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I finished observations of the Mizar A spectroscopic binary. Calibration for the Hα line made on water lines contained in the Earth's atmosphere. I used LowSpec spectrograph with 1800 grooves/mm reflective holographic grating, APM APO 107/700, QHY163M camera and HEQ5 mount with guiding. It turned out that the Earth's movement practically compensated for the radial velocity of the Mizar A system. Based on the analysis, I received the result: vr = -8.8 km/s in fact the system is approaching at a radial velocity of -6.3 km/s. I also determined the phase plot of radial velocities based on my measurements for the Na (together for both lines) and separately for Hα line: Error is based on half my spectral resolution (0.2 Å/pix corresponds to rv = 10 km/s). Each measurement corresponds to the stack a few images. The most important purpose of observing this binary system was to record the historical Ca II line (often called as CaK, 3933.66 Å). The distances in the violet part of the spectrum are almost 2x smaller than the corresponding shifts for the Hα line. This line initiated the discovery of spectroscopically binary systems, and Mizar A was the first discovered system of this type. These were the spectroscopic observations in the 19th century: Source: https://www.leosondra.cz/en/mizar/#b20 I've made several observations of this line in the last two weeks: Animation showing the changes in the CaK line based on my observations: Not only the Ca II is split, but the surrounding lines also, shown below in a wider environment: Balmer hydrogen lines are becoming more dense as Balmer's gap approaches (3646 Å). Observation result of the Hα line: And animation showing the changes in this line: The Na I doublet was much more difficult to observe, because stars with A spectral type contain very faint lines of this metal: Animation showing the changes in the sodium doublet: We received the sodium quartet
This system consists of two yellow giants having types G0III and G8III (some sources give K0III), similar masses and brightness. The orbital period of the components is 104 days. The fact that one of the stars has a later spectral type is very convenient . It has stronger spectral lines of metals, including sodium. This allows you to immediately recognize which star is approaching and which is currently moving away. I made 3 observations so far with using a DIY 3D printed LowSpec spectrograph in the version v2 designed by @Paul Gerlach and a 1800 l/mm holographic grating. Based on these observations, the spectral spread for both observations for the sodium line is 0.79 Å (0.079 nm) or 4 pixels, which gives a difference of radial velocities of 40 km/s. Assuming that component A belongs to G8III and component B to G0III: 2019-12-03 component A was moving at relative vr to the barycenter of the system of -20 km/s and component B was moving at a relative vr of +20 km/s. 2020-01-23 component A was moving at a relative vr of +20 km/s and component B was moving at a relative vr of -20 km/s. I called radial speeds relative, because the radial velocity of the Capella barycenter to the Solar System wasn't included. I took the radial velocity of the Capella barycenter into account and I received this phase plot: The background is the plot of radial velocities from paper: M. Weber, K. G. Strassmeier, 2011, The spectroscopic orbit of Capella revisited https://arxiv.org/pdf/1104.0342.pdf
1. Alcyone (Eta Tauri, η Tau, 25 Tau) in the Pleiades open cluster, spectral type B7IIIe+A0V+A0V+F2V. This star is a multiple system, but my goal of observation was the H-alpha profile of the main component: Horizontal axis scaled to radial velocity: 2. Pleione (28 Tau, BU Tau) also in M45, spectral type B8Vne, variable star, the brightness changes in range: 4.83 - 5.38 V. This is the faintest star, which I observed with using APO 107/700 & Low Spec spectrograph 1800 l/mm. It was difficult, but obervation was positive (high gain, exposure time 4 min): 3. Tianguan (Zeta Tauri, ζ Tau), spectral type B1IVe+G8III: (mark ":" according to the VSX database means uncertainty). This is an eclipsing binary with variability type E/GS+GCAS, period is 133 d. The brightness changes in range: 2.80 - 3.17 V. 4. Cih, Tsih (γ Cas), spectral type B0.5IVpe, variable star with a magnitude range of 1.6 to 3 V: 5. Alnitak (Zeta Orionis, ζ Ori), spectral type O9.5Ibe+B0III. Variable star with a magnitude range of 1.74 to 1.77 V. Spectral lines have characteristic P Cygni profile, below H-alpha:
Recently I observed profiles of hydrogen Balmer lines in Sirius spectrum with spectral type A. I used LowSpec spectrograph with 1800 l/mm diffraction grating and APO APM 107/700 on HEQ5 mount. H-alpha: H-beta: H-gamma: H-delta & H-epsilon: I had some problems with stacking, so I used the best single frames in analysis.
I've called it LOWSPEC.2 as it's the updated version of Paul Gerlach's LOWSPEC, a DIY 3D printed spectrograph. I built the first version but had trouble aligning the guide mirror (which was fixed), and locating the slit by waving a torch down the scope made it difficult to use. The updated version is a vast improvement, for me at any rate. 1. The guide mirror can now be adjusted forward and backwards and side to side. I can now actually guide the spectrograph. 2. Adding an Illumination device (Baader). The slit can now be illuminated and the overlay in PHP2 used to locate it. No more trouble getting the star on the slit. There is also the option to use a 30mm dia camera lens instead of 24mm. The camera lens used is 100mm focal length; I had a 30mm dia lens left over from a previous diy project which is 90mm focal length so I used that. I'm not sure of its quality as I bought it for £15 from ebay, but it seems to work ok. I also had a defraction grating of 600 l/mm from a previous project so used that. Paul reckons LOWSPEC will now cope with anything up to a grating of 1800 l/mm. For calibration I used a Philips S10 starter bulb because I found some calibration charts for it, (I think on one of the French websites) and these bulbs are about £1 in B & Q, significantly less than the Relco ones (if you can get them). I made a hole in the top cover, made a container on the 3D printer and now I simply insert it when I need to get a calibration reading. Not the most practical solution but again, it seems to work. If Paul manages to add a calibration unit inside LOWSPEC, that would be the icing on the cake. And if it could just be attached to the existing body that would be a bonus, as it took me 29 hours to print! Here's a couple of shots of the thing itself. The long tube houses the Philips lamp. Here the calibration unit is inserted into the top cover. The first reasonably clear night was moonlit and there was high cloud coming and going, but I went first for Vega as it's easy to image and calibrate with the Hydrogen lines. The salmon coloured line is the A0V reference. The image of Vega looked quite good on the laptop, so I moved on to P Cygni, one of my favourite subjects, and here are the results. I've taken some of the readings from a PDF version of Richard Walker's 'Spectroscopic Atlas for Amateur Astronomers'. It doesn't seem to be available for download any more, I think there's now a book which you have to buy. I may need to get a better guide camera; I'm using an Altair Astro GPCAM mono and when guiding it used a star with a S/N ration of 9.8, the brightest available. But having said that, it managed to keep P Cygni on the slit for 5 minutes at a time. LOWSPEC is a great project if you've started out using the StarAnalyser and want to move to a higher resolution. It takes a lot of patience and persistence, but worth it. I reckon the total cost for LOWSPEC is about a quarter of the cost of an equivalent 'off the shelf' spectroscope, so if you can't justify spending loads of dosh then this is a viable option. Eric.