Note: This was originally posted on the Rensselaer Astrophysical Society website in late 2009. Since that website is currently no longer available (2015), this article has been imported into the blog for posterity.

Can Hubble take pictures of Earth?

Unfortunately, the answer is no. The surface of the Earth is whizzing by as Hubble orbits, and Hubble’s pointing system is designed to track the distant stars, not objects on the Earth. The shortest exposure time on any of the Hubble instruments is 0.1 seconds, and in this time Hubble moves about 700 meters, or almost half a mile. So a picture taken by Hubble of the Earth would be all streaks. However, the US government has numerous spy satellites capable of resolving individual people, and some of these may be more powerful than the Hubble when it comes to viewing the Earth. All information on US spy satellites has been confidential since 1972, but it is conjectured they are capable of tracking people based on their gait (walking pattern), clothing, and hair color. For instance, the  HK-12 series of infrared spy satellites are believed to have 3 meter mirrors, which are larger than Hubble’s 2.4 meter. Based on launch data, the HK-12 series is believed to have a mass of 19,600 kilograms, which is heavier than the HST, which is 11,110kg.  It is believed the HK-12 series can take pictures every 5 seconds and has a resolution of 6 inches or better. Furthermore, the US military now has launched the HK-13 series, which is described as a “major upgrade over the HK-12”. There is no information on this series of satellites, and we can only conjecture what kind of technology they have.

Can this telescope (or Hubble) see the Apollo landing sites on the Moon?

The landing sites are easy to see, but it is not possible for any existing telescope to distinguish any man made structures on the moon. An object on the Moon 4 meters across, viewed from Hubble space telescope (HST), would be about 0.002 arcsec in size. The highest resolution instrument currently on HST is the Advanced Camera for Surveys at 0.03 arcsec. So anything we left on the Moon cannot be resolved in any HST image. At best, it would just appear as a dot, but even that is probably not possible. It is possible, however, to see the quartz-corner reflector left by astronauts on the moon by shining a powerful laser bean at its location. This is done fairly often to track the motion of the moon with extreme precision.

What is a good first telescope?

When buying a first telescope, it is important to spend enough to get something which will be enjoyable to use. A lot of amateurs start with a low cost telescope, figuring they can upgrade later as they become more experienced. This ultimately ends up being a waste of time and money. What often happen is they become frustrated when their mount is not stable enough, and they cannot track objects, or when they have trouble seeing nebula and deep sky objects. Many quit astronomy at this point. It is highly recommended that a first telescope be a reflector of at least 5-6 inches in diameter. It is also recommended that people interested in buying a new telescope visit the observatory and try out the various telescopes we have. The Hirsch Observatory has a variety of amateur scopes available and club members are always on hand to answer questions.  Another decision when buying a first scope is whether to get a “go-to” or computerized telescope. There are various options and philosophies to this regard. If one is willing to learn how to properly align and set up a go-to scope, the go-to technology will make it very easy to align and track objects. However, go-to telescopes can be more expensive and it is important to learn how to find objects on your own as well. Go-to systems are never perfect, and it can be frustrating to use without some experience guiding a telescope yourself. Manually finding and locating objects, which is sometimes called “star-hoping” is a skill which takes patience and practice. Even in the era of go-to telescopes, it is worth learning how to find a variety of objects manually, as it will make your overall experience more enjoyable and give you a deeper understanding of the location of objects in the sky.

Is Pluto a planet?

The answer is no. Pluto is not a planet, and this is justified by an International Astronomical Union ruling based on what we know about Pluto. The decision to no longer denote Pluto as a planet has been suggested for decades, but only recently became necessary after several other bodies around the same size of Pluto were found. Pluto is a dwarf planet, which means it is large enough to be spherical in shape, orbits the sun, but is not large enough to clear other objects away from its orbit. So, in a way, Pluto is a planet, but it is important to stress it is a “Dwarf Planet”, and not one of the 8 “Classical Planets”. Many astronomers hesitate to use the term “Dwarf Planet” because it can be confusing, however, this is the official IAU designation. Another dwarf planet is the largest asteroid Ceres. Ceres is only a 12th the mass of Pluto, but is large enough to have a spherical shape. Ceres is an interesting object in its own right and serves as an example of why nomenclature sometimes needs to be changed. When Ceres was discovered in 1801, it was hailed as the “missing planet” between Mars and Jupiter. (Astronomers had long noted that the planets where evenly spaced, but there was a gap between Mars and Jupiter). Astronomy textbooks listed Ceres as a planet for over 50 years, until more bodies where discovered in the region. Sir William Hershel coined the term “asteroid” (“star-like”) for these objects, and eventually, Ceres was no longer considered a planet. Instead, it was 1-Ceres, the first and foremost of the Asteroids. In the same way, Pluto is a member of a newly-discovered class of objects called “Plutoids” or “Trans-Neptunian Objects”(TNOs), and has the distinction of being the first Plutoid discovered. Many other Plutoids have been found, such as Eris, Makemake, Haumea, Sedna, Orcus, Quaoar, and  Varun.  Eris is actually larger than Pluto, and was sensationalized as a “10th planet” in media reports. The fact that Eris was called a planet further confused the public on the issue. It is believed there are probably several  thousand such bodies in a large belt called the Kuiper belt. Appart from not knowing about these objects, another reason Pluto was called a planet in the earlier part of this century is because its mass was believed to be much larger than it actual is. Measuring the mass was essentially impossible in the early part of this century, and was only conjectured to be large in order to accommodate for an unexplained disturbance in Neptune’s orbit. In 1955, it was reported to be about the mass of Earth, and further calculations in 1971 brought its mass down to the mass of Mars. In 1971, measurements of the albedo (reflectivity) of Pluto’s surface found that it was very reflective, and therefore could not be more massive than 1% of Earth’s mass. The discovery of Pluto’s moon Charon in 1978 enabled a very accurate determination of Pluto’s mass using Newtonian physics. We now know that Pluto is tiny: Pluto’s mass is 1.31×1022 kg; less than 0.24 percent that of the Earth, and its diameter is roughly 2,390 km, or roughly 70% that of the Moon. Pluto is less massive than 7 moons in the solar system: Ganymede, Titan, Callisto, Io, Earth’s Moon (Luna), Europa and Triton.

