Video data, posted to YouTube channel "Cabrillo Astro"
This is a bright event, with good rank, and high probability of getting good data from inside the predicted shadow. Karl von Ahnen and I are both inside the path. Kirk will be out of town and not doing this one. It's near the 97% moon, however, at only 9 degrees away - the sky will be bright. I would not go more than 2x setting, and maybe even 1x setting if the star is bright enough. Minimizing sky noise will be good. Probably 2x is best, as my guess.
W band (my nomenclature) is the "Watec 910hx band" magnitude. This turns out, from photometric calibrations by Hristo, to be close to the "r" magnitude, which I've used at the title here.
Alt=42, Az=88 in the East. Target star and asteroid are about 1/3 of the way from the Plieades to the Hyades star clusters, above the rising moon.
I was the only observer. I observed from Cabrillo College Observatory, 15 ft from the door to the Dome building. The target was bright and easy to follow at 2x, so I disconnected the external monitor to slightly improve the video signal to the camcorder, and just watched it on the flip-out screen of the camcorder. This would eliminate noise caused by a splitting of the video signal. Earlier tests I did in 2024 showed the resulting noise from having the external monitor in parallel with the camcorder, the rise was so small as to be negligible. Now, Kirk Bender has shown that the video signal voltage did drop to the camcorder when the external monitor was connected. However that lowered voltage is auto-raised inside the camcorder. Nevertheless, for this event, it's a non-issue as the external monitor was disconnected during the recording.
W. Longitude 121 55 26.87"
N. Latitude 36 59 33.71"
Altitude 216 ft
Target star= TYC 1814-01633-1
name | V | g | R | r | source |
TYC 1814-01633-1 | 11.35 | 10.94 | -- | OWc | |
11.46 | 11.64 | 11.345 | C2A | ||
Julian Date of occultation timings: 2460631.70132
The UCAC4 catalog description and photometric (B,V,g,r,i) sources are given here. The r band is from the APASS photometric database (AAVSO Photometric All-Sky Survey)
V band center= Width=
R band center= 658nm Width=138nm
r band center=?
r band in APASS seems to be Sloan Digitial Sky Survey r band. But what I see in the reference for Sloan is instead labelled as r' band in: https://amostech.com/TechnicalPapers/2018/Poster/Castro.pdf . No r-r' or R-r' transformation graphs are given. I conclude it's best to look at UCAC4 V and r for target as well as the other stars, to stay consistent in bands between the reference stars and target.
From Hristo Pavlov and associated camera tabular calibration data used along with:
V - W = + 0.315 * (B-V) + ZeroPoint +/- 0.10, where W = "instrumental magnitude for Watec 910hx"
So, W
= V - 0.315(B-V) - Zero point (note: zero points cancel out if only concerned with magnitude differences, as we are in this case). The table, based on the "Analysis #5" photometry below, has the resulting W magnitudes calculated from the C2A tabular V and B-V values, gotten by left-clicking on the different stars in C2A. I use a zero point=0 since the zero point cancels out for finding magnitude differences.
