March 2009 - Utah-Astronomy - mailman.xmission.com

Re: [Utah-astronomy] Magic Moments
by Jim Gibson 19 Mar '09

19 Mar '09

Jay, Joe took the words right out of my mouth. I have had similar moments with my daughter, my sons and my grand kids. In fact my grandson, stephen, just the other day said, "Hey 'grampa', when are we going to go look at stars and drink hot chocklet?" Jim

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Re: [Utah-astronomy] Bias & Flats
by Jim Gibson 19 Mar '09

19 Mar '09

So, Jerry in your dark library you only need the 16 images (4x) per time/temp? When I first looked up Berry’s book on the web I believe it was going for $99.00. I was able to find a copy for $30.00, so I better check out the version of the AIP4WIN CD that came with it. The book is very thorough. It is like a collage level course. I have been reading mine with a pad of paper and a calculator handy to work out the answers for my 350D. I am still trying to figure out the differenced between what applies to a “one-shot” DSLRs and the LRGB try-color guys. One thing I learned is that DSLR guys can’t bin at the imager and don’t bin in processing. I can bin a DSLR later in post processing, but I only get noise reduction at the much greater cost of loss of resolution. It's generally not worth it for DSLR. But, I still read about it. I may get a LRGB outfit someday. For the time being I want to learn all I can using what I have. Jerry, I am glad to know you are so versed in these things. I am sure when I can’t understand a concept you will be able to enlighten me. I am heading back to the book right now. Jim --- On Wed, 3/18/09, Jerry Foote <jfoote(a)scopecraft.com> wrote: From: Jerry Foote <jfoote(a)scopecraft.com> Subject: [Utah-astronomy] Bias & Flats To: utah-astronomy(a)mailman.xmission.com Date: Wednesday, March 18, 2009, 1:58 PM Hi Jim, Actually taking the bias frames would be doubling your effort. Since the darks will already contain the bias information then merely subtracting the darks from either the actual image or from the flat image will remove the bias noise. The only time bias frames need to be taken is if you are going to scale your darks for either exposure time or temperature. Frankly scaling darks is usually a poor substitute for keeping a set of Master darks handy for both exposure time and temperature. Usually darks are very stable over a long period of time (months or even a season). Taking 64 darks might be a little overkill as it produces an 8x reduction in noise. Comparing this with the noise from the actual frame puts it down in the mud. With that said, when it is cloudy and you are tired of the tube why not take them. It will be harder to get sets with varying temperatures which, with their relatively long life, allows you to get them throughout the season and use them next season. Strictly speaking the flats should also be taken at the temperature of the actual image as there is a very slight change in pixel sensitivity with changing temperature. Again this is way down in the mud. I really like Berry's book. It is always ready at hand for that nitty-gritty question. By the way there is a new version of AIP4WIN that has many enhancements particularly for DSLR imaging. Check out the Willman-Bell web site. Jerry Foote ScopeCraft, Inc. 4175 E. Red Cliffs Dr. Kanab, UT 84741 435-899-1255 jfoote(a)scopecraft.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://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com

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Re: [Utah-astronomy] Magic Moments
by Joe Bauman 19 Mar '09

19 Mar '09

Great! That's what it's all about. -- Joe --- On Thu, 3/19/09, JayLEads <jayleads(a)gmail.com> wrote: From: JayLEads <jayleads(a)gmail.com> Subject: [Utah-astronomy] Magic Moments To: "Utah-Astronomy" <utah-astronomy(a)mailman.xmission.com> Date: Thursday, March 19, 2009, 12:03 AM Not sure if anyone likes these type of posts but I'll share it nevertheless. Sometimes while observing, I find I have these moments that for me are truly magical. Often I observe alone and though comfortable being alone and doing this, I find sometimes the company of someone else nearby is not only comforting, but a great way to build friendships. Tonight I got everything set up in the backyard prior to the son, and had the scope cooling. I came out and as night came on about 8:30p.m., I began to look for the Planetary Nebula NGC 2371/2 in Gemni. I was able to locate it rather easily and spent the next forty five minutes or so, observing, logging details and sketching it. Toward the end of this object, a knock was given from inside the backdoor (they way the wife or kids let me know they are coming out so I'm not blinded) and out came my 16 year old daughter. I was finishing a low power sketch of the PN and she suddenly started asking me questions after identifying the two constellations she knows, Orion and Ursa Major. She saw a "fuzzy" in the sky and asked what it was. I replied that she should go get one of my binoculars and look. She did and she then described to me that the fuzzy was made up of many stars, with the brightest making up a dipper shape. She asked me the name and I told her and afterwards she said she'd call it the seven sisters since that was easier to see. I was done with NGC 2371 and so swung the scope over to the sisters and showed her those in a wide field in the scope. Next she learned a new constellation Canis Major and took the binoculars and started scanning around. She found another fuzzy and asked what it was. I put the scope on M41 and she was simply amazed. This was her first open cluster along with the sisters and in both cases it was a thrill to be around her excitement. I next pointed out the Tao Cluster which also blew her away. We visited Saturn next and then went on to try and see some galaxies with no luck. She used the binoculars to scan Leo and to scan Virgo but no luck. She finished up in Cassiopeia and saw a fuzzy there that I didn't look at as she was finish. As she put the binoculars back in their case, she gave her Dad a hug and said "We have to do this again, it was fun. Not boring like I thought it would be.? So, in the end I bagged two objects from my list for tonight, and left many more hanging, but I'm hoping I bagged a daughter who just might gain some interest in the hobby. It also reminded me of the thrill of using binoculars to visit the night sky and how much we can truly see with just those aids. That was my observing tonight (Sunday night's session was incredible) and again, not sure if anyone likes these, but I wanted to share the experience. It's just wonderful when one's own kids take up an interest in Dad's hobby. No to get the wife . . . _______________________________________________ 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://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com

