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Alpy 200, for very faint spectroscopics targets

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#1 Olivier_Garde

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Posted 29 January 2024 - 10:28 AM

Shelyak Instrument is organizing a zoom workshop on their new Alpy 200 spectrograph on Thursday February 8 at 9:00 pm UTC.

This workshop will be led by François Cochard, with the participation of Robin Leadbeater, expert in supernova spectroscopy and enthusiast of extreme targets in spectroscopy, to present the very first results. The workshop will be presented in English and is free of charge:

To register, click here:
https://click.mlsend...Md3BZfN3f0770Qw


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#2 robin_astro

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Posted 29 January 2024 - 10:41 AM

As I expect many of you know I have been using my own version of this for ten years now so it is good news to see this is now commercially available. I developed it primarily for supernova confirmation and classification (In 2016, the first amateur to do this) but here is a quick example of what can be done with such an instrument on faint QSO
https://britastro.or...5f4b3ebf4faaefe

Cheers
Robin


Edited by robin_astro, 29 January 2024 - 10:52 AM.

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#3 pvdv

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Posted 29 January 2024 - 01:24 PM

As I expect many of you know I have been using my own version of this for ten years now so it is good news to see this is now commercially available. I developed it primarily for supernova confirmation and classification (In 2016, the first amateur to do this) but here is a quick example of what can be done with such an instrument on faint QSO
https://britastro.or...5f4b3ebf4faaefe

Cheers
Robin

Very impressive - may I ask how dark your site is / what your non-spectrographic, unfiltered detection limit at SNR 10 on those 1200 secs exposures is ?
I trying to come up with a ballpark estimate of what can be achieved from my site.

TIA



#4 robin_astro

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Posted 29 January 2024 - 03:02 PM

My location is in a small rural village with light domes from nearby towns and some local village light pollution. This is what clearoutside.com says 

 

THO_sky.png

 

I don't really do much deep imaging /photometry so I am not sure what my limiting magnitude is. Perhaps this image (40x20s) gives an idea ?  

https://britastro.or...5ee57a23e83677e

(Though sky conditions then were not as good as for the QSO spectra)

 

This shows an image of the typical sky spectrum with one of the QSO. 

https://britastro.or...70f474be2035d42

The typical LED spectrum dominates the light pollution 

 

Cheers

Robin


Edited by robin_astro, 29 January 2024 - 03:07 PM.

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#5 pvdv

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Posted 29 January 2024 - 06:07 PM

Thanks Robin, very helpful - about half a magnitude better than my skies according to clearoutside.


 



#6 revans

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Posted 30 January 2024 - 06:38 AM

Is this ALPY 200 in production now?  I looked a couple of days ago on the net and didn't see it mentioned on the Shelyak Instruments site and I don't see it listed at the US Shelyak retailer, Woodland Hills Telescopes.

 

Rick



#7 robin_astro

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Posted 30 January 2024 - 07:09 AM

I have been testing a pre-production model. The newsletter sent to subscribers says available early February. I expect Francois Cochard will explain the roll-out at the workshop

 

Robin



#8 revans

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Posted 30 January 2024 - 07:48 AM

I have been testing a pre-production model. The newsletter sent to subscribers says available early February. I expect Francois Cochard will explain the roll-out at the workshop

 

Robin

It would certainly seem to be a powerful new tool well worth adding to any spectroscopists arsenal and with the likely added benefit, at least presumably, of compatibility with the existing ALPY modules and software.  Hope I'm not getting ahead of myself with that thought...

 

Rick



#9 robin_astro

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Posted 30 January 2024 - 08:53 AM

Details of my original version from 2014 are well documented

http://www.threehill...troscopy_20.htm

but I expect full details of the commercial version will be confirmed soon

 

Cheers

Robin



#10 Olivier_Garde

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Posted 30 January 2024 - 10:58 AM

Is this ALPY 200 in production now?  I looked a couple of days ago on the net and didn't see it mentioned on the Shelyak Instruments site and I don't see it listed at the US Shelyak retailer, Woodland Hills Telescopes.

 

Rick

Alpy 200 will be available for sale on the Shelyak website on February 6 or 8, as well as from retailers.


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#11 revans

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Posted 30 January 2024 - 11:24 AM

Alpy 200 will be available for sale on the Shelyak website on February 6 or 8, as well as from retailers.

Will that likely be a pre-order being placed, or are the instruments expected to be deliverable at the time of the order being placed?  Either way is fine, I'm just curious.  I think, if I can afford one, I'd be very interested.  I'm hoping Demetra can be used in its ALPY version with this instrument, but even if this were not the case I would still be very interested in getting one.

