0308280134.66b38138@posting.google.com, Andor at an2or@mailcircuit.com wrote on 08/28/2003 05:34:> santosh nath wrote: > ... >> It can be shown for such system, >> H(z)=z^-(N-1)/2HZP(z) >> where H(z) is transfer function of linear phase filter and HZP(z) is >> that of >> a zero phase filter i.e linear phase filter is a delayed version of >> zero phase filter. >> >> Now if the original poster has a requirement of causal system then the >> above >> MATLAB function can not serve the purpose. > > There is no causal linear-phase IIR filter (except for the identity) - > just approximations.and these Truncated IIR filters are such approximations. they are actually FIR filters built with IIR components...> I think the OP is looking for the time-reversal > algorithm, as he explained himself in another post. This can > implemented using the filtfilt() function.... even with the filtfilt() function, there is an issue of how long to keep your IIR filter ringing after the last input sample goes in. with an FIR, the answer is obvious, but in either case, you need some finite cutoff so you can flip the sequence around and run it through the same filter backwards. r b-j
Reply by ●August 28, 20032003-08-28
an2or@mailcircuit.com (Andor) wrote in message news:<ce45f9ed.0308280137.6a89991b@posting.google.com>...> Jerry Avins wrote: > > > > robert bristow-johnson <rbj@surfglobal.net> writes: > > > > > > > can you guys down-under see Mars as well as us guys? it's even a little > > > > cloudy and i can see it really well. > > > > > > Yup! It's pretty impressive. :-) > > > > > > Ciao, > > > > > > Peter K. > > > > > > -- > > > Peter J. Kootsookos > > > > > > "Na, na na na na na na, na na na na" > > > - 'Hey Jude', Lennon/McCartney > > > > It's obviously a disk with binoculars, but the seeing hasn't beem good > > enough for me to see the polar caps with my 5" scope. Not likely > > tonight, either, but maybe tomorrow. > > > > Jerry > > My astronomy program tells me that seeing should be better in early > September, when Mars will rise higher into the sky.The term "seeing" refers to local visual conditions. Some times the air is stable, at other times various atmospheric effects make the air (and thus the view) "wobbly". While elevation does have an effect on the "seeing", I don't think Mars will rise very much higher above the horizon in the next week or three. As for "seeing", this summer I have used a spotting scope to view a beach full of birds. The house is on one side of a fjord and the beach on the other, so I view over water. Even at a modest distance, some 500 to 700 meters, and at not all that high magnifications (30-40x), the view was "glary" and unstable whenever the sun was shining. I guess it was the humid warm air rising from the sea surface that made the view unstable [*]. For birds, the best days appears to be the cool overcast ones, with no wind. Unfortunately, overcast weather isn't entirely ideal for astronomy... Rune [*] Actually, this isn't *completely* off the comp.dsp topic: The bad "seeing" is in fact a very visual, easily understood manifestation of degraded signal coherence in a rapidly varying optical transmission channel.
Reply by ●August 28, 20032003-08-28
Rune Allnor wrote:> The term "seeing" refers to local visual conditions. Some times the > air is stable, at other times various atmospheric effects make the > air (and thus the view) "wobbly". While elevation does have an effect > on the "seeing", I don't think Mars will rise very much higher above > the horizon in the next week or three.I was quite impressed when I read about the VLT down in Chile - it uses a Laser beam focused into the stratosphere to measure the "wobblyness" of the atmosphere. Computers (DSPs?) then "deconvolve" the picture to get best viewing quality. Another thing that impressed me was the visual delay lines of the VLT: The four telescope mirrors (perhaps 100 meters apart) can be tuned on the same spot in the sky, giving a resolution of a mirror with the diameter of the distance of the telescopes. To avoid phase cancellation when mixing the four inputs, the visual signals are run through a system of moveable mirrors which delay the signal for maximum performance at some given spectral band. BTW, Jerry, I use Starry Night Backyard ($49), which I'm very happy with. Regards, Andor
Reply by ●August 28, 20032003-08-28
Reply by ●August 29, 20032003-08-29
"Rick Lyons" <ricklyon@REMOVE.onemain.com> wrote in message news:3f4e0b1a.15888312@news.west.earthlink.net...> On 28 Aug 2003 13:17:36 +1000, p.kootsookos@remove.ieee.org (PeterJ.> Kootsookos) wrote: > > >Jerry Avins <jya@ieee.org> writes: > > > >> It's obviously a disk with binoculars, but the seeing hasn't beemgood> >> enough for me to see the polar caps with my 5" scope. Not likely > >> tonight, either, but maybe tomorrow. > > > >Here in Brisbane last night it was glorious astronomy weather. The > >city lights are a little bright for "serious" astronomy, but for > >seeing Mars it was great. > > > >Ciao, > > > >Peter K. > > Hi Dr. K, > > Northern California had good viewing last night. > > When I first saw Mars I thought it was an > airplane, so I looked in another direction. > Then I noticed the 'airplane' wasn't moving. > Wow! > > Now I wished I hadn't donated my home-built > 6-inch reflector to the local high school. > I wonder if I could have seen Mars' > polar caps with a 6" reflector and my old eyepieces. > > See Ya, > [-Rick-] >I like Keith's picture - great to see what can be done on an individual basis. The "big bucks" version can be seen here: http://www.ananova.com/news/story/sm_813543.html Regards Ian
Reply by ●August 29, 20032003-08-29
Andor wrote:> BTW, Jerry, I use Starry Night Backyard ($49), which I'm very happy with.I use the Linux-based xplns ($0.00). I hear KStars is also pretty good (also $0.00). -- Jim Thomas Principal Applications Engineer Bittware, Inc jthomas@bittware.com http://www.bittware.com (703) 779-7770 Dyslexics of the world, UNTIE!
Reply by ●September 2, 20032003-09-02
Hi Ian You may want to re-check my web page tommorrow as I will proabably post some more pictures. The seeing quality this last weekend was considerably better :-) If you are wondering how I do this, my set up is a low-light PC-165 color camera from Super-Circuits, Clestron CG-14" Schmidt Cassegrain, 8mm video tape/monitor combo (arguably the weakest link), Radeon 7500 video capture card and some AVI stacking software that I wrote. In this last go-around I am achieving 0.5" (arc-sec) or better. A lot of the delay is me poking away at the AVI stacker. Best regards, Keith Larson Ian Buckner wrote:> > I like Keith's picture - great to see what can be done > on an individual basis. The "big bucks" version can > be seen here: http://www.ananova.com/news/story/sm_813543.html > > Regards > Ian+------------------------------------------+ |Keith Larson | |Member Group Technical Staff | |Texas Instruments Incorporated | | | | 281-274-3288 | | k-larson2@ti.com | |------------------------------------------+ | TMS320C3x/C4x/VC33 Applications | | | | TMS320VC33 | | The lowest cost and lowest power | | floating point DSP on the planet! | | 500uw/Mflop | +------------------------------------------+
