22 replies to this topic

[KiwiRay]

Thanks to Jeff and Grant for the info on this. I've never tried to capture one of these before so I'm sure I didn't use the optimal approach. I recorded 810 frames, and the gif linked below shows frames 450 to 600. Firecapture recorded these capture times for all 810 frames:

 

Start(UT)=051709.804
Mid(UT)=051911.528
End(UT)=052113.253

 

Here's the animated gif with an overexposed Uranus and the star at lower left:

https://live.staticf...e707eda24_o.gif

 

[Faster animation added in post #16]

 

After a few seconds the star blinks out and returns later. The gif starts over when the planet shifts upwards. It would be nice if I could find a way to print times on this. Exposure time was 300 ms with gain of 450 for the ASI224MC camera (Nexstar Evolution 9.25 scope, no Barlow or ADC). With only 3.33 fps, it's not very smooth.

 

I'd appreciate any advice on what else I might do with this recording to make it scientifically useful. If I can get the exact occultation time, I should be able to work out the length of the chord the star tracked behind Titania.

 

Edit: From the original AVI, the star blinks out at frame 480 (05:19:33.8 UT) and reappears at frame 581 (05:20:04.1 UT; full brightness at frame 582). So it was gone for 101 frames (480-580), which is 30.3 s.

Edited by KiwiRay, 21 November 2023 - 08:19 PM.

[Borodog]

Very cool!

[Jupiterastro]

Interesting GIF! Like it very much.

[RedLionNJ]

That's absolutely AWESOME, Ray!!!!   Fantastic you actually got the occultation from Washington State, too.  I was under the impression the likely path was much further south. Great job!

 

As far as timestamp goes, if you captured in SER, each frame has a timestamp associated with it - not sure how best to get it out, though (i.e. what tool). But you'd still be at the mercy of your computer clock and its accuracy relative to genuine UT.

 

When I do occasional occultation work, I use FireCapture and enable the per-frame timestamp on the top left of the display, which gets embedded into the individual frame images.  Prior to that, I have my observatory laptop synced with NTP over the internet to a structure of designated time services. I repeatedly check this prior to a potential event to make sure my offset is in the millisecond range.

 

Again, great work, Ray. Your efforts paid off!

[KpS]

A rare phenomenon and congratulations for capturing it!

 

As RedLionNJ writes, every SER frame has its time recorded. Then one can use e.g. PIPP to decompose the SER into individual FITS. For time information view their headers.

Edited by KpS, 21 November 2023 - 08:49 AM.

[happylimpet]

Superb work. I knew about this but Uranus was only 10deg high and behind a lot of trees and houses.

 

Heres a similar one I did for Triton occuting a star in 2017.

 

https://vimeo.com/ma...ideos/237626476

 

I wish I'd done the firecapture timestamp thing, but i think i used SER so each frame has a time embedded in it anyway.

[Tapio]

Congrats!
You could make a photonetric light curve.
There are numerous software for it.
I've used Tycho Tracker, HOPS and FotoDiff.
ASTAP works too. AstroImageJ is one more comprehensive software.

[Winteria]

Very nice work! Ditto on making a light curve.

[KiwiRay]

Thanks for the comments and advice. Unfortunately I recorded an AVI not a SER as I was ignorant of the timestamps. I didn't think to sync the laptop time either. If I ever get another chance, I'll prepare better. I didn't even think I'd have a clear sky and only got the scope outside about 40 minutes before the event.

 

It was cool to see live onscreen. I had no idea what to expect so to see the star blink out close to the predicted time was kind of exciting.

 

I'll look into the light curve measurement software - thanks for the suggestion, Tapio and Winteria.

 

As for the path, it presumably has some width to it, with those of us off-centre getting a shorter occultation time than those in the middle of the path.

Edited by KiwiRay, 21 November 2023 - 10:13 AM.

[JMP]

This is so cool, Ray! Fabulous!    

 

You can report at IOTA Occultations:   https://occultations...g-observations/

Since this is a first for you, go ahead and email for suggestions. Yes, try to generate a curve, Titania itself is clearly resolved in some of the frames!

