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Old 2020-02-19, 17:47   #1
Spherical Cow
 
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Default Tiny Shadows of Minor Planets

Finally, after 6 or 7 attempts thwarted by clouds and equipment problems, I got my first asteroid occultation data. Yesterday morning, the asteroid Thyra occulted a 10.9 magnitude star along a narrow path a few hours north of here. Below is a quick lightcurve plot from the video for my system. X-axis is just the frame number; frame rate is 29.957 fps, so this is about 116 seconds of data. Y-axis is light level. The red dots are the light levels for each frame for the target star; green is the light level for a fainter, nearby star, and blue is light level for a background part of the frame, with no stars, so it just bounces around near-zero,

At frame 3707, the light level for the target star drops dramatically to the level of the asteroid (which is fainter than the star) as the asteroid passes between us and the star, and recovers just as sharply at frame 3895. So, about a 6.27 second occultation.

There were 21 systems set up by amateurs at different distances from the center of the path, ranging from 70 km north of it to 50 km south. With GPS times on each frame, and knowing our locations on the ground, all this data is put together to generate a silhouette of the asteroid; plus, it's used to refine the orbit of the asteroid. Neat stuff- and being useful science makes it even better.

Norm
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Old 2020-02-19, 18:38   #2
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Originally Posted by Spherical Cow View Post
Finally, after 6 or 7 attempts thwarted by clouds and equipment problems, I got my first asteroid occultation data. Yesterday morning, the asteroid Thyra occulted a 10.9 magnitude star along a narrow path a few hours north of here. Below is a quick lightcurve plot from the video for my system. X-axis is just the frame number; frame rate is 29.957 fps, so this is about 116 seconds of data. Y-axis is light level. The red dots are the light levels for each frame for the target star; green is the light level for a fainter, nearby star, and blue is light level for a background part of the frame, with no stars, so it just bounces around near-zero,

At frame 3707, the light level for the target star drops dramatically to the level of the asteroid (which is fainter than the star) as the asteroid passes between us and the star, and recovers just as sharply at frame 3895. So, about a 6.27 second occultation.

There were 21 systems set up by amateurs at different distances from the center of the path, ranging from 70 km north of it to 50 km south. With GPS times on each frame, and knowing our locations on the ground, all this data is put together to generate a silhouette of the asteroid; plus, it's used to refine the orbit of the asteroid. Neat stuff- and being useful science makes it even better.

Norm
Yay! Good work!

Not something I can do at all as I don't have a camera with a high enough frame rate.
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Old 2020-02-19, 21:24   #3
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Knowing that Pluto's atmosphere was first observed by the Kuiper Observatory and the effort that went it Arrokoth, it got me thinking about a fixed robotic system. With all of the minor objects and all the data from Gaia, a system could be set up that would get a few transits a year. And if there was nothing anticipated, could be used for follow-up on exoplanets, eclipsing binaries, etc.

Minor Object Transit Experiment could have facilities in a number of dark sky areas. The first image has 8 telescopes marked out on a circle of 200km diameter. Images 2 and 3 have just the circles. The issue is having infrastructure to support the installations. A 16 inch class SCT for each site should provide enough light.
Other shapes may be as useful. Most of the transits should be generally occurring along the E-W axis.
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Old 2020-02-20, 07:56   #4
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Knowing that Pluto's atmosphere was first observed by the Kuiper Observatory and the effort that went it Arrokoth, it got me thinking about a fixed robotic system. With all of the minor objects and all the data from Gaia, a system could be set up that would get a few transits a year. And if there was nothing anticipated, could be used for follow-up on exoplanets, eclipsing binaries, etc.

Minor Object Transit Experiment could have facilities in a number of dark sky areas. The first image has 8 telescopes marked out on a circle of 200km diameter. Images 2 and 3 have just the circles. The issue is having infrastructure to support the installations. A 16 inch class SCT for each site should provide enough light.
Other shapes may be as useful. Most of the transits should be generally occurring along the E-W axis.
Nice idea but the circle is too big for La Palma. I'm not sure whether there is anything but Atlantic ocean at a 100km radius from El Paso.

Could put a telescope on (perhaps 2 on each of Tenerife and Gran Canaria) each island I suppose.

Do you fancy the challenge of coming up with an optimal (in some sense) design for a Canarian telescope array?
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Old 2020-02-20, 15:28   #5
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Do you fancy the challenge of coming up with an optimal (in some sense) design for a Canarian telescope array?
I wasn't looking to do this myself. Rather an organization could work up the design of the robotic scope and dome. One of the reasons that I thought that that area of the USA would be a good location to start is, there are enough farms and farm houses in that area that the domes could be sited near the homes for power, connectivity, and road access. I plopped the other two images out at random but well known locations. In the USA in the area I chose, it would be possible to add scopes as support becomes available. Communities could sponsor the placement of a scope. If a line of scopes ( with 20-50 mile spacing between them) went from Saskatoon to Amarillo, it could give amazing coverage and improve the chances of snaring events.

