Remote Imaging with a Lisa?

Olivier Garde of Shelyak was kind enough to answer the question. The problem with true remote imaging is temperture change. The inner lens doublet may change focus with changing temperatures and this cannot be adjusted remotely. Since we have large temperature changes at our Texas Hill Country observatory I have concluded that remote imaging with the Lisa is not for me.

Ed

Hi Ed,

I would forget the LHIRES for remote operation. It is very difficult to operate remotely reliably and has worse stability than the LISA

The ALPYmight be a better bet. I dont have the fast large swings in temperature you have but mine seems pretty stable even from winter to summer. Did you find that when you had the ALPY ?  It it is easy to operate remotely ( I do this routinely without needing to intervene physically, if only over a few dozen yards over wifi)

Getting  photometry from spectra is tough though (Not so much the data reduction side but getting a good spectrophotometric, absolute calibrated spectrum)  Unlike differential photometry, you cannot measure both target and reference simultaneously with a slit spectrograph. This means you need photometric quality skies (or at least spatially and temporaly stable atmospheric conditions long enough to take both target and reference spectra). Also unlike photometric comparison stars, good spectroscopic standards are few and far between.

Alternative approaches could be 

1. Add a seperate scope dedicated to photometry on the same mount

2.  Select the photometry filter wheel plus camera or the spectrograph via a motorised flip mirror 

3.  Do photometry on the guider image (I know someone doing this with the ALPY though the size of the field with sharp enough stars might limit the choice of comparison stars

Robin

Mostly addressed to astro-spectrograph designers/vendors:

(1) When someone makes a high/medium-res spectrograph capable of remote operation out of the box, spectroscopy will get the broader interest from advanced photometrists that we all want it to have. Unlikely before. Yes, we're watching.

(2) It's the most photometric skies that cause the widest temperature ranges. And changing fastest in early evenings when people most want to observe, remotely or not.  Bad luck, but there it is. So you'll simply need to design for that, I suspect.

Hi Robin and Eric:

Thanks to both of you for your comments. Eric, I agree about design.

Robin: Like you, I found the Aply 600 pretty stable and very useable in its full configuration. The problem for my interests is resolution. The Aply simply did not have the resolution I wanted for the targets I am interested in studying. So when I went remote I sold the Aply to a university who could use it for student projects. I note that the AAVSO Spectroscopy programs are mostly for instruments with a minimum resolution of R=1000, so when I thought to acquire another instrument, the Lisa was the minimum-resolution spectrograph I considered. 

I greatly appreciated Olivier's comments and evaluation, I have always found the Shelyak folks to be honest and helpful about their products.

Ed

Hello Ed,

Thank you for initiating the discussion - through it, I am learning more about instruments available for small telescopes! To your point: true, most targets would need R~1000 or more, but lower resolution can provide good information on specific types of stars. For example WR stars (they have huge emission lines which change with time), HerbigAeBe (see our relevant alerts) and some Miras. I can recommend specific objects, if you are interested ...

I hope this helps!

Best wishes - clear skies,

Stella. 

Hi Ed,

I'd keep an eye on the project that a number of SAS folks are working on.  They are 3D printing the spectrograph body, and are designing their units to be remotely controlled.  The jury is still out as to the stability and scattered light issues, but it shows promise at a very low cost.  You have to build your own, though.

I'm modifying a 10-C spectrograph for remote operation, and if you are handy with tools and electronics, refurbishing an existing design is another option.

The Starlight Xpress spectrograph is nearly robotic.  It might be useable for entire nights without changes.

I think a fully robotic commercial spectrograph is likely to be available in the near future, but it isn't available yet!

Arne

I'm sorry to reply so late to this subject....

For my opinion :

- Alpy 600 is a good spectrograph to use it in remote. We have install one on our 2SPOT project in Chile since May 24th and it work very well.

- LISA and LHIRES III are not very stable in temperature variation and no motorisation are available to focus the inner doublet on both spectrograph (and no motorisation for the grating angle for the LHIRES III). LISA can be remotely control if you don't have a large temperature variation during a night, let say around 2-3 degrees.

- Eshel spectrograph is a good choice because it is very stable but cost a lot of money

I think the best solution at this day is the UVEX (available soon with motorisation of the internal mirror and grating angle). You can adjust the resolution you want with many grating (150, 300, 600, 1200 and 1800 gr/mm). UVEX need to be at f/8 to work in good condition. You go far in the near UV and far in the near IR (a typical range coverage is around 3300Å to more than 10000 Å)

Thermal and mechanical stability are key parameters of a spectrograph even if not operated remotely. Good stability should be built in at  the design stage. For example  none of the critical components in the ALPY carry any load which is good for mechanical stability. Thermal and mechanical stability measurements should be part of the manufacturers specification but unfortunately cannot be found for any of the spectrographs for the amateur market. Are there any figures for the UVEX ?

Cheers

Robin