Home made Spectroscopes?

[Merlin66]

Any members building or have spectroscopes? ( Other than Robin!?)
I'd be interested to hear what types and experiences in building/ using them. I've built four so far; both reflection and transmission type but still have to come to terms with Vspec and guiding them on a star!!!

[NickH]

I have the DG spectrum one, to be honest not used in a while, as I have new toys to get used to  with deep sky, but it was fascinating to see spectral lines in very distant objects and use vspec to get the curve data. Robin is a renowned expert in this field, so he is probably the best source of information on use and types. Mine cost about £60 ish and is used with a Meade LPI and with my old C8 it could easily map out hundreds of stars

Here's a link to some of my images, and the main page for VREH

http://www.vreh.com/optics/users.htm

Very simple to use, and superb instructions.

The star analyser is a UK made similar system and a yahoo group exists for that with plenty of support and help

[robin_astro]

The star analyser is a UK made similar system and a yahoo group exists for that with plenty of support and help

 :)

As Nick says, mounting a diffraction grating between telescope and camera/eyepiece is just about the simplest way of getting into stellar spectroscopy.  The Star Analyser group is here but you don't have to own one to join and similar techniques apply to all the makes of spectrographic  "filters"
http://tech.groups.yahoo.com/group/staranalyser/
Many of the postings there are to do with getting to grips with Vspec (There is a simple guide to creating your first spectrum graph in the files section)

Maurice Gavins website is also a good place to visit if you are interesting in building your own
http://www.astroman.fsnet.co.uk/spectro.htm

If anyone is at  Kielder next month I am talking about starting in spectroscopy on Saturday and, weather permitting, hope to demonstrate some too.

Robin

[alexthegreek]

Some phots as asked .

[alexthegreek]

Some more

[alexthegreek]

I hope they are helpful .
 I don't have any desing plans .

[Merlin66]

Can you "walk us through" the photos?
Is it a transmission grating or reflection grating type?
Is the grating angle adjustable? How?
The slit size?
Which CCD/ camera do you use?
How do you achieve focus of the spectrum on the camera?

[alexthegreek]

You are right :)

It's a reflection grating with 250 lines/mm .

It's not adjustable .The  whole spectrum fits in the image .I usually use a NIKON D 50 model .Otherwise B&W film .Most 99% of the times it's the DSLR .
  The slit is 25 ?m .
  Inside there is a 50mm lens acting as collimator .It's focused at infinity .
     See the first image . Ath the left M 42 thread I screw a telens. I usually use a 135mm one .Then I mount this lens on the camera and I focus at infinity .
   The on axis guider at the right side of the first image is a lens .You can see it in one of the  images attached .   
    I use extenders to focus either the eyepiece or the webcam .
     This way the slit is seen , but it's seen more easy when I change the focus of the scope .Usually I change it a bit and then it's really sharp . That doesn't  affect the focus of the spectrum , because everything is focused at infinity .
   The light goes through the slit , then the collimator , then the prism and then the diagonal .

  The spectrograph is very light , but  I haven't  weighted to be honest .
   You can see some more images of this set up it the thread " Some solar spectra " .

 Be well mates
   Alex

[Merlin66]

Thanks for that Alex.
It's a little surprising to see the collimator at 50mm fl and the objective at 135mm focal length; this will effectively turn the 25 micron slit to a 25*135/50 = 67micron image on the camera/ CCD. It's more usual to try and make the objective a shorter focal length than the collimator to give a narrower image on the CCD. The resolution will be dependent on the pixel size of the CCD.
If you used a Webcam, for instance, with a 5.7micron pixel; the slit image would illuminate almost 12 pixels.
You should try using it with a 50mm lens, it would give you twice the resloution you're currently getting with the 135mm lens.
As far as I can see the Nikon has a pixel size of 7.8 micron, so a 50mm lens would illuminate 3 pixels.
A 250 lpm grating is a good starting point and gives, as your finding, a very complete spectra in the image, without the added hassle of rotating ( and controlling!) the grating.

[robin_astro]

It's a little surprising to see the collimator at 50mm fl and the objective at 135mm focal length; this will effectively turn the 25 micron slit to a 25*135/50 = 67micron image on the camera/ CCD. It's more usual to try and make the objective a shorter focal length than the collimator to give a narrower image on the CCD. The resolution will be dependent on the pixel size of the CCD.
If you used a Webcam, for instance, with a 5.7micron pixel; the slit image would illuminate almost 12 pixels.
You should try using it with a 50mm lens, it would give you twice the resloution you're currently getting with the 135mm lens.

Only if you increase the grating l/mm at the same time though. Reducing the camera lens fl will reduce both the slit image width and dispersion proportionately.
(using a 50mm lens will allow you to go about 1 mag fainter at the same resolution though)

Robin

[alexthegreek]

Thank you for the info mates :)

[robin_astro]

.Otherwise B&W film

Aha!  I would guess this spectrogrph was designed for 35m film use which generally has less resolution than CCDs. (ISTR Kodachrome II for example had ~30um "pixels") That would explain the magnification factor used.

Robin

[alexthegreek]

I don't know about that guys .
 I give him a call in the next days and will also ask him that .

  My friend who has designed it never uses film  .In fact we haver spoken for using film SLRs  with the spectrograph .   When I bought it last year he opened the spectrograph to show me the design .It was only once , but I rememer telling me that it was a 50mm collimator .
 BTW the same guy has built a spectrograph just for the solar spectrum .It has a dispersion of 0.0923 ?/pixel .
  Here some photos of an article using the big spectrograph to test a Coronado 60 .

   I hope that it won't be Greek to you 

  http://astronomy.gr/main.cfm?module=article&id=1208&action=detail

  He has also made a heliostat of two mirrors , and he used it to guide the sunlight in the slit .
   The spectrograph can be really long . He also uses a Jean Zeiss 1200 f/11 as a collimator .

 you might wish to see this link as well .
 It's also in Greek but there are photos of the equipment .

 http://www.astronomy.gr/main.cfm?module=news&id=1229&action=detail

[robin_astro]

Thanks for posting those links Alex. (Google did a reasonable job of translating them) That spectrograph and Heliostat is quite a setup.

My LHIRES III has about the same dispersion (0.09A/pixel) but perhaps not quite as high resolution. My avatar is a solar spectrum taken with the LHIRES. I have attached a couple of details from it (NaD and Mg regions)
(It probably does not strictly count in this thread though as I built it from a kit  )
I think one of the highest resolution home made solar spectrographs I have seen is Fulvio Mete's one made from two department store telescopes :-)
http://www.lightfrominfinity.org/Hirss/HIRSS.HTM

Robin

[Merlin66]

I took a couple of images of the sun last year with the SM40 etalon; to show the resonance pattern across the whole spectrum.
What I see in the post excites me!!
Here we have a close-up of the band width around the Ha - not only does it show the resolution of the etalon, he has, by monitoring and controlling the tilt, established the off-band movements. This is used for seeing the Doppler shift shift in Proms; but I'm thinking of something else.
I've recently aquired a SolarMax60 with an additional SM60 to make a double stacked configuration. It should be possible, using the same techniques to determine the DS bandwidth and the optimum settings for each etalon.
It's still all Greek to me!!