Spectro talk at IAS?

[Gasman]

Hi guys

Wondered if anyone attended the spectro talk at the International astro show at Warwick today?. Also wondered if anyone bagged an Alpy spectroscope if they were selling them?. Wanted to attend but had other things to do! Seems like the event went down well.

Steve

[WhiteShiva]

I went to the talk. It was very informative, had a lot of information on how to start off although it sounds like the easiest bit is to acquire the date, the hard bit is analysing it and interpreting the results correctly. They had a stand but were only displaying, not selling. I'm interested in the slit system but it is pricey.

[ronin]

I went as the title was spectroscopy with a small scope, I was hoping they it would have a design for an inexpensive spectroscope available, or ideas. Realised that in effect it was given by Shalyak. Their spectroscopes are good but there is just one at around £1K and the rest are over £2K, so didn't do what I had hoped for.

As was said previously it seemed that collecting the data was fairly straight forward, bit like imaging takes time to get, however the processing appeared quite involved.

Unlike AP it appeared that you could not just get some nice images and leave the top end to the real enthuasiasts, it appeared a bit more all or nothing.

[Merlin66]

A couple of comments....

You can start you journey into spectroscopy with a simple Star Analyser grating (or Rainbow Optics) for around 100gbp.

Combine this with your existing scope and camera and you'll obtain good low resolution spectra of various objects - stars, variable stars, Be stars, novae, nebulae etc.

Processing spectra images is no different (well similar!) to processing AP images - the fun part comes when you start to calibrate and prepare a profile for comparison and analysis. There are many free software programs to help you; VSpec, ISIS, SPCaude'ACE, and others. The commercial offering, RSpec is also very good. Each have pretty good tutorials and help menus.

The cost of the "next step" - slit spectroscopy has always been an issue for amateurs. We are a niche area of an already small niche in the "hobby/ pastime" market. It's not like golf or cycling or even stamp collecting - astronomy and spectroscopy have very few followers on a global scale. There's no volume producer of spectroscopes. SBIG ceased production of it's DSS7 and the SGS, Baader are in back order with the DADOS and this only, at the moment, leaves Shelyak with it's various offerings.

It was with this in mind that I started designing (2007) an "IKEA" Kit for amateurs - Spectra-L200. This 200mm Littrow Kit is available to members of the Yahoo group astronomical spectroscopy - the last batch selling for less than $1000. Other DIY designs; Classical ( a flexible multi-resolution design), MG80 (a low resolution 300 l/mm grating) and the FC125 ( a medium resolution folded Classical design ) are available and can be constructed for a couple of hundred dollars.

I honestly believe that amateurs can make a significant contribution to astronomy through spectroscopy. Just takes a bit of effort and some dedication.

The astronomical spectroscopy group is one of the largest support group available and provides 24/7 support to all amateurs interested in spectroscopy and can assist on any problem/ issue you come across on the journey.

"Astronomical Spectroscopy - the final frontier" - to boldly go where few amateurs have go before........

[Gasman]

Very well said Ken !

[ronin]

I know that the area is specialist however the title of the talk was "Spectroscopy with a very small telescope".

It was the "very small telescope" aspect of the title that was of specific interest to me, I had hoped it might point to instruments not in the £2K+ range, a small inexpensive spectrometer perhaps in the £200-300 range other then the grating alone. The thought being you are not going to stick a £2500 spectroscope and £500 camera on a scope costing £300 . Well most of us are not .

They had a talk at Norwich UEA about 3 or 4 years back, through the BAA, that covered spectroscopy and the amauteur contribution to the professional field - interesting talk. If my memory was any good I suspect that Olivier was there at that.

Olivier's talk as good and very enthuastic, however the title and the content didn't meet for me, and it was the title that drew me to the talk. I cannot recall any mention of whatever scopes were used to collect any of the spectra that were presented. Something like "This spectra of Vega was obtained using a 102mm refractor with a 600 second exposure" was never there, would have been useful as well to have some idea. Are we talking of 5 hour exposures or 5 minutes?

Olivier was as said very keen, the talk was good and during the talk I suspect many wanted to tie him down to one spot = In his enthuasium he kept ending up standing in front of the screen and blocking it off - lost count of the times someone asked him to move out of the way, but he still bounced back there eventually :grin: . Walk past his stand and a small handheld spectroscope was thrust into your mit with him telling you to stare at the assorted lights around location he had. He didn't advertise the Shelyak products through the talk, so it wasn't used to push their products - which many would have.

