June 2006 - Utah-Astronomy - mailman.xmission.com

Collimation
by Chuck Hards 12 Jun '06

12 Jun '06

More evidence that the star-test is the best method of collimation. June S&T, page 94, "Secrets of Telescope Resolution" by Daniel W. Rickey: "It's important to note that the difficulty of achieving and maintaining collimation increases quickly with decreasing focal ratio. For example, if you use a laser collimator to align the optics of a 200-mm f/4 reflector, the returning beam of light must fall within 0.35mm of it's target, which is much smaller than the central hole in most collimators. However, for a 200-mm f/8 instrument, the returning laser beam must be within a relatively achievable 2.8mm of center. Obviously a laser collimator alone isn't going to be enough for a fast telescope - the alignment must be fine-tuned by star testing." I've seen this quite often, especially with larger, truss-tube Dobs that must be assembled before each use. The resolution is rarely what the aperture is capable of, and often really bad- even when the owner has used a laser to "collimate" the optics. (Those grid-projection types are even less dependable.) These folks should take the time to familiarize themselves with the diagnostic capabilities of diffraction rings. It's well worth the effort, and doesn't take much time once mastered. Another benefit is that you can detect other optical problems besides poor collimation. Strain, surface irregularities, over/under correction, etc. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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Re: [Utah-astronomy] Norway Meteorite updated
by sjseebergp＠webtv.net 12 Jun '06

12 Jun '06

Sorry, sent to wrong email address! Jan

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Re: [Utah-astronomy] Norway Meteorite updated
by sjseebergp＠webtv.net 12 Jun '06

12 Jun '06

Darin Some folks contact you two through other clubs links, including Griffith Observatory, etc. Especially folks in Australia and Saudi Arabia, etc. I`ll let Stan decide whether to put Ray on the list. My own thought is to wait til he`s better. Hopefully not a long time. Jan

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Saturn/Mars conjunction
by Chuck Hards 12 Jun '06

12 Jun '06

Patrick, it looks like you have the SPOC refractor reserved for the night of the 17th. Are you planning to use it to image or observe the Saturn/Mars conjunction that night? __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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New photo
by Chuck Hards 12 Jun '06

12 Jun '06

I added a photo to my Gallery, page 4: http://www.utahastronomy.com/view_album.php?page=4 A blast from the past! __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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Re: [Utah-astronomy] Video tape or DVD?
by cpclark＠xmission.com 11 Jun '06

11 Jun '06

On Sat, 10 Jun 2006, Michael Carnes wrote: > Compare that to carrying along a handful of DV tapes. They're > cheap, hold a lot, and aren't compressed. Not compressed? That may depend on how you define "compression". The DV formats I'm aware of do store video in a compressed format--just not a "highly compressed" format. :-) The video data recorded on a DV tape (and uploaded to a computer via firewire) isn't compressed temporally, which is why it works so well for nonlinear editing, but each individual frame *is* compressed with both 4:1:1 chroma subsampling and a DCT. http://en.wikipedia.org/wiki/DV25 Chris

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RE: [Utah-astronomy] Today's APOD is by list member Rob Ratkowski
by Tyler Allred 11 Jun '06

11 Jun '06

Nicely done Rob! Great image. _____________________

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Video tape or DVD?
by Patrick Wiggins 11 Jun '06

11 Jun '06

First, an overview of an experiment I just completed concerning moving video to computer: First I tried it my standard way and ran the video output from a video camera into the video input of a combination VCR/monitor and video taped a couple of minutes of test footage. I then played the video tape video signal into an Analog to Digital converter and captured the video signal on my iMac using iMovie. I was then able to edit the video and export the results in various formats that could be posted to the web or emailed. That done I then ran the same camera's video into a DVR and out to a monitor (as you probably know, in both cases the monitor was in the system so I could see to focus the camera and view what was being recorded). I then put a DVD-R disk into the recorder and recorded a few minutes of test footage. Next I removed the disk from the DVR and inserted it into the iMac and used a free program called HandBrake to convert from DVD format to MP4. Once that was done I imported the file to iMovie and, as before, was able to edit and export the results in various computer formats. In the end the results of both methods looked pretty much the same. So here's where I seek your opinions. Both techniques required manually converting the recorded signal into a format the computer could recognize. That being the case, is there any advantage to recording on a DVD as opposed to video tape (ignoring the facts that DVRs cost more than VCRs and that video tape is probably on its way out)? Thanks for your thoughts, Patrick

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Re: [Utah-astronomy] Meteor hits Norway
by astrodeb＠charter.net 10 Jun '06

10 Jun '06

I saw this on Astromart news. I'd really like to see the impact crater. Debbie "I saw a brilliant flash of light in the sky, and this became a light with a tail of smoke," Bruvold told Aftenposten.no. He photographed the object and then continued to tend to his animals when he heard an enormous crash. "I heard the bang seven minutes later. It sounded like when you set off a solid charge of dynamite a kilometer (0.62 miles) away," Bruvold said. ---- Canopus56 <canopus56(a)yahoo.com> wrote: > --- Chuck Hards <chuckhards(a)yahoo.com> wrote: > <snip> > > A "Hiroshima" sized > > impact would certainly have registered on the > > closest station in the network, so perhaps > > your skepticism is warranted, Patrick. > > A Norwegian newspaper with a seismograph trace. > > http://www.aftenposten.no/viten/article1345940.ece > > - Canopus56 > > > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > > _______________________________________________ > Utah-Astronomy mailing list > Utah-Astronomy(a)mailman.xmission.com > http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > Visit the Photo Gallery: http://www.utahastronomy.com

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Meteor hits Norway
by Patrick Wiggins 10 Jun '06

10 Jun '06

I'm still putting something together for tomorrow's News but if you want an advance look do a Google search for "Norway meteorite" One Norwegian astronomer is being quoted as saying "If the meteorite was as large as it seems to have been, we can compare it to the Hiroshima bomb." Patrick

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