spectro-aras.com

Hello, I just joined, and would appreciate some advice. I am fortunate to have
access to two 0.6M telescopes, an RCOS24 and a PlaneWave CDK24, and a C-14.
Currently I am using the 24" scopes for exoplanet candidate follow up (and some
lrgb imgaging too), and the C14 for planetary/lunar imaging. I would like to add
spectroscopy, and need some help in equipment selection. I am generally aware of
the SBIG SGS, and have been reading about the Shelyak LISA and Lhires III. I do
not know what type of science can be done with the size and type of telescopes I
have (the RC24 is f/7.8 an the CDK24 is f/6.8, and C14 is f/11). In the price
range of the above instruments, the Shelyak seems to be more fully outfitted, in
that it appears to have an option of adding a calibration module. Some years ago
I had the less expensive SBIG spectroscope, but never used it for a variety of
reasons, including the calibration issue.
Thanks for any direction. I realize that a bit more information on what I want
to do would be ideal, but I am very open to advice on what type of work would be
reasonable for these systems. I plan on attending the SAS meeting in California this year, and hope
to meet some of the members of this group.
With best regards,

Hi Mark,

This is how I see it

It is good idea to match the spectrograph to the scope and seeing as far as practicable and all things being equal the size of the spectrograph scales with aperture. Considering the Shelyak offerings, the LHIRES would be ok on the C14 but, although it can be used with large apertures, is likely to be quite a way from optimum with a 0.6m scope and will either be rather inefficient (You will get some benefit from the larger aperture but not as much as an optimised spectrograph would achieve) or it will not achieve the specified resolution. The LISA and eShel are better matched to this sort of aperture.

It all depends on what you are planning to do though. For example if you need an R of 15-20000 to do what you want then it has to be the LHIRES. (The LHIRES also has the most flexibility allowing you to trade resolution for sensitivity over a wide range by changing gratings but works optimally at high resolution with typically a 200-300mm aperture) Note that it can only look at a part of the spectrum in any one exposure. If you want to go as deep as possible with the big scopes but an R of 600/1000 is adequate then the LISA is what you want. If high stability eg for high precision RV measurement or wide wavelength coverage of relatively bright objects at high resolution is what you are after then the eShel on the big scopes is the setup to go for.

Cheers
Robin
www.threehillsobservatory.co.uk

Thanks Robin, that is a very succinct answer, and is very helpful. I am doing a good bit of reading this week on the topic, and will be back with more specific and focused questions soon.
Best,
Mark