Name | V | B-V | r | Avg Counts |
Watec 910hx =W Mag |
W Mag Drop |
Target | 11.46 | 0.473 | 11.34 | 517 | 11.31 | 0.00 |
Ref1 | 10.03 | 0.815 | 9.95 | 9.77 | -- | |
Ref4 | 12.47 | 1.326 | 11.99 | 256 | 12.05 | -0.74 |
Ref5 | 13.09 | 1.611 | 12.08 | 155 | 12.58 | -1.27 |
Ref6 | 11.73 | 0.698 | 11.49 | 460 | 11.51 | -0.27 |
Ref7 | 12.32 | 0.719 | 12.09 | 274 | 12.09 | -0.78 |
Ref8 | 12.65 | 1.141 | 12.24 | 219 | 12.29 | -0.98 |
Ref9 | 13.01 | 0.856 | 12.71 | 140 | 12.74 | -1.43 |
Ref10 | 13.084 | 1.024 | 12.71 | 115 | 12.76 | -1.45 |
Ref11 | 13.30 | 0.79 | 13.03 | 87 | 13.05 | -1.74 |
Occ 1 | -- | -- | -- | 80 | ||
Occ 2 | -- | -- | -- | 80 | ||
no-star1 | -- | -- | -- | 0 |
The asteroid is listed in OWc with a magnitude (band not given) of 17.0. If no-star has counts=0, as the new PyMovie 4.0.9 now correctly factors in, and as is shown in the PyMovie light curves, then a drop of 11.31 to 17.0 = 5.7 magnitudes or .0052 x 517 unocculted targets counts = 3 counts. Clearly the occultation limiting magnitude doesn't reach this far down. From the table above, the magnitude of the bottom of the light curves is about W=13.2, so I appears that from 13th to 17th magnitude and below, is beyond the limiting magnitude of 13, and is lost in the noise. Some light curve bottom points do reach to zero, but might be caused by Fresnel diffraction.
Finder chart for the reference stars, from C2A. The UCAC4 catalog numbers, and the V and r magnitudes are given. |
Note that except for the very red star Ref5, the W magnitude is closely the same as the r magnitude. This will be useful in giving the W magnitude in the future on my webpages, as the r magnitude is available for nearly all UCAC4 stars.
Hristo's table also gives:
K - InstrumentalMag = - 3.004 * (J-K) + ZeroLevel +/- 0.12
So W = K+3.004(J-K) + zero level (but, we don't have K magnitudes given for ref stars in C2A, only Ks magnitudes, so I've not used this to find W magnitudes)
The temperature was in the high 30's F, as there was frost on the wooden tables, and this was at 8:30pm, not that late into the night. Frost warnings were indeed issued by the local Monterey Bay weather people. The cold probably helped reduce thermal noise in the camera. Even though only 9 degrees from the 97% moon, the 2x setting and clean skies made for a background sky that was clearly below the target star and other fainter stars. I set gamma=1.0 to maximize any partial drop, and since I did not need to brighten the dark side of the sky pixel levels histogram, as shown in PyMovie.
My visual impression as I watched, was that I had a double occultation.. I commented "Eyeah!" on the first D, and then was taken aback by seeing it reappear after 0.3s and then immediately disappear again for about 0.3s. I took some Dark video to accompany this tape if it is valuable for other astronomers to do their own reductions. I had to wait a few more days to get a clear twilight sky and take flat field video, at the same focus and optics. After this flat field video, I then did a cleaning of the Watec chip (air blower) and removed a few dust motes seen on the Martschmidt video. None of the dust motes were over stars used in the reductions, however.
I used PyMovie, and static circular 4px apertures. I used the two bright stars on either side of the target as my reference stars. The upper one remained w/o saturated pixels, while the lower ref2 star did have saturated pixels and was not used as a reference, but only as the second tracking star.
