Tag Archives: International Occultation Timing Association

IOTA Announcement – Occultation By Neptune’s Moon Triton – 5 October 2017

Greetings, fellow astrophiles!

The following recently came across the ASRAS email list from ASRAS and IOTA member Brad Timerson. If you’ve the gear for it, this is an excellent chance to contribute to some far-out science.

There will be an occultation of a 12.5-mag. star by Neptune’s large satellite Triton the early evening of October 5th (just before 8pm EDT) that will be visible from east of the Appalachian Mountains. It’s the brightest star to be occulted by Triton since the Voyager flyby showed that the satellite has a substantial atmosphere with interesting dark plumes. The occultation will allow us to learn more about the atmosphere, and its variation with altitude and latitude. Sofia plans to fly over the Atlantic, to try to catch the central flash, where Triton’s whole atmosphere will focus/amplify the star’s light, probing deeper parts of the atmosphere. This might also be observed from Florida, but observations anywhere from the East Coast area are sought, to sample a wide range of latitudes of Triton’s atmosphere. Details of the occultation are available at MIT’s Web site for the event at hubble.mit.edu/prediction.html.

The central time for the Rochester area is within several seconds of 7:55:40 pm EDT on October 5th. For an observer near the center of the path, the event could last as long as 3 minutes. Because the Rochester area is north of that path, any occultation or atmospheric dimming would likely last some fraction of that time. You should plan to record the event for about 10 minutes before and after the time shown here.

A main challenge of the event will be to record Triton and the target star with a good signal, preferably with clear separation between 8th-mag. Neptune less than a quarter arc minute away. You will need good scale to separate the objects well enough. More observing tips are given on the MIT web site. The target star is about a magnitude brighter than Triton.

Telescopes as small as 8″ Newtonians will show the target star. (see included image from a European observer) For occultation work, we don’t need to “see” the occulting body (Triton in this case), just the object being occulted. Low light and/or integrating video cameras are best for this observation. However, standard astronomical cameras operated in a mode so as to produce images as quickly as possible will also work. Testing ahead of time to determine the correct exposure to just barely detect Triton should be done. This is to insure that the light from nearby Neptune doesn’t overwhelm that of the nearby moon and star at the time of the event.

Target star, Neptune, and Triton.

I plan on using my 10″ Meade LX200GPS at either f/6.3 (focal reducer) or at the normal f/10 prime focus. I will be using a Watec 120N+ low light video camera and integrating for 64 or 128 frames (2 seconds and 4 seconds). I’m still experimenting and might even need longer integration times.

Triton occults 4UC 410-143659, 5 October 2017 – visible regions from Earth.

Everyone with suitable equipment is encouraged to try this event. And I would appreciate it if this message is forwarded to any nearby universities that might have the ability to observe this event. If individual images are taken (instead of video) the exact time for each exposure is required (don’t depend on the computer’s internal clock. Use a GPS-based time). For analysis, it may be possible to measure the light level on individual images or the images can be combined into a video and measuring software used on the video.

Please contact me (EMAIL) for additional information or to submit observations.

Observing Announcement: Spectacular Grazing Occultation Of Aldebaran On 4 March 2017

Greetings, fellow astrophiles!

The following came in from Brad Timerson of ASRAS and the International Occultation Timing Association (IOTA). We had a few posts back in 2014 about an occultation of the star Regulus by asteroid Erigone (on what turned out to be an overcast March 20th. For information about the event and the observing process, see the original CNYO occultation post.

Local observing path for the lunar occultation of Aldebaran on March 4th.

Folks in Rochester and between Syracuse and Binghamton are ideally placed to not only observe the occultation, but also to take data to provide to the IOTA. Information about the occultation, including links to how you can help with the observations, is provided in Brad’s original email below:

I want to alert the membership about this great opportunity (if the weather cooperates!) of seeing a lunar grazing occultation involving a bright star, Aldebaran, along the northern edge of the nearly first quarter moon on the evening of March 4, 2017. In small telescopes, it should be a spectacular sight.

IOTA (International Occultation and Timing Assoc.) has prepared a webpage outlining this event. If you scroll down the page, you will find a section for the Rochester area with a couple of static maps as well as a Google Map for the area. Graze events are dependent on distance from the predicted graze limit as well elevation above sea level. So, the Google Map has been created for the elevation in the Rochester area. (100 feet either way makes little difference)

Main webpage for event: occultations.org/aldebaran/2017march/

Direct link to Google map for approximate elevation in Rochester area: occultations.org/wp/wp-content/uploads/2016/12/500ft.htm

Zoom in to see path through your area. Set the line A to a value of +0.2 km (enter value in box and then press “Click here”). Set line B to –0.1 km. This will produce 2 gray lines, one just north and one just south of the green line. These 2 lines (with the green line in the middle) will mark the best locations for an observing site.

