White light non-spectrohelioscope

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Merlin66
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White light non-spectrohelioscope

Post by Merlin66 » Wed Mar 05, 2014 8:14 am

Discussing a possible design for a SHG with a local guy, I got thinking......
Why not "trial" a white light version just to tune the acquisition speeds/ software...could we come up with an "acceptable" white light scanned image????

The idea is pretty simple - you add a slit to the end of your favourite white light scope then image the slit gap with a camera lens/ DMK.....
As the slit scans across the solar disk you generate a series of "white light" strips - to be combined into a final image...
Hmmm sounds like a good mini- learning project.
Keep you posted...
"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

Nick
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Re: White light non-spectrohelioscope

Post by Nick » Wed Mar 05, 2014 11:07 am

There's two ways to do this - during capture or post processing.

Post processing thoughts first:
It's possible to capture at a rate X then in software sample at a lower rate. Interpolation allows for fractional variation. This takes more imaging storage space but allows the fine tuning of the sampling rate to create a circle.
The main issue is that the earths atmosphere will change the rate as the sun rises, peaks and then retreats due to the bending of light.
Lastly - it would be prudent to image and stack the slit in realtime then assemble the stacked slit images.

Capture - guide assistance
A guider that can capture basic details - such as sun spots - can be used to provide a registration point. This could be done in a set of ways:
* FFT alignment with an updated reference image to keep up with solar changes
* FHWM of the solar disk itself - probably best to make a multi-point to cope with convection.
The resulting registration point allows the accurate positioning of the slices.

Oddly enough my own app is built for realtime processing ;) (already has a form of FFT alignment, stacking etc)
Lastly it's possible to transform and register the spectra against known spectra.. a sort of astrotortilla but for spectra.

I think that the main issue is slit-wide resolution.. perhaps a diagonal scan is more preferable in this instance - map and then drizzle.

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Re: White light non-spectrohelioscope

Post by Cschur » Wed Mar 05, 2014 4:30 pm

Ken, you could also set a scope up in the daytime and point at a distant scene and just turn on the drive to scan this scene across the slit. Hold the fast button for accelerated scans.

Chris
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Birch Mesa Observatory, Payson Arizona

Clear Creek Canyon Observatory, Happy Jack, Arizona

Nick
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Re: White light non-spectrohelioscope

Post by Nick » Wed Mar 05, 2014 6:28 pm

Good point - or you could use a circular target with a lower fl scope/lens at the end of the garden. Just use a laser pointer to align the centre point.

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Re: White light non-spectrohelioscope

Post by swisswalter » Thu Mar 06, 2014 5:30 am

Hi Ken

that project sounds great
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: White light non-spectrohelioscope

Post by alex » Fri May 01, 2015 6:32 pm

Nick wrote:There's two ways to do this - during capture or post processing.

Post processing thoughts first:
It's possible to capture at a rate X then in software sample at a lower rate. Interpolation allows for fractional variation. This takes more imaging storage space but allows the fine tuning of the sampling rate to create a circle.
The main issue is that the earths atmosphere will change the rate as the sun rises, peaks and then retreats due to the bending of light.
Lastly - it would be prudent to image and stack the slit in realtime then assemble the stacked slit images.

Capture - guide assistance
A guider that can capture basic details - such as sun spots - can be used to provide a registration point. This could be done in a set of ways:
* FFT alignment with an updated reference image to keep up with solar changes
* FHWM of the solar disk itself - probably best to make a multi-point to cope with convection.
The resulting registration point allows the accurate positioning of the slices.

Oddly enough my own app is built for realtime processing ;) (already has a form of FFT alignment, stacking etc)
Lastly it's possible to transform and register the spectra against known spectra.. a sort of astrotortilla but for spectra.

I think that the main issue is slit-wide resolution.. perhaps a diagonal scan is more preferable in this instance - map and then drizzle.

Hi Nick!

Do you gave any info on this app? Sounds really interesting.

Cheers
Alex

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