MagDrop report: percentDrop: 76.5
magDrop: 1.572 +/- 0.258 (0.95 ci)
DNR: 3.78
D time: [04:49:53.3336]
D: 0.6800 containment intervals: {+/- 0.0080} seconds
D: 0.9500 containment intervals: {+/- 0.0197} seconds
D: 0.9973 containment intervals: {+/- 0.0402} seconds
R time: [04:49:53.6536]
R: 0.6800 containment intervals: {+/- 0.0080} seconds
R: 0.9500 containment intervals: {+/- 0.0197} seconds
R: 0.9973 containment intervals: {+/- 0.0402} seconds
Duration (R - D): 0.3200 seconds
Duration: 0.6800 containment intervals: {+/- 0.0115} seconds
Duration: 0.9500 containment intervals: {+/- 0.0257} seconds
Duration: 0.9973 containment intervals: {+/- 0.0452} seconds
MagDrop report: percentDrop: 86.1
magDrop: 2.144 +/- 0.736 (0.95 ci)
DNR: 4.25
D time: [04:49:54.2736]
D: 0.6800 containment intervals: {+/- 0.0089} seconds
D: 0.9500 containment intervals: {+/- 0.0223} seconds
D: 0.9973 containment intervals: {+/- 0.0439} seconds
R time: [04:49:54.6302]
R: 0.6800 containment intervals: {+/- 0.0089} seconds
R: 0.9500 containment intervals: {+/- 0.0223} seconds
R: 0.9973 containment intervals: {+/- 0.0439} seconds
Duration (R - D): 0.3566 seconds
Duration: 0.6800 containment intervals: {+/- 0.0128} seconds
Duration: 0.9500 containment intervals: {+/- 0.0287} seconds
Duration: 0.9973 containment intervals: {+/- 0.0521} seconds
Since clipped low end histogram of sky pixel values is not an issue for this occultation, due to the bright sky only 9 degrees from a 97% moon, then the magnitude and % brightness drops can be taken as not affected by this issue. Nominal 76% and 86% light loss for the two occultations, taken from the PyOTE log files and copy/pasted above.
PyOTE D and R confidence intervals for the first occultation. |
False Positive (FP) test for the first occultation |
PyOTE D and R confidence intervals for the second occultation. |
False Positive (FP) test for the second occultation |
The histogram of tone values and default range. In the images below, I've tightened the limits to help show the stars better. But the point of this image is that despite the IRE=0 hardwired into the PAL Watec camera, the complete range of sky values is is not clipped at the low end, as can happen in much darker skies and short integrations. |
First question. Was one of the occultations due to a dust mote or bad pixels? Here, on the extreme left side frame in the image table below, is the Fourier Finder image for a stack of 111 frames in PyMovie (about 4 seconds of stacking), and also a screen capture of the chip 1 second after the occultation, to show the relative positions of the target and reference stars. I've used this to then locate where to put an "x" for the target at the time of the occultation on the 111 frame finder image. The tracking was good, and very little drift during the full recording of the event. The vertical banding that seems characteristic of my camera or set up is evident, but the intensity contrast of the pixel brightness variations are highly amplified in these images below. You can see how I've taken the actual dynamic range and compressed it severely for the sake of ID'ing fainter stars, by looking at the pixel value histogram plotted vertically on the right side of the image. You can also see that for this bright-sky event, the IRE=0 issue is not relevant. No offsetting of the "no-star" level due to clipped values at the low end, as often happens in dark skies and/or short integrations events.
A 111 frame Fourier stack , from the beginning of the recording |
A 25 frame stack just before the start of the 1st occultation |
A 12 frame stack just after the first occultation ended |
A 12 frame stack just before the first occultation began |
A 12 frame stack just after the 2nd occultation ended. |
A 999 frame Fourier Finder. Now, we see the stars are trailed, and the vertical banding is not. So it does seem that the vertical banding is inherent in the column pixel sensitivities. And, Fourier finders should be confined to durations less than significant star trails. Another feature I see is that the pixel-to-pixel variance rapidly damps out as you raise the number of frames in the Finder. This suggests that the "speckled" noise is mostly due to read out and Poisson and other moment to moment noise sources and that the pixels themselves are (at least vertically) pretty consistent in their sensitivities. |
A stack of 444 frames; Fourier Finder with the "horizontal median filter" option checked |
A stack of 444 frames; Fourier Finder with the "vertical median filter" option checked. I don't see any real difference with the median filtering. The source of the banding is believed to be due to differences in the amplifiers for each column. Each column has its own amplifier and they are not perfectly the same, it seems. |
Conclusions: The target remained in the evenly lit area to the left of the prominent vertical dark bar until over 25 seconds after the occultations, when it was then affected. That is likely the cause of the light curve slight but extended dip seen in the full duration light curve of the target, Also, the occultation events and ref stars were not affected by bad pixel clusters or the dust motes at far right.
