Today was a nice day. The weather was sunny, but not hot and the sky was fairly clear. I already had my telescope in my car for plans that were not starting until after sunset. But I decided to do a bit of sun gazing while the sun was up. “Sun gazing” is a term that might raise a bit of concern since looking at the sun directly can be damaging to one’s vision. Don’t worry, I wasn’t doing that. I was using proper equipment. I grabbed some video clips from my gazing and shared them on my YouTube and Instagram accounts. This post gives further information about that video.
Acquired for the 2017 eclipse, I have a solar filter that covers my telescope’s opening. These filters block more than 99.9% of sunlight. A hole even as small as a pin head would render the filter unusable by letting too much light in. Without the filter, simply pointing the telescope at the sun could be damaging; there could be heat buildup inside the telescope, and whatever is on the viewing end of the telescope will suffer serious burns with exposure of only a moment.
I have a couple of telescopes at my disposal, but that telescope on the motorized mount is generally preferred for a couple of reasons. One is that it automatically points at the planet, star, or nebula that I select from a menu in a hand controller (after some calibration). Another is that it will automatically adjust in response to the earth’s rotation. This last item might not sound significant, but it is! With my manual telescope, once I’ve found a heavenly body, the body is constantly rotating out of view. With proper alignment the body can be tracked by turning a single knob. But it can be a bit annoying when one looks away for a moment only to return and must hunt down the body of interest. The downside of the motorized mount is the weight and the need for electricity. My full motorized telescope setup is over 100 pounds. At home this isn’t a problem, as I can carry the full assembled setup in and out of my home and connect it to my house’s power. For usage in other locations, I must either bring power with me or have my car nearby to provide electricity.
My telescope is a much older unit. It is a Celestron CGEM 800. This specific model is no longer sold since it has been replaced with newer models. With the CGEM 800, there were additional accessories I purchased to add functionality that comes built into some other models. I added GPS to my telescope, which enables it to get the time, date, and the telescope’s location (all necessary information for the telescope to automatically aim at other bodies). I’ve also added WiFi to my telescope. With WiFi, I can control the scope from an app on a mobile device. For some scenarios, this is preferred to scrolling through menus on the two-line text only display on the scope’s hand controller.
While one won’t be viewing any sunspots with it, I also keep a set of eclipse glasses with my setup. I use these when aligning the telescope with the sun. While they are great for looking at the sun, you won’t be able to see anything else through them🙂. If you want to be able to see more details you would need a telescope that filters out specific wavelengths of light. The Meade Solarmax series are great for this. But they are also expensive and only useful for viewing the sun.
These telescopes cost about 1,800 USD.
At this time of the year from where I live, there are only a few bodies from the solar system visible; the sun and the moon. If I were to use the telescope at 5AM I might be able to catch a glimpse of another planet just before the sun begins to wash out the quality of the image. Not something I’m interested in doing. I’ll take the telescope back out later in the year when there is an opportunity to see more.
On another YouTube channel someone mentioned they thought it would be cool if it were possible to control a telescope with a Raspberry Pi. Well, it’s possible. I might try it out. I’ve controlled my telescope from my own software before, and may try doing it again. Later in the year when the other planets are visible, it might be a great solution for controlling the telescope and a camera to get some automated photographs.
On 25 December 2021, the James Webb Telescope (JWT) launched. This last month up to the launch had a couple of delays due to weather and an incident for which they had to ensure there was no damage. At the time that I am writing this, the JWT has not yet been brought up to full operation. But thus far, things have been going well. The JWT is often thought of as the successor to the Hubble telescope. Some call it a replacement, but its capabilities are not identical to that of Hubble. It was designed based on some of the findings of Hubble. I’ve got some readers whose living memory does not go back as far as the Hubble telescope. Let’s take a brief walk-through history.
Edwin Hubble (the person, not the telescope) is most well-known for his astronomical observations and discoveries. Some of his discovers included that there were galaxies beyond the Milky Way, found methods to gauge cosmic distances, and discovered that the further aware from earth that an observed galaxy is, the faster that it is moving away from other galaxies (this is known as “Hubble’s Law”). Edwin Hubble performed many of his observations using what was then the world’s largest telescope, named after James D. Hooker. Naming large telescopes after people was a bit off a tradition.
