Category Archives: Telescopes

How Did Karl Jansky Measure Galactic Radio Emission at 20.5 MHz When the Earth’s Ionosphere Reflects Radio Waves at This Frequency?

Question: If 20MHz waves are ‘bounced’ by the ionosphere, how is it that Karl Jansky detected 20.5MHz waves coming from the galactic centre in 1932?  Also, what sort of receiver would he have used?  — Brendan Answer: I had to … Continue reading

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Is There a Place Where One Can See Daily Radio Images of the Sun?

Question: Is there a place that posts daily images of the Sun in a radio frequency, perhaps 21 cm, something like SOHO does for shorter wavelengths?  — Donna Answer: Unfortunately, I am not aware of a source for regular radio … Continue reading

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How Can One Tell What Telescope Made an Image of a Deep Space Object?

Question: When looking at an image of a deep space object,  how can you tell what type of telescope was used to take the photo?  — Jeni Answer: Unless the caption or other description of the image lists the telescope … Continue reading

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Why are Telescopes Better at Observing Astronomical Objects than the Naked Eye?

Question: Why are telescopes better than the naked eye?  — Amanda Answer: Well, in fact, there are circumstances when the naked eye is a better way to observe astronomical phenomena than a telescope.  For example, if you are interested in … Continue reading

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How to Calculate Heliocentric Julian Date from a Given Julian Date and Object RA/Dec

Question: What is the algorithm for calculating Heliocentric Julian date from a given Julian date and object RA/Dec?  I would like this for a variable star application I’m writing.  — James Answer: I would start with the online calculator provided … Continue reading

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Tatoo Me with the VLA

Question: Hi.  Would you do me a favor to send to me through email the old aerial view graphic of VLA? It is like the Mercedes Benz logo without the circle, with a small rectangular at the intersection of the … Continue reading

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Advice for Purchasing a First Telescope

Question: I am purchasing my first telescope and for good viewing of Saturn, Mars, Jupiter and the Moon, am I best to buy a 130mm aperture or 200mm aperture telescope? Also, I’m deciding whether to go with a telescope that … Continue reading

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What Type of Antennas are Used with ALMA?

Question: Which type of antenna arrays are used in ALMA site?  — Aloka Answer: You can get the answer to this question plus a lot more facts about the Atacama Large Millimeter/submillimeter Array at NRAO’s summary of ALMA.  The antennas … Continue reading

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How Do Very Large Antenna Arrays Synchronize and Work?

Question: How do very large antenna arrays synchronize with each other and why VLAs are used?  — Aloka Answer: Let me point you to a nice description of how radio telescopes and radio telescope arrays work that has been produced … Continue reading

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Why is the Very Large Array Located Where It Is?

Question: Why was the area outside Socorro chosen for the VLA?  — Mary Answer: The following is courtesy of Dave Finley, Public Information Officer at NRAO Socorro. One of the signs on the walking tour addresses this question. The VLA … Continue reading

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