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I was wondering if it would be possible to measure red shift from distant galaxies using consumer grade telescope equipment and spectroscopy filters. (like this one)

I imagine it would require a tracking mount, and enough aperture to gather data on distant faint objects, but I wonder if it would require more sensitive equipment then a consumer grade tools available for under 5-6 thousand.

A long term goal would be to replicate Hubble's work, and directly measure the expansion rate of the universe from backyard equipment.

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3 Answers 3

up vote 7 down vote accepted

Looks like you can measure the cosmological redshift of quasars using that equipment and an 14" reflector:

http://www.rspec-astro.com/sample-projects/ (halfway down the page)

So the answer appears to be yes, you can do it, assuming that page isn't a total fabrication. Seems plausible to me: the redshift of that quasar is sizable at 0.15 (though that's small for a quasar), which means that the spectral lines will be shifted by something like 15%. So you don't need to have a very fine diffraction grating to see the shift. And that quasar is pretty bright for a quasar, at magnitude 13, so you can easily spot it with a good scope. Sounds like a fun project!

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True - the only thing about galaxies are that they're non-point sources, and intrinsically not as bright as quasars. You might have to wait a while if you aim to get spectra. –  astromax Dec 10 '13 at 15:22
Absolutely. I figured quasars would be a good target here because they have such high redshifts and because they're so bright. And technically, they are distant galaxies... –  freelanceastro Dec 10 '13 at 19:59
Interesting! I wonder how you would find a list of quasar coords for my latitude. –  asawyer Dec 10 '13 at 20:38
Here's a place to start: heasarc.gsfc.nasa.gov/W3Browse/all/milliquas.html –  freelanceastro Dec 10 '13 at 22:02
@astromax I'm looking into tracking mounts capable of the long exposures needed. I'm think you'd also need fairly long focal length, maybe a Maksutov-Cassiagrain like telescope.com/Telescopes/Cassegrain-Telescopes/… –  asawyer Dec 11 '13 at 14:01

As freelanceastro noted in his answer: Yes, you can measure the cosmological redshift of quasars with simple equipment.

The page he referred to is not a fabrication. (See the article on amateur astronomical spectroscopy in the August 2011 issue of Sky & Telescope.) Many amateurs have made this measurement with a variety of instruments, including a modified security camera on an 8" SCT. (That one took just 15 minutes total integration time, which is about what most most amateurs find using typical equipment.)

As you noted, asawyer, quasars are good targets for red shift measurements because their radial velocity is so high. The Doppler shift of objects that are closer than 3C 273 is more difficult to measure because their radial velocity is so much lower.

As astromax notes, capturing the spectra of extended objects generally requires a slit, but not always! For example, a lot of amateurs captured spectra of comet ISON, which certainly isn't a compact object! Check out this one, done with just a DSLR and an 80 mm refractor:

enter image description here

If you're interested in 3C 273, in case you missed it, there's a wonderful transcript of an interview with its discoverer, Maarten Schmidt here: http://www.aip.org/history/ohilist/4861.html. It's rather long. Search the text for the text "December 1962" for the relevant section. It's a fun read about how he made the discovery and his personal experience of the process.

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Also see this: http://www.threehillsobservatory.co.uk/astro/spectra_21.htm. The designer of the Star Analyser grating has observed the red shift of compact galaxies with a video camera!

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