AllSky meteor camera homebrew tests - notes on
I have an interest in portable allsky meteor cams and the following are my setup experiments based on the prior camera setups of Chris Peterson at Cloudbait Obs: Chris Peterson AllSky Mark II - http://www.cloudbait.com/projects/allskycamera.html Chris Peterson AllSky Mark I - http://www.cloudbait.com/projects/allskycamera1.html While Chris's permanent installation designs are superior in performance, I wanted something that would be more suitable for portable and causal shower imaging and that relied on equipment that I already had. Hopefully, the following examples will inspire other amateurs to engage in causal allsky meteor imaging. Both the examples can capture down to 1 mag meteors in urban or suburban settings. I believe they will both reach mag 2.0 in rural suburban settings but have not successfully tested them to that magnitude. There are two major design considerations for homebrew portable digital meteor cameras - adapting a lens with a high TFOV and external storage for larger video files. Timestamping is a third issue. 1.0 Setup experiments with 75 deg to 160 deg TFOVs 1.1 Reflecting Setup - Mark I With respect to the first design consideration, I made a quick 80 deg TFOV "Mark I" meteor camera based on adapting an DMK 31AU03.AS ImageSource camera to a simple reflector model after Chris's Mark I setup - (All images discussed here are in directory - http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/ ) Mark I quick reflector setup with automotive convex mirror 80 TFOV - zenith set up http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/05All... http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/07All... http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/08All... http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/09All... Mark I - off zenith 80 TFOV configuration http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/11All... Mark I test images - Leonids 2009 http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/10All... http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/02Len... http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/04Len... 1.2 Refracting Setup - Mark II Last night, I performed a first quick test of my Mark II allsky meteor that has a 160 deg TFOV - a refracting setup that follows Chris's Mark II design. The test target was an ISS-Shuttle overpass. Mark II refracting version setup images Mark II refracting version with 160 TFOV http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/12Met... Mark II version DMK31 on tripod with 160 deg TFOV micro lens. http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/13Met... Close up Mark II - DMK31 with Edmund Micro Video Lens 1.68mm fl http://fisherka.csolutionshosting.net/astronote/atm/AllSkyMeteorSetups/14Met... Youtube video link to test capture of -3.8v ISS-Shuttle overpass from urban light polluted setting (ZLM v3.5-4.0) http://www.youtube.com/watch?v=aR09ZxsNumo&feature=player_embedded In the test video, CalSky reports a computed magnitude of -3.8 for the ISS and Shuttle The three brightest stars at the top (west) of the image (plus a hot pixel) are Vega 0.0, Altair 0.8, and Deneb 1.3. The small triangle of stars at the bottom of the screen (northeast) are the brightest stars in the head of Cas: alf Cas 2.2v, bet Cas 2.3v, gam Cas 2.5v. In the southeast quadrant of the video (lower right), three of brightest stars in the Pegasus square are visible. Moon and Jupiter (ephemeris -2.3v) are the two bright objects to the west (right center). A second test was immediately run after the ISS overpass. A mag 4.0 satellite was passing north-south along the meridian. It did not register on the captured digital video. The Mark II refracting setup has the advantage that it can easily be mounted on a tracking tripod. A collection of tracked radiant images, as opposed to fixed zenith image collections, can be made. This Mark II refracting allsky camera is based on an Edmund Micro Video Lens 1.68mm fl with M12 threads that is adapted to the DMK31 that has a "C" thread. Micro Video Lens 1.68mm FL Edmund NT59-776 160 deg TFOV $39 http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=2196&... C-Mount to µ-Video Lens Adapter w/O ring Edmund NT59-241 $25 http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=3188&... M12 Lock Nut for Micro-Video Lenses (Optional Edmund NT64-102 $7.5 http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=3188&... The focus distance between the back of the Edmund 1.6mm fl lens and the chip is about 8mm to 10mm. 1.3 Alternative gear and setups Other allsky options to adapt the Edmund Micro Video Lens 1.68mm fl to almost any 1/4" or 1/3" CCD chip format astronomy camera are as follows: Male T-Mount to Female C-Mount Adapter (Needed local machine shop work to turn out interior metal space to get Edmund NT59-241 closer to the focus point) Edmund NT58-753 $39 http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1316 Alternative to Edmund NT58-753 Scopestuff #T2CA - C-Mount to T-Thread Adapter, With Spacer Washer $24.00 #T2CW - Extra .062" thick T to C Spacer Washer $5.00 http://www.scopestuff.com/ss_t2ca.htm Pre-built option: Scope Stuff C-Mount to T-Thread Adapter for Meade DSI #T2CF - DSI SkyCam Kit - #DSIF Faceplate, 2.8mm CS Lens, C2CA Adapter, Spacer and End 75 deg TFOV $79.00 http://www.scopestuff.com/ss_t2ca.htm Straight DSLR option: Canon EOS Rebel XSi Digital Rebel with/EF-S18-55mm 75 deg TFOV Price Point $650 with lens http://www.ritzcamera.com/product/541162194.htm Canon lens with 74 deg TFOV $200 but is included in EOS Rebel http://www.ritzcamera.com/product/EP25196680.htm 