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<div class="moz-cite-prefix">On 9/17/2020 5:52 AM, Anna Bartkiewicz
via Daip wrote:<br>
</div>
<blockquote type="cite"
cite="mid:59a67b60206fbb6e3ac339933d24c630@astro.umk.pl">
<br>
Dear All,
<br>
<br>
I am using the AIPS TST version. Since ca. 13/14 April, the ISPEC
task shows too high amplitudes for the spectrum of the image cube
generated by IMAGR. That is likely 10 times higher.
<br>
<br>
The brightest spot is 3.9 Jy and the spectrum from ISPEC shows 70
Jy as you can see in the attached print screen. Can it be related
to some changes in IMAGR or calculating the noise in ISPEC?
<br>
<br>
I would appreciate your help.
<br>
<br>
<br>
Greetings,
<br>
Anna Bartkiewicz
<br>
<br>
----------------------------------------------------------------
<br>
Dr hab. Anna Bartkiewicz, prof. NCU
<br>
Institute of Astronomy
<br>
Nicolaus Copernicus University
<br>
Gagarina 11
<br>
87-100 Torun
<br>
Poland <a class="moz-txt-link-abbreviated" href="mailto:annan@astro.umk.pl">annan@astro.umk.pl</a> phone: +48 56 6113040
<br>
mobile: +48 885 101 723
<br>
<br>
----------------------------------------------------------------
<br>
<br>
Imstat over the whole cube (201 channels)
<br>
<br>
<blockquote type="cite">imstat
<br>
</blockquote>
AIPS 1: Mean= 3.797E-04 rms= 8.431E-03 JY/BEAM over 85838256.
pixels
<br>
AIPS 1: Maximum= 3.9012E+00 at 312 813 82 1 1
1 1
<br>
AIPS 1: Skypos: RA 18 35 08.1400000 DEC -07 35 04.150000
<br>
AIPS 1: Skypos: 115.3 km/s IPOL
<br>
AIPS 1: Minimum=-4.4189E-01 at 318 844 79 1 1
1 1
<br>
AIPS 1: Skypos: RA 18 35 08.1395965 DEC -07 35 04.119000
<br>
AIPS 1: Skypos: 115.6 km/s IPOL
<br>
AIPS 1: Flux density = 1.0627E+03 Jy Beam area = 30.67
pixels
<br>
<br>
<br>
Imstat for one channel image with no emission
<br>
<br>
<blockquote type="cite">imstat
<br>
</blockquote>
AIPS 1: Mean=-9.454E-05 rms= 2.530E-03 JY/BEAM over 522443.
pixels
<br>
AIPS 1: Maximum= 1.2832E-02 at 405 258 201 1 1
1 1
<br>
AIPS 1: Skypos: RA 18 35 08.1337453 DEC -07 35 04.705000
<br>
AIPS 1: Skypos: 104.9 km/s IPOL
<br>
AIPS 1: Minimum=-1.2264E-02 at 366 843 201 1 1
1 1
<br>
AIPS 1: Skypos: RA 18 35 08.1363682 DEC -07 35 04.120000
<br>
AIPS 1: Skypos: 104.9 km/s IPOL
<br>
AIPS 1: Flux density = -1.6103E+00 Jy Beam area = 30.67
pixels
<br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
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</pre>
</blockquote>
<p>The peaks that you mention are in brightness (Jy/beam) at a
single pixel. The plot is the summed brightness over a large area
X pixels from 254 to 766 and Y pixels from 197 to 926 corrected to
Jy by dividing by the number of pixels in a Clean beam. So these
are TOTAL fluxes in your cube not brightnesses. OPTYPE in ISPEC
controls what is plotted and BLC and TRC control the area over
which sums or averages are done. If you ask for AVER and set
BLC=405,258 and set TRC=BLC then you will get 12.8 milliJy/beam at
channel 201.</p>
<p><br>
</p>
<p>Eric Greisen<br>
</p>
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