"Imaging Sunlight - Using a Digital Spectroheliograph"

I LOVE finding out about different ways to appreciate the Sun and light in general. Use this forum to post your info or questions about various outside the mainstream ways to appreciate our life giving star!
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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Derek Klepp » Wed Jun 08, 2016 8:32 am

Over here in Oz Mark it will be a while for me even with a pre order.

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by highfnum » Wed Jun 08, 2016 9:05 pm

well its here for me
here is shot below my German Sonne lithograph :D

Nice tribute to SwissWalter
bookshg.jpg
bookshg.jpg (192.64 KiB) Viewed 5657 times

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by [whrudey] » Wed Jun 08, 2016 9:29 pm

Congratulations Ken - just ordered my copy from Amazon.com

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Merlin66 » Tue Jun 21, 2016 3:00 pm

some positive comments over on CN....
Any feedback/ comments from the members??
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
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"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by solarscope180 » Tue Jun 21, 2016 3:09 pm

Great book, i have been reading it with great interest.
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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by highfnum » Tue Jun 21, 2016 9:13 pm

chapter 8 (software) makes it all worth it to me
i also like the historical images (has any one tried to build an image by memory only?)

but i would not give a review until i absorb more (completion)

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Montana » Thu Jun 23, 2016 11:42 am

I have it but not read it yet :)
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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Spectral Joe » Thu Jun 23, 2016 5:38 pm

Particularly for those interested in building one of these, and also for explaining the nature of these to the unfamiliar, this is a well written overall view . The details necessary to construct a working instrument are there, the theory and history are explained and examples are given. One of the unfortunate things I have seen over the years is that people underestimate the magnitude of these projects and get frustrated after starting, when they realize that success isn't coming overnight. The process is laid out here in sufficient detail that the mystery is swept away and prospective builders can launch into the effort pre-informed. Even if you are not interested in building one of these it is worth reading, so as to have a more complete understanding of the "other" way of doing monochromatic imaging. Well done, Ken!
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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by highfnum » Thu Jun 30, 2016 12:44 am

i like to try 6.7.13 to reproduce days of old

is 100u slit wide enough ?

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Merlin66 » Thu Jun 30, 2016 8:32 am

Huggin's method was to find a prominence using a narrow slit setting, probably around 30 micron and then open up the slit gap, tangential to the disk to >1mm.
I've tried this, using the PST to locate the prom and then positioning the SHG (pre-tuned to Ha) slit to match.... fiddly but achievable.
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"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by thesmiths » Sat Jul 02, 2016 8:28 pm

I just received my copy today from Amazon. What an amazing amount of time and dedication to detail to produce such an impressive volume. I have copies of Ken's other two books on astronomical spectroscopy, which I bought and read mainly to understand solar spectroscopy (despite their being mainly oriented towards night-time work).

As Ken points out, the part of the SHG that is evolving the quickest today is the camera (due to continued advances in semiconductor technology). Ideally, a camera should have small pixels, a large chip size, excellent noise characteristics and very fast frame rate. This allows building smaller and lighter instruments with comparable resolution and faster scan speeds.

My SHG work was done with the ZWO ASI 120MM, a USB 2.0 camera with 3.75 micron pixels and 1280 pixels wide sensor. Although I have not done any SHG imaging in the last year, I would definitely look to upgrade my camera to something like the newer ZWO ASI 290MM, a USB 3.0 camera with 2.9 micron pixels and 1936 pixels wide sensor. This would probably allow a reduction by at least a factor of two in the data acquisition time. Also, the ASI 290MM, because of its back-illuminated CMOS image sensor, claims to have "two or more times the sensitivity in the visible-light region and three or more times the sensitivity in the near infrared light region" than previous Sony sensors.

