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as well today the sun is shining brightly here. I set up the Lunt to have a look at it, at first just for observing. However, somehow I cannot resist and have to do a sketch This time I've chosen reddish pastels on grey paper to better catch the color of the view in the eyepiece.
Telescope: Lunt LS50THaB600PT
Eyepiece: Celestron X-cel 10mm
Date & Time: May 15th, 2020 / 1400-1430 CEST
Location: home terrace, Dusseldorf region, Germany
Technique: red and orange Koh-i-Noor pastels and pastel pens on grey Canson Mi-Teintes pastel paper
Size: 24 x 32 cm
Clear (and sunny) skies!
Taken with the 450D & baby Tak on the Star Adventurer. This is about 5.5 hours of 1.25 minute exposures over two nights, which is the longest I’ve ever managed to image. I just left the camera clicking until the battery ran out. Processed in Pixinsight with flats & bias but no darks. I usually find it very difficult to align the camera with the previous night’s, but this time I left the scope in the same position overnight & placed Merak in the bottom right hand corner which actually worked.
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:
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
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:
By Mandy D
I've just bought a Daystar Solar Scout 60mm DS for H-alpha imaging of the Sun. I am now looking for a suitable camera to use with it. I know I could use my DSLR, but for H-alpha that is not going to give best results, so am looking for a dedicated monochrome imaging camera. I have identified the ZWO ASI178MM as a possibility that fits my budget and has a large enough (I think) sensor to image the entire Solar disc if I use a 0.5 focal reducer which will give me a total focal length of 465 mm.
Does anyone have any experience of this camera in this application, or know if it will be suitable? I know it does not have an IR blocking filter, which I understand is an advantage for H-alpha. The spec is available here: