Friday, January 30, 2009

Good weather for tonight

All is set for our attempt tonight. Amazingly, it looks like the weather forecast is good for southern California (Palomar), southern Arizona (Vatican Observatory), southern New Mexico (Apache Point, Magdalena Ridge Observatory), and also Mauna Kea and Haleakala (UH 88inch and Faulkes 2m, respectively). I believe this to be some sort of record.

Bill Ryan at MRO got a nice comparison light curve from last night, which will be quite useful for definitely identifying tonight's event.

Between all of the observatories we will have two full rotations, so even thought it might be painful, I believe we will be able to stitch together a full dataset for comparison.

Wednesday, January 21, 2009

Jan 13th eclipse

no known attempts

Jan 5th transit shadow graze

no known attempts

Dec 26th eclipse

Attempts were made from Bulgaria and Armenia (on Christmas night!), but complete cloud cover prevented any telescopes from opening.

Dec 18th transit shadow graze

No known attempts

Dec 7, 2008

no known attempts

Tuesday, January 20, 2009

Observing strategy

The main goal for these observations is to obtain accurate relative photometry with sufficient cadence to resolve the events (ingress and egress each last ~15 minutes, but there might be interesting structure within) and sufficient accuracy to detect the event (Namaka's disappearance during an eclipse will make the overall brightness of Haumea decrease by only about 1.3%).

The optimal exposure time for your observations depends on your telescope and on your camera. The main things to worry about are:
-readout time for your camera
-time to saturation
-time until you are sky background limited

I would shoot for having exposure times be at least 2-3 times the readout time of your camera, as long as you are not coming close to saturating Haumea. Even with a very fast readout camera, exposure times under a minute or two are probably not worthwhile. The best cadence, if it fits your camera characteristics, is probably around 2 minutes per exposure. At Palomar, we will be doing 2 minute exposures with 45 second readouts in between.

Previously I said this:
In general, the optimal filter is the one that gives you the highest signal-to-noise. Haumea is almost precisely solar colored, so observing in something like a V filter is a good bet, though it is possible that you might want to go totally unfiltered (at Palomar we will be using a special filter that cuts out some of the worst of the sky lines from the bright Palomar sky).

However, after the 1/31 event I now believe that it is best if everyone observes in as common a filter as possible. Because some of the events will have heavy moonlight, R seems the best choice. At Palomar we used a slight variant of R that cuts out the strong sodium lines from San Diego, but as long as everyone is R-ish I think we will be able to compare all of the data well.

At some point in the night you will want to insert a single image in a different filter. This single image will be used to get the colors of all of the stars relative to Haumea. The relative photometry can then be done using only stars that are close to Haumea's solar color. This selection will be important given the very wide range of airmasses Haumea is likely to go through (at Palomar we will start at an airmass of 4!).

Before Haumea rises (or on an earlier night, at twilight, or with dome flats):
  • take images of the night sky/twilight sky or just dome flats
  • look for a particularly well behaved region on the chip where the flat field is as flat as possible, there are no bad pixels or columns, nothing funny is going on for a moderately good sized region.
  • Note that location for later; that is where you will put Haumea

The observing strategy is quite simple:
  • point to Haumea as early as your telescope possibly can.
  • place Haumea in the very nice region of the chip that you identified earlier.
  • track at Haumea's rate; do not dither! Dithering is great if you want to average out CCD variations over time, but we instead want to keep them constant with time.
  • observe all night until you can't anymore
  • pause for nothing.
  • if you fear focus changes, focus on an image-by-image basis rather than stopping to focus.
  • Be sure to insert one or two images in a second filter.
We believe that the best strategy will be to track on the rate of Haumea but perform no dithering of the telescope. If your telescope cannot track at a moving target rate, track siderally, but, again, perform no dithering.

If you believe your night to be photometric, good solar colored standard stars at the begining and end would be helpful, but not essential.

Jan 31: Our first good attempt

The first good attempt to observe a mutual event will come on Jan 31st UT (the night of Friday, Jan 30th), as Namaka goes into the shadow of Haumea. The ingress is predicted for 11:02 UT = 3:02 AM PST Thursday morning; the egress follows almost one hour later at 11:52 UT = 3:52 PM. The uncertainty in the timing, however, could be as much as 3 or 4 hours!

This event is particularly important, because if we can get just one good clear detection, we will greatly decrease the uncertainty in the times of all future events.

To my knowledge, the following telescopes/observers are attempting observations:

Palomar 5m (Caltech group)
Apache Point 3.5m (Nancy Chanover & Chas Miller)
Magdelena Ridge 2.4m (?)

University of Hawaii 2.2m (Emily Schaller)

We are in good shape to get somebody to see this event unless the entire western US is clouded out. Which can definitely happen this time of the year. We should have eyes on the event if it occurs anywhere from about 4 hours early until about 8 hours late.

Our difficulty for fast analysis of this event will be that no one will be able to observe more than about 5 hours. Haumea rotates every 4 hours. Ideally, one would observe for 8 hours and see Haumea with and without an event. With luck, though, we will be able to stitch together enough observations to get this figured out very quickly. We would like to know in time for the Next event, occuring on Feb 18th, over India and China.

Welcome to the Haumea Namaka mutual events page

I will continuously update this sight throughout the season to give as much up-to-the-minute information as possible on the mutual events. To learn more, please read the full mutual event page.