 

As Grant says; "AWESOME!"

[lajoswinkler]

Smashing result! So cool!

[KiwiRay]

This is so cool, Ray! Fabulous!    

 

You can report at IOTA Occultations:   https://occultations...g-observations/

Since this is a first for you, go ahead and email for suggestions. Yes, try to generate a curve, Titania itself is clearly resolved in some of the frames!

 

As Grant says; "AWESOME!"

Thanks again for drawing this to our attention, Jeff!  I thought I could see Titania too in some frames. The other three bright moons are all visible in the stretched, stacked image, so I'm sure if I did the same for just the 101 occultation frames, I'd get a clear view of Titania.

[Borodog]

Ray,

 

Is there any chance you can make a higher speed version of your GIF? 30 fps would be a 5 second loop.

[KiwiRay]

Ray,

 

Is there any chance you can make a higher speed version of your GIF? 30 fps would be a 5 second loop.

About to head to work, but I can do that this evening. The 30 seconds feels pretty long when nothing's happening, doesn't it?

[bunyon]

That's beautiful. Congratulations. 

[KiwiRay]

As promised, here's a faster version, sped up to 20 fps (so 6 times original). I also increased the input gain in PIPP so now not only is it easier to see Titania during the occultation, but Oberon shows up in most frames to its left.

 

https://live.staticf...31a8214a5_o.gif

 

Looks like flickr repeats it once, although I disabled looping in PIPP.

Edited by KiwiRay, 21 November 2023 - 08:16 PM.

[Borodog]

That’s what I’m talking about! Very VERY cool!

[happylimpet]

Not to detract from this observation, which is superb, but while we're on the subject a good opportunity to share this video which i think is one of the coolest astro things ive ever seen. An occultation of a binary star by Titan.

 

https://www.syfy.com...nic-occultation

 

Video about halfway down.

Edited by happylimpet, 22 November 2023 - 04:49 AM.

[dcaponeii]

Really nice Ray.  Well done

[KiwiRay]

I looked at some of the software suggested above for estimating light curves. Most seemed more complex to figure out than I have time for, but I managed to quickly get something out of AstroImageJ. I had cropped the video frames into 40x40 pixel squares centred around the star/Titania to remove the pulsating blob of Uranus. AstroImageJ produces a mean pixel brightness value for each frame, which is a pretty intuitive thing to do. Here's the plot of those mean values by time for the video in post #16.

 

 

I don't think it shows anything new: brightness drops sharply during occultation, and poor seeing makes for noisy data, things we already knew from the recording.

[JMP]

I caught an occultation by the asteroid Varsavia some years back. Several of our club members set up a picket line along the McKenzie River and we caught several cords. I was surprised when the star winked out and I was surprised again when it came back. I was using a WWV radio and an audio cassette to record the event.

 

It is a way to experience how dynamic the solar system really is. Thanks for the video and the light curve and letting us share the excitement!

 

Jeff

[RedLionNJ]

I caught an occultation by the asteroid Varsavia some years back. Several of our club members set up a picket line along the McKenzie River and we caught several cords. I was surprised when the star winked out and I was surprised again when it came back. I was using a WWV radio and an audio cassette to record the event.

 

It is a way to experience how dynamic the solar system really is. Thanks for the video and the light curve and letting us share the excitement!

 

Jeff

I tried for an occultation by 110 Lydia a few years back (Jan 20, 2015) - entire US (at least, where occultation imagers were) was clouded out. I had a lovely hole in the clouds for about five minutes in exactly the right location. I made sure my PC clock was synched properly, I turned on the relevant options in FireCapture, I found the target star and tracked it until - it blinked out!  And a few seconds later, it reappeared, still well within the field. I sent the data off to IOTA and was horribly disappointed to find nothing new could be derived from a single measurement

[JMP]

We recently had a space probe discover a binary asteroid. IOTA has been discovering binary asteroids for years now. These discoveries were initially controversial, but have since been confirmed many times!