Jupiter moon transit, or what?

[AKB]

Last night I was setting up to make my very first image of Jupiter, and I caught this event in a few of the frames in one of my test captures.

Scope: Celestron Evolution 9.25" with x0.63 reducer

Camera: ASI120MC with IR pass filter, ~3 ms frames.  Sorry about the lack of focus.

This is successive images in the capture stream, so it all happens within the span of 50ms.

So, if I understand correctly, this can't be a shadow transit, is it an actual moon? 

 

 

[spaceman_spiff]

I don't think its anything orbiting Jupiter, otherwise it would be in-line with Jupiter's axis of rotation. I would say you captured an artificial satellite transiting Jupiter...if that's true, it's a rare sight!

[furrysocks2]

Cool, satellite?

Stellarium gives apparent diameter of Jupiter last night as 43.4 arc-seconds, so could estimate an approximate speed of around 0.24 degrees a second.

What time of night?

[John]

Is it just me or does it appear like the silhouette of a bird against the planets disk ?. Almost looks like wings flapping ?

Probably can't be that - just the way it appears to me.

[jabeoo1]

Have you got the time (roughly)?

[AKB]

2 minutes ago, furrysocks2 said:

What time of night?

My mistake, it was in the name of the file, but that's no help to anyone!

21:48:12 UT

[furrysocks2]

9 minutes ago, John said:

Is it just me or does it appear like the silhouette of a bird against the planets disk ?. Almost looks like wings flapping ?

I can see that... sure I remember someone capturing a bat across the moon recently.

[Knighty2112]

Probably a bird. I was looking at the moon a few nights back and when I looked into the eyepiece I saw three black shadows flap across the face of the moon. This was around 9:30pm or so, so most likely a nocturnal bird flying around. 

[Craney]

"Open the Pod Bay doors HAL"..........

[hornedreaper33]

On a slightly different note, would it be better to remove the reducer for planetary work?

[furrysocks2]

It could be an object in low Earth orbit but I'm a sucker for this kind of thing - so let's suppose it is a bird or a bat...

If, as John reckons, we can see a wing beat across the disc, then can we determine frequency? It looks to me light it might be a full cycle, perhaps even two... very hard to tell. At 50ms to cross the disc, that would imply a wingbeat frequency of 20-40 Hz, so I'm tempted to see just a single beat.

 

Quote

...  at a body mass of 2 g the wingbeat frequency is 16 Hz for bats and 21 Hz for birds and at 1 kg it is 3.1 Hz for bats and 4.0 Hz for birds ...

Source: http://jeb.biologists.org/content/215/5/711

So it could conceivably be a bird or a bat, but it would have to be a very small one.

 

The disc of Jupiter measures about 80 pixels across and the object in flight perhaps 3-5 pixels, say 4. If Jupiter is 43.4 arc-seconds, a "bird or bat" at 4 pixels would be perhaps 2.17 arc-seconds. Judging a possible size by the high wingbeat frequency, I'm going to say something like 3-4 inches for a combined side elevation of body and wing - already feels as if I'm grasping, though... but that would put it at a distance of roughly 7-10km away.

From Oxford at the time of capture, apparent altitude of Jupiter was something like 12.2 degrees, the distance away would put it at between 1.5 and 2 km up. For comparison, if size was 6-8 inches, then between 3 and 4 km up, and at 2 inches 1km up.

Staying with the 3-4 inch size, at a speed of 0.241 degrees per second, flight speed (perpendicular to line of sight) could be 68-90 mph... unlikely. At 2 inches, 45 mph. If it's six pixels, not four, then 2 inches would be 30 mph... starting to get within a more likely range.

 

So if (big if) it was a bird or a bat and if (another big if) I've not mucked up my maths, then it appears it would need to be small, high and fast. When I started this, I hoped I was going to hit something mid-range, but this hypothesis currently feels way out on the edge.

 

Could it perhaps be a moth or other insect?

I'm off for a pint.

[AKB]

Thanks all for your excellent theories, opinions, speculations, and calculations!

4 hours ago, furrysocks2 said:

I can see that... sure I remember someone capturing a bat across the moon recently.

Yes, I recall seeing that too.  Rather a better picture than mine.  I had seen it as rather rounder...

2 hours ago, Craney said:

"Open the Pod Bay doors HAL"..........

...but not quite THAT round.

2 hours ago, hornedreaper33 said:

On a slightly different note, would it be better to remove the reducer for planetary work?

Yes indeed, I was just setting up at the time.  In fact, I still had an IR filter on the camera too.  I later added a 2x Barlow, tried (but failed miserably) to improve the focus and ended up with my first ever real image of Jupiter:

 

I'm aware that this is sadly lacking in several respects, especially in comparison to some of the spectacular images posted even within the last day such as:

20 hours ago, michael.h.f.wilkinson said:

Grabbed some data on Jupiter tonight, using the ASI224, Celestron C8, and Meade 2x TeleXtender. Seeing was far from perfect, but stacking 1500 out of 4000 frames gave pretty good results

or

10 hours ago, broadway1 said:

This image was captured through my C14 scope with 2x Televue barlow and taken my ASI 224MC camera using Firecapture 2.5. It was processed using Autostakkert, Registax 6, Winjupos, and Topaz De-noise

but it's a start.

I noticed that the Ha image gave a rather good luminance image, so I may try and combine those sometime.  I'm aware that this is commonly done for DSO, but for planets???

Anyway, thanks for looking (and commenting.)