2.0 Digital storage capacity and storage rate With respect to the second design consideration - storage capacity - digital video storage presents a barrier in some capture modes. The Mark I reflecting test was done at 3.4 second integration times, 3.5 frames per second capture and 4 second storage intervals to an AVI file. This capture format has little or no storage issues. A one hour recording stores to about 1 meg. Recording overnight for 6 hours presents no problems for the available free space on most disk drives. . This integration and storage combination also has a review advantage. Captured uncompressed AVI files are inherently replayed at compressed speeds. One hour plays back in between one or two minutes. This makes it easy to visual find the brightest bollides by timestamp for later frame extraction using Registax. The Mark II refracting test integrated and stored at 1 fps. 1 minute of video resulted in 0.2Gigs (200mb) in stored an AVI file. That translates into 12 Gigs per hour or 72 Gigs over 6 hours. Recent price and technology improvements provide economical solutions for high capacity scenarios. USB 2.0 and Firewire pocket drives are now widely available at $125 for 500Gigs, e.g. - WD Passport Portable Drive 0.5Tb $120 USD http://www.westerndigital.com/en/products/Products.asp?DriveID=701 These are small, portable, rugged drives. I have one that I carry and store all my astronomy related hobby work on and routinely carry it in a brief case. The drive is temperature rated down to 0 C and "non-operating" at -4 C, although I have used one outside for an hour at -2C without difficulty. However, such drives only support USB 2.0 and I have not tested mine for frame dropping in continuous frame capture storage 1 fps mode. While in theory, a USB 2.0 and Firewire connection transfer data at 400 to 800 mbs, in practice, I have found they have problems transfering small individual files at anywhere near the published rates. They may not support continuous 1 fps capture. The WD Passport is NTFS formated. Some portable and external drives are FAT32 formatted - which means the largest supported file size is 4Gigs - a barrier for continuous 1 fps digital recording. For 1 fps recording, external desktop 1.5Tb (terabyte) eSATA drives are now down to less than $200. External eSATA drives can transfer video capture data at 3.0Gigs per second - sufficient to reliabily support 1 fps digital recording. For laptops, SIIG makes an eSata Card in the ExpressCard/54 format. SIIG eSATA II Express Card $85 USD http://www.amazon.com/SIIG-SC-SAE612-S1-Esata-Expresscard-Raid/dp/B000EMAXQA An eSATA laptop card that plugs into a PCMICA port will not work at SATA speeds. The PCMICA port has a limited data transfer rate. The practical impact of an eSATA verses Fireware connection is that when backing up 20Gigs of files, Fireware can take a hour half. eSata is done in two or three minutes. Conversely, an external eSATA drive, unlike the Passport pocket drive, is not something I would want to take to a remote observing site. A 1.5Tb external drive might be transportable if it was stored in a custom foam hard camera case. For a high speed digital recording setup, I purchased and am testing the following gear: SIIG eSATAII Express Card $65 to $85 USD (above) Seagate 1.5Tb FreeAgent Xtreme drive $160 USD http://www.seagate.com/www/en-us/products/external/freeagent/freeagent_xtrem... Many of the 1Tb and 1.5Tb external drives now being brought to market come in two flavors - one that only has USB 2.0 and Firewire connection ports and those that also have an eSata port. Check the box and make sure you are buying one with an eSata port. Some security camera software comes with image change capture options (an image is stored only when the image changes) but I have not had any success in finding anything cheap or freeware that can be cross-purposed for this astronomy task. I understand MeteorRec referenced on Chris Peterson's website to be a low-light video feed program recorder. http://www.metrec.org/#3 As the wesite of the program's author (Sirko Molau) notes "MetRec neither works with TV cards or any frame grabber from a different vendor, nor is it able to read AVI or other video files." 3.0 Timestamping The final design consideration is timestamping. The individual maker of the $500 OSI video time stamper (for tradional low-light video signals) has retired from making those units. Alternative market hardware costs $1500 USD. For the DMK series, ImageSource provides the option to record to an AVI output stream or to individual bmp or jpg files that are date and time stamped in the file name to a minimum interval of 1 second. Registax can be used to gather individual bmp or jpg files in groups of about 1000 frames and review them using Registax's Goto frame button. (Click and hold the frame down button is get a movie-like experience.) I have not found any good solutions or freeware solutions for digital software timestamping an AVI file, including confirming whether ImageSouce captured DV AVI places a frame timestamp in the file. If anyone has any suggestions, please let me know. Presumably, streamed digital video from a Canon Rebel or EOS would have the DV AVI timestamp encoded in frames. Again, hopefully the above discussion will inspire other amateurs to adapt their existing astronomy CCD and CMOS camera gear into allsky or large TFOV capture for meteor observing. The Edmund 1.6mm lens with an M12 to C and-or a C to T adapter provides a low-cost fisheye lens solution for 1/4 inch and 1/3 inch class chips. Clear Skies - Kurt
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Canopus56