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andrew s

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Posts posted by andrew s

    What draws you to SGL?

    in The Astro Lounge

    Posted

    Obviously, the subject matter is of interest giving both a chance to learn and contribute. 

    However, with some long past exceptions (one when I was reported for abuse) it is the civility of the discussions, the good humour (and bad jokes) that keep me coming back. 

    This is in stark contrast to say the RSPB community which I recently joined.One where I had expected the same friendly behaviour as at their sites. However, some of the replies just make me wince and reluctant to post.

    Regards Andrew 

    • Like 4

    How to get from spectra to magnitude?

    in Radio Astronomy and Spectroscopy

    Posted

    1 hour ago, dan_adi said:

    Thanks Andrew seems to be what I'm looking for, but where do I find these equations? are they specific for a given catalog?

    I am referring to eq. B=B0 -13.028 - 0.01(B0 - V0) etc

    It's  a long time since I looked seriously at this. It's explained in part 3. For a given rig you observe standard photometric stars and then use these to calculate the linear fit constants I.e. an adaptive and multiplicative constant.

    Regards Andrew 

    How to get from spectra to magnitude?

    in Radio Astronomy and Spectroscopy

    Posted

    25 minutes ago, vlaiv said:

    To do that - calibrate on a known star. Take a spectrum of star whose magnitude you know - do the same integration to find numerical constant and then apply this constant back in the case of star you are interested in.

    As explained in the link this assumes you have a wide slit so that you collect equally all the wave lengths. Obviously, it depends on how accurate you want it to be. However,  there are many issues for example atmospheric effects if the known star and target star are at different altitudes.  It's certainly not as easy as differential photometry.

    Regards Andrew 

    • Like 2

    Deconstruction of a life time in astronomy.

    in The Astro Lounge

    Posted · Edited by andrew s

    I always enjoyed building telescopes and instrumentation as much as using them. However,  the time has come to take them all apart and sell them on. Look out for a flood of bargains!

    I will advertise the first on SGL for what I think is a fair price but will consider discounts and offers from long-term members. 

    20231230_130014.thumb.jpg.8590456f4967c128791407372bb18eb4.jpg

    This is just the tip of the iceberg the Paramount and ODK are to big for the loft!

    Regards Andrew

    • Like 1

    First attempt at photometry of an exoplanet transit- HAT-P-53 b

    in Observing and Imaging Double and Variable Stars

    Posted

    30 minutes ago, catburglar said:

    @lunator I did look at the BAA/VSS web pages - but the AAVSO pages seemed a bit more coherent with links / guides that went from start to finish. I’d hope to go back to the BAA (I like to keep it local 🙂 ) and contribute something meaningful when I’ve got a bit better. At this point I’m just seeing if I can get to a useful level of precision without needing major upgrades to my equipment.

    I started with exoplanets because they sound exotic…However, it seems like similar techniques apply to study of CV’s of which there there are also lots of fairly bright targets that can show clear results from a single session…whenever the weather cooperates.

    To me this seems like an almost ‘instantly rewarding’ observational activity, much more so than monitoring many other variable star types- I might get hooked.

    I posted my results on the AAVSO site although there is/was a bug in the search which had not been fixed when I retired from observing. A bonus is NASA may pick up your data! The BAA data base does not take relative flux which is the normal. Nice start, well done.

    Regards Andrew 

    • Like 1

    Photons and mass

    in Physics, Space Science and Theories

    Posted · Edited by andrew s

    2 hours ago, iantaylor2uk said:

    I'm pretty sure people have fired single photons at double slits to show that photons only interfere with themselves (rather than other photons) to create the well known diffraction pattern associated with the wave like behavior of photons.

    Indeed they have. They are dilute beams so that on average only one photon goes through at a time. The beam is not a single photon state in the sense I intended. 

    Regards Andrew 

    PS It might be worth adding for those less familiar with the topic that a single photon doesn't make an interference pattern.  It just makes a localised "hit". You have to pass a large number of single photon throught for the pattern to appear in line with the quantum perdition. Or better still prediction . Thanks @MalcolmP.

     

    • Like 2
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