A grazing informational image from the IOTA page.

Based on recent grazes, it appears that you will want to be exactly on the green line shown on the Google map or just barely south of it to see the maximum number of events. Many of the events will be gradual or partial (the star not completely disappearing) because Aldebaran is a large star and at the moon’s distance, won’t be completely covered for some locations.

I plan on observing the graze from a store parking lot (after getting permission) along Rt. 96 near Clifton Springs, NY. Anyone near this area is welcome to join me. I will have more details on my location as the date approaches. I will be videotaping the event using a special camera and video time inserter so that important details of the lunar limb and, possibly, the star, can be determined.

Profile maps of the Aldebaran occultation from the IOTA page.

Central graze time for the Rochester area is 11:17:57 pm on the 4th. You’ll want to be setup well ahead of this time with a clear western horizon. The moon will be about 18° above the horizon. You may see events occur for up to a minute before and after this central graze time. Below is a profile of the lunar limb showing the predicted graze limit as well as a dotted line at about 0.2 km south of the limit. The gray bar graph at the left shows the number of events that can be expected to occur. Time is along the bottom with 11:17:57 pm centered.

Please email me individually (btimerson [_at symbol_] rochester.rr.com) if you’d like information about a specific site along the graze path. Include the latitude, longitude, and elevation of your site taken from Google Earth of the Google map. Also, any other questions you might have can be directed my way.

Here are links to the pages summarizing observations made at the last two grazes. Many observations have YouTube videos available so you can see what to expect.

* www.asteroidoccultation.com/observations/AldebaranGraze_29July2016/
* www.asteroidoccultation.com/observations/AldebaranGraze_19October2016/

Brad Timerson
Newark, NY

Central New York: Take Note (And Help Out)! – The Occultation Of Regulus By Asteroid Erigone On March 20th

Furthermore! CNYO members will be performing a test run of the occultation event for those attending both our lecture at Liverpool Public Library this Thursday (March 6th) and our session of the International Sidewalk Astronomy Night this Saturday (March 8th, weather-pending).

The official IOTA Press Release can be read on the CNYO site HERE.

Greetings fellow astrophiles,

Our daytime skies are (often) filled by starlight from our blindingly bright Sun, while our nighttime skies are a very sparse but more complicated arrangement of the Moon, planets, artificial satellites, stars, and a precious few galaxies and nebulae that can be seen without anything more than the 1x7mm binoculars built into our heads.

Occasionally, events happen “up there” that remind us that we live in a busier part of the Milky Way than the quiet regularity of our own Solar System lets on. All were treated to a nova in the constellation Delphinus last August, where a star otherwise invisible to the naked eye grew bright enough to see without optics, only to fade again weeks after. Comet ISON, heralded as a possible “comet of the century” almost a year before anyone had actual data, at least qualified for “comet of the year” as a dim fuzzball visible away from city lights in November (before fizzling out more dramatically in NASA images). The real winner of 2013 was unquestionably the meteor over Chelyabinsk, a 20 meter/14,000 ton near-Earth asteroid that surprised everyone (most especially the people of Chelyabinsk) last February 15th. The world benefited from the general mistrust of the police in Russia by its citizenry, as thousands of dashboard cams otherwise used to record traffic stops instead provided thousands of high-def videos and images of atmospheric entry.

Technology has dramatically changed amateur astronomy in the past decade, with CCD cameras and commodity telescopes in the hands of trained amateurs providing images that would give many NASA images a good run for their money. Amateur astronomers are now at the vanguard of the space monitoring movement, discovering near-Earth objects, watching the evolution of impacts on Jupiter, identifying supernova in our own and nearby galaxies, even tracking satellites that governments don’t acknowledge existing.

With all that in mind, CNY is going to have front row seats this coming March 20th as the Main Belt asteroid (163) Erigone slides briefly between ourselves and Regulus, the brightest star in the constellation Leo the Lion. This event, called an occultation, will dim or completely block the light coming from Regulus for up to 14 seconds, simultaneously giving scientists a chance to learn more about Erigone.

If you’re an amateur astronomer, citizen scientist, or just someone willing to look to your South at 2 a.m. once this year, fellow observers in CNY extend an invitation to you to report your findings to an organization that will use everyone’s data to determine the shape of Erigone.