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Re: [Utah-astronomy] snagging space debris
by Canopus56 18 Mar '09

18 Mar '09

The Japanese tether microsat design proposal to capture larger space debris parts: http://www.ard.jaxa.jp/eng/info/prm/2008/027/no27-02.html - Kurt

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Re: [Utah-astronomy] snagging space debris
by Canopus56 18 Mar '09

18 Mar '09

I have long held a fantasy of designing a solar powered debris clearing microsatellite to get the small stuff. Something along the lines the ham radio operators' CubeSats and later Amsat designs. I thought I saw a JPL design once. The reality is: Japan pioneers debris-killing kamikaze satellites Russia Today 16 March, 2009, 12:10 http://www.russiatoday.com/Top_News/2009-03-16/Japan_pioneers_debris-killin… Satellite Smashers Space-faring nations: Clean up low Earth orbit or you're grounded. Air and Space Museum March 1, 2008 http://www.airspacemag.com/space-exploration/space_debris.html?c=y&page=1 Fifth European Conference on Space Debris http://www.congrex.nl/09a03/ Wiki entry on impact debris http://en.wikipedia.org/wiki/Lottie_Williams#Significant_debris_impact_even… NASA Orbital Debris Program http://orbitaldebris.jsc.nasa.gov/ Cubesats and Amsat http://en.wikipedia.org/wiki/CubeSat http://www.amsat.org/amsat-new/information/faqs/Intro_sats.pdf http://www.amsat.org/amsat-new/AboutAmsat/amsat_history.php - Kurt

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Messier Hunting
by Troy Davidson 18 Mar '09

18 Mar '09

(I sent this earlier and it doesn't seem it showed up. Forgive me if it's a double email.) I wanted to say thank you to Kevin and David Hays for their presentation last night on viewing Messier objects. I have also found the Wikipedia entry for the Messier objects to be helpful when looking for them. Here is the link to the page: http://en.wikipedia.org/wiki/List_of_Messier_objects The page includes all objects, NGC numbers where applicable, common name, a picture of the object (The most valuable thing listed, in my opinion.), what the object is, distance, location, and magnitude. I just wanted to pass this info along to help fellow observers hunting for these objects. -- ++++++++++++++++++ Troy Davidson

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Bias & Flats
by Jerry Foote 18 Mar '09

18 Mar '09

Hi Jim, Actually taking the bias frames would be doubling your effort. Since the darks will already contain the bias information then merely subtracting the darks from either the actual image or from the flat image will remove the bias noise. The only time bias frames need to be taken is if you are going to scale your darks for either exposure time or temperature. Frankly scaling darks is usually a poor substitute for keeping a set of Master darks handy for both exposure time and temperature. Usually darks are very stable over a long period of time (months or even a season). Taking 64 darks might be a little overkill as it produces an 8x reduction in noise. Comparing this with the noise from the actual frame puts it down in the mud. With that said, when it is cloudy and you are tired of the tube why not take them. It will be harder to get sets with varying temperatures which, with their relatively long life, allows you to get them throughout the season and use them next season. Strictly speaking the flats should also be taken at the temperature of the actual image as there is a very slight change in pixel sensitivity with changing temperature. Again this is way down in the mud. I really like Berry's book. It is always ready at hand for that nitty-gritty question. By the way there is a new version of AIP4WIN that has many enhancements particularly for DSLR imaging. Check out the Willman-Bell web site. Jerry Foote ScopeCraft, Inc. 4175 E. Red Cliffs Dr. Kanab, UT 84741 435-899-1255 jfoote(a)scopecraft.com

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Re: [Utah-astronomy] Bias & Flats
by Jim Gibson 18 Mar '09

