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KBO encounters
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post Jun 27 2011, 08:12 PM
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Dan, re variable stars: No real idea how to filter them out during the initial screening, and apparently neither does the project at this time; looks like they're going to rely on follow-up observations. I've been thinking that most variables are going to appear more point-like than a KBO, but this might not be a valid assumption based on the occasional glimpses of unprocessed imagery around the edges of the main images...they ALL look like KBOs there!


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elakdawalla
post Jun 27 2011, 08:19 PM
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I would assume that all light sources in these images are points of light -- remember that we can't even resolve relatively big Pluto as a disk, so the size of KBO you're looking for wouldn't be resolveable as a disk with even the most powerful of telescopes. They are spread out not because they are disks but because the pointlike light is spread out across the detector a little bit for various reasons.


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post Jun 27 2011, 08:25 PM
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Yeah, you're right, Emily...it was my best guess.

I & obviously many others would still be very interested in knowing what a realistic detection rate should be. Probably even the project isn't sure yet, though; this is raw science, so of course there are always surprises in the data... wink.gif


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centsworth_II
post Jun 27 2011, 09:49 PM
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QUOTE (elakdawalla @ Jun 27 2011, 03:19 PM) *
....the pointlike light is spread out across the detector a little bit for various reasons.

Maybe one reason is the same as explained in your Planetary Society Blog in relation to Deep Impact's exoplanet search?

I sent an email to EPOCh's Principal Investigator, Drake Deming, at Goddard Space Flight Center, to ask him how the search would work. It turns out that he plans to turn Deep Impact's flaw to his benefit....
That's what I call making lemonade from lemons. The camera blur spreads the point-source light from stars out over several pixels on the camera's CCD. Deming explains here how that helps.... "to get high signal to noise, we have to collect lots of photons from the star. That's where the defocus helps. Each pixel of the CCD has a limited capacity to collect photons before it saturates. With a defocused image, we have about 75 pixels collecting light for us, so we can collect lots of photons in each exposure without saturating, and that gives us the high signal-to-noise ratio that we need."

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ugordan
post Jun 27 2011, 10:34 PM
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I think the point sources are not actually points primarily because of two reasons:
1) telescope point spread function
2) atmospheric turbulence averaged out over the exposure duration


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john_s
post Jun 27 2011, 10:36 PM
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QUOTE (nprev @ Jun 27 2011, 01:25 PM) *
Yeah, you're right, Emily...it was my best guess.

I & obviously many others would still be very interested in knowing what a realistic detection rate should be. Probably even the project isn't sure yet, though; this is raw science, so of course there are always surprises in the data... wink.gif


Yes, variable stars and KBOs are indistinguishable by image size for the reasons Emily gives. But we can distinguish them after all the clicks are compiled because a KBO will produce a series of detections aligned along its orbital path, while variable stars have no such pattern.

Regarding detection rates, we expect there to be a KBO (on any orbit, whether accessible to New Horizons or not) in perhaps every 50th thumbnail, given their known density in the sky. So most of these point sources are going to be variable stars, but at the rate you guys are clicking through them, you've probably nailed quite a few KBOs too.

John
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post Jun 27 2011, 10:55 PM
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Timely response, John, thanks!

Okay, so I just did image 3000 with 622 flags for a detection rate of 20.7% (asteroids included, and I'd guess that those represent about 10% of my total, so my KBO rate would be around 18%). Looks like the project is expecting genuine KBO finds in 2% of the images, so my rate is 9 times greater than expected.

Mentioning all this as feedback to the project, is all. This is hella fun, John! smile.gif


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ilbasso
post Jun 29 2011, 03:29 AM
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I'm finally gonna be able to see cross-eye stereo pairs after going cross-eyed staring at these images.

I had 5 objects which were perfectly round in one image. Clicked on them all and was sent to an error screen telling me that perhaps I was being over-zealous for selecting 5 objects in one image. But I KNOW they were right!

I'm certain that I am seeing the same star field multiple times per session. I try to limit myself to 50 - 75 screens per session so that I don't get a massive headache.

It would be nice if we could enlarge the image on the screen. I have a lot of screen real estate that is not being used. For us folks with older eyes, it would be a real blessing if we had the option to make the image 25-50% bigger.


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Explorer1
post Jun 29 2011, 06:03 AM
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Can you use keyboard commands (like the ones that make browser text bigger)? For example ctrl + or ctrl and mousewheel (on my keyboard at least).
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ilbasso
post Jun 29 2011, 03:20 PM
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Thanks - the CTRL+mousewheel worked this time. It didn't work the first several days I tried it. Perhaps updating my browser and clearing the cache reset something that was screwing things up.


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hendric
post Jun 29 2011, 03:43 PM
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You must have seen the same image I did with 5 objects. I also got the note about selecting too much, but talked to Pamela and she said that those are legit selections, but that they are most likely variable stars. I don't think the variable star database will compare with Kepler, but it might still be interesting to someone.

Is this what you saw?
Attached Image


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centsworth_II
post Jul 3 2011, 05:00 PM
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Up to 2500 views now and this is easily the most artistic (and one of the least scientifically useful) images I have seen.
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I don't know a lot about art but I know what I like.
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pjam
post Jul 3 2011, 06:36 PM
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That's a beaut cents! ...& Just think of the marketing value -postcards, coffee mugs, caps etc.

I just joined -found what look like two near field asteroids and ~24 variables/KBOs in 96 images. Let's see if my "find" rate stays the same for the next 96...


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centsworth_II
post Jul 4 2011, 12:03 AM
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Up to now I haven't felt the need to break my viewing rhythm to use the click-on list available for comments on image quality, but for some reason a lot of horrible images (and not very artistic to my eye) have cropped up and I've been clicking on the "Simply terrible image" comment a lot. I gave up after about twenty unreadable images in a row. Tried again later and still about half the images are useless. I saw nothing like this in my first 2500!

Yuk!
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Holder of the Tw...
post Jul 4 2011, 01:28 AM
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We may be getting the leftovers no one else wanted (here's a good place to quit and loggout), or they may have been deliberately presenting the better images first in order to get the best return soonest, or both, or something else. I've been noticing it too, but I still get the occasional good image.

Just today, I had to quit when I got some kind of terrible SQL violation error. I'm heading back to see if I can get back on.

EDIT at 45 past the hour: Okay, I can't even get logged on. Anyone have any idea what this is about:

Warning: mysql_connect(): Unknown MySQL server host 'zoobuilderdatabases.cvqgcgieedcl.us-east-1.rds.amazonaws.com' (2) in /home/zoobuilder/public_html/icehunters/admin/database_functions/mysql_functions.php on line 5 Unable to select database icehunters. Please verify the name is correct in admin/zoo-config.php
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