Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

  • Announcements



Advanced Members
  • Content count

  • Joined

  • Last visited

Community Reputation

138 Excellent

1 Follower

About robin_astro

  • Rank
    Star Forming

Contact Methods

  • Website URL

Profile Information

  • Gender
    Not Telling
  1. Speed Of Stars.

    You already have an estimate of the recession velocity for the galaxy. (The average radial velocity calculated from the redshifts of the two stars) You can then use Hubble's law to estimate the distance. This is only an estimate though as it assumes the recessional velocity is only due to cosmological expansion. In practise galaxies also move due to local gravitation effects and this can give significant errors in distances to nearby galaxies calculated this way (for example the Andromeda galaxy is actually moving towards us!) Robin
  2. Speed Of Stars.

    Strictly speaking this is not the speed of the star it is the radial velocity (The component of the speed in the direction of the observer) Interestingly measurement of galaxy rotation is within the capability of amateurs eg as here by Christian Buil and Valerie Desnoux Robin
  3. Atik 414ex sensitivity claim

    How about just in camera 2x2 binning your ATK460 ? This would give you 9um "pixels" with no increase in read noise per "pixel". ie half (1/sqrt(4) ) of the read noise/area. This is how I use my similar ATK428 for faint object spectroscopy. Robin
  4. I thought the BICEP2 discovery did not stand up to scrutiny and they withdrew it ? eg https://www.space.com/28423-cosmic-inflation-signal-space-dust.html http://sci.esa.int/planck/55362-planck-gravitational-waves-remain-elusive/
  5. Atik 414ex sensitivity claim

    In general I tend to take QE measurements with a degree of caution but this reference suggests the Sony ICX674/694 (the ICX825 is probably similar) has a higher QE than the KAF3200 between 370 and 540 nm http://blog.astrofotky.cz/pavelpech/?p=864 Robin
  6. Atik 414ex sensitivity claim

    Depends how you define sensitivity. If you are looking at the ability to detect faint objects then read and thermal noise matters (and those figures are extremely low for the 414) For example in Christian Buil's comparison of cameras for spectroscopy, even the old 314 matched the KAF3200 cameras in terms of limiting magnitude, despite having a much lower QE at H alpha. (Though the result would likely have been different if the KAF CCD had been cooled to a lower temperature.) http://www.astrosurf.com/buil/isis/noise/result.htm Robin
  7. Six Supernova challenge anyone?

    SN2018pc? That is one that I confirmed spectroscopically :-) https://wis-tns.weizmann.ac.il/object/2018pc/classification-cert Here is how it looked in the spectrograph guider 2018-02-06 Cheers Robin
  8. Unlike the asymmetric events we have observed gravitational waves from (colliding black holes and neutron stars), Spherically symmetric events (such as the collapse of a stellar core of a massive star to produce a black hole) do not produce gravitational waves. Robin
  9. Star Analyser Gamma Ursae Majoris

    Very nice ! Once the IR cut is removed you should be able to see H alpha clearly as well giving you 7 Balmer lines which is an excellent result. Robin
  10. Yep the bigger dips are certainly possible to see using very modest equipment. Here is an observation of mine back in 2004 using just a modified webcam when the technique was in its infancy even for professionals. http://www.threehillsobservatory.co.uk/astro/TrES_1.htm The Sky at Night magazine even got me to write up a tutorial on how I did it, published back in 2005 and reprinted here http://www.skyatnightmagazine.com/feature/how-guide/how-find-exoplanet Cheers Robin
  11. Yes though the exact relationship depends on the wavelength where you make the measurement. As the temperature of a black body increases the total amount of radiation goes up as T^4 and the distribution by wavelength shifts towards the blue. Here is a nice little simulator which shows the effect of temperature on the spectrum of radiated energy. https://phet.colorado.edu/sims/blackbody-spectrum/blackbody-spectrum_en.html Cheers Robin
  12. Yes, measuring an object by allowing it to drift across the field is a standard procedure in radio astronomy. (A radio telescope is effectively a one pixel camera so you have to scan it over the sky to create an "image".) You could track the moon though if you wanted to measure changes with time. I would not expect much over the course of a day, though it might be interesting to compare the signal at full and new moon. The new moon is definitely a strong radio signal. I attended a weekend practical course at Jodrell Bank a few years ago where we were measuring the signal from a galactic radio source (I forget which one) during the day using the drift transit technique. We saw the expected signal and then another unexpected huge signal appeared. Checking a planetarium program we saw that the new moon was next to our intended target in the sky ! Robin
  13. Yep the Sun, Moon and deep space are all approximately black bodies. The distribution of radiated electromagnetic energy with wavelength depends on the temperature. (The Planck curve) For example the maximum of the Planck curve for the Sun at ~5000K is in the visible region. The radiation from the big bang at 2.7K peaks at microwave wavelengths. Cheers Robin
  14. My measurement at microwave wavelengths showing the moon radiating its surface heat away http://www.threehillsobservatory.co.uk/astro/radio_astronomy/radio_astronomy_1.htm Robin
  15. Hi Adam, yes remove the IR block to give you better sensitivity at the far red (and possibly violet) end. The spectrum and sky background regions may not be well set up by default. I forget exactly how it is done in Rspec but you can manually set up the zones that the spectrum and sky background are measured in. It is important not to get any cross contamination. You need to include the full height of the spectrum in the spectrum binning region and only the sky background in the sky subtraction regions. Turn up the brightness in the image to see this more clearly. You can see an example of the selected regions here using ISIS for example. There should be something similar in RSpec (A faint star in a crowded field, yours will be easier !) Cheers Robin