> Begin forwarded message: > > that 1K for OH should be for the 4.5 m. W49 is about 200 Jy, i think. so for > our old 85 foot, which got 0.1 K/Jy, the ant temp was about 20 K. cutting > down the diameter from 25m to 5m loses a factor of 5^2, so the ant temp would > drop from about 20K to 1K, > > On Tue, 18 Aug 2015, Sander Weinreb wrote: > >> Carl, >> >> Thanks very much! I looked at the attachments and the four experiments >> including the write-ups are an excellent introduction to radio >> astronomy. >> >> A question about OH. You mention <1K antenna temperature on the strongest? >> maser source, W49. Is this with the 4.5m telescope or with an older, >> smaller telescope? I assume we would need narrow bandwidth, probably 5 >> kHz, and with a 100K Tsys it will take many minutes of integration to see >> the signal. We also have RFI around 1667 and it will be a challenge to >> get the filtering and dynamic range. On the other hand, the polarization >> and multiple lines, make this a very instructive venture. >> >> I think we have had talks at URSI about educational radio telescopes but >> maybe should devote a session to this at the 2017 meeting. >> >> Sandy >> -----Original Message----- >> From: Carl E. HEILES [mailto:hei...@berkeley.edu] On Behalf Of heiles >> Sent: Tuesday, August 18, 2015 4:08 PM >> To: Sander Weinreb <swein...@caltech.edu> >> Cc: heiles <hei...@astro.berkeley.edu>; 'DAVID DEBOER' >> <ddeb...@berkeley.edu>; 'Alan Rogers' <arog...@haystack.mit.edu>; 'Han' >> <st...@kasi.re.kr>; 'Steve Smith' <ste...@caltech.edu>; 'Monroe Ryan M' >> <ryan.m.mon...@jpl.nasa.gov>; 'Gregg Hallinan' <g...@astro.caltech.edu>; >> 'Andrew Janzen' <ajan...@caltech.edu>; 'Ahmed Akgiray' >> <ahmed.akgi...@ozyegin.edu.tr>; asoli...@caltech.edu; 'Hamdi Mani' >> <hamdi.m...@gmail.com>; 'Joe Bardin' <jcbar...@gmail.com>; 'glenn.caltech' >> <glenn.calt...@gmail.com>; 'GLENN WEINREB' <gwein...@gwinst.com>; 'Anthony >> Readhead' <a...@astro.caltech.edu>; 'Shri Kulkarni' <s...@astro.caltech.edu> >> Subject: Re: FW: Educational 6m Radio Telescope at Caltech >> >> hi sandy... >> >> in our undergrad radio astro lab, we currently do four major experiments, >> the writeups for which are attached. >> >> the first lab is devoted to bench experiments and learning about digital >> sampling. the lab in in two halves, and in fact we treat it as two separate >> labs. the first half uses test equipment; the second uses a horn on the >> roof, baseband complex sampling with the students writing their own software >> to get the power spectrum fromthe time series. i regard this first lab, >> which covers the basics of sampling and Fourier tranforms, as absolutely >> crucial for anybody who intends to pursue a technical career, and also >> everything that follows in the lab course. >> >> the second lab uses our 12 GHz interferometer (freq chosen so that we can >> look at the strong methonal masers--which we haven't gotten to yet). >> baseline is about 12 m. students do vlbi fringe fitting to determine >> accurate declinations of sources like Ori A (well, more accurately, the >> combination (baseline times cos delta). also look at fringe amplitude >> modulation to determine angular diameters of the sun and the moon. >> >> the third lab uses our 4.5m dish located about a half hour away to map HI >> 21-cm line, look at OH, and look at pulsars. Haven't done OH successfully >> yet because of equipment problems, but hope to do so this coming year, and >> include polarization. hope to get to pulsars this coming year, but that >> requires some programming for our FPGA spectrometer and might not happen >> this year. >> >> generally, course philosophy is that students must write their own software. >> we use IDL. these days, Python would be more approppriate, but at my age I'm >> not going to learn yet another language. anyway, the programming experience >> gained helps the students a lot in REU research programs and getting a >> flavor of instrumentation for later career use. >> >> if you desire, you can find some more info (handouts, writeups, etc) on my >> web page astro.berkeley.edu/~heiles/ >> >> it strikes me that if you can't do OH simply because of resolution of your >> spectrometer, then this is an excellent project for them to do direct >> voltage sampling on and they could do their own FT power spectra with >> arbitrary resolution. this would be very instructive. >> bandwidths can be small so you can keep up with the data rate and disk files >> don't need to get too big. many OH masers are highly polaarized, so a good >> excuse for them to learn polarization basics. W49 is a particulary good >> example. Also there are very strong OH masers associated with IR stars, also >> polarized. >> >> our telescopes are pointed now by commercial motor controllers, thanks to >> dave deboer. doing this well (or even at all) is difficult. i suspect alan >> has a simpler and cheaper alernative. also, our telescopes are home grown; >> the hardest part is the pointing hardware and software... >> >> good luck and have fun! there are some other similar labs...i know UW at >> madison has one. we ought to convene a get-together so we can exchange >> ideas... >> >> --c >> >> On Sun, 16 Aug 2015, Sander Weinreb wrote: >> >>> >>> (Corrected email address for Heiles) >>> >>> >>> >>> From: Sander Weinreb [mailto:swein...@caltech.edu] >>> Sent: Sunday, August 16, 2015 10:31 PM >>> To: carl heiles (hei...@vermi.berkeley.edu) >>> <hei...@vermi.berkeley.edu>; Alan Rogers (arog...@haystack.mit.edu) >>> <arog...@haystack.mit.edu> >>> Cc: Dave Deboer (ddeb...@berkeley.edu) <ddeb...@berkeley.edu>; 'Han' >>> <st...@kasi.re.kr>; Steve Smith (ste...@caltech.edu) >>> <ste...@caltech.edu>; Monroe, Ryan M (382F) >>> <ryan.m.mon...@jpl.nasa.gov> >>> Subject: Educational 6m Radio Telescope at Caltech >>> >>> >>> >>> Carl and Alan, >>> >>> >>> >>> I need some advice from old salts about how to demonstrate radio >>> astronomy observing techniques to new graduate students. >>> >>> >>> >>> We are paying some attention to the 6m telescope on the roof of the >>> EE building at Caltech and are trying to make it into a good >>> teaching instrument. The front-end covers 1.3 to 1.7 GHz with about >>> 100K Tsys on two linear polarizations and we recently installed a >>> Roach 1 spectrometer with two 500 MHz bandwidth channels and 60 kHz >>> resolution. There is much RFI and a lesson we want to teach is how to work >> around it. >>> >>> >>> >>> Our weakest link is the software to integrate telescope pointing with >>> receiver output. We are working on developing a convenient system >>> but I wonder if it already exists on other small telescopes. Do you >>> have any suggestions for integrated telescope and data taking >>> control system we should look at? >>> >>> >>> >>> A second topic is what to observe with the telescope as >>> educational demonstrations. We can certainly map galactic hydrogen >>> and look at the stronger continuum sources. The spectrometer can >>> cross correlate the two linear polarizations and we could get into >>> polarization measurements. Do you have suggestion for observations? >>> >>> >>> >>> I would like to observe OH (again, since I have not observed it or >>> followed what has been done since 1963 !). Where is a good summary >>> of the observations? I think our 60 KHz resolution is too broad >>> and we will need to improve it by a factor of 10 or more. >>> >>> >>> >>> Sandy >>> >>> >>> >>
