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More than a year has passed since the construction of the Low Spec spectrograph in version 2.0 provided by the author of the project (@Paul Gerlach).
The project provided for the purchase of a ready-made module for illumination of the slit.
From the beginning, I missed a decent calibration module and slit illumination.
But why buy something for almost PLN 100, when you can illuminate the slit while building a spectrum calibration module and add additional functionality.
Everything is great on the "project":
Inside the device:
But the electrical diagram I drew was not correct (I don't know anything about it at the time).
Not everything worked, so the modifications during soldering and compromises started: D, after a few attempts with soldering and desoldering, my calibration module finally works as it should.
It was important for me that the calibration standard should be stationary (not moving), and this of the available components on the market only provides an imaging flip mirror with a tilting mirror.
It is sold under various brands with T2 threads, so it has a lot of possibilities for mounting various accessories and I made the right module for it.
No store in Poland undertook to order it, so I had to buy it on my own (UK).
RELCO 480 starter spectral lamp:
The cylindrical mirror is a piece of aluminum foil stuck to it for packing sandwiches
Slit illumination also works:
Finally, only one LED informing that the slit illumination is on (the RELCO lamp with the diode on doesn't work).
Now it's time to put together the set:
Low Spec with 2 cameras and a calibration module is very big and heavy:
Solar line tests in diffused light on clouds:
RELCO 480 spectral lines have two values, the upper one is measured by calibrating the spectrum with solar lines, and the lower value is taken from
Richard Walker, CH-Rifferswil, 2017, Glow Starter RELCO SC480 Atlas of Emission Lines, available online: https://www.ursusmajor.ch/downloads/sques-relco-sc480-calibration-lines-5.0.pdf
The difference between my measurements and the data from the Echelle spectrograph from the above atlas is basically negligible, everywhere smaller than 0.2 Å, which means that on my scale it is below 1 pixel.
It seems that the construction of the calibration module was successful.
The calibration module will facilitate a sufficiently accurate calibration of the spectra of faint stars without clear metal spectral lines and in regions where there are no atmospheric oxygen and water absorption lines used for accurate spectral calibration.
I had to capture pictures quickly because I have a drift on the diffraction grating holder (the spectra move over time).
Rather, it is loose, there is a micrometer screw and a spring, so the holder isn't very stable.
I would to improve it next.
On 3-rd of September, just before sunset, I set up my equipment, aimed the telescope towards the zenith, set the spectrograph on the double sodium line and every now and then ran a series of photos, adjusting the exposure time (30-120 s) and gain. At the end it was so dark that the gain had to be increased almost to "what the factory gave".
I was not sure if we would be able to register anything at the resolution of 1800 l/mm holographic diffraction grating, slit with 40 μm wide. I also tracked the height (the depth of the sun below the horizon). I read in some publications that when the Sun is about 8° below the horizon, mesospheric sodium layer is in emission near the zenith above the observation site.
Two disappearing absorption lines and emission lines appearing in their place were recorded:
And an animation with the given position of the Sun relative to the horizon:
The capabilities of the printed in 3D technology my Low Spec spectrograph are amazing.
this little active region put on quite a show and i captured till i ran out of drive space.
160 frames x 40ms delay. (220 frames in each stack) (8 seconds per video capture) (160 captures)
Animated with https://gifmaker.org/
Cropped with avidub. Logo applied with avidub . Levels adjusted with avidub.
Files converted with PIPP and registax 5.1
Three pass Processing done in ImPPG (.xml files attached)
127mm x 1200mm explore scientific first-light achromat with Meade 2x tele-negative barlow. Basler aca720-520um camera.
Baader planetarium 36mm B-BCCD filter for energy rejection
1 angstrom calcium filter from Apollo Lasky @ http://calcium.solar
Thanks for watching!
1.xml 2.xml 3.xml
Today after the midnight I recorded the spectrum of C/2020 F3 (Neowise). I couldn't change new diffraction grating (300 l/mm) before the midnight in my Low Spec 2 spectrograph. I have printed second unmodified mounting for grating and I had to use it, because dispersion angles are different than the 1800 l/mm diffraction grating. It was also necessary to assemble and run the setup. Not all lines were identified, the spectrum is different than spectra published on the internet. The violet range is worse due to the poor correction of chromatic aberration in achromatic lenses in my Low Spec and my APO, so lines are weaker. Intensity hasn't been corrected. I think that this comet was too low above the horizon to do it well. This is also the first light with a diffraction grating 300 l/mm used in the Low Spec 2.
Slit position, PHD2 screen:
Spectrum with stretched histogram, faint LP of my city is present in the background, 5x60s stack:
I hope that I correctly substracted LP from the comet spectrum.
The result obtained in the BASS software:
We have carbon C2 bands, CN and strong emission of sodium doublet. Some lines are unidentified yet.