AK

[furrysocks2]

It looks flappier after a couple of jars, but open to it being my alignment, the bright central band or atmospherics throwing me off, if not the beer.

 

Or is it the other way up?

 

If it is indeed a bird, bat or similar, and not "just" a satellite, this is a phenomenal capture!  

 

8 hours ago, AKB said:

Camera: ASI120MC ... ~3 ms frames.

... span of 50ms.

I'm not familiar with the camera but assume you're using ROI to achieve this rate, or was this the exposure setting? Is this definitely what you were getting back from the camera?

[AKB]

5 hours ago, furrysocks2 said:

It looks flappier after a couple of jars

Nice work on the image 'stabilisation' ... how did you do that?  Yes, indeed, that looks flappy now.

5 hours ago, furrysocks2 said:

I'm not familiar with the camera but assume you're using ROI to achieve this rate, or was this the exposure setting? Is this definitely what you were getting back from the camera?

Yes, I was using ROI.  I've just gone back to the original acquisition parameter file (FireCapture) and see this...

FireCapture v2.5  Settings
------------------------------------
Camera=ZWO ASI120MC
Filter=L
Profile=Jupiter
Diameter=43.35"
Magnitude=-2.41
CMI=306.5° CMII=220.5° CMIII=333.5°  (during mid of capture)
FocalLength=1100mm
Resolution=0.69"
Filename=Jup_214812.zip
Date=150317
Start=214812.065
Mid=214815.640
End=214819.215
Start(UT)=214812.065
Mid(UT)=214815.640
End(UT)=214819.215
Duration=7.150s
Date_format=ddMMyy
Time_format=HHmmss
LT=UT 
Frames captured=500
File type=FIT
Binning=no
ROI=336x384
ROI(Offset)=0x0
FPS (avg.)=69
Shutter=5.157ms
Gain=50 (50%)
HighSpeed=off
AutoExposure=off
WRed=52
SoftwareGain=10 (off)
Gamma=50
WBlue=95
Brightness=0
USBTraffic=80
AutoHisto=75 (off)
Histogramm(min)=0
Histogramm(max)=144
Histogramm=56%
Noise(avg.deviation)=n/a
Limit=500 Frames
Sensor temperature=17.8 °C

...so, actually, it seems like I did get the figures wrong.  Many apologies, mea culpa.  So this is about 5ms shutter speed and 69 fps, which then would give about 14ms per frame, not the 3ms I originally thought (which was what I believed the exposure to be.)  Too many numbers!  So this scales the speed calculations, somewhat!... definitely flappy territory now? 

Thanks for the patience in working though this.  I'll just stop examining individual frame captures from now on.

 

[furrysocks2]

Nice one... yes, I think that'll fall in a better range. I'll work through the numbers when I get a chance.

Stabilisation was by drunken patience in GIMP.

[furrysocks2]

Average framerate of 69 fps (average frame period of 14.5ms) gives a transit duration of approx 230ms - a speed of 1.2 degrees per second.

Distance and height remain unchanged. At my original 4 pixel width, 3-4 inches gives 15-20 mph, (2 inches 10 mph, 6-8 inches 30-40 mph). If travelling slightly towards or away from you, then flight speed would be slightly higher.

I reckon I can see three full wing beats edge to edge, perhaps 2.8 - I'm not going to count pixels here though. That would yield a wing beat frequency of approximately 12-13 Hz... so likely no longer at the very bottom end for weight/size, perhaps order 10g or more.

Basically, the revised framerate puts the estimate more firmly within range.

 

If my calcs aren't way off, it's nuts what can be derived from your short clip and a few location/timing parameters.

Magic capture, I'm astounded! 

 

One more question to satisfy my curiosity - out of the two stabilised images I posted, which represents the right way up as would be viewed naked eye? To me, the flight in the lower one appears to me the more natural of the two... any idea?

[furrysocks2]

10 hours ago, AKB said:

... my first ever real image of Jupiter:

Well done with this! I'm yet to try Jupiter - last night (on the way back from the pub), the sky seemed very stable but the wind ensured no drunken imaging was attempted.

[AKB]

5 hours ago, furrysocks2 said:

out of the two stabilised images I posted, which represents the right way up as would be viewed naked eye? To me, the flight in the lower one appears to me the more natural of the two... any idea?

I agree, the lower one looks more flight-like.  I suppose I should be able to work this out?  This was on an Alt-Az mount.  The SCT inverts, IIRC, the Barlow doesn't, but the camera was mounted upside down...  no, really, haven't a clue.

 

[furrysocks2]

1 minute ago, AKB said:

I agree, the lower one looks more flight-like.  I suppose I should be able to work this out?  This was on an Alt-Az mount.  The SCT inverts, IIRC, the Barlow doesn't, but the camera was mounted upside down...  no, really, haven't a clue.

No worries - good bit of fun!

Still trying to get my head around how small this thing was compared with Jupiter - one in a million, a capture to remember.

[Swoop1]

On 3/17/2017 at 01:39, furrysocks2 said:

It looks flappier after a couple of jars, but open to it being my alignment, the bright central band or atmospherics throwing me off, if not the beer.

 

Or is it the other way up?

 

If it is indeed a bird, bat or similar, and not "just" a satellite, this is a phenomenal capture!  

 

I'm not familiar with the camera but assume you're using ROI to achieve this rate, or was this the exposure setting? Is this definitely what you were getting back from the camera?

Ooooh! That take me back to my youth. Had me reaching for the controller to play low grade ping pong on the T.V. with one of those new fangled video game thingies