I used TME apertures on a larger range of stars, including fainter stars, and also 3 no-star apertures in different spots near the target. The goal is to find if both mag drops are significantly and clearly deeper than stars whose brightness is less than half the brightness of the target, and also above the brightness of 3 different "no-star" static circular 4px apertures. If yes, this would make a very strong case that the double dip was due to a binary asteroid and not a binary star. I think such a case is made, below.
A 66 frame Fourier finder frame, with TME apertures set on the stars above. C2A provided the V and r magnitudes as shown. Target star has V=11.46, r=11.34, so W=11.40 |
PyMovie screen capture, with apertures shown. |
The calibrated (using ref1) light curve of the target, together with ref5's light curve. Ref5 has V=13.09, r=12.08. So W=12.58. So ref5 is 34% of the target star's brightness in the Watec band. This star is quite a bit redder than the target star, and than the Ref 7 and Ref8 star's shown at right, and which have similar color to the target. |
Target, ref7, and no-star1 light curves. Ref7 is V=13.03, r=12.63, so W=12.83. So ref7 is 27% of the target star's brightness. Ref7's light is clearly above that of the empty sky, and the empty sky is, inside the occultations, virtually identical in level with the target's brightness. The color of this star is V-r = 0.4, vs target star's color of V-4=0.1.. |
Target and Ref8. Ref8 is V=12.65, r=12.24 so W=12.44. So Ref8 is 38% of the target's brightness. The color is 0.4 again. The star is clearly above the depth of the target's occultations, making the occultations at a level below 38% for both events. |
magDrop report: percentDrop: 82.1 magDrop: 1.867 +/- 0.485 (0.95 ci)
DNR: 4.48
D time: [04:49:53.2411]
D: 0.6800 containment intervals: {+/- 0.0084} seconds
D: 0.9500 containment intervals: {+/- 0.0202} seconds
D: 0.9973 containment intervals: {+/- 0.0407} seconds
R time: [04:49:53.6536]
R: 0.6800 containment intervals: {+/- 0.0084} seconds
R: 0.9500 containment intervals: {+/- 0.0202} seconds
R: 0.9973 containment intervals: {+/- 0.0407} seconds
Duration (R - D): 0.4125 seconds
Duration: 0.6800 containment intervals: {+/- 0.0123} seconds
Duration: 0.9500 containment intervals: {+/- 0.0276} seconds
Duration: 0.9973 containment intervals: {+/- 0.0486} seconds
magDrop report: percentDrop: 85.1 magDrop: 2.067 +/- 0.681 (0.95 ci)
DNR: 4.64
D time: [04:49:54.2713]
D: 0.6800 containment intervals: {+/- 0.0081} seconds
D: 0.9500 containment intervals: {+/- 0.0209} seconds
D: 0.9973 containment intervals: {+/- 0.0391} seconds
R time: [04:49:54.6284]
R: 0.6800 containment intervals: {+/- 0.0081} seconds
R: 0.9500 containment intervals: {+/- 0.0209} seconds
R: 0.9973 containment intervals: {+/- 0.0391} seconds
Duration (R - D): 0.3571 seconds
Duration: 0.6800 containment intervals: {+/- 0.0122} seconds
Duration: 0.9500 containment intervals: {+/- 0.0272} seconds
Duration: 0.9973 containment intervals: {+/- 0.0476} seconds
The TME solution light curves above are seen to have deeper and better DNR's than analysis #1 with static circular apertures. This adds to the confidence in the binary asteroid interpretation. The duration of the first event is also now longer than in the first analysis with circular 4px apertures. Mark Simpson also felt that tighter 2.4px apertures were better, and that would go with the TME also being better, so that is consistent. For a drop to W magnitude ~16.6, the light loss should be 99%, but within the scatter during these short occultations, the measured 93% and 96% light loss is consistent.
