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Off-band H-alpha images

Posted: Mon Jul 18, 2022 1:58 pm
by thesmiths
By using the "pixel shift" feature of our software, we stepped through the H-alpha line from slightly blue (top left) to slightly red (bottom right). The mosaic below is from -7 to +7 pixels. Data is from a single SER file taken at 06:56 UTC on July 16. Click on the image to see at a larger scale.

The centre (minimum brightness) of the H-alpha line corresponds to the central image. Each shifted image corresponds to a wavelength displacement of 7.9 picometers. The theoretical spectral resolution is about 20 picometers (0.2 angstroms). The range of wavelength shift from blue to red is a total of only 1.1 angstrom. This shows how important the proper tuning of an etalon filter is.

Mosaic of SHG images, pixel shifted from -7 to +7. 700mm FL, 106mm aperture, 2400 l/mm grating, 9 micron lithographic slit.
Mosaic of SHG images, pixel shifted from -7 to +7. 700mm FL, 106mm aperture, 2400 l/mm grating, 9 micron lithographic slit.
075633_shift=--7-to-7-smaller.jpg (628.3 KiB) Viewed 316 times

If you look carefully, you can see the Doppler shift due to the solar rotation. Assuming the rotational speed at the equator is v = 2 km/s, the Doppler shift from the east to the west limb is 2 x v/c x 656.3nm = 8.75 picometers.

Re: Off-band H-alpha images

Posted: Thu Jul 21, 2022 6:59 am
by Montana
I really love it how you can extract so much data from just one video file :bow :bow :hamster:

Alexandra

Re: Off-band H-alpha images

Posted: Fri Jul 22, 2022 5:45 am
by marktownley
Brilliant comparison Douglas.

I'm going to make a copy of this for the reference library as a lot of etalon users will find this useful to I think.