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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
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-delta & H-epsilon:
I had some problems with stacking, so I used the best single frames in analysis.
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:
I bought this filter about one year ago with the aim to protect both my Tak-100 DF and a Quark eyepiece which eventually I never bought. Therefore, I am selling it, hoping that it will go to a good home and be used as it deserves.
It is a top quality Baader ERF for solar viewing with Quarks. It is in excellent condition and comes complete with housing measuring 146mm. The previous owner used to fit it on an Altair 115mm F7 refractor. With some minor modification (essentially adding some padding to the internal side of the housing) it can be fitted on many other telescopes.
It cost £550 but selling for £320 including postage. I will accept PayPal (pay as a friend) or direct bank transfer.
Also advertised on ABS.
Thank you for looking,