Building a basic spectroheliograph

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taratasy
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Re: Building a basic spectroheliograph

Post by taratasy » Fri Aug 12, 2016 3:13 pm

Tadaaa ! I'm getting better at this !

CaH sun, treated with photoshop thanks to Wah's awesome tutorial ;) (couldn't get ride of the horizontal lines...)
I seriously need to dump my webcam. The resolution is atrocious and even the minimum exposure is too high -> EVERYTHING is overexposed except the CaH and CaK lines.

This is my first "not so bad" picture !
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Re: Building a basic spectroheliograph

Post by Merlin66 » Fri Aug 12, 2016 10:49 pm

Taratasy <name?>
Certainly improving!
The horizontal banding must be related to camera artifacts....
Onwards and Upwards.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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Re: Building a basic spectroheliograph

Post by Montana » Mon Aug 15, 2016 11:59 am

:hamster: fabulous! keep up the good work :hamster:
Alexandra

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taratasy
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Re: Building a basic spectroheliograph

Post by taratasy » Mon Aug 15, 2016 12:42 pm

Many thanks, all of you guys are a great support !

I put the project on standby untill I get my new camera, I can't get anywhere with my current webcam :roll:

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Re: Building a basic spectroheliograph

Post by highfnum » Mon Aug 15, 2016 2:13 pm

much much better !!!

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Re: Building a basic spectroheliograph

Post by highfnum » Mon Aug 15, 2016 4:27 pm

Once your done with this project
Start monochromator!

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Re: Building a basic spectroheliograph

Post by taratasy » Wed Aug 17, 2016 10:00 pm

taratasy wrote:I put the project on standby untill I get my new camera
In fact, no.
I made some improvement :

- a new holder for the grating, I am very proud of it :mrgreen:
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- a new slit made with cutter blades, more rigid than razor blades -> it makes it easier to set the correct slit width. I didn't tested it yet, it could cause horizontal lignes, I hope not.
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- a new imaging lens which will better fit the new Zwo ASI 120MM camera. This is a Vivitar 75-205mm F3.8, it will be set around 160mm for a good fit of the sun's heigt on the sensor. I think it will also be nice to visualize a wider portion of the spectrum at 75mm :)
(yeah still haven't got rid of rubber bands)
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If the SimSpec excel sheet is right (I'm sure it is) I will achieve a resolving power of 13600 and a dispersion of 0,23Å/pixel (binning on x axis at 2), that's not bad at all for what I hoped to achieve !

I just have one question for the correct slit width :

The pixels are 3.75μm and I need 2 pixels for recording the best signal -> thereby my slit should be 3.75x2 = 7,44μm wide
However I have a reducing factor of 160/200 = 0.8, so the slit gap should be adjusted at 7,44x0,8 = 6μm wide.
Am I correct on this ? 6μm is very tiny :shock:

Thanks all !

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Re: Building a basic spectroheliograph

Post by Merlin66 » Wed Aug 17, 2016 11:57 pm

Taratasy,
Your arithmetic is good....but I think you'll end up with a gap closer to 10-15micron...
This will still be OK due to the anamorphic factor.....
You may find pencil sharpener blades (flat side towards telescope) work even better.....
taratasy SHG.JPG
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"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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taratasy
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Re: Building a basic spectroheliograph

Post by taratasy » Thu Aug 18, 2016 6:35 pm

Thanks Merlin !

I downloaded the spreadsheet "SimSpec SHGa.xls" from the yahoo group "Astronomical Spectroscopy for Amateurs".
There is an typo error : cell D29 and D30 are referencing cell G18 (blank), I think it should be cell G17 :idea:

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Re: Building a basic spectroheliograph

Post by Merlin66 » Thu Aug 18, 2016 10:56 pm

Whoooops,
You are correct!
I'll amend and update.
Thanks.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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Re: Building a basic spectroheliograph

Post by taratasy » Thu Aug 25, 2016 2:54 pm

Welp, I am having problems.

My construction is definetly too poor for correct imaging.
The component can't be aligned correctly, focusing is really difficult to achieve, the camera can't fit tightly to the imaging lens, the whole setup is too heavy for my mount, it shack during acquisition, I got fringe patern on the AVI... and more and more frustration.
A total mess.

I need to reconstruct my SHG in a solid and efficient way, I got some ideas and the motivation.
However I won't be able to do it before next summer (I go back to studies), the project is now definetly in standby.

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Re: Building a basic spectroheliograph

Post by highfnum » Thu Aug 25, 2016 3:42 pm

sorry to hear this

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taratasy
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Re: Building a basic spectroheliograph

Post by taratasy » Thu Aug 25, 2016 3:56 pm

It was something I expected when I first decided to build a SHG. I lacked proper tools and materials, plus it was the first time I built something "complicated".
When I wrote my previous comment I was a little bit frustrated by the amount of time it takes for me to set everything right and take a picture, it is not so bad as I said.

I'm a still very happy to have been able to take a few shot of the sun :D

btw here the best picture I could get of the sun. It is not bad at all, it is just very difficult and time consuming to get this result with my SHG so I prefer stop and rebuild the thing later in order to get the SHG easier and less frustrating to setup and use ;)
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Re: Building a basic spectroheliograph

Post by highfnum » Thu Aug 25, 2016 6:15 pm

image focus is good - not sure how you got that split image did you bump it or wind gust

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Re: Building a basic spectroheliograph

Post by taratasy » Thu Aug 25, 2016 7:19 pm

It is caused by dropped frames.
The two parallele dark lines are caused by the slit but they normaly should be horizontal. Here they appear tilted because the optical train disalign itself during the capture...

