Valerio

I had this new attempt with planet Uranus Image taken with Celestron C6 with Lowspec v.3 at 600 l/mm, 40 minutes total (5min x 8subs) with dark frames. Camera ASI 294 MC pro. I had a pretty bad noise ... but anyway I think that the spectrum is not so bad

Yes I am pretty happy with the results. Fun and science, a perfect match 🙂 I must say that sometimes the program does some strange things, above all with labels, and I have to reload everything and start again. You are right the Telluric bands are not perfectly matched, it's strange because I had many good lines in the RELCO reference and I think I have put them correctly in the calibration

I made some more experiments with calibration and acquisition of Sun spectra and Mars spectra. I think that I am getting a pretty good calibration, which I got with a halogen lamp (Flat) and the RELCO lamp. Valerio

Hello, still struggling a little bit on calibration. I was trying to obtain a "final" instrumental response for my telescope+spectroscope. I have read this web page that seems to be pretty clear http://spectro-uvex.tech/?p=1585&lang=en, and also something similar here https://www.horiba.com/fileadmin/uploads/Scientific/Documents/OSD/203_Instrument_Response_Corrections.pdf So I have created with an halogen tungsten lamp (2950K) this spectrum that gives me this 1D profile that I compared with a planck curve at 2950K (green). Dividing one by the other I should obtain the Instrument_response = lamp_signal / black body profile - blue line that "should" be pretty universal for my setup (telescope C6 f/10+spectroscope). Of course this is not valid for the atmospheric corrections, I know, I should follow the second "long" part of the process to add that calibration, too. What I am not yet sure is the curve of the halogen lamp. In the examples in those websites they show a "mountain-like" curve, that goes almost to zero on the right part of the spectrum, but with my setup all the spectra I get are getting more and more bright toward the red part of the spectrum, even if they should go to black I think. Is this due to the IR part of the spectrum that my camera (ASI 294MC PRO) is too sensible to? Should I use an IR-Cut filter to obtain the right spectra (in general)? Also, not still sure which slit to use... it depends on the brightness of the source? Less bright... thicker slit? thanks! Valerio

Very bad weather these past days so I couldn't get more spectra. I hope soon... and I hed no time to look deeply into your great explanation. Next week end I think I will try something Thanks!!!

Hi I tried to get the spectrum of 2 bright stars and analyze them with BASS project. Still learning but improving First one Capella: I was able to calibrate it and try a response correction. Not sure if I went through the best steps for the response correction. After the calibration with the RELCO lampI used a G5III ref spectrum and divided my spectrum bt this one, then I used that curve as the correction response curve. This seems pretty similar to the spectra I found online. I couldn't find a way to add elements lines with the Element name as Ken did in a previous post... just the lines I then tried with Aldebaran. I thought that I could use the same response file, but it doesn't seem to work, it transforms my spectrum too much I think... This is the original spectrum, only with calibration the purple one is with Capella response curve So I tried with a reference spectrum K5III (the same as aldebaran) and I got this curve, that seem more similar to the reference K5 spectrum but it seems it has less "resolution" A lot to learn but something nice is happening 🙂 Valerio

Ken, First of all thank you for your great help. I know, now I have to study BASS project and replicate your graphs. If I understood well you just imported a Sun (G2V) spectrum as a reference to see the absorpion lines in my spectra, correct? Are these spectra available in BASS project? I will improve the calibration with RELCO lamp using 4/5 lamps and install them in fromt of my scope. I see now that the spectrum #1 is not overexposed, but is there some kind of rule of thumb to determine the best exposure of the spectrum to avoid overexposing? I think that it must be more some kind of "visual" rule, but (considering my 4 spectra) lighter spectra in general are better ones? To ceate the Instrument response curve I can use a known star spectrum and divide my spectrum of that star by that one, to obtain the Instrument response ... but once I get it is it always valid with any other object and in every weather condition? thanks Valerio

I finally had an almost clear sky and i tried to get my first "real" spectrum. I used my Celestron Nexstar evolution C6 f/10 with Lowspec version 3. The only visible bright body tonight was Mars (with clouds everywhere) and after a few trial and errors to focus everything I think I got a pretty good result. I'm not sure which is the best spectrum in terms of brightness (exposure time). I tried 4 versions, all with 30um slit: Probably the first one is overexposed... which one is usually the best to use in Bass project to have the best analysis? After that I captured the RELCO calibration lamp, with the same exact positions in the spectrograph, except I had to detach it from the telescope because the lamp was to faint to capture though the telescope lens. Best Valerio

Ken, I am happy my spectrum are improving! :-))) Now I am studying the BASS project and I hope to be able to analyse my own spectra soon. It's possible that something moved in the assembly with these two spectra because I didn't completely close the screws of the cover. I will test with stars and close everything perfectly next time! Camera and grating data are ok but the imaging lens is 100 mm. probably this is the error in your calculations? When sky gets clear I will try with a star. I hope I will not have issues with focus and guiding... Thank you again for your great help Valerio

Ken, thanks for your great analysis. I flipped the grating and tried again with Relco lamp and a blue day sky. The slit is 30um. I tried to keep the central part in focus. What's the better way to obtain a full spectrum in focus? Should I take more images rotating the grating with the micrometer and then compose them together? Are the dark horizontal lines a problem? Valerio

Hi, this is a second test with the inverted grating and full resolution capture. I used a RELCO SC480 lamp What do you think about collimation and focus? I still have to start using BASS Project and of course try to connect the telescope (Celestron C6 f/10) with some real tests Thank you for any feedback Valerio

Thank you Ken, always very kind and precise!

Thanks Ken, very helpful. I have not yet installed BASS Project and will do soon. I must say that the image I posted was a screen grab with cel phone so probably I will have a better resolution with the camera image (ASI294MC PRO) :-)) I will also flip my grating to have the spectrum with blue on left as you say. I will check again the slit disk but since I had difficulties in assembling it in the plastic holder I don't know if I can remove it now --- hahaha --- without breaking it or bending it, but if you say that this probably is not a problem I will try this way. I will post soon another test with full resolution after these changes Question: is it better to use the 1st order spectrum (brighter) or a 2nd order (darker but more spread out?). It depends on the source? Thanks Valerio

the disk I bought is perfectly the same in both sides. Mirror on boh surfaces

Hi I finally finished my lowspec assembly and tested it. First light seems promising. I tried with a normal lamp in front of the opening where the telescope should be. This is the first order spectrum with a 600 lines grating. After that I searched for the central maximum and I found it to the right (micrometer completely pushed in) but when I try to use a longer exposure time the result is this As you can see besides the slit I see around it a strange image, that seems the border of the hole in the plastic of the piece holding the slit disk this is the piece photographed in normal light this is the piece photographed with a light that reflects on the inside of the hole, that shows the orange part around the slit Is this normal? I understand that I was using a very bright light and probably with a star I cannot see this border, but I wanted to know if this happens to you too... Thank you! Valerio