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robin_astro

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Everything posted by robin_astro

  1. Hi Andy, I think you need to address this issue with your spectrograph first. You need to be able to produce a clean spectrum image of the RELCO lamp similar to the one I posted here. Robin
  2. Hi Andy, CF lamps can give you a rough calibration to get your eye in on better calibration sources like the RELCO etc but for precise calibration you need a wide range of narrow unblended lines. It is worthwhile persisting with the RELCO because once you have identified a set of suitable lines, you can produce a file so that programs like ISIS will find the lines for you automatically and produce a very precise reliable non linear calibration every time with a couple of clicks. Cheers Robin
  3. Yes I guess it will be tough to pull this out with this beamwidth. (How about a second dish to do some interferometry ?) If you are an early riser you could perhaps try for Tau A which is better isolated. I found this useful chart of comparative signal strengths a while back somewhere on line. Robin
  4. A very nice signal ! I guess the dish will have a better front/back ratio too which should improve SNR. I would be interested in the details of the feed design Cheers Robin
  5. The clue is in the thread title This explains the measurement. (From the Jodrell Bank radio astronomy course) http://www.jb.man.ac.uk/distance/radio/course/sourcesII/sourcesII4.html EDIT: also here from University of York. http://www-users.york.ac.uk/~phys38/galhydexp.htm A classic practical experiment for any radio astronomy student Robin
  6. Hi Coto, I think you need to reread your course notes . This shows the spectrum of neutral hydrogen at 21cm, Doppler shifted by different amounts in different spiral arms. You cannot measure these Doppler shifts in continuum spectra like synchrotron or thermal emission. Robin
  7. Very clear, We really do live in spiral galaxy Congratulations ! Robin
  8. More info from Marcello Cucchi on how to drive the RELCO using the photo flash circuit here on astronomical-spectroscopy https://groups.yahoo.com/neo/groups/astronomical_spectroscopy/conversations/topics/7811 and some hints and tips from Francois Cochard of Shelyak in this thread on spectro-l https://groups.yahoo.com/neo/groups/spectro-l/conversations/topics/14084 Robin
  9. Hi Andy, Probably worth hanging on to a few. There is some variability in how well they perform and they dont last so long unless used in a more sophisticated current controlled circuit with a particular DC polarity that Shelyak use for example . http://www.spectro-aras.com/forum/viewtopic.php?f=8&t=606#p2392 Shelyak supply selected ones as spares for their spectrographs but at 30 euro for 3 your 25 probably still worked out cheaper. https://www.shelyak.com/produit/se0148-argon-neon-spare-bulbs/?lang=en Robin
  10. Hi Carl, Can you pick up the increased noise from the sun ? That will give you a benchmark signal to gauge your sensitivity from. Amateurs doing moonbounce (EME) on 23cm for example use it to optimise their receivers Robin
  11. Yes, when I am giving talks on spectroscopy I use artificial stars. (A box with pinholes in front of 3 hidden lamps Tungsten incandescent, Compact Fluorescent and warm white LED. The pinpoint light sources all look like stars of with same colour but when you look at them through a grating they have very obviously different spectra, just as real stars do. Cheers Robin
  12. Ah yes Richard Walker has updated the document since then and the link address has changed. ( Despite his English sounding name he is actually Swiss) Here is the latest version http://www.ursusmajor.ch/downloads/sques-relco-sc480-calibration-lines-5.0.pdf from this page ttp://www.ursusmajor.ch/astrospektroskopie/richard-walkers-page/ There he uses mains power so is a bit risky out in the field so I used the flash circuit from an old disposable camera as devised by an Italian amateur http://www.marcellocucchi.altervista.org/html/neonlamp.html You can use a neon indicator lamp instead but unlike the relco starter spectrum which is a mix of several gasses (mainly neon and argon), neon does not have any lines at the blue end. The lines which would be best for your spectrograph are shown in the spectrum on page 22 (DADOS 200l/mm) It is not bright enough to use in front of the telescope aperture so I injected the light via a flip mirror before the spectrograph, mounted the wrong way round. (This was before Shelyak brought out the calibration module for the ALPY.) The ALPY calibration module also has a flat lamp. It might even be possible to adapt it for use with your spectrograph. Cheers Robin
