Dipping my Toe into Spectroscopy

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Dipping my Toe into Spectroscopy

Post by Carbon60 »

A year or two ago I decided to make a solar spectrometer. My intention was to capture spectra at different locations on the solar disk, possibly during solar flares to see if I could detect the changes in the spectral output. My first attempts were fairly crude and the rig is still not yet fully optimised, but wanted to share my results so far. I know this won't be up to Ken's standard, or Peter's, and indeed it is work in progress.

This is the full spectrum from Calcium to Hydrogen Alpha. It comprises around 30 individual frames stitched together manually as ICE couldn't seem to cope.
R-Spec_Full Spectrum.jpg
R-Spec_Full Spectrum.jpg (142.36 KiB) Viewed 2327 times
This is the Calcium K and H image:
Calcium K and H.jpg
Calcium K and H.jpg (593.05 KiB) Viewed 2327 times
...and the specific spectrum for this section.
Calcium K_H 20220301.jpg
Calcium K_H 20220301.jpg (62.46 KiB) Viewed 2327 times
Some other key absorption lines:

G-Line
CH G-Line.jpg
CH G-Line.jpg (573.75 KiB) Viewed 2327 times
Sodium D Lines
Sodium D1 and D2.jpg
Sodium D1 and D2.jpg (819.39 KiB) Viewed 2327 times
Hydrogen Alpha
Hydrogen Alpha.jpg
Hydrogen Alpha.jpg (508.63 KiB) Viewed 2327 times
Hydrogen Alpha 20220301.jpg
Hydrogen Alpha 20220301.jpg (58.59 KiB) Viewed 2327 times


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Dipping my Toe into Spectroscopy

Post by rsfoto »

Hi Stuart,

Great result. Did not know you also work with RSpec ;)

Please describe or send some images of your spectroscope.

I have a french LISA on a TOA 130 with a QSI520i CCD camera.

:bow2


regards Rainer

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Re: Dipping my Toe into Spectroscopy

Post by Carbon60 »

Thanks Rainer. Will do. I’d be interested to see how my spectrum compares with yours.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Dipping my Toe into Spectroscopy

Post by rsfoto »

Hi Stuart,

I have only a resolution of 2.9596 Å per pixel.

I do get in one shot from about 3200Å to 7950Å.

The LISA is working at 1000mm focal length and a slit width of 23µm.

I have been fighting lately with BIAS DARK and FLAT applying.


regards Rainer

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Re: Dipping my Toe into Spectroscopy

Post by p_zetner »

Nice work, Stu.

I’ve always found very interesting spectra associated with proms and active regions. Here is a result from 2019 showing the Ca H region in the disk centre versus an active region. The differences can be spectacular!
Solar Spectrum CaH Region.png
Solar Spectrum CaH Region.png (91.86 KiB) Viewed 2294 times
The BASS2000 spectrum plotted in the figure is based on the data available here:
https://bass2000.obspm.fr/solar_spect.php
You can download the portion of the spectrum you're viewing in csv format using the little "notepage" icon below the display.

I find the BASS2000 spectrum indispensible for calibrating my spectra. On the website, these are displayed at quite high resolution (0.001 angstroms), though, and I have to smooth them to approximate the effect of convolution with my much lower instrumental resolution (~ 0.2 angstroms).

Cheers.
Peter


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Re: Dipping my Toe into Spectroscopy

Post by marktownley »

Be interesting to see how you get on Stu! :)


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Re: Dipping my Toe into Spectroscopy

Post by Merlin66 »

Stu,
Welcome to spectroscopy!
What design of spectrograph have you gone for?
Your spectral image looks a little sharpened/ processed???
I use and recommend BASS Project ( https://groups.io/g/BassSpectro) for all the necessary spectral processing.
It will allow you to stitch together your spectral images (or the individual 1D profiles)
Onwards and Upwards.
Ken


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"Astronomical Spectroscopy for Amateurs" and
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Re: Dipping my Toe into Spectroscopy

Post by Carbon60 »

p_zetner wrote: Thu Mar 03, 2022 5:25 pm Nice work, Stu.

I’ve always found very interesting spectra associated with proms and active regions. Here is a result from 2019 showing the Ca H region in the disk centre versus an active region. The differences can be spectacular!

Solar Spectrum CaH Region.png

The BASS2000 spectrum plotted in the figure is based on the data available here:
https://bass2000.obspm.fr/solar_spect.php
You can download the portion of the spectrum you're viewing in csv format using the little "notepage" icon below the display.

I find the BASS2000 spectrum indispensible for calibrating my spectra. On the website, these are displayed at quite high resolution (0.001 angstroms), though, and I have to smooth them to approximate the effect of convolution with my much lower instrumental resolution (~ 0.2 angstroms).