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Re: Building a basic spectroheliograph

Post by Merlin66 » Fri Aug 26, 2016 10:39 pm

Taratasy,
Don't be to hard on yourself...
You have managed to assemble a great "proof of concept" SHG and obtained your first spectroheliograms. Well done!
This experience will help you to understand the critical aspects of the SHG design and allow you to better appreciate the accuracy and rigidity required for ongoing success.
You've travelled a good way down the path, your next SHG I'm sure will be much better.
Onwards and Upwards
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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Re: Building a basic spectroheliograph

Post by highfnum » Sat Aug 27, 2016 12:21 am

you are at a more advanced point then I was at same point in time (based on your post)
it took me a long time to get decent images
I still suck at post image processing
I plan to spend more time at this in my retirement
and with chapter 8 in Ken's book

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Re: Building a basic spectroheliograph

Post by taratasy » Sun Jul 30, 2017 8:55 pm

Hi Guys, It has been a long time!
Since last time I completely stopped my SHG project because of a lack of time (end of holidays, had to go back to study) and lack of motivation, I must admit.
Now, I still don't have much time, but I want to try again and build a new SHG (the old one was too wonky, I dumped it). I still have my diffraction grating, the telescope, collimator, and I recently got the famous adjustable optic slit from SupluShed! Now I just need to put everything together in a non-wonky way :mrgreen:
You will hear from me in the coming months.

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Re: Building a basic spectroheliograph

Post by taratasy » Sun Aug 06, 2017 1:26 am

Hi Merlin66,
In your book, chapter 7 page 132, you write that the "Small Refractor Classical Spectrograph" would achieve "a dispersion of 0.15 Å/pixel, a resolution (at Hα −6563 Å) of 0.61 Å (R = 10800) and a wavelength coverage of 244 Å.".
With:

- Telescope—80 mm, 400 mm focal length, f5
- Collimator—50 mm, 180 mm focal length, working at f5
- Entrance Slit—15–20 μm gap, 6 mm long
- Grating—50 × 50 mm, blazed 5000 Å, 1800 L/mm reflective grating
- Total angle between collimator and imaging lens = 35°
- Imaging lens—50 mm, 150 mm focal length, working at f3
- Imaging camera—Webcam/DMK21, 5.6 μm pixel, 480×640 array, 2.8×3.7 mm chip.


However, when I use the SHG spreadsheet (July 16 revision) and enter the configuration above I get a different result:

- Dispersion (r): 0.39 Å/ pixel
- Resolving power (R) : 8460
- Spectral resolution (at 6563 Å): 0.78Å
- Wavelength range 93Å

Am I doing something wrong or is the spreadsheet working differently now?

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Re: Building a basic spectroheliograph

Post by Merlin66 » Sun Aug 06, 2017 2:55 pm

Hmmmm
OK double checking, the answer you achieved seems to be correct.....I note you have selected x2 binning. Without this option the R value increases dramatically, from R=8460 to R=16921
I think I've found where the differences have crept in...During evaluation I varied the cameras and the results shown/obtained were with a DMK51 and x2 binning.
Sorry for the confusion-hope this helps.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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taratasy
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Re: Building a basic spectroheliograph

Post by taratasy » Sun Aug 06, 2017 4:00 pm

Merlin66,
Thank you for your response. Mystery solved :D

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Re: Building a basic spectroheliograph

Post by taratasy » Wed Aug 23, 2017 9:33 pm

So, I played a while with the SHG spreadsheet and I found out a good design for my new SHG. It will have a classical design using camera lens, greatly inspired by Chagnard's work.

The different parts are:

Telescope: a 50mm f/10 lens, fited in a PVC tube
Slit: the one from Surplus Shed
Collimator: 200mm f/5.6 Tele-Takumar lens
Grating: 25x25 1800 lines/mm
Camera lens: 200mm f/3.5 Vivitar lens
Camera: ZWO asi120mm-s

I should get a resolving power of 18000, a spectral resolution of 0.37A and the solar height will fit just right (102%)!
Now I need to find out how I will fit the optical elements on a plywood base and how to correctly align them.
IMG_5954.JPG
IMG_5954.JPG (424.33 KiB) Viewed 1426 times

I already found a way to fit the slit on the Tele-Takumar lens cap:
IMG_5956.JPG
IMG_5956.JPG (348.56 KiB) Viewed 1426 times
Last edited by taratasy on Wed Aug 23, 2017 11:59 pm, edited 2 times in total.

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Re: Building a basic spectroheliograph

Post by Merlin66 » Wed Aug 23, 2017 10:12 pm

Looking promising....
The slit assembly needs to be reversed - the flat side of the slit should face the incoming beam from the telescope.
(I remove the four small screws and use the larger "adaptor" on the other side. Hope that makes sense)
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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taratasy
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Re: Building a basic spectroheliograph

Post by taratasy » Wed Aug 23, 2017 10:22 pm

Oh, the flat side is already facing the incoming beam from the telescope.

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Re: Building a basic spectroheliograph

Post by Merlin66 » Wed Aug 23, 2017 10:57 pm

Ah....
I mis read your message....
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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