Is 2012 the End of the World?

Modern astrophysics has shown there are several ways that the Earth could be destroyed. (These include being hit by a massive asteroid, being swallowed up by a rouge black hole, or being vaporized in a neutron star gamma ray burst). However, these events are very unlikely, and there is no reason for believing that any of those events are more likely to occur in 2012 then any other year. It is also not true that the Mayan calendar ends in 2012. Rather, December 21, 2012 is the beginning of “long year” 13 of the Mayan Calendar.( A Mayan “long year” is about 394 solar years.) The Mayan calendar references ceremonial dates beyond this year, and there is no apocalypse mentioned in Mayan mythology on 2012 or any other date. The idea of the 2012 doomsday was created by various new-age cult leaders during the past 25 years to attract people to their cults. There are countless examples throughout human history of cult and religious leaders hailing the end of the world and enticing followers to prepare themselves for a new age. As is obvious by the continuing normal existence of the human race and planet Earth, none of such predictions have been correct. It is not true that the Mayan calendar is any different. They made some predictions, most mythical, more like legends than myths, and not one has been showed to have come true. And they certainly were not able to predict the end of their own civilization in the 1600s.

Can you see the ISS/Space Shuttle with the naked eye?

The answer is yes, but you need to know where to look. The easiest way to find the Space Shuttle is when it docks with the ISS. It takes about 1-2 days to approach the ISS and 1-2 days to leave. During that time you can see both the Space Shuttle and the ISS together. I have seen this from the Hirsch Observatory and it is very neat experience. Incidentally, on rare occasions when the Shuttle visits the ISS you can see the Shuttle during launch if you live on the east cost of the US. I was lucky enough to see this from the Hirsch Observatory on March 15 2009. A good website for finding out when the ISS will be visible in your area is

Can you tell that planets are round with the naked eye?

The short answer is that you can see the roundness of Venus, but not of any other planets, because they are much too far away and our eyes cannot resolve their shape. However, a small pair of binoculars will resolve a planet’s disk. It is sometimes possible to see the crescent shape of Venus when it is at perigee, or closest approach to the Earth. The crescent will look like a miniature moon and is very neat to see. It is worth noting though, that there are two major reasons that astronomers have known that planets are different than from stars, even though they appear as points. The first is that they move across the sky during the course of months. The second is that they appear in the sky before stars. This is partially because they are more bright, but it also because they are very small disks, and not points like stars. (Technically or course, stars are extremely small disks as well, but many orders of magnitude smaller than the planets). Since planets are more extended in space, they are less susceptible to atmospheric distortions so they are easier to see.  This is also why planets do not “twinkle” as much as stars.

Have UFOs ever been spotted at the Hirsch Observatory?

We have seen many strange phenomena at the Hirsch Observatory, however, since we have veteran observers on hand, in all cases we have been able to figure out what we are looking at, so as far as I know, no UFOs have ever been seen. It is interesting that among the general public, the object most often taken as a UFO is the planet Venus. Other than the moon, the planet Venus is the brightest object in the nighttime sky, and often hangs low on the horizon. Haze and atmospheric turbulence can give make it blink in and out of view, and even lead to strange changes in colors. We have also witnessed several strange satellite phenomena. The first are Iridium Flares, which are actually very common. You can get predictions for these flares at On one occasion, I also saw a very strange satellite which was blinking on and off with a period of a few seconds. This is possible if the satellite is rotating and the geometry of it’s reflecting surfaces is correct. Birds, illuminated from below by city lights, can also look very strange.

Are the colors we see in astronomy photos correct?

Usually. You have probably noticed that color is often enhanced in astrophysical images for aesthetic reasons. It is true that nebula are actually quite colorful, even though they may not appear colorful through the telescope. Human eyes are not very good at perceiving color under low-light conditions, so the perception of color is very difficult and subjective among different observers. CCD cameras, on the other hand, are much more sensitive. However, color CCD cameras are more expensive and not as sensitive overall, so usually they are black and white. To make color photos, filters are used which take primary colors such as Red, Green and Blue. Three images are taken and then combined. For instance all the cameras in the Hubble Space Telescope are black and white, and colorized later using filters. The colorization process is usually done to best mimic what the human eye would see, but it is never exact. When an image is enhanced, astronomers usually note this in the image caption, so it is helpful to read such  captions. Other times, color is added to show the chemical composition of various gases, or the temperatures of a region. The Hubble website has more information on how they colorize photos.