The Occultation of a W=13.3 Star by Asteroid Dannymeyer

Sat eve Aug 2 at 10:51:36pm

OWc page

This is a good long 2.9 sec event with a very high rank. I and Kirk at home are just outside the southern limit. Aptos and Carbonera are both inside. Karl's near the centerline. This looks like perhaps a good "movie night" opportunity to help Karl in his computer reporting issues, too.

Alt=34, Az=171 in Sagittarius. Just above the lip of the "Teaspoon".

The target is only about 10" away from a brighter neighbor, so we'll want to remove our focal reducers once we're on target and are sure the telescope is not drifting but is stable.

The target is about 10" below the brighter star seen on the usual LCD image at left. This image zooms in (and shows the FOV of the 36" MIRA scope at f/10)

Results:

Kirk, Karl and I all tried this one together, from "The Rock" at Karl's place. Kirk and I got the occultation. Karl had trouble ID'ing the star field and missed it.

Richard Nolthenius

I removed the f/3.3 reducer. That meant I needed to then turn the focus knob 20 times to the right (not 20 x 360deg rotations! 20 normal wrist turns), to achieve focus again. The focus wasn't great in terms of what I saw on screen. The stars were not tight, but a hodge-podge of pixels against a still fairly bright sky. I cut the aperture box to 11, so that the brighter star above the target 10" away would not leak in and get grabbed during the occultation. I left the mask at 3.2px. I was at 8x, and while I tried initially to use dynamic or TME apertures, they were worse, so I just used the fixed circular aperture.

magDrop report: percentDrop: 85.0 magDrop: 2.063 +/- 0.613 (0.95 ci)

DNR: 1.88

D time: [05:51:33.6918]
D: 0.6800 containment intervals: {+/- 0.0635} seconds
D: 0.9500 containment intervals: {+/- 0.2120} seconds
D: 0.9973 containment intervals: {+/- 0.4920} seconds

R time: [05:51:35.9318]
R: 0.6800 containment intervals: {+/- 0.0635} seconds
R: 0.9500 containment intervals: {+/- 0.2120} seconds
R: 0.9973 containment intervals: {+/- 0.4920} seconds

Duration (R - D): 2.2400 seconds
Duration: 0.6800 containment intervals: {+/- 0.1009} seconds
Duration: 0.9500 containment intervals: {+/- 0.2590} seconds
Duration: 0.9973 containment intervals: {+/- 0.5254} seconds

8x means 4 frames per integration.

There's a 3-integration drop to zero 8s (3 diameters of the primary) after the event which might be something. It's at 5:51:43.6 UT. If Kirk recorded this as well, it may be worth reporting. There are a number of other single frame or single integration drops to zero throughout the 3 minute video, but no other consecutive 3-integration drops to zero.

Secondary Event?

magDrop report: percentDrop: 94.4 magDrop: 3.134 +/- 0.920 (0.95 ci)

DNR: 2.40

D time: [05:51:43.4517]
D: 0.6800 containment intervals: {+/- 0.0348} seconds
D: 0.9500 containment intervals: {+/- 0.0922} seconds
D: 0.9973 containment intervals: {+/- 0.1925} seconds

R time: [05:51:43.9317]
R: 0.6800 containment intervals: {+/- 0.0348} seconds
R: 0.9500 containment intervals: {+/- 0.0922} seconds
R: 0.9973 containment intervals: {+/- 0.1925} seconds

Duration (R - D): 0.4800 seconds
Duration: 0.6800 containment intervals: {+/- 0.0505} seconds
Duration: 0.9500 containment intervals: {+/- 0.1182} seconds
Duration: 0.9973 containment intervals: {+/- 0.2254} seconds

PyMovie showing all frames in the primary and possible secondary event.

Kirk Bender

I got a 2.0020 sec. event for Dannymeyer, 8x at The Rock at Karl's place. I don't see a second event. I used size 11 aperture to isolate the target from the bright nearby star. There's a large dip at the beginning from the scope being bumped, but it kept tracking afterwards. I trimmed out the scope bump for PyOTE. I tried several size static masks and got the best results from size 2.0, sigma distance 11.1. I didn't see signs of a second event in any of the aperture sizes. I've attached screenshots of the primary event, and of the light curves with a line at Rick's proposed second event time.


magDrop report: percentDrop: 80.8  magDrop: 1.791  +/- 0.514  (0.95 ci)

DNR: 2.10

D time: [05:51:33.8148]
D: 0.6800 containment intervals:  {+/- 0.0547} seconds
D: 0.9500 containment intervals:  {+/- 0.1800} seconds
D: 0.9973 containment intervals:  {+/- 0.4745} seconds

R time: [05:51:35.8168]
R: 0.6800 containment intervals:  {+/- 0.0547} seconds
R: 0.9500 containment intervals:  {+/- 0.1800} seconds
R: 0.9973 containment intervals:  {+/- 0.4745} seconds

Duration (R - D): 2.0020 seconds
Duration: 0.6800 containment intervals:  {+/- 0.0859} seconds
Duration: 0.9500 containment intervals:  {+/- 0.2326} seconds
Duration: 0.9973 containment intervals:  {+/- 0.5156} seconds

RN bumped KB's tripod leg when reaching to turn on the AC power to the recording Lenovo computer. That was trimmed out of the reductions in PyOTE.

No evidence of a 2nd event at RN's observed time, in KB's data.

KB's observation at the possible secondary event seen by RN a few feet away, indicates the RN 2nd event was likely a noise drop.

Interesting that both Kirk's and my light curve show a central rise. Real? Too hard to tell. But, worth noting here. At my possible 2nd event, Kirk shows 2 consecutive integrations which were low but not zero, and would normally be dismissed as noise. This "2nd" event is not statistically significant enough to get more than a suspicion.