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Paul Gerlach

LOWSPEC 3.0 now on Thingiverse

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Looks great, but I've already printed version 2.0.
Are you planning to add a calibration module with a spectral lamp in next version?

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Yes, I'm working on it. Still waiting for some components from China...
As soon as I have produced a good working prototype I will place it online. The plane is to incorporate the calibration unit in the lid. That's why I moved the screw that tightens the guide camera to the other side of the instrument in this version 3. That way I have more space available on the lid side.

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Paul, I am a noob with a tenuous grasp on the slope of a steep learning curve in astrospectroscopy! 

I have been scouring "astro" sites for some good DIY and "How To" projects related to astrospectroscopy, since sometimes, knowing the hardware involved helps me understand the theory but, first and foremost, I am not at all a photographer "looking for a subject".  I am interested in imaging to the extent I can get some useful information from images.  A few months or more ago, I viewed your LOWSPEC on Thingiverse but, at that time, I didn't know why it was designed in any particular configuration.  Since, I have gotten a much better feel for why you designed the LOWSPEC the way you did.  Thanks!

Now, closing in on my question(s),  I see your device uses either a 300 or 1800 line grating.  (BTW, I looked at the graphs and the resolution looks fantastic!)  What is the calculated resolution for each of the two gratings (given some favored slit width)?  (I came across this calculation not long ago but lost the source and haven't done any spectroscopy to have gained an intuitive feel for what the "R" (resolution) number translates to, yet - except, of course, a higher resolution is better.)

What is the full spectral range for each grating (and favored slit combo)?  (This is all assuming that I eventually get some hardware/software for capturing the images - this will be the least expensive of either a DSLR camera or a dedicated imaging device).

Another question is:  What is the estimated cost for all the non-printed parts?  (I have a printer and can manage downloading and printing the body parts. Thanks, again!)

Last question:  What software could I use, or one you'd recommend, for anlaysing data? (My preference is for open-source software - especially at this stage of my abilities and my retiree's budget!)

Regards,

Joe

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Joe,

Everybody started out as a noob 😉, so don't worry.
I've used a 300 and 1800 grating but you can use anything in between. As for the calculations, Ken Harrison has placed a link to an 'adapted' version of SIMSPEC that has the LOWSPEC optical specs already filled in. With that spreadsheet you can play with the numbers (telescope parameters, slit, grating) and see what the resolution is. I've found that it underestimates the resolution a little bit. The measured resolution of the LOWSPEC with the 300 l/mm grating is about 800 and with the 1800 l/mm grating I've measured a resolution of 9500 at H-alpha.
The resolution 'R' is a dimensionless number that is calculated by taking the Full With Half Maximum (FWHM) of a spectral line and divide that with the wavelength of that line. It is not a constant across the spectral range.
The LOWSPEC is designed so that you can scan the whole optical range 400 - 700 nm with gratings up to 1800 l/mm.
As for the cost of the non-printed parts; the optics (lenses, mirrors and one grating) will cost about 600 Euro. But that could be more if you don't live in the EU (customs etc.). The other hardware (nuts, bolts etc.) 10 to 15 euro. It depends where you are. As they all are metric components it's easy for me here in the Netherlands to get them cheap. Especially when a hardware store like 'Hornbach' is in the neighbourhood. There you can even buy things like nuts, bolts, springs etc. per piece. You'll just have to weigh them. If you happen to live in a county like the US then getting your hands on metric components can be a bit of a challenge.

As for software for analysing  spectra, all the ones I know of are Open-Source: Vspec and BASS are the best known.

Regards,
Paul

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I'm at the final stages of constructing LOWSPEC3. I've incorporated the Relco holder provided by drjolo on another thread. When the UK weather gives me a break I'll try it out, but so far so good.

Eric.

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