Low res spectrograph

[clive milne]

I'm considering options for a high sensitivity spectrograph, I presume that limits the choice to either Lisa, SGS or Baader dados.

I would appreciate thoughts from members on the best value for money between these three (or any other alternatives).

regards,
~c

[Merlin66 (Ken)]

Clive,
The SBiG spectroscopes are no longer manufactured and were designed for use solely with SBiG cameras.
The Baader Dados has a 200 and 900 l/mm grating option so is more versatile than the fixed 300 l/mm in the LISA.
(Check out Richard Walker's spectral Atlas - he uses the Dados
http://www.ursusmajor.ch/astrospektr...age/index.html
- down the bottom rhs for the latest English version)
On our Astronomical_spectroscopy group we have the plans available for a simple DIY "faint-object" spectroscope - the MG80.
This uses an adjustable 300 l/mm grating, an 80mm collimator and recommends a 50mm f1.8 camera lens for imaging the spectrum.
There's also a FC125, a folded Classical design with various options for the grating (150/300/600 etc), designed around a 125mm f5 collimator...
Let me know if I can help.

[clive milne]

Hi Ken,
thanks for the quick response...

Yes I am aware that SBIG no longer sell their spectrographs, I wasn't aware however that they were only usable for the ST series cameras.... It wouldn't be so much of an issue however as I own an ST10.

I would also be interested to learn more about the MG80 & FC125.

In the interim, I'll read Richard's website.

Thanks once again.

best
~c

[OICURMT]

Richard Walker's Page ... piped through Google Translate...

http://translate.google.com/translat...e%2Findex.html

[Terry B]

Dear Clive
I own a LISA but cant comment on the dados as I havent seen one.
I decided to purchase the LISA as I found that my scope was not big enough to give bright enough spectra with a higher resolution spectrograph.
The purchase process was very easy. I had it freighted directly from Shelyak. I had to pay GST but the customs system worked well.
With the neon calibration unit it is very easy to achieve accurate calibration and the processing pipeline using Isis is simple.
It is a well built device and coupled with a good guider is easy to use.
Using a C11 scope I can obtain reasonable spectra down to mag 14 for SN etc
Cheers
Terry

[el_draco (Rom)]

I'm exploring the possibility of building a LHires III based on the technical drawings I've found online. I've worked out most of how it functions but the drawings call for a fixed reflective slit and I am not sure this is what I want. I'm looking at alternatives at the moment and am open to advice/suggestions if anyone has tried modifying this design. If you're interested in building one, we may be able to colaborate. It's a steep learning curve but doable, I think

Rom

[Merlin66 (Ken)]

Rom,
The original slit was two polished stainless steel blades, which could be "set" to any nominated gap width. The latest LhiresIII uses a chromed multi-slit plate (4 slits).
We found it VERY difficult to cut and polish s/s slit jaws to the required accuracy; then position them to maintain parallel, square surfaces to give the required consistant guide star image. In the end we gave up.

The Astronomical Spectroscopy group has recently got around this problem by designing, developing and getting OVIO (France) to make a Custom chromed reflective slit plate. This plate has 9 slits (100 to 20 micron) and three pinholes (100 to 20 micron). These are now available to members.
We are currently designing and prototyping an indexable holder and guide transfer mirror/ lens system (this will also incorporate a flip mirror/ lens system for reference lamps).
Hope this helps.

[el_draco (Rom)]

Originally Posted by Merlin66

Rom,
The original slit was two polished stainless steel blades, which could be "set" to any nominated gap width. The latest LhiresIII uses a chromed multi-slit plate (4 slits).
We found it VERY difficult to cut and polish s/s slit jaws to the required accuracy; then position them to maintain parallel, square surfaces to give the required consistant guide star image. In the end we gave up.

The Astronomical Spectroscopy group has recently got around this problem by designing, developing and getting OVIO (France) to make a Custom chromed reflective slit plate. This plate has 9 slits (100 to 20 micron) and three pinholes (100 to 20 micron). These are now available to members.
We are currently designing and prototyping an indexable holder and guide transfer mirror/ lens system (this will also incorporate a flip mirror/ lens system for reference lamps).
Hope this helps.

Hi Ken,
My research ruled out tying to construct a set of jaws. Tedious and difficult without the right gear and the cost of a comercial adjustable slit is not that much compared to the sweat required to build one.

The technical drawings for the LHire III demonstrated the principle of the reflective plate to allow guiding but I was not convinced by the technique used. I have been contemplating an adjustable slit with an OAG for guiding but this is only a thought at this point in time.

The OVIO plate may be the answer but this is a new concept for me and part of the learning curve I still have to climb. I assume the OVIO reflective slit will eventually use indexing based on the Hall-effect and I am very interested in this idea.

Rom

[Merlin66 (Ken)]

Rom,
I have to acknowledge that 99.9% of all professional spectrocopes use reflective slit guiding......
It works!
The OVIO Custom plate will be a manual index arrangement....once the telescope/ spectroscope combination has been established there's more need to be able to quick change the gratings than change the slit gap...