Recent content by JeffOCA

  1. J

    Accretion disk around galaxy NGC 4261

    Ok, the picture link I posted is taken at visible wavelengths that why dust material is not bright. Am I right ? Regards JF
  2. J

    Accretion disk around galaxy NGC 4261

    Hello, When you look at the accretion disk around NGC 4261 (see here), you can read that the dark, dusty disk represents a cold outer region which extends inwards to an ultra-hot accretion disk with a few hundred million miles from the suspected black hole. So, from the outside, you have...
  3. J

    Why Does the Analemma Show an Ellipse for Solstices?

    This analemma (where I see an ellipse for delimiting the solstice) is engraved in the ground, so i think it is an permanent analemma, for multiple years...
  4. J

    What is the significance of JD and how is it calculated?

    Hi Philosophaie, hi everyone For setting, the formula is also : T = alpha - H or, if you prefer : LMST = alpha - HA ? That's it ? Can you tell me what do you mean with "just time changes" ? JD = julian day ? Why giving me the formula for Greenwich Mean sidereal time ?
  5. J

    Why Does the Analemma Show an Ellipse for Solstices?

    Sorry for the misunderstanding, but english is not my mother tongue. I agree analemma makes a figuer 8. On this figure 8, you have on the floor 365 marks for the 365 days of the year. You have also other indications like months, equinoxes, solstices, etc. But, on the figure 8, the position of...
  6. J

    Exploring the Ecliptic Plane's Tilt

    Hi, 1/ The ecliptic plane is tilted at a constant angle (23,45°) as compared to the celestial equator. So, why the angle between ecliptic and equator is +23,45° at spring equinox and -23,45° at autumnal equinox ? 2/ On this document, ε = 23°27'. Why don't we have ψ = ε = 23°27' ? The...
  7. J

    Determining Mass Ratio of Double Star Systems with Spectroscopy

    Ok, but by doing this, you don't use spectroscopy at all (look first post of the thread...) ?
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