Space telescopes were proposed in the early 1920s. As is the case with many high investment scientific endeavors, Hubble’s planning was a joint venture that crossed international borders. The USA’s NASA and the European Space Agency both made contributions to Hubble. The project was started in the 1970s with plans to launch in 1983. There were delays that prevented this. But it finally launched in 1990. Much to the disappointment of many, after launch it was discovered that the Hubble’s main mirror was incorrectly manufactured; the telescope was taking distorted images. It was possible to use software to make some corrections in the image, but servicing was needed to correct the problem. Hubble, being positioned in low earth orbit, was accessible to astronauts by way of the space shuttle. A few years after its launch in 1993 a servicing mission corrected the optical problems. Through several other missions Hubble was maintained and upgraded until 2009. The telescope had been used for over 30 years. The telescope is still partially operational now. Some of the gyroscopes have failed as has one of the high-resolution cameras. But some other cameras and instruments are still operational. A near-Infared telescope is functional but remains offline for the time being. It is expected to be able to maintain functionality until 2040.
While Hubble was operating in its earlier years, plans for its successor had begone. Planning for the James Web Telescope began about 1996. The year prior, in 1995, was the Hubble Deep Field photograph. The Hubble telescope was aimed at a dark patch of sky and took a long exposure photograph. For 10 days the telescope collected whatever bits of light that it could. The result was an image that was full of galaxies! Around 10,000 galaxies were observed through the deep field imaging. Visible, infrared, and ultraviolet wavelengths were used in the imaging.
Earlier I mentioned Edwin Hubble’s discovery of how galaxies further aware are recessing from earth at a faster rate than ones that are closer. The faster the galaxy is moving away, the more red-shifted the light from it is. Red shifting is a form of the doppler effect observed on light. Just as the pitch of a sound will be higher in pitch if it is moving toward and observer and lower in pitch when it is moving away, visible light shifts to become red if the source is moving away from an observer and blue if it is moving closer. Part of the purpose of the JWT is to make observations of astronomical bodies much more distant than the Hubble could. Since these bodies will be more red shifted, the JWT was designed to be sensitive to light that is red shifted. While both the Hubble Telescope and JWT have infrared capabilities, the JWT is designed to see light that is much more red. Because of this goal, the JWT has some rather unusual elements of design and constraints.
Objects radiate their heat out as electromagnetic waves. For objects that are hot enough, we are able to see this radiation as light; a hot piece of metal may glow red or orange. Objects with no glow in visible light may still give off light in the Infared spectrum. Such objects include the earth and the moon, which reflect infrared from the sun and emits heat.
The Hubble was positioned in low earth orbit, about 570km above earth. The moon is about 385,000 km from earth. To avoid the glow of the earth and moon, the JWT is much further aware at 1,500,000 km. The Hubble was in orbit around the earth, but the JWT isn’t really in orbit. It is in a Lagrange point. Objects positioned in a Lagrange point tend to stay in position with very little active adjustments needed.
The telescope is still exposed to the sun, which would potentially heat the telescope up and cause the telescope to have its own glow that would interfere with imaging. To prevent the sun from being a problem, the telescope has a multilayered shield on the portion that is facing the sun. The shield is designed to reflect light away and to dissipate heat before it reaches the imaging elements of the telescope. Another unique element of the telescope is the exposed reflector. The reflector is composed of several hexagon-shaped mirrors coated in gold. Gold reflects infrared light very well. Using hexagon segments for the mirror simplifies manufacturing and allows the elements to be more easily folded; the telescope was launched in a fairing with the mirror folded and the sunshield sandwiched over the mirror.
The JWT’s field of vision is much wider than that of Hubble. It collects about 15 times more light than the Hubble and has a wider field of view. The telescope’s look stands out in that there is no tube wrapped around the optical elements. Optical tubes on terrestrial telescopes protect the elements from debris and stray light. Because of the telescope’s sun shield and its position, it won’t be exposed to stray light from the sun. I’ve not been able to find references on any concern for the mirror being exposed to debris in space (despite being a hard vacuum, it isn’t without debris) but unlike on earth, there are not concerns with it collecting dust. With these differences in design and capabilities and design, what are the plans on how this telescope will be used?
