First Light spectrum obtained with new spectrograph.

Anthony,

Here is a link which highlights a users L200 on the bench;

www.stargazing.net/david/spectroscopy/SpectraL200Bench.html

Unfortunately it is not a commercial spectrograph, therefore there is no webpage. The kit is produced and sold by Ken Harrision a well known amateur spectroscopist. He produced this so that interested folk could have a high quality slit spectrograph at a reasonable price. The cost was 880usd. This conpares to about 1/2 of some commercial units.

Unfortunately Ken's run was small and I beleive that there is none left Maybe Ken will run off another batch. I'm sure he would if there was an interest.

For more info on this visit the astronomical spectroscopy group on yahoo;

tech.groups.yahoo.com/group/astronomical_spectroscopy/

Some details of th unit. Its a littrow design so there the same lens is used for collimation of the incoming beam and focusing the spectra. The grating provided is 600 lines/mm giving a resolution of R=3000. Wavelength adjustment is provided via a micrometer and the slit can be opened or closed from zero to about 1mm in VERY fine resolution

If anyone is interested in learning more about spectroscopy, Ken Harrison has just published a great book on the subject, including theory, design and operation and lots more besides.

If Ken evr does make another batch, I'd highly recommend the kit as long as you don't mind a bit of spraypainting and assembly.

Hi Dave,

Congratulations on entering the spectroscopy field. You'll have great fun in imaging spectra. Not many amateurs carry out observations in this field. Its got easier now with off the shelf systems that are affordable and user friendly.

I entered the field about 12 years ago having bought a 'Rainbow Optics'
grating for $200. Worked really well for spectra of bright stars. Resolution at 200 grooves/mm. Certainly recommend the Rainbow Optics' as a starter. Once you get the bug you want to adventure into a wider range of candidates that may be difficult to obtain spectra.

However, because I was interested in wide field spectra for comets and emission nebulae, I couldn't find anything in the market place off the shelf. So, I designed and built a wide field spectrograph.

It's FOV 3 deg x 3 deg (resolution 400 grooves/mm) . I designed it to provide a new capability for measuring the spectrum of the sky across fields of view much larger than the full moon as compared to the conventional narrow systems. The instrument uses a high speed optical system to form an image on the entrance slit of a matching stigmatic spectrometer, this then disperses the spectrum of a strip of the sky onto a CCD camera. A separate imaging system is used for pointing and tracking. The system is very heavy at about 40 kilos. It's excellent for imaging comets and emission nebulae. I have a paper published providing the details of construction and application called

'A new wide-field spectrograph' Proc. SPIE 5492, 1290 (2004)

I also have a Zerny Turner design for narrow FOV at 600 grooves/mm. Because it is a heavy construction I am using a fibre optic feed from the eyepiece holder exit of the telescope.

Since then, I have dismantled the parts of the wide-field spectrograph and I am applying it for a solar spectroheliograph. The idea is to tune into hundreds of wavelengths. So far half built. This project has become more complex in building.

Eamonn A

Eamonn, I would also second your racommendation about the Rainbow Optics unit. I managed to get hold of a Star Analyser from Paton Hawksley. It's 100 l/mm blazed to the first order. This one costs 87stg. Combine it with a 3deg wedge prism from edmund optics for around 40eur and you end up with a capable unit for low resolution spectroscopy, without the big price tag. A great idea for someone on a budget or whos mount/scope might not be up to the demanding requirements of a slit based spectrograph. You can still measure some radial velocities and lots of other useful observations.

I look forward to having a chat with you about this soon.

Dave/

Dave,

I bought the Rainbow Optics (RO) as a complete system. ie. grating plus spectrum-widening cylindrical lens for $200. It has advantages over the wedge prism type. Unlike a prism wedge, which distorts a spectrum by spreading out blue light more than red, this grating creates an undistorted, constant dispersion across the entire visible spectrum.

I was aware of the Paton Hawksley grating, but the res was lower. RO are still making them for $249, which is good value.

Eamonn A

RO no longer sell outside of the USA

Dave,
Nice work.
Would be good to see it if you are coming down to COSMOS.

Eamonn,
Good to hear the spectrohelioscope is under construction.
They are certainly not easy to build.
I had considered it but just felt there was too much involved in it.
What size flat are you using for your heliostat?
How are you motorising it?

Michael.