  13. You can do some impressive stuff with simple antennas though, like this pulsar measurement at 70cm http://neutronstar.joataman.net/sites/iw5bhy_barga_3/index.html Something I would not have thought possible without a large dish Robin
  14. Absolutely ! A dish the size of the wavelength will have very low gain. Yagis and dishes have their advantages and disadvantages and it is around this wavelength where the crossover between using dishes and Yagis is found. Typical dish size at 21cm are at least 2m though and have much higher gain than any single Yagi so there is not much practical work to directly compare. I expect if you Google you will find an amateur radio operators who have used a small sat dish on 23cm BTW my knowledge on the subject is from the hands on radio astronomy course at Jodrel Bank, (sadly no longer run) and my days as a radio amateur (Any amateurs doing moonbounce (EME) at 23cm would be very good source of practical information if you are building a setup for H line work.) Cheers Robin
  15. Not seen small dishes used at this wavelength but theory says a 1m dish would match a 45 ele long yagi for gain. I am not sure how dishes behave as the diameter approaches the wavelength though. The feed horn would presumably block a significant proportion of the aperture ? Robin
  16. http://www.britastro.org/radio/projects/Low_Cost_H_Line_Telescope.pdf Robin
  17. I made a quick analysis of your spectrum images for star I and II on your blog using Visual Spec Note how the H alpha and H beta emission lines in star II (in pink) line up with the absorption lines in star I (in blue) If they were bright stars in Cassiopeia, I suspect star II is Gamma Cas a well known Be star. The other star might be Delta Cas. Interestingly these were two targets I used on a Sky at Night programme back in 2005, taken with a prototype of the Star Analyser http://www.threehillsobservatory.co.uk/astro/spectra_12.htm
  18. Star I looks like an A class star like Vega. The Balmer absorption lines are very clear in the image but don't seem to have come out very well in the profile. I suspect your software is not doing a good job for some reason. (The dip you identified is probably H beta at 4861A) Star II is much more interesting. Note the bright spot at the red end. This looks like Hydrogen alpha emission. This is seen in various types of interesting stars, for example among others, Be stars and Novae. Is their any chance you can identify it's location ? Robin
  19. Alternatively you can use a star with known lines to make an approximate wavelength calibration (eg using the Balmer lines in your Vega spectrum) provided your spectrograph is stable enough (ie the lines do not move significantly due to flexure as you move between targets) Robin
  20. They are similar as we are seeing reflected sunlight but not identical as the planet superimposes its own spectral features. These are subtle for the rocky planets (mainly a change in overall shape (eg the lunar spectrum is less blue than the sun) but the gas giants show clear bands from Methane for example. eg as here Cheers Robin
  21. Hi Andy, The RELCO lamp starter as discovered by Swiss amateur Richard Walker and used in the Shelyak and starlight Xpress instruments is commonly used. See here for example Cheers Robin
  22. There is the Star Analyser of course, and the grisms at the heart the ALPY (and the CCDSpec) are also made in the UK Robin
  23. Yep and the website has been abandoned. http://www.elliott-instruments.co.uk/ The patent application is also out of time http://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1120579.6 (To prevent the possibility of a whole raft of existing spectrograph designs being outlawed, I submitted a comment pointing out Prior Art, though I doubt it would have got through any way) Robin
  24. I think to be fair it should be pointed out that the ALPY 600 spectrograph is actually ~1400ukp for the equivalent core and guiding module which is similar to the price of the CCDSpec when it was launched, though it may now be discounted. Robin
  25. Thanks for the "heads up" on this. I pointed my low resolution spectrograph at it last night. The spectrum confirms the z=2.4 redshift https://stargazerslounge.com/topic/300597-11-billion-years-ago/ Robin
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