While I’m not a fan of this description, I often see its purposed summarized as “looking back in time.” Despite my dislike of this description, it isn’t inaccurate. Light takes time to travel. If you look toward the moon, the light reflected from the moon took 3 seconds to travel to your eyes. You are seeing how the moon looked three seconds ago. For the sun, it’s eight minutes ago. These bodies to change dramatically enough for the delay to make a significant difference. But as we look at bodies that are further away, the time it takes to travel becomes more significant. From Mars to earth is about 22 minutes. Jupiter to earth is about 48 minutes. It takes a few hours for light to travel between Pluto and earth. For other galaxies, light takes years. While light-years is a unit of distance, it also tells you how long it takes for light to travel from a body. The JWT’s light collection capabilities make it capable of seeing light far enough aware to collect information on the earlier universe. The Hubble telescope was able to collect information on the universe from about ~13.4 billion years ago while the James Webb Telescope is expected to collect data from about 13.7 billion years ago. That 300,000,000 difference
As of yet, the James Webb Telescope hasn’t taken its first image. This is about 4 days after launch. It has deployed the sun shield. It will take about another 25 days for the telescope to reach its intended position. Before then, the mirror segments must be unfolded into place. If you are waiting to see images from the JWT, it will be a while. There’s calibration and preparation needed. Other than test images, we might not start seeing full images for another six months.
If you want to keep track of where the telescope is and its status, NASA has a site available showing the tracking data.
Developments on the James Webb Telescope will be slow to come at first, but it should be interesting.
It’s 10:39 AM on January 4th, 2019 as I sit and begin typing this in the Buckhead area of Atlanta. Around the world, if other people were to read that (with appropriate language translations applied), there would be an overwhelming agreement as to how long ago that was. Such an agreement wasn’t always the case throughout human history. Throughout time humans kept different calendars and clocks in different civilizations. It hasn’t always been possible to take a statement like my first sentence and reach the same consensus on it that we do today.
My thoughts in this article are reflecting on the changes in time keeping methods throughout history and how they differ. They are related to a simple question that someone asked me: how do I know what time the sun will set. There are some other astronomy related programs that I plan to discuss in the future and will be referring back to this post when expanded information is needed on a topic.
Across human cultures, one concept of time measurement is derived from the apparent movement of the sun. This is a frequent and common celestial observation that is shared among humanity in most areas on the earth that are populated. Most of us regularly see the sun appear to rise above the horizon in one area of the sky and go back below the horizon in another. At areas close to the polar regions, depending on the time of the year, the sun might not go below the horizon, but instead travels in a circle around the observer (circumpolar movement). The same areas at other times of the year might not see the sun, but they still have the experience of being able to make the celestial observation.
From this observation humans have created the concepts of the day and the night and can communicate about past and future events in terms of the number of instances of this observation. The first division of this period is the instance in which the sun is above the horizon and the times in which it is below the horizon (day and night) and the instances at which it is making this transition (sunset, sunrise). There is also the instance at which the sun is at its apparent highest point in the sky; solar noon.
In East Asia a day was divided into 24 periods. During one of these divisions the starts of the night sky appear to move about the pole by 15 degrees. (Note: you can use the word “hour” to talk about 15-degree increments absent the concept of time). An even finer division of these periods is thought to have come from the Sumerians through the Babylonians. They had a counting system that instead of being base-10 was base-60. The Sexigesimal.
Mean Solar Day
If you measure the passage of time from one sun rise to another you’ll find that it isn’t the same every day and wobbles throughout the year. This is in part from the earth’s orbit around the sun being eliptical instead of circular and part from the 23 degree tilt of the earth with respect to it’s orbit around the sun. The longest period between sunrises is experienced about December 21 or December 22 (the winter solstice) and the shortest is at the summer solstice about June 20. As it turns out the apparent movement of the sun isn’t a great way by itself to keep track of time. But we can take the average (mean) of the length of these periods over a year and use that as a measurement of time. This is the time that our watches and other time pieces are based on; the mean solar day.