What is needed to make a best-case here, is to use the newly calculated (not estimated) (Hristo Pavlov's formula) W magnitudes for a range of faint reference stars and show their light curves relative to the occultation bottoms, and no-star sky. I use circular apertures of 3 px size, based on curve of growth under the seeing and sky brightness. I use the median filtering both horizontal and vertical. Also, to do a 'Fourier Finder' just including the first occultation period (it'll be noisy) and compare what it sees of the target vs the fainter W stars.
magDrop report: percentDrop: 83.9 magDrop: 1.981 +/- 0.431 (0.95 ci)
DNR: 4.13
D time: [04:49:53.2381]
D: 0.6800 containment intervals: {+/- 0.0077} seconds
D: 0.9500 containment intervals: {+/- 0.0196} seconds
D: 0.9973 containment intervals: {+/- 0.0392} seconds
R time: [04:49:53.6536]
R: 0.6800 containment intervals: {+/- 0.0077} seconds
R: 0.9500 containment intervals: {+/- 0.0196} seconds
R: 0.9973 containment intervals: {+/- 0.0392} seconds
Duration (R - D): 0.4155 seconds
Duration: 0.6800 containment intervals: {+/- 0.0116} seconds
Duration: 0.9500 containment intervals: {+/- 0.0258} seconds
Duration: 0.9973 containment intervals: {+/- 0.0468} seconds
magDrop report: percentDrop: 87.4 magDrop: 2.246 +/- 0.596 (0.95 ci)
DNR: 4.30
D time: [04:49:54.2708]
D: 0.6800 containment intervals: {+/- 0.0074} seconds
D: 0.9500 containment intervals: {+/- 0.0180} seconds
D: 0.9973 containment intervals: {+/- 0.0379} seconds
R time: [04:49:54.6038]
R: 0.6800 containment intervals: {+/- 0.0074} seconds
R: 0.9500 containment intervals: {+/- 0.0180} seconds
R: 0.9973 containment intervals: {+/- 0.0379} seconds
Duration (R - D): 0.3330 seconds
Duration: 0.6800 containment intervals: {+/- 0.0108} seconds
Duration: 0.9500 containment intervals: {+/- 0.0245} seconds
Duration: 0.9973 containment intervals: {+/- 0.0435} seconds
==========================================================================================================
Dave Gault: Produced a sky plane of this event, assuming my chord went across the middle of two spherical objects. And, Mark Simpson did an independent analysis of the photometry using his own set of stars, several in common with my own. He used static circular apertures, and arrives at the same conclusions: The binary star hypothesis is essentially ruled out, in his judgement, mine, Mark Simpson's, and Jean-Francois'.
Mark Simpson: Took my .avi file and did his own analysis using static circular apertures, and got good confirmation of my own analysis: The .csv in particular, you’ll need to enter your timing manually when loaded. Sorry, but I use Astrid and I’m not familiar with the craziness of OCR, camera delays and entering those, at least not enough to be confident of your setup, so I just played it safe and entered the first time in the first time field in the video and the same for the last frame.
But I see nothing wrong with your data, or analysis (assuming you’ve correctly entered the OCR and delays), so I used your times for SkyPlane plot as they are valid. Also my DNR came out similar to yours, but I settled on a mask radius was 2.4, as it was slightly better (but that’s not really that relevant here). Your data was consistent in the drops over reasonable mask sizes, which is also further confirmation what you are seeing is real when noise is high. I used Reference3 to normalize a bit (just because there was a bit of variance) and smoothing of 10 periods (but I probably didn’t need to normalize, it didn’t hurt by doing it anyway in this case).
For the reference stars, timing doesn’t matter at all, so primarily I was just interested in excluding the binary star hypothesis. Once that’s excluded, then you’ve poven it’s a binary asteroid.
Hope that makes sense. Please write a paper on it, nice catch and it should be out there.