I don't think that working an optimal system for the dog islands is anything more than getting a scope or 2 on each significant islands. Worrying about getting equal spacing is less important than getting more stripes. Hawaii is another case were accepting that one can't choose the orientation is a given.

Again the idea is not to chase a specific object like Pluto or MU69, but rather have a system in place to snare objects of opportunity. The difference between spear fishing and casting a dragnet. Having a common design able to be replicated would help to keep the cost down. Also having a fleet of identical scopes that can be used for things like exoplanet follow-ups, etc. in a co-ordinated fashion would benefit the community. Also, once the firehose of LSST comes online, there should be lots of work for smaller scopes to follow-up.
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Old 2020-02-20, 16:26   #6
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I don't think that working an optimal system for the dog islands is anything more than getting a scope or 2 on each significant islands. Worrying about getting equal spacing is less important than getting more stripes. Hawaii is another case were accepting that one can't choose the orientation is a given.

Again the idea is not to chase a specific object like Pluto or MU69, but rather have a system in place to snare objects of opportunity. The difference between spear fishing and casting a dragnet. Having a common design able to be replicated would help to keep the cost down. Also having a fleet of identical scopes that can be used for things like exoplanet follow-ups, etc. in a co-ordinated fashion would benefit the community. Also, once the firehose of LSST comes online, there should be lots of work for smaller scopes to follow-up.
I would be very happy to have one of these on my land. I would fund its power and connectivity requirements myself in return for appropriate acknowledgement but the capital expenditure would have to be funded by some other organization. OTOH, if I could be guaranteed a percentage of the non-urgent telescope time (i.e. when no asteroid occultations are predicted) I might contribute a corresponding fraction of the capital cost.
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Old 2020-02-20, 17:13   #7
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Minor Object Transit Experiment could have facilities in a number of dark sky areas....
This would be really nice- earlier in the evening before the Thyra event above, there was a possible occultation by a Centaur asteroid, and the group was encouraging observations from pretty much anywhere in the western US. The uncertainties in the paths of those remote objects is pretty high. The MOTE systems you describe could be called on for those kinds of needs. The group that sort of specializes in Centaurs, TNOs, is called RECON, http://tnorecon.net/ . I am hooked in to the IOTA crowd ( https://occultations.org/ ) but now that I'm up and running, I'm going to chase any TNO opportunities I can.

Is the MOTE name a nod to the old science fiction novel "The Mote in God's Eye"? One of my favorites from many years ago.

Norm
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Old 2020-02-20, 18:48   #8
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Is the MOTE name a nod to the old science fiction novel "The Mote in God's Eye"? One of my favorites from many years ago.
No. Haven't read that. It was several things that lead to the idea of the name. The need for an acronym (but not a forced one.) Mote, like they are dust motes in the SS. A southern one could be called SMOTE :)

The other advantage of having the initial install in the USofA (and Canada), is the easy of moving in reinforcements, if there is a particular need. 3 groups setting up 3 extra scopes (each) before an event would sharpen the center of the expected path.
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Old 2020-02-24, 14:12   #9
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Got clouded out of an occultation by the asteroid Schalen last night- this attempt was in support of observations the VERITAS array was going to try. They're using the diffraction patterns during occultations to calculate the star size, with two successful events so far. Below is the link to an S&T article on VERITAS. There were 8 amateur systems set up; only two reported clear skies, and haven't heard about the VERITAS folks yet.

https://www.skyandtelescope.com/astr...measure-stars/
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Old 2020-02-24, 18:55   #10
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Got clouded out of an occultation by the asteroid Schalen last night- this attempt was in support of observations the VERITAS array was going to try. They're using the diffraction patterns during occultations to calculate the star size, with two successful events so far. Below is the link to an S&T article on VERITAS. There were 8 amateur systems set up; only two reported clear skies, and haven't heard about the VERITAS folks yet.

https://www.skyandtelescope.com/astr...measure-stars/
I hadn't heard of using asteroid occultations to measure stars - I guess there's much less stray light than the lunar-limb method, and you can do it for stars that don't get occulted by the Moon.
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Old 2020-02-24, 22:43   #11
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They're using the diffraction patterns during occultations to calculate the star size, with two successful events so far.
Very cool.
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