No problems with the talk, or what he talked about, I am familiar with spectroscopy, just what I had hoped might be present wasn't, and I suspect means there is no such item.

The reason I was interested in an inexpensive spectroscope isn't even for me, someone I know has an interest and may have a need/use for one, but the Shelyak items are well outside their budget.

[Merlin66]

Unfortunately there are no small cheap astronomical slit spectroscopes currently on the market. It is possible to buy a direct vision prism spectroscope from eBay and "adapt" it to astronomy ( See "Astronomical Spectroscopy for Amateurs", p 170)

The results are "interesting" - but not exciting.....

The exposure required for optimum spectral imaging depends on the SNR required. For good data extraction you want to target SNR>100, but SNR=20 still can give minimal data say on nova etc.

I have a spreadsheet, SimSpecV4 which will allow you to enter all the parameters - telescope details, spectroscope details, and camera details; this combined with the magnitude of the target star will give a very good "first estimate" of the required exposure....

SimSpec V4_01.zip

[robin_astro]

I

They had a talk at Norwich UEA about 3 or 4 years back, through the BAA, that covered spectroscopy and the amauteur contribution to the professional field - interesting talk. If my memory was any good I suspect that Olivier was there at that.

That was me I suspect. ( I've done about a dozen BAA talks on spectroscopy over the past few years) This was ISTR was a double hander (with me as the amateur) on the WR140 periastron Pro Am campaign .

Shelyak's Alpy is their attempt to bridge the price gap from my Star Analyser to their LISA. The entry module (Alpy 600) is around 550UKP I bought this and the guiding module which works our around 1200UKP in total to complement by LHIRES III (bought as a kit from the original not for profit project) . my ALPY saw first star light last night, report here

http://www.spectro-aras.com/forum/viewtopic.php?f=8&t=598&p=2252#p2252

Cheers

Robin

[Gasman]

Some nice detail there Robin, sounds like you are pleased with the Alpy. Would you recommend it for an F7 refractor at all?

Steve

[robin_astro]

Would you recommend it for an F7 refractor at all?

It should work well provided it is reasonably well corrected. (There were clear signs of achromatic effects from the focal reducer on the C11which meant I had to compromise on the focus of the star and take a wider binning zone than I would have liked to be sure of including all the spectrum)

Robin

[robin_astro]

It should work well provided it is reasonably well corrected. (There were clear signs of achromatic effects from the focal reducer on the C11which meant I had to compromise on the focus of the star and take a wider binning zone than I would have liked to be sure of including all the spectrum)

Here is an example (Using my Alpy with the C11 and focal reducer pushed to higher than designed reduction ratios) of the nasty effects chromatic aberration in the telescope optics can have on low resolution slit spectra.

The chromatic aberration means that the throughput depends on the wavelength as the starlight of a particular wavelength is more or less well focused on the slit. You can see the result of focusing first in the visible and then in the UV.The effect on the throughput at different wavelengths was dramatic and would severely affect the shape of the continuum unless care was taken to make sure the reference star used for instrument response correction was taken with the same focus setting. Note in contrast the sharp Balmer lines running far into the UV due to the well corrected Alpy optics

Cheers

Robin

www.threehilsobservatory.co.uk

[Gasman]

Robin

The ghosting above the spectrum in the UV image, is that the CA you refer to as I used to get quite a lot of that with my C8 when I used its f6.3 Celestron reducer without a slit with the Star Analyser?.

Steve

[robin_astro]

Hi Steve,

It may well be the same effect, though there is also always some scattered light from the grating too. With slitless systems CA affects the resolution rather than the shape of the spectrum as you can still collect all the light.

In this case the inside and outside focus star images in the guider looked very different which I suspect is an effect of running the focal reducer at greater than its design distance. When I optimised focus in the UV, the star image in the guider looked horrible with a sharply focused core surrounded by a huge fainter asymetrical halo. I have now reconfigured the setup to run close to the design distance and the star image looks much more sensible. The effects of chromatic aberration are still apparent in the spectrum but with less of the ghost effect.

Robin