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Old 13th May 2015, 18:21   #76
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No idea why the speed of light does not change in this example. I am not even sure if I am right.



As for a stationery observer outside of the car, the ball is traveling at the speed of the car. But for someone inside the car, the ball is stationery and is not moving. So, probably when thrown outside, X+Y?
1. Speed of light (or any electromagnetic radiation) is constant because it is not a physical wave requiring a medium. The basis of EM radiation is that there is a changing magnetic field which creates an electric field, and if this electric field also changes with time (which it does), it creates a magnetic field, ... ad infinitum. This is the essence of Maxwell's equations. And this what leads to propagation. The propagation of this field happens at the "speed of light". The only thing that affects this propagation speed is the electrical (permittivity) and magnetic (permeability) properties of material through which these travel.

Hence, there is no reference frame requirement for measuring the "speed of light". All EM waves always travel around in the speed determined according to the Maxwell's equations.


2. We assume X+Y because we (1) observe this to happen in our practical lives (2) Newton's laws lead to this result. (Newton's laws also came about to explain all that we were coming across and observing in the 17th century)

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Old 14th May 2015, 10:14   #77
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1. Speed of light (or any electromagnetic radiation) is constant because it is not a physical wave requiring a medium.
Thanks for the explanation. I will read it thoroughly and will take the help of google uncle as well. But your explanation is probably the most clear cut one compared to what I have come across online as yet.

Regards.
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Old 14th May 2015, 10:46   #78
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Thanks for the explanation. I will read it thoroughly and will take the help of google uncle as well. But your explanation is probably the most clear cut one compared to what I have come across online as yet.

Regards.
Sorry, but actually I jumped on the point no1
I just tried thinking yesterday after my post: why would someone assume that light should also go X+Y, and I got my answer perhaps this was also what was going in your mind:
People believe that light comprises of some particles. So the expectation is that the light particle jump off the moving platform and thereby achieve a greater velocity.

But we have experimental results to show that light/EM is actually a wave (yes, it is wave-particle duality - but these particles are not exactly like mechanical slug balls, so let me continue calling them waves).
A wave always propagates at speeds governed by the media properties (elasticity and density), and has no relevance to the source's speed. (This is why we have doppler's effect)

Now the only objection to this is the point that a mechanical wave relies upon a medium. A medium might be moving itself. Therefore the speed of such mechanical waves might change with the frame of reference.
Maxwell's equation led to results that EM waves do not require any medium. Therefore all the light, everywhere has to have same speed.

So there are two things:
1. Light is a wave, and therefore speed depends on medium properties
2. Light is a special wave, and therefore does not even require the presence of a medium!

Now expanding upon this concept, we must also understand that every "reality" that we experience is based on information. And that information is always based on EM radiation.

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Old 30th June 2015, 12:03   #79
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Venus and Jupiter are coming close today evening, will appear like a binary star! Train your eyes westwards today!
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Old 1st July 2015, 19:59   #80
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7:45 pm. Awesome view of Jupiter and Venus holding hands in the western sky. Wish I had a good telescope. The crappy Bushnell 10x25 binocs we have sucks big time.
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Old 28th October 2015, 17:45   #81
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Glad to have stumbled upon this thread. I will now spend a few days to digest this thread

Just a few days ago, I had penned down some thoughts on astronomy, which can be found here. Cheers!
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Old 29th October 2015, 20:52   #82
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Astronomy is also a hobby of mine ...........I also like to read on Aliens/extraterrestrials; any bhp-ians with this hobby?
Hello nitinbose,
Am very glad to know that astronomy is your hobby and that you are also interested in aliens/extraterrestrials. I have been interested in paranormal phenomena - including the field of UFOs & alien/human interactions in general - for many years.

At the time of becoming a T-BHP member (in my introduction thread) I had mentioned my abiding interest in the field, and also that I had been at the recieving end of a lot of ribbing from family members and friends for this unholy interest!

My initial interest was in astronomy too (Stephen Hawking, Sir Fred Hoyle, Carl Sagan) till I came across the writings of Jacques Vallee, J. Allen Hynek, John E. Mack and others. Since then there has been no looking back, and the interest has only deepened!
Cheers,
Shashanka
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Old 2nd December 2015, 10:56   #83
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Folks, here is a moon shot I took yesterday early morning (using a Nikon D5100 hooked to a telescope using a variable eye-piece projection and T-ring)
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Old 2nd December 2015, 11:43   #84
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Folks, here is a moon shot I took yesterday early morning (using a Nikon D5100 hooked to a telescope using a variable eye-piece projection and T-ring)
Goodness gracious, and imagine a few centuries ago who would've thought that common man could get to see the moon barring a few great ones like Galileo, Brahe, Kepler etc!

