AstroSpectroscopy - a type of astrophotography

CCD vs Film? Lots of time vs no patience? Alright, this is your place to discuss all the astrophotography what's and what's not. You can discuss about techniques, accessories, cameras, whatever....just make sure you also post some nice photos here too!
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geyes30
Posts: 132
Joined: Sun Jun 04, 2006 10:07 pm

AstroSpectroscopy - a type of astrophotography

Post by geyes30 »

Recently I started working with spectroscopy, using a DIY grating and a software called RSpec. Since the imaging of the spectra is a type of photography, I thought I'd post it here. However, if this is out of place, please let me know.

Anyway, it is easy to make the grating. Details are here: https://theamateurengineersg.wordpress. ... ctroscopy/

The camera with grating installed:
Image2018-08-31-01-11-21 by Cyrus Beh, on Flickr

Here's the spectrum of Vega, before instrument calibration
Imagevega-with-hydrogen-balmer by Cyrus Beh, on Flickr

And here it is after calibration
ImageVega Emission Lines Labeled by Cyrus Beh, on Flickr

Usually, stars exhibit absorption spectra. However, yesterday I came across Gamma Cassiopaeiae, also known as Navi. This star has emission lines at H-alpha and H-beta!
ImageNavi Emission Lines Labeled by Cyrus Beh, on Flickr

Lots of fun, and science anyone can do.
geyes30
Posts: 132
Joined: Sun Jun 04, 2006 10:07 pm

Re: AstroSpectroscopy - a type of astrophotography

Post by geyes30 »

One of the biggest discoveries in astronomy was that of the nature of nebula. In the early days, it was unclear whether nebulae were under-resolved stars or gas clouds. It was believed that the former was the more likely explanation. So, it was a big deal when it was demonstrated that the nebulae had distinct wavelengths, i.e. they were emission sources with discrete wavelengths, and not continuum emitters. Planetary nebulae are suitable for this sort of experiments. Here is an image of M57, the Ring Nebula, taken with a diffraction grating.

ImageM57 Ring Nebula Spectrum Image by Cyrus Beh, on Flickr

The orange arrow and oval show the position of the diffracted image of the nebula, which shows not a smear, as with stars, but rather a fairly well-defined image. This was the clue that they were in fact gases excited by nearby stars. To determine the wavelength of the emitted light, and hence the type of gas involved, we can calculate it using the spectroscope.

ImageM57 Ring Nebula Spectrum by Cyrus Beh, on Flickr

The wavelength of the diffracted image is around 500 nm, corresponding to the O-III emission line. That is, the gas can be identified to be oxygen, though erroneously identified as a new element dubbed "nebulium" in the 1860s when first observed.
kochu
Posts: 817
Joined: Tue Sep 30, 2003 9:51 pm
Favourite scope: Sharpstar-107PH Triplet.
Location: Jurong West

Re: AstroSpectroscopy - a type of astrophotography

Post by kochu »

Hi geyes30,
Nice to see your posting
I was also considering getting the software Rspec and their 100 lines Grating .
It was good to see from your posting that there is a cheaper alternative and thanks for the same. I will also buy the one through AliExp as it is so much cheaper.
How did you cut the rectangular grating?.
Admin can also consider making a "Spectroscopy" section in the forum.
Kochu/3-9-18
geyes30
Posts: 132
Joined: Sun Jun 04, 2006 10:07 pm

Re: AstroSpectroscopy - a type of astrophotography

Post by geyes30 »

Hi Kochu,

Glad it was helpful to you. Just a word on the cheap grating though - the efficiency seems to be a bit low. That is, the direct star image is quite bright compared to the diffracted image. Although it makes a serviceable spectroscope, the SA-100 may yield better results.

The grating is made of PET, which is quite a soft plastic. So I just snipped a tiny triangle off all four corners. That gets them small enough to glue onto a filter retaining ring.
kochu
Posts: 817
Joined: Tue Sep 30, 2003 9:51 pm
Favourite scope: Sharpstar-107PH Triplet.
Location: Jurong West

Re: AstroSpectroscopy - a type of astrophotography

Post by kochu »

Thanks
No harm in trying the PET grating first.
Kochu
kochu
Posts: 817
Joined: Tue Sep 30, 2003 9:51 pm
Favourite scope: Sharpstar-107PH Triplet.
Location: Jurong West

Re: AstroSpectroscopy - a type of astrophotography

Post by kochu »

Hi,
Did you buy the 100 L one . It is only available in 36 x 18 mm size.
Kochu
geyes30
Posts: 132
Joined: Sun Jun 04, 2006 10:07 pm

Re: AstroSpectroscopy - a type of astrophotography

Post by geyes30 »

Yes I think that's the one I got. It doesn't cover the whole filter, but of you orientate it right it should cover an entire sensor, up to Micro4/3rds.
kochu
Posts: 817
Joined: Tue Sep 30, 2003 9:51 pm
Favourite scope: Sharpstar-107PH Triplet.
Location: Jurong West

Re: AstroSpectroscopy - a type of astrophotography

Post by kochu »

Thanks,
Then I think I will have to go for SA 100. No choice . My Camera sensor is APS C Type and FF
Kochu
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