David Dunham notes: Congratulations on this discovery! (10430) Martschmidt is in neither the Johnstone archive of binary asteroids nor is it one of the GAIAMOONS (from Gaia astrometry) object, so there are no previous hints of duplicity. There are no observations of any occultations by this asteroid, in the latest Occult asteroidal occultation observations database. For GAIAMOONS, you can check for them in the attached plain-text file (can open with Notepad) Gaia_Binaries.dat whose format is explained in the attached ReadMe.txt file. The next step now is to alert the best observers of asteroid rotational lightcurves; for a high-numbered relatively small asteroid like this, there is probably little or no photometric information. Of course, this asteroid was not on my radar when I generated the predictions of occultations by special main-belt asteroids a few months ago, so I’ll make a new Occult run to find events in the future through the end of 2025.
Scott Young comments: According to the Light Curve Database, (10430 Martschmidt) has a photometric period of 15.577h (somewhat uncertain, uncertainty code "2" out of 3) and a maximum amplitude of 0.6mag. A bit faint for my scope, but I will see if I can get one of the iTelescope scopes onto it this week and see what we can see.
Jean-Francois Gout: Last night (=Nov 19 local Mississippi time), I managed to get 5 hours of photometry data on (10430) Martschmidt. After a mostly flat lightcurve, there was a sudden drop in brightness. The observing session ended due to the asteroid reaching 30 degrees altitude) before the end of the brightness recovery. I'm attaching the data as a csv file and also a screenshot of the lightcurve. We will need more observations to confirm the presence of mutual events (eclipses and transits), but this is promising. I'll keep looking at this asteroid in the upcoming nights. Weather forecast calls for clear sky here in Mississippi, but the wind might cause some trouble for the fairly long (3 minutes) exposures that I need to get a descent SNR on this object. Observations from Europe/Asia would be especially valuable to complement my own observations.
RN: My comment here - if Jean-Francois' light curve drop is matched by another drop (one a transit, one an eclipse), and if the drops in light are Algol-eclipse-like, rather than gradual e.g. such as perhaps sine waves, this indeed argues they are mutual eclipses and not albedo or shadowing changes, which should highly likely be more gradual. The new data from Matthieu clinches the case this is a binary asteroid, the period is most 23.2 hrs, but 1/2 that or 11.6 hrs can't be entirely ruled out yet. If 23.2 hrs then Mattheiu's data show a secondary eclipse halfway between the primary eclipses seen by Jean-Francois, see below. Cabrillo College Observatory's 12" f/6.3 with SBIG ST2000xcm may be able to reach this magnitude as well, but we have had cloudy skies so far (as of Nov 30). Student Bernard H from Astro 9ABC is also doing photometry on the asteroid itself.
Dec 1 RN did a pencil and calculator calculation of the semi major axis using Kepler III and assumed possible orbital periods of 23.2 hr and 11.6 hrs. P=11.6 hr gave semi major axis a = 4.4km and for P=23.2 hr, a=6.95km. These are both too small to be consistent with the occultation, in which the minimum possible a is 10.6 km. This can be remedied if we increase the density from 2g/cm3 to rather larger. I won't take that as final; more calcs to come....
JF Gout's first photometry from his telescope in Mississippi. Cut short by limits. |
Here is more photometry data from JF Gout, showing 3 apparent eclipses. The eclipses are spaced 23.2 hrs apart. But is there a secondary eclipse hidden in the unseen portion? |
Matthieu succeeded in getting a long series of data that ended just as Gout's began. The eclipse at the beginning of Mattheiu's data (in red, at left) has an eclipse profile looking a bit different and is 11.6 hr or 0.5x23.2 hrs before Gout's data. The eclipse narrowness and shape make this highly inconsistent with an albedo or self-shadowing effect; these have classic eclipse shapes of nearly identical sized components. But is the period 23.2 hr, or is it 11.6 hr? An 11.6 hr period would require a highly elliptical orbit sufficient to miss a secondary eclipse. This would be very unusual and the most likely conclusion is a 23.2 hr period. As of Nov 30 am.
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