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Old 2nd December 2015, 11:46   #85
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Goodness gracious, and imagine a few centuries ago who would've thought that common man could get to see the moon!
I agree Alpa1. We are blessed to be in this age of science and technology.
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Old 3rd December 2015, 19:50   #86
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Half moon shot. I am starting to love the night sky. Moon is just the beginning! Woke up at 1am yesterday ☺
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Old 12th December 2015, 05:48   #87
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Great thread. My colleague and good friend had mentioned yesterday that his son is very excited about astronomy and he got him a beginner's telescope from his recent US visit. He was looking if there were any meetups of such astronomy enthusiasts. I saw in earlier posts had some suggestions about meet ups of bhpian astronomers. Do you have them going or do you know of any such meet ups in bangalore?
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Old 16th December 2015, 09:11   #88
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Great thread. My colleague and good friend had mentioned yesterday that his son is very excited about astronomy and he got him a beginner's telescope from his recent US visit. He was looking if there were any meetups of such astronomy enthusiasts. I saw in earlier posts had some suggestions about meet ups of bhpian astronomers. Do you have them going or do you know of any such meet ups in bangalore?
It sure is a very good idea to get a telescope for kids Sure shot way to kindling love for science and nature.

I don't have information about a BHPian astronomy club. However, you can search the internet to find local astronomy clubs. E.g. I found this in Bangalore. You may also visit a local planetarium and inquire about such clubs/events. Planetariums usually host cool events. Hope this helps.

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Old 16th December 2015, 13:15   #89
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. E.g. I found this in Bangalore. You may also visit a local planetarium and inquire about such clubs/events. Planetariums usually host cool events. Hope this helps.
Hey, thanks! This site looks good. We will explore and let you know if this helped
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Old 18th December 2015, 11:27   #90
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With the urge to hook my Nikon DSLR (D5100) to a Kids telescope (50mm aperture, 600mm focal length), I started hunting for some simple adapters to do the trick. Sharing this information to help others aspiring for the same i.e. astrophotography.

1. You would need a T-Ring specific to your camera make (e.g. Canon, Nikon, etc.) This mounts on to your DSLR body (without the lens) and also hooks onto a T-Adapter (read below).
Quote:
A T-ring converts a camera's mount to a standard T-thread. All camera adapters will fit this T-thread.
•Useful accessory allows you to attach a 35mm DSLR or SLR camera to a telescope, camera adapter, and other astrophotography accessories
•Ring attaches securely to DSLR or SLR camera body and provides a T-thread interface
•Couples camera body to standard T-thread found on many camera adapters used for astrophotography
•Securely fits 35mm DSLR and SLR cameras via bayonet-style attachment
•Made of rugged anodized aluminum
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2. You also need a 1.25" T-Adapter. Telescopes generally come with eyepieces of size 1.25". Hence, same size T-Adapter ensures that you can fit it in the telescope eyepiece holder, instead of your normal eyepiece.
Quote:
This T-1.25" Adapter allows for prime focus photography through any telescope with a standard 1.25" eyepiece rack-n-pinion focuser. It is threaded for filters.
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Text and Image source above: Galileo Telescopes India. I bought my adapters from this Mumbai based store. Easy transactions and delivery was made via DTDC. No issues at all

3. A wireless camera shutter release remote. This helps immensely to take steady shots. Without this, the act of steadying the camera+telescope will be a daunting task (due to the weight of the camera and length of the telescope). Due to the great distances involved in observing and shooting astronomical object, the slightest of vibrations/shakes may totally render your object out of the camera viewer. I bought a Nikon ML-L3 wireless remote which does the job for me.
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4. Now, you can couple one end of the T-Ring to your camera body. And you can couple the T-Adapter to the other end of the T-Ring. At this point, you have a camera body (without the normal lens) that is attached to a T-Adapter. This looks like (Image source)-
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Voila! You are now set to hook your camera to a telescope and take some beautiful shots. I would recommend a romantic rendezvous with the moon Trust me, you will be hooked on for months to come. And in the process you will also learn how to perform the balancing act and clicking shots (Trial and error).

I will take a few shots of my apparatus and post them here, for reference sake. Till then, cheers! Hope this post helps
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