Cheers.
Peter
Many thanks, Peter. This is really interesting.
I don’t know if I’ll get to your level, but I’ll see how far I can fine tune this device.
Thank you for the tips.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Dipping my Toe into Spectroscopy

Post by Carbon60 »

Merlin66 wrote: Thu Mar 03, 2022 10:41 pm Stu,
Welcome to spectroscopy!
What design of spectrograph have you gone for?
Your spectral image looks a little sharpened/ processed???
I use and recommend BASS Project ( https://groups.io/g/BassSpectro) for all the necessary spectral processing.
It will allow you to stitch together your spectral images (or the individual 1D profiles)
Onwards and Upwards.
Ken
Thank you, Ken. I’ll post some images of my instrument later today.
Yes, the monochrome spectral line images have been sharpened a little for the purpose of presenting them here.
I’ll take a look at the BASS Project website. Thank you for your reminder. I do have a copy of your book on all this, so I’ll review the chapters on processing for more information there.

Cheers.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Dipping my Toe into Spectroscopy

Post by Carbon60 »

Here's my spectroscope.
Spectroscope Internals_1.jpg
Spectroscope Internals_1.jpg (411.88 KiB) Viewed 2216 times
Basically its a wooden box with a 80mm f10 lens on the front (OTA from a Vixen scope). The slit is home made and the grating is a 1200 line/mm 12.5 mm square (at this stage). The collimating lens is a 10mm diameter f10. Both the slit and the collimating lens are mounted on sliding mounts to allow focussing. A pushrod from the collimating lens passes up through the front of the box to facilitate adjustment when the lid is in position.

Two mirrors redirect the output spectrum through a focussing lens onto the sensor. This lens is also mounted on a sliding mechanism with a pushrod to facilitate focussing at the front of the box.
Spectroscope Internals_2.jpg
Spectroscope Internals_2.jpg (718.28 KiB) Viewed 2216 times
The grating is rotated using a third pushrod which is connected to a device that converts rotation motion into linear motion to push and pull the rod and crank the grating around on its turning axis via a clevis and control horn from my RC model aircraft box of spare parts.

The sliding mounts are actually repurposed tile cutter parts.
Tile Cutter.jpg
Tile Cutter.jpg (10.67 KiB) Viewed 2216 times
...and the rotation to linear converter for rotating the grating is a repurposed lipstick case, kindly donated by my wife :D This provides a super smooth rotational action at the grating.
Light Path.jpg
Light Path.jpg (780.13 KiB) Viewed 2216 times

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Dipping my Toe into Spectroscopy

Post by rsfoto »

Hi Stuart,

WOW :o what a great and simple construction

:bow :bow :bow

Just add a few stepper motors for remote adjustment :mrgreen:


regards Rainer

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Re: Dipping my Toe into Spectroscopy

Post by p_zetner »

Stu, that is a terrific instrument!
Beautiful and well constructed.
Love the use of the tile cutters repurposed as optical rails……ingenious!
Cheers.
Peter


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Re: Dipping my Toe into Spectroscopy

Post by Merlin66 »

Stu,
Interesting arrangement!
You don't mention your slit gap, imaging lens detail or camera.
If you add your data to the SimSpec spreadsheet it will give you a good idea of probable performance.
SimSpec V4.3_stu.xls
(78.5 KiB) Downloaded 58 times


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
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Re: Dipping my Toe into Spectroscopy

Post by Carbon60 »

Thanks Guys.

Ken, Thanks for the link to SimSpec.
My imaging lens has a focal length of 400mm and I'm using a Basler acA2440-75um with 3.45um pixels. I'm unsure about the slit width at the moment as I haven't measured it. My estimate is that it's more on the 100um scale rather than 5um but that's all I can offer on this parameter at this stage.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Dipping my Toe into Spectroscopy

Post by Merlin66 »

Stu,
Thanks for that.
The spectral coverage looks like 176A/ frame
If your slit is roughly 50 micron ( a visually narrow gap) then due to the anamorphic ratio and the magnification ratio Collimator/Imager =x4 the effective slit gap will be about 140micron - which is extremely large!!!
This has the effect of reducing the resolving power to around R=2200. With a 10 micron gap this would improve to almost R=10000.
SimSpec V4.3_stu.xls
camera/ imager added
(78.5 KiB) Downloaded 60 times


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
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Re: Dipping my Toe into Spectroscopy

Post by Carbon60 »

Thanks, Ken.
For sure the slit is too wide at the moment for optimal performance and it is in my improvement plan. I was thinking of purchasing one of these at some point https://www.graticulesoptics.com/produ ... slit-glass I just worry about the effect of heat.

A quick question, or two, about the R number. What would be a respectable value? The higher, the better, but for context, what is the R value for your SHG instruments?