2014mar4_erigone_path

The path of Erigone’s shadow on CNY. Highest confidence of observing the occultation is between the blue lines, some additional confidence of observing it between the blue and red lines.

The International Occultation Timing Association (IOTA) has been planning for the Regulus occultation for many months, from mapping out the best places to observe the occultation to corralling amateur astronomers to help in the data collection. On the morning of March 20th (in the 2:00 to 2:10 a.m. EDT range), observers along a very thin stretch of our planet will point their scopes, cameras, and eyes to the sky to see the star Regulus either dim or go out completely for several seconds, only to reappear unscathed. Those few seconds mean everything to members of the IOTA planning to calculate the shape and size of Erigone, and they will not complain if more observers provide more data.

And just how will this timing data be used to estimate the shape of the distant asteroid Erigone? Consider the old Indian story of the blind men and the elephant. The elephant, being much larger than the stationary men, is believed to be very different things depending on where the measurement is taking place. One old man thinks the trunk is a snake, while another thinks that the leg is a pillar, while yet a third thinks that the tail is a rope.

Instead of a large, stationary animal, Erigone will be a swiftly moving rock that will cast a Regulus-powered shadow on the Earth, and CNY in particular. If Erigone were that elephant, observers at the trunk edge of the shadow would see Regulus disappear for only a second, those at the tail edge for less than a second, those at the center line of the belly for 10 seconds, and those lined up with the legs for 15 or so seconds. Consider the series of images below, showing the elephant’s shadow overlaid on blue lines that represent an observer seeing light from Regulus (Figure 1), red lines marking when those observers didn’t see the light from Regulus (Figure 2, and note that observers on the trunk side would have seen Regulus blink twice!), and finally the estimated shape of the elephant (in green) as taken from everyone’s submitted data (Figure 3).

2014mar4_elephant_erigone_2

Figure 1. The hypothetical elephant’s outline over the light (blue) of Regulus.

2014mar4_elephant_erigone_3

Figure 2. The locations and timings of when the light from Regulus was NOT observed (red).

2014mar4_elephant_erigone_4

Figure 3. The outline of the hypothetical elephant (green) as estimated from the occultation measurements (red). You see? It works!

Taking the disappearance times and the locations of the reports, IOTA members can put together a complete disappearance map of the asteroid like that shown below for asteroid (234) Barbara. In the case of Erigone, the shadow it casts will almost certainly be visible from Utica (east edge) to Auburn (west edge) and might be observable from Little Falls to Seneca Falls. This approach to determining the asteroid’s shape means that people who DON’T see Regulus disappear are just as important as people who DO see it disappear, as the “DON’T”ers help narrow the maximum estimated width of the asteroid. All measurements are important measurements!

2014mar4_234_barbara

The shape of asteroid (234) Barbara from occultation data.

The Solar System is a kind of shooting gallery of small and not-so-small objects, a fact we can only rarely appreciate given the distances involved. As technology improves and more people keep eyes on the sky, we may find more direct evidence of just how busy things are just in our own Solar System. Meantime, CNY observers can appreciate that we’re finally the best place to be to both study and enjoy an astronomical rarity (weather-permitting, of course).

But wait! There’s more! Only in the past few weeks have IOTA members stepped up their game, proposing to expand the range of observers here on the ground to look for evidence of a moon (or more) around Erigone. The process is the same, measuring any dips in the brightness of Regulus as Erigone approaches to occult. The difference here is that the dimming by a body orbiting Erigone may dip the brightness only slightly before or after Erigone does depending on its size. If the object is too small to obstruct our view of Regulus completely, it will drop Regulus’ brightness by what might be a pebble’s worth placed on top of your smartphone screen compared to Erigone’s cement block’s worth. If the object is large enough, it may occult Regulus completely as well, making the data processing all the more complicated. As you might expect, measuring that small change in brightness is not a task for lousy equipment, but is within the realm of possibility of local observers with good quality CCD cameras on their scopes. If any caught moon is significant in size, it will be easy for all to see and time.

Provided the sky is clear, anyone in CNY should be able to see the occultation with or without binoculars. Those interested in reporting their timing and dimming data are encouraged to check out the occultations.org/Regulus2014 website for all there is to know about the event, then the www.occultwatcher.net/regulus-erigone/ website to see what data the IOTA is looking for. To be kept in the orbital loop about the occultation and any observing plans around CNY, you can contact members of CNY Observers (www.cnyo.org) or check in with any of the other local astronomy clubs in CNY, all of whom have members planning on observing (and, hopefully, recording) the occultation.