Plate Scale for Hinode/XRT -- resolved

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

Hello all:

In April we had some discussion on the plate scale of Hinode XRT.
At that time I mentioned that I measured the plate scale to be
about 1.0417+/-0.0005"/pix.

But if you know about optics, you know in your heart that the
value of 1.042"/pix is just impossible.

And indeed it was. Apparently I thought that the plate scale of
a SOHO/EIT image compares well with another image taken at Earth's
orbit, not L1. The difference between being at L1 and at Earth
makes a correction factor of 0.9901 for the plate scale. So I
rederive the plate scale, based on the corrected SOHO/EIT284A image
and a Hinode XRT image taken simultaneously, to be

	1.0314 +/- 0.0005"/pix

which, I believe, is statistically consistent with Shimizu-san's
measurement based on the transit of Mercury event.

Astrophysicists sometimes need to be reminded that the Sun is at
the finite distance...thanks Narukage-san to point this out to me.

Bish


Leon Golub wrote:
> 
> 
> -------- Original Message --------
> Subject: Re: [Fwd: [Fwd: Plate Scale for Hinode/XRT]]
> Date: Mon, 23 Apr 2007 12:09:39 -0400
> From: Peter Cheimets <pcheimets@cfa.harvard.edu>
> To: Mark Weber <mweber@cfa.harvard.edu>
> CC: Leon Golub <golub@head.cfa.harvard.edu>, Paul Reid 
> <preid@cfa.harvard.edu>,        edeluca <edeluca@cfa.harvard.edu>
> References: <462CA4F6.7060306@head.cfa.harvard.edu> 
> <462CB1E9.1070004@cfa.harvard.edu> 
> <462CCABE.5050104@head.cfa.harvard.edu> 
> <462CD6FD.9060508@cfa.harvard.edu> 
> <C8F65D57-C3E5-4BE8-B61E-48D5B934F7C9@cfa.harvard.edu>
> 
> plate scale is: 13.5e-3/2707.157 = 4.987e-6 rad = 1.0286 arcsec/pixel
> (give or take).
> 
> Peter
> 
> Mark Weber wrote:
>  > 13.5 micron per pixel. --Mark
>  >
>  > On Apr 23, 2007, at 11:55 AM, Peter Cheimets wrote:
>  >
>  >> What size are the pixels and I'll tell you?
>  >>
>  >> Peter
>  >>
>  >> Leon Golub wrote:
>  >>> Right. So what's our plate scale?
>  >>>
>  >>> Leon
>  >>>
>  >>>
>  >>> Peter Cheimets wrote:
>  >>>> Goddrich measured the F/L as 2707.5mm, we measured is at 2707.157mm.
>  >>>>
>  >>>> Peter
>  >>>>
>  >>>> Leon Golub wrote:
>  >>>>
>  >>>>> Paul,
>  >>>>>
>  >>>>> One of our Japanese colleagues raises the quesiton of XRT plate
>  >>>>> scale. In
>  >>>>> principle, since we know the focal length now to better than 1mm,
>  >>>>> we ought
>  >>>>> to be able to specify the plate scale to better than 1 part in
>  >>>>> 2700, right? Or
>  >>>>> am I wrong about that?
>  >>>>>
>  >>>>> Leon
>  >>>>>
>  >>>>>
>  >>>>
>  >>>
>  >>> ***********************************************************
>  >>> 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
>  >>> ***********************************************************
>  >>
>  >> --
>  >>
>  >> Peter Cheimets
>  >> Smithsonian Astrophysical Observatory             ,__o-
>  >> Smithsonian Institution                         _-\_<,
>  >> 60 Garden St.                                  (*)/'(*)-
>  >> Cambridge, MA 02138
>  >> pcheimets@cfa.harvard.edu
>  >> (617)495-7350      (voice)
>  >> (617)495-7098      (FAX)
>