 

Rick



#12 Olivier_Garde

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Posted 31 January 2024 - 02:31 AM

The Alpy 200 will be available for sale (without subscription) on February 6 or 8. Several units are already in stock.

Demetra can be used with the Alpy 200 in manual mode, but more information will be given during the workshop on how to calibrate this type of spectra.


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#13 Xilman

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Posted 31 January 2024 - 05:09 AM

My location is in a small rural village with light domes from nearby towns and some local village light pollution. This is what clearoutside.com says 

 

attachicon.gif THO_sky.png

 

I don't really do much deep imaging /photometry so I am not sure what my limiting magnitude is. Perhaps this image (40x20s) gives an idea ?  

https://britastro.or...5ee57a23e83677e

(Though sky conditions then were not as good as for the QSO spectra)

 

This shows an image of the typical sky spectrum with one of the QSO. 

https://britastro.or...70f474be2035d42

The typical LED spectrum dominates the light pollution 

 

Cheers

Robin

I'd guess g=20.5 for bare detection (SNR=3) in that image, which seems well in line with my results with a 0.4m.

 

Send me the original FITS and I should be able to give you a much more accurate estimate, both for 0.1m precision photometry and for bare detection with heavy-duty contrast stretching, the latter of which is fine for astrometry to half a pixel or better.

 

Paul



#14 zoltrix

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Posted 31 January 2024 - 11:05 AM

 Hope I'm not getting ahead of myself with that thought...

 

Rick

your DADOS with L 200 grating and 50 micron slit allow a  R = 272 mm resolution at 550 nm covering a 656 spectral range

it might be comparable to Alphy 200  in term of resolution and luminosity



#15 robin_astro

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Posted 31 January 2024 - 01:18 PM

your DADOS with L 200 grating and 50 micron slit allow a  R = 272 mm resolution at 550 nm covering a 656 spectral range

it might be comparable to Alphy 200  in term of resolution and luminosity

I have not see any spectra of particularly faint targets with the DADOS (please let me know if you have any) but I checked the DADOS manual which quotes a limiting magnitude of for the 200l/mm grating of mag 8 at 50 SNR in a 20minute exposure. 

 

mag 8 is very bright for my ALPY200 (It is really only used for magnitudes fainter than mag 15) but I did find this spectrum I took of RW Cep at Vmag 7.5

https://britastro.or...hp?obs_id=13300

I have just checked the SNR in the  individual exposures. The SNR in the V band was 100 in 30 seconds  so on that basis I think the DADOS would struggle to get to  mag 18 

 

Cheers

Robin



#16 revans

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Posted 31 January 2024 - 02:40 PM

I have not see any spectra of particularly faint targets with the DADOS (please let me know if you have any) but I checked the DADOS manual which quotes a limiting magnitude of for the 200l/mm grating of mag 8 at 50 SNR in a 20minute exposure. 

 

mag 8 is very bright for my ALPY200 (It is really only used for magnitudes fainter than mag 15) but I did find this spectrum I took of RW Cep at Vmag 7.5

https://britastro.or...hp?obs_id=13300

I have just checked the SNR in the  individual exposures. The SNR in the V band was 100 in 30 seconds  so on that basis I think the DADOS would struggle to get to  mag 18 

 

Cheers

Robin

It would seem to me that the number of problems to be encountered getting spectra of faint stars is substantial starting with just getting the target properly identified let alone getting a decent SNR.  But I'm still very keen on picking up an ALPY 200 when one becomes available. I have a long way to go before I break the magnitude 9 barrier :)

 

Rick



#17 zoltrix

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Posted 31 January 2024 - 07:13 PM

I have not see any spectra of particularly faint targets with the DADOS (please let me know if you have any) but I checked the DADOS manual which quotes a limiting magnitude of for the 200l/mm grating of mag 8 at 50 SNR in a 20minute exposure. 

 

mag 8 is very bright for my ALPY200 (It is really only used for magnitudes fainter than mag 15) but I did find this spectrum I took of RW Cep at Vmag 7.5

https://britastro.or...hp?obs_id=13300

I have just checked the SNR in the  individual exposures. The SNR in the V band was 100 in 30 seconds  so on that basis I think the DADOS would struggle to get to  mag 18 

 

Cheers

Robin

 

I simply made a basic consideration

with a C8 and a 50  slit you can get the whole flux from the star yet, according to DADO's specs you should still rely on a good R 272 nm resolution over a 658 spectral range

even on an higher resolution with L900, of course at a cost of a narrow range but DADOs allow to make mosaic

I wonder why a newton 200/1000 and alpy L 200 should perform much better

what are the technical reasons ?

maybe there are no spectra of  faint stars around since DADOs ls not that popular

anyway I think thar Rick should give it a try before picking up an Alpy 200


Edited by zoltrix, 31 January 2024 - 07:21 PM.