Cheers.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Dipping my Toe into Spectroscopy

Post by Merlin66 »

Stu,
That's a good find!
We've been looking for such a supplier for some time.
The LG10 (10 micron x 10mm) looks perfect for the majority of spectroheliograph applications/instruments. The pricing is unfortunately very high!!!

A cheaper and more flexible slit disk is the reflective multiple slit plate produced by Jeulin (based on my original custom design)
https://jeulin.com/jeulin_en/pr-193206.html

If you use a pre-erf in the optical layout (ie a W47+UV-IR for CaK, ND0.9+UV-IR for Na etc and a 35nm (or better) CCD Ha +UV-IR for Ha) then there's no problems using the reflective glass slit plates.
I've been using the 10 micron x 6mm Jeulin slit gap for the past year - no issues.

My MiniSHG uses 125/125 lenses, 10 micron slit, 2400 l/mm grating and the ASI 178MM. I can achieve close to R=35000. Aim for at least > 20000.


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
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Re: Dipping my Toe into Spectroscopy

Post by Carbon60 »

Hi Ken,
Many thanks for this information.
The multi slit plate certainly is a cheaper option and has the advantage of flexible choice of slit width. I’ll look into purchasing one of these.

I’ll also run Simspec to optimise the design for optimal resolution. Thanks for the target R value. This is helpful.

Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: Dipping my Toe into Spectroscopy

Post by MapleRidge »

Very impressive Stuart :bow

It will be great to follow your refinements!

Brian


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Re: Dipping my Toe into Spectroscopy

Post by DeepSolar64 »

This is some interesting stuff. I have thought about buying a basic spectroscope. I wouldn't know where to start on something like this!

James


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Re: Dipping my Toe into Spectroscopy

Post by rsfoto »

DeepSolar64 wrote: Fri Mar 11, 2022 5:55 am This is some interesting stuff. I have thought about buying a basic spectroscope. I wouldn't know where to start on something like this!

James
Hi James,

The simplest spectroscope is the so called Star Analyzer which is a 1.25" screwable filter with a 100 lines per mm pass through grating but in its form not usable at all on the Sun. For analyzing the Sun you would need to take a hand sewing needle or a chrome plated steel ball and measure that reflection.

Here is more information about this

https://www.rspec-astro.com/star-analyser/

A lot of people have started spectroscopy in this way. Me too ...


regards Rainer

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Re: Dipping my Toe into Spectroscopy

Post by DeepSolar64 »

Rainer,
I think I have seen this spectroscopy filter before. Are you talking about one of those chrome plated balls used as yard decorations? They are called “ gazing balls “ or something like that. What prevents the filter from working on the sun behind a hershel wedge?

James


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Re: Dipping my Toe into Spectroscopy

Post by rsfoto »

DeepSolar64 wrote: Fri Mar 11, 2022 2:36 pm Rainer,
I think I have seen this spectroscopy filter before. Are you talking about one of those chrome plated balls used as yard decorations? They are called “ gazing balls “ or something like that. What prevents the filter from working on the sun behind a hershel wedge?

James
What you need for this filter is a point like light reflection of the Sun like a star and only that is the way it would work with the Sun. On stars no problem as the are are pin point light sources.

The smaller the diameter the better for Sun spectroscopy.


regards Rainer

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Re: Dipping my Toe into Spectroscopy

Post by DeepSolar64 »

rsfoto wrote: Fri Mar 11, 2022 2:50 pm
DeepSolar64 wrote: Fri Mar 11, 2022 2:36 pm Rainer,
I think I have seen this spectroscopy filter before. Are you talking about one of those chrome plated balls used as yard decorations? They are called “ gazing balls “ or something like that. What prevents the filter from working on the sun behind a hershel wedge?

James
What you need for this filter is a point like light reflection of the Sun like a star and only that is the way it would work with the Sun. On stars no problem as the are are pin point light sources.

The smaller the diameter the better for Sun spectroscopy.


Yes, makes sense. Like the reflection off of a sewing needle.


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Meade Coronado SolarMax II 60 DS
Meade Coronado SolarMax II 90 DS
Meade Coronado AZS Alt/Az Mount
Astro-Tech AT72EDII with Altair solar wedge
Celestron NexStar 102GT with Altair solar wedge
Losmandy AZ8 Alt/Az Mount
Sky-Watcher AZGTI Alt-Az GoTo mount
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Re: Dipping my Toe into Spectroscopy

Post by Merlin66 »

Guys,
The Star Analyser grating and similar basic spectrographs will not work as a spectroheliograph.
You need a slit spectrograph with a very narrow entrance slit gap (around 10 micron), a 2400 l/mm reflection grating and a fast CMOS mono camera which has small pixels (around 2.4 Micron)


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
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