Re: xrt_co: - Draft proposal

[Bish ishibashi <bish@cora.nwra.com>]

 From my experience doing astrometry with CCD, you could reasonably
expect to measure a proper motion of an object to the accuracy of
one-quarter pixel size at ease. With 2x2 binning, that's about 0.5".
That accuracy ought to be more than sufficient for this. At the rate
of 1.8"/day, you don't have to worry about the variation in physical
pixel size, either (I don't have a first hand experience in how good
fabrication technique E2V possesses in making a CCD). Like Mark says
good statistics will help alleviate such concern anyway.

I think that someone really needs to estimate how much data will
be required to obtain enough statistics to do analysis, though.

Bish



Ed Deluca wrote:
> Do we need full resolution observations? I was assuming 2x2 binned.
> 
> Ed
> On Aug 20, 2008, at 4:24 PM, Mark Weber wrote:
> 
>> That is ~ 1 to 2 CCD pixels per day. This might be do-able with good 
>> statistics, I think.
>> --Mark
>>
>>
>> On Aug 20, 2008, at 4:14 PM, Leon Golub wrote:
>>
>>> Sorry, I actually used 15 m/sec in the calculation; I just mistyped 
>>> it in my message. The motion is ~15 m/sec X 86,000 sec per day, so 
>>> it's 15X86 km = 1290 km per day.
>>>
>>>
>>>
>>> Ed Deluca wrote:
>>>> The meridional circulation is ~15m/s not 15km/s!!
>>>> This is going to be hard to see.
>>>> Ed
>>>> On Aug 20, 2008, at 4:01 PM, Leon Golub wrote:
>>>>> Ed
>>>>>
>>>>> OK, our visitor has given me his A&A paper, so this is a follow-up 
>>>>> on my previous message. (Sorry about sending that to everybody; I 
>>>>> hit the wrong button.) Again, I would think that you should stay 
>>>>> away from the 7-day lifetime regions, even though they may not 
>>>>> rotate with a different differential coefficient. They will, 
>>>>> however, become fairly large, so that defining their location might 
>>>>> become difficult.
>>>>>
>>>>> So, what can you do with one-day lifetime regions? At a speed of 15 
>>>>> km/sec, the latitudinal motion will amount to about 1300 km per 
>>>>> day. That's about 2 arcsec, and I think is probably about equal to 
>>>>> the best you could expect in terms of locating a central position 
>>>>> for each XBP.
>>>>> That's not so terrible if you measure, say, 100 of them and figure 
>>>>> that the statistics go as N^1/2. I'd say you have a chance of 
>>>>> succeeding.
>>>>>
>>>>>
>>>>> By the way, you will only have a few 1-day regions regions each 
>>>>> day. If you go for 2-day regions (might as well, while you're at 
>>>>> it) there won't be many of them.
>>>>>
>>>>> Leon
>>>>>
>>>>>
>>>>> Ed Deluca wrote:
>>>>>> Attached is a draft proposal for a set of observations designed to 
>>>>>> measure the
>>>>>> meridional circulation from XBPs. It is a difficult and time 
>>>>>> consuming task,
>>>>>> so please review and comment on the feasibility and science value. If
>>>>>> we think this is worthwhile I will present it to the SSC in 
>>>>>> September.
>>>>>> Ed
>>>>>> ------------------------------------------------------------------------ 
>>>>>>
>>>>>> ===================================================================
>>>>>>       Dr. Edward E. DeLuca           Smithsonian Astrophysical 
>>>>>> Observatory
>>>>>>       edeluca@cfa.harvard.edu     MS 58
>>>>>> Office 617 496 7725                     60 Garden Street
>>>>>> Fax     617 496 7577                     Cambridge, MA  02138
>>>>>> Cell    508 728 5424                     USA
>>>>>> ===================================================================
>>>>>
>>>>> -- 
>>>>>
>>>>>
>>>>> ***********************************************************
>>>>> Dr. Leon Golub; Harvard-Smithsonian Center for Astrophysics
>>>>> 60 Garden Street, Cambridge MA 02138
>>>>> Ph: 617 495 7177; Fax: 617 496 7577
>>>>> e-mail: lgolub@cfa.harvard.edu
>>>>> http://hea-www.harvard.edu/~golub/HomePage.html
>>>>> ***********************************************************
>>>
>>> -- 
>>>
>>>
>>> ***********************************************************
>>> Dr. Leon Golub; Harvard-Smithsonian Center for Astrophysics
>>> 60 Garden Street, Cambridge MA 02138
>>> Ph: 617 495 7177; Fax: 617 496 7577
>>> e-mail: lgolub@cfa.harvard.edu
>>> http://hea-www.harvard.edu/~golub/HomePage.html
>>> ***********************************************************

-- 
"Bish" K. Ishibashi, Ph.D.

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