#18 revans

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Posted 31 January 2024 - 10:16 PM

 

anyway I think thar Rick should give it a try before picking up an Alpy 200

I'm more like a wave than a particle.... I tend to go through both slits at once :)

 

Rick



#19 zoltrix

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Posted 01 February 2024 - 02:57 AM

old fashion quantum mechanics  :)

there are no waves just particles which do not behave in an ordinary manner



#20 robin_astro

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Posted 01 February 2024 - 09:28 AM

Note that the ALPY200 is a specialist option for the ALPY. For almost all applications the standard ALPY600 will be the better option. The ALPY200 is for a very specific application (Very faint targets with strong broad features at the limit of detection using  very low resolution  ) This is primarily for experienced spectroscopists who  have already developed the skills to measure faint objects but want to explore this demanding region which is currently inaccessible using existing spectrographs. If you use it on bright targets you will be disappointed with the very low resolution results compared with the standard ALPY600.

 

Cheers

Robin



#21 zoltrix

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Posted 01 February 2024 - 11:27 AM

hello

 

that's clear but my remark was:

is it worth while purchasing  also an ALPHY 200 for faint stars if you already own a DADOs ?

do you mean , that ALPHY 200 resolution is even lower than R 272  but still sufficient for supernova in order to get a much higher luminosity ( mag 18) ?

generally speaking  I think that also the sky condition you should  be taken into consideration for a proper  comparison

if I remember you live under a Bortle 4 sky which just a few amateurs can dream of , at least in the over crowded Euiropean countries

maybe the German company Baader was on a realistic side when declaring the performance of its istrument


Edited by zoltrix, 01 February 2024 - 11:28 AM.


#22 robin_astro

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Posted 01 February 2024 - 04:08 PM

hello

 

that's clear but my remark was:

is it worth while purchasing  also an ALPHY 200 for faint stars if you already own a DADOs ?

do you mean , that ALPHY 200 resolution is even lower than R 272  but still sufficient for supernova in order to get a much higher luminosity ( mag 18) ?

generally speaking  I think that also the sky condition you should  be taken into consideration for a proper  comparison

if I remember you live under a Bortle 4 sky which just a few amateurs can dream of , at least in the over crowded Euiropean countries

maybe the German company Baader was on a realistic side when declaring the performance of its istrument

This reply was not directed to you but was a clarification for those interested in the ALPY200

 

I did not make any comparisons with the DADOS, that was you. 

 

All I can do (which is what I always do) is publish the results I get with the equipment and conditions I have.(It is up to others to make equivalent measurements with other equipment) The observations I have made with the ALPY200  can  be found in the BAA database and the supernova classifications are on the Transient Name Server website. 


Edited by robin_astro, 01 February 2024 - 04:15 PM.


#23 Xilman

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Posted 03 February 2024 - 06:21 AM

Note that the ALPY200 is a specialist option for the ALPY. For almost all applications the standard ALPY600 will be the better option. The ALPY200 is for a very specific application (Very faint targets with strong broad features at the limit of detection using  very low resolution  ) This is primarily for experienced spectroscopists who  have already developed the skills to measure faint objects but want to explore this demanding region which is currently inaccessible using existing spectrographs. If you use it on bright targets you will be disappointed with the very low resolution results compared with the standard ALPY600.

Is it not possible to trade off sensitivity and resolution by binning along the wavelength axis? Or am I missing something?



#24 robin_astro

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Posted 03 February 2024 - 10:32 AM

Is it not possible to trade off sensitivity and resolution by binning along the wavelength axis? Or am I missing something?

Yes but  there are also other factors at play here  (primarily efficiency of the optics and camera noise) which don't matter with bright targets at high SNR but become important here at the limit with very low signals and long exposures at low SNR)

 

Cheers

Robin


Edited by robin_astro, 03 February 2024 - 10:37 AM.


#25 JingyuanZhao

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Posted 03 February 2024 - 10:13 PM

I am an amateur astronomer, and I and my collaborators (most of whom are also amateurs) have discovered many transient objects, many fainter than 17 mag. For a long time, Mr. Robin has provided spectroscopic confirmation of some of the transient objects we have discovered using his instruments (Alpy 200/Alpy 600), thank you very much!

 

Since last spring, we have also bought the Alpy 600 spectrograph and have made some classifications, the faintest reaching ~17.5 mag (for example, AT 2023ypg, a nova in M33: https://www.wis-tns.org/object/2023ypg ). Now we can't wait for Alpy 200, which will allow us to reach fainter objects. Hopefully more details will be announced at this workshop.


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