Relative to each other the stars appear to not move. From one night to another they appear to be in fixed positions rotating around the earth. This is sometimes visualized as a rotating sphere on which lights are fixed known as the celestial sphere.
Solar observations are not consistent from day to day, but observations of the stars over a considerable period of time are consistent. your face towards the sun at noon on one day and then turned your face to the sun at noon at another day (let’s say 180 days later) you would not be facing in the same direction. If you turn your face towards a star on one night and then turn your face towards the same star on another day both days you are facing the same direction. movements with respect to the starts are sometimes described using a Latin word for stars, sidera. An adjective form of this word is sideral (prnounced sahy-deer-ee-uhl)
Unlike the sun, the stars are in the same apparent position for every 360 degrees of the earths rotation (at least if we are talking about periods of time of a lifetime or less). The earth completes a rotation every 23 hours 56 minutes and 4 seconds. This period of time is called a Sidereal Day. But because a sidereal day is slightly shorter than a solar day on any given calendar date there are 3 minutes and 56 seconds of Sidereal time that occur twice within the same calendar day.
Sidereal time is especially useful in communicating celestial observations. Since sidereal time is related to the position of an observer a celestial observation that is communicated with a direction and a sidereal time can easily be interpreted as the same direction by someone else on the earth. With mean solar time more work is required to do such a conversion.
For Solar Meantime there’s a contemporary preference to using UTC (Universal Time ) instead of Greenwich Time. But since Sidereal time is relevant to a longitude any agreed-up sidereal timezone is inextricably connected to locations. So you will see Greenwich Sidereal Time communicated as one zone of sidereal time with there being a continuous number of Local Sidereal Times as one circumnavigates the earth. Sidereal times, like someone’s position, are continuous and not segmented into a discrete number of zones like solar mean times.
In an era in which a considerable amount of time was needed to move from one populated region to another each area had it’s own local time. There could be variation in the agreed upon time from one region to another, but it didn’t matter much. Once faster forms of transportation became an option (in the form of trains) . It was necessary to coordinate actions in different areas in order to keep schedules.
The second brightest object in the sky, the moon, is also a the inspiration for another time division that is commonly used. Like the stars over the course of 24 hours the moon appears to move with the rest of the celestial sphere. But the moon also appears to move along the celestial sphere. One cycle of the moon moving about the celestial sphere is called a sidereal month. This period last 27.32166 solar mean days. One can also measure the moon’s change in illumination cycles driven by the changing geometry of the positioning of the earth, sun, and moon. The time for this cycle is 29.53059 solar mean days. This period is called a synodic month. The moon goes through 12 complete cycles in a year in addition to a fraction of a cycle. Constructing months based on the whole number of moon cycles will result in a calendar that drifts around the calendar.
The seven day week were followed by Judaism and Islam with one of the days being a day of rest. The Romans had an 8 day week with one of the days being for market day. But eventually roman astrologers assigned a wandering star (planet) to each day of the week. They named the days of the week after Saturn, the Sun, Moon, Mars, Mercury, Venus and Jupiter.
While preparing for a full moon / blue moon, I was looking at an algorithm for calculating sidereal time and had a mini epiphany. The algorithm is basically an elaborate modulo operation. Modulo is generally applied to integer values, but it can be used with decimal numbers and even fractions.
For the algorithm that I have generally used, a lot of the calculations are only for converting the date to some linear expression of time. The calendar that is usually used does not express time linearly.
The amount of time from the beginning of one month to the beginning of another month could be 28 to 31 days. With linear representations of dates, a subtraction operation is all that is needed to know the amount of time between two moments in time.
Acquire the getTime() value for the date in question.
Subtract 1547138420000 from that value.
Get the modulo 86164100 for the resulting value.
Multiply the result by 24/86164100.
The result of these operations is the sidereal time in decimal. If you want to convert it to hour:minute:second format do the following:
var hour = Math.floor(result);
var minute = (result % 1) * 60;
var second = (minute % 1) * 60;
minute = Math.floor(minute)