18 Mar '09

Jerry, Thanks for filling in the huge blanks I left. You wrote: >If you want to get into this in depth I would recommend Richard Berry and James Burnell's book "The Handbook of Astronomical Image processing".< As a matter of fact that is exactly what I have been reading. Very good book. I have worked out the math for most of their formulas for my specific camera, in the early chapters. I was also reading Jerry Lodrigus’s CD book, “A Guide to Astrophotography with Digital SLR Cameras” on the same subject. >From my reading I am looking forward to making a Dark library about 5 to 10 degrees apart. I am not sure if I want to do scaling yet. Most of my shots will be at ISO 400, 800 and 1600 so when the sky is too lousy to image I can create darks. Jerry Lodrigus makes about 64 darks per ISO and temperature (he goes 10 degree apart) then make a master from that. Too bad Flats are so light train dependant or I would do flats too. But at least with the Dark library I can cut down on the time that they take and spend more time imaging deep sky objects. Flats should be rather fast. >From what I read I should take 16 flats, followed by 16 darks for the flats, followed by 16 bias frames, then create a master flat from all that. That will take some discipline because I know when I get to where I can start imaging, it is hard to give up image time for flats. But in the end it should be worth it. Jim --- On Wed, 3/18/09, Jerry Foote <jfoote(a)scopecraft.com> wrote: From: Jerry Foote <jfoote(a)scopecraft.com> Subject: [Utah-astronomy] Bias & Flats To: utah-astronomy(a)mailman.xmission.com Date: Wednesday, March 18, 2009, 11:06 AM Hi Jim, I bias frame is an image of the noise that is contained in the readout register of the chip as well as the noise contained in the readout electronics plus any electronic offset built into the readout electronics. Ideally it should be taken with zero exposure time but on a practical side your fast exposure is so close to zero that it doesn't make any difference. The reason for a zero exposure time is to make sure that there isn't any thermal contribution to the bias frame. Every time an image is taken the contribution to the image from bias is included. This includes darks and flats as well as the actual image. In addition to the artifacts you mentioned in flats there is the individual photo site sensitivity of each pixel. Think of it as each pixel having a slightly different ASA speed rating. This comes about from uneven polishing of the silicon chip before fabrication of the imager and slight variations in the gate structures for each pixel. Remember that a flat image when ready to apply to an actual image has been normalized: the individual pixel values have been divided by the average pixel values in the central portion of the frame. The actual image is then divided on a pixel by pixel basis by this normalized flat frame. When making flat frames, be sure to take dark frames of the same exposure and temperature to subtract out from the flat frame. This also subtracts out the bias from the flat image. One additional thing about flats is that anytime the optical train is changed new flats must be taken. This includes focusing, filters, cleaning the optics or re-collimation. One additional item is that all frames taken with cameras, DSLR, CMOS or CCD contain noise and the only way to reduce that noise is to use take multiple darks and flats and then averaging, or median combining them. This reduces the noise content by a factor of the square root of the number of the frames. Thus if ten frames are combined the noise is reduced by over 3 times. If you want to get into this in depth I would recommend Richard Berry and James Burnell's book "The Handbook of Astronomical Image processing". As it also includes some very powerful software it is real value. Check out Willman-Bell. Jerry Foote ScopeCraft, Inc. 4175 E. Red Cliffs Dr. Kanab, UT 84741 435-899-1255 jfoote(a)scopecraft.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://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com

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"It looks like a banana!"
by Raeburn Kennard 18 Mar '09

18 Mar '09

I got my 10" Dob out last night to show the grandkids Venus. The 5-year old said "It looks like a banana!" All were impressed. Even the parents were asking good questions, like "What makes it a crescent?" "Why is it so bright, when so little of the surface is illuminated?" "Why is it so much bigger than it was when you showed it to us last January?" And after the naked-eye "star" disappeared into a cloud, "How come we can still see it in the telescope?" Hopefully, I'm sowing seeds of interest for new generations of star gazers. Now is a great time to view Venus: crescent phase, good spring weather! (While both last.) Raeburn G. Kennard Kirton & McConkie 60 East South Temple, Suite 1800 Salt Lake City, UT 84111 (801) 321-4867 direct telephone (801) 328-3600 main switchboard (801) 321-4893 facsimile rkennard(a)kmclaw.com<mailto:rkennard@kmclaw.com>

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Re: [Utah-astronomy] snagging space debris
by Joe Bauman 18 Mar '09

18 Mar '09

My thought was that the snag boats would match the orbital speed of various pieces of debris, by traveling in the same direction. That would get rid of any problem caused by the debris' problem. Just a thought, Joe --- On Wed, 3/18/09, Chuck Hards <chuck.hards(a)gmail.com> wrote: From: Chuck Hards <chuck.hards(a)gmail.com> Subject: Re: [Utah-astronomy] snagging space debris To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> Date: Wednesday, March 18, 2009, 10:46 AM If it's small enough for aero-gel, it's not a hazard. The shuttle doesn't carry enough fuel to maneuver a whole heck of a lot, plus that would get expensive in a hurry. Also it's being de-commissioned soon. 2009/3/18 Dunn, David <David.Dunn(a)supervalu.com> > Would the aerogel that they used in "Star Dust" work for the smaller > debris? > > For the big stuff, maybe after the missions are finished, we could send > the shuttle up and have them chase down and capture them. They could > then push them to a lower orbit so that they would de-orbit. > > _______________________________________________ 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://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com

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