The other area of SHG design that I think deserves more attention is better slit design. I used a Thorlabs 3mm long, 5 micron wide fixed stainless steel slit. The main problems with this choice are: 1) a bit too short [better if they were more than 5mm long]; 2) they easily get dirty and are difficult to clean; 3) there does seem to be some gradual damage to the metal from the intense solar radiation after long usage. Perhaps a better solution is a custom-made lithographically defined slit (e.g., chrome on quartz). These are often used now in night-time spectroscopy [chrome on quartz masks are used in semiconductor processing and hold up well under intense radiation]. This could either be a transmission slit or perhaps even a reflective slit. Such slits would be more uniform and more stable.

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Merlin66 » Sat Jul 02, 2016 9:03 pm

Douglas, thanks for the comments.....
I agree the SHG needs good quality long (>5-6mm) slit assemblies.
There are varying opinions as to whether or not they need to be fully adjustable - to maximise the usage across different telescopes/ focal lengths, spectrograph magnifications and camera pixel sizes.
Making a DIY slit assembly can be time consuming, but the results can also justify the effort.
I tried with the Spectra-L200 to offer the alternative of a rotary multi slit reflective slit plate. This provides a range of 6mm long slits from 19 to 100 micron. These are produced by etching the slit gap on a chrome plated glass (1.5mm thick) substrate. This arrangement works well for conventional spectrographs but does, I admit, have some restrictions for the SHG. I don't know if it is possible to replicate this design on quartz disks, but I can at least investigate.....
"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: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Carbon60 » Thu Jul 07, 2016 8:23 pm

Arrived in the post today. :)

Nice job, Ken.

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by highfnum » Sun Jul 10, 2016 12:43 pm

going thru some software links
Wah!'s spectral line merge not listed in links??

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Merlin66 » Sun Jul 10, 2016 4:09 pm

Wah!, hasn't given a direct web link to his software...it exists as an email link...
I can however send anyone interested a copy from my files.
Let me know.
"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: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by highfnum » Mon Jul 11, 2016 11:02 am

it would be nice if a link existed in this forum or this forum had a download section
or a section of links of all needed software collected in one point

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by marktownley » Mon Jul 11, 2016 1:14 pm

highfnum wrote:it would be nice if a link existed in this forum or this forum had a download section
or a section of links of all needed software collected in one point
Start a thread with the info you want then we can sticky it at the top of the page :)
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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by p_zetner » Mon Jul 11, 2016 4:18 pm

Finally got my copy. A very nice read, Ken and a sorely needed, up to date, compendium of amateur achievements.

Cheers.
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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by highfnum » Mon Jul 11, 2016 6:54 pm

ok

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Sungrazer » Mon Jul 25, 2016 2:43 pm

Where is the best place to buy it and your other book in Sydney please ??
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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Merlin66 » Mon Jul 25, 2016 4:29 pm

Good question!
Honestly don't know, you'd have to check around.
I think most of the members have been purchasing from Amazon...
I'll be back in Oz next week, if you still have problems let me know - I can probably help..
"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: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by highfnum » Fri Aug 05, 2016 2:50 pm

Sitting around a saltwater pool
In NJ I'm reading thru 7.5 about how to take avi sequence. Nice job on how to use eq mount setting to set up for sequence.

An idea poped in my head


Instead on turning off tracking before actual sequence set slew speed to a low value and then force tracking to that speed to shorten time it takes the sun
To run across slit


Would that work or introduce ugly things???

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Merlin66 » Fri Aug 05, 2016 3:59 pm

Yes, you can certainly use the fast slew rates of your mount to speed up the solar scan.
Wah! uses x2 or x4 sidereal rate.
"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: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by Spectral Joe » Fri Aug 05, 2016 5:04 pm

The only limitations are exposure time (getting enough light) and how fast your camera can acquire the data. My instrument scans the solar image across the slit internally while the telescope is tracking. A full disk is done in 6 seconds.
Observing the Sun with complex optical systems since 1966, and still haven't burned, melted or damaged anything.
Not blind yet, either!
Light pollution? I only observe the Sun, magnitude -26.74. Pollute that!

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Re: "Imaging Sunlight - Using a Digital Spectroheliograph"

Post by highfnum » Fri Aug 05, 2016 7:18 pm

Thx

Cool I gotta try at first opportunity

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