(510) Mabella visits SPSP

[DaveGee]

Observers,

There will be an asteroid occultation observable from the South Pacific Star Party, next week end.

The target star is bright(ish) at mag. 9.8 which is comfortable for these types of events. The event will occur at 2:59am (daylight savings time) Sunday morning. The ranking for the event is 84.

I'd like to encourage as many observers on the field to observe this event. The asteroid will be at mag.13.2 so it should be possible to see the asteroid appulse the star (scopes >10") up to 10 minutes before the event time when the two will appear to merge. If the event occurs, the star will disappear leaving the asteroid in view for a maximum of 4.6 seconds.

I have prepared some finder charts(see below)

If anyone attending the SPSP and wishes to observe this event and doesn't have access to UT timebase, please contact me.

thanks...

[Inmykombi]

Hi DaveGee,

This sounds like a real opportunity for me to observe something special.

I will be able to load the co-ordinates into my scope and I will plan to watch the event at the anticipated times.

Thanks for the information, and good luck in looking yourself.

Geoffro

[DaveGee]

To visually observe this event scientifically, you'll need;
1) an eyeball Mk1, it's optional to have a second on standby spaced about 70mm from the first.
2) a voice box to create the mandatory "Gone" and "Back" signals at appropriate moments.
3) a bionic computer connected to the aforementioned eyeballs and also connected to the equally aforementioned voice box. It is somewhat preferable to keep said connections between the peripherals as short as possible and as clean as possible to allow for efficient signal propagation.
4) a telescope of aperture larger than 150mm (6" in the old scale)
5) For Wiruna observers, an FM receiver or radio that will supply UTC time beeps. We will let you know the frequency to tune the radio during Saturday afternoon. (that's if a certain person remembers to bring the transmitter)
6) a recording device, tape recorder, mobile phone, Edison Dictaphone... than kind of thing...
7) finder charts will be available at the Wiruna Hall during the Saturday Afternoon festivities or alternatively BYO.


Any other equipment is purely at the observer's convenience and preference.

Technique (starting from 1:45am Sunday Morning)
- Place telescope on ground. (You can place it above the ground but alas the writer won't guarantee how long it stays put)
- Ensure you can see an area of the sky centred on Alt46deg, Az300deg
- Ensure the telescope works by finding Spica, the brightest star in the vicinity mentioned above.
- about 15 deg. (1 hand span, fingers and thumb outstretched) under Spica you'll find mag. 3.4 Porrima. You can stand there and admire Porrima for a couple of minutes if you wish but sooner or later it would be desirable to point the telescope at it.
- Using the MabellaFinderB chart you should be able to star hop to the mag. 9.8 target star. Hint... for dobsonians turn the chart upside down (or downside up) for scopes with star diagonals turn charts inside out (or outside in)
- Confirm that you can recognise the target star by comparing the pattern of stars around it.
- observers with telescopes larger than 8" might be able to see (510) Mabella separated from the star and moving slowly in a westward direction. Take note of this because during the event (510) Mabella will be visible. Meaning the star will dim rather than disappear.
- by 2:45am Mabella and the target will have merged
- by 2:50am tune your FM radio to the previously advised frequency.
- by 2:55am start your recording device and place it such that it will detect and record the time beeps and you voice as you call out.
- by 2:57am your preferred eye should be placed to the eyepiece and it should not (repeat NOT) be removed from the eyepiece for any (repeat ANY) reason, at least for the next 4 minutes. You whole being should be focused on that star and the word "gone" should be about 0.5mm behind your lips ready to spring forth at the slightest provocation. Listen to the time beeps to gauge the time but under no circumstances should you look at your watch. It’s a good idea to have a helper whisper “that's 2:58am”, “and 30”, “that's 2:59”... GONE!!! the star disappears and the word escapes.
- Keep looking! Immediately replace the GONE with the word BACK
- Observers with telescopes smaller than 8” will have to guestimate where the star was and continue watching that spot. Observers with telescopes larger than 8” can watch the asteroid.
- In the span of 3 to5 heartbeats be ready… “BACK” the star reappears (or brightens) and the word escapes.
- Continue to observe for another minute if you can, you never know, you might just see the star blink for the briefest of moments, meaning you just saw a sateroid (satellite of an asteroid), but in essence it’s all over and only the paperwork to complete, but before that…
CONGRATULATE yourself on your achievement.
-You have just measured a chord across an asteroid! An asteroid who’s diameter spans 0.048 arc seconds. Not only that, you have probably placed the limbs of the asteroid to 0.005 arc second precision For the technowizzes that’s 5MAS! The Dawes Limit is nowhere to be seen and is probably off sulking in a remote corner of the observing field but is ready and anxious to return to your telescope the next time you look at something.


That’s asteroid occultation observing.
Be prepared, be ready, react swiftly.


Do the opposite and you won’t see a thing. An asteroid waits for nobody!