Rare occultation by the moon Nereid 25 August

Barberskum wrote:

I have is a Philips SPC900 webcam.
I'm not sure if this will be adequate.

Frank, I doubt if a webcam will get you than faint. However your DSLR would easily get that. (I could get pluto at mag 13.9 in 30 seconds at ISO 400 in a 9.25" scope. Keep the resolution low to minimise the dead time and just keep shooting during the period.

Barberskum wrote:

I have is a Philips SPC900 webcam.
I'm not sure if this will be adequate.

This setup is more than adequate for I.Ec.R. at 19:46 UT!

Vagelis Tsamis wrote:

Hey Dave! How are you?

I am very well and missing my Greek friends!

Vagelis Tsamis wrote:

Have you done it before?

No. I haven't tried this before. I just invented it especially for you If there is any chance I will try this out before Monday's event. However I can't see why this won't work.

Vagelis Tsamis wrote:

(Well, I don't expect it to be a smooth dimming indicating atmosphere on Nereid!)

True, but no harm in looking anyway!

Vagelis Tsamis wrote:

In case this doesn't work, I believe the best way to do it is Eamonn's suggestion about binning (2X2).
My CCD download time is 17 sec (1X1) and 7 sec (2X2).

Or you could use the ROI (region of Interest) feature to get an almost instantaneous download.

Vagelis Tsamis wrote:

PS: Greetings from Kyriakee!

Please pass on lots of hugs to the wonderful and beautiful Kyriakee. Oh how I miss those salads!

Vagelis Tsamis wrote:

I expect to have a nice video from that event, too.
(At least a guarenteed result, since Nereid occ. has a considerable uncertainty)

I'd take a half hour of clear sky around 11:20 personally

Well, I 'll try to learn what this ROI thing is...

Last night I took some more CCD images of Neptune and company... The motion of the planet on the celestial sphere is obvious. It has moved SW, so it is on a retrograde motion, whatever that meaning for our occultation observing expectations

Vagelis

Some further helpful information:

Mid-event hits Ireland at 22:25:45 UT.
The *formal* uncertainty is about 1.5-2 min. We do not know, in fact, what the real uncertainty is but we can only plan based on what we know.

Those with CCD cameras suggest that you take a series of 180 sec exposures (as many as practically possible), one of which *MUST* start 1.5 min before your mid-time. In other words, this exposure should start precisely from Ireland at 22:24:15 UT.


Neptune will probably saturate and even produce some "bleed", but that shouldn't create any problems, unless the star is in the same rows (or columns) as the planet.

Then aim is to see the star dim slightly (about 9%) in one of these exposures in the subsequent photometric analysis. Read-time is to be kept to a minimum, say, under 20 sec). If you can do binning or subframing to
keep that time down, do use it but try it out first to make sure that it doesn't create problems of its own. In any case, I advise you to make at least one dress rehearsal an hour or so before the occultation, weather permitting.

The position of that star is

RA = 21h 40m 4.72s
DEC=-14d 19m 02.95s

Magnitude is +13.6

This info and more is available at www.iota-es.de/nereid2008.html

Some field shots (20 arcmin wide or so) were taken during the past couple of nights by Vagelis: see above shots

Or they may be found at

farm4.static.flickr.com/3185/2791911131_a00dc36cbd_o.jpg

farm4.static.flickr.com/3150/2791975901_afac479abb_o.jpg

but keep in mind that they are vertically and laterally *inverted*.

They may not correspond right away to what you see in your screen.

As you can see from the event track at IOTA-ES, we will be counting on observers like you if the track is more North, so please observe if you can
and if the weather allows it. Chances like that do not come very often.

For Nereid, this is the first prediction of an occultation since its discovery in 1949.

The weather is predicted to be nearly clear around the time in the North West. However, this is still uncertain as to the timing of this gap when the clouds will disperse.

Clear skies

Eamonn A

www.kingslandobservatory.com

Hi Folks,

It was clear skies here for about 2 hours before the event. Then up to 10 minutes before the occultation
tonight here Co. Roscommon the clouds rolled in from the NW. I did some practice runs an hour before the event. It was frustrating to miss this important event.

Did anybody else have any success?

Eamonn A