The Solar Global Oscillation Network Group (GONG) is a worldwide network of six solar telescopes operated by the National Solar Observatory (NSO https://nso.edu ) to provide 24/7 continuous observation of the Sun. A solar Hα image (6562.8 Å) shows the chromosphere, a dynamic plasma layer of plasma above the photosphere (solar surface). In an Hα image, filaments are seen as dark plasma structures and are cool regions in the chromosphere. Plages are seen as bright regions and are hot plasma regions above magnetic fields associate with sunspots.
The GONG archival data site can be found HERE
Data sets are maintained by Global Oscillation Network Group, The National Solar Observatory, of Hα images:
https://gong2.nso.edu/products/tableView/table.php?configFile=configs/hAlpha.cfg
https://nso.edu/data/nisp-data/h-alpha/
Note: Wolfram Solar Image Function Repository does not have Hα imagery ( e.g. see
https://community.wolfram.com/t/exploring-solar-imagery/23467 )
URL or local file path to a GONG H-alpha FITS file:
​LINK​
FITS = Flexible Image Transport System
JPG = Joint Photographic Experts Group
URL = Uniform Resource Locator
HTTPS =Hypertext Transfer Protocol Secure
For a particular year and month (2024 , 08) and for a particular day (2026, 08, 01) one can see the
available jpg-files using this link:
​https://gong2.nso.edu/ftp/HA/hag/202608/20260801/​
and the URL location for one particular fits image is given by:
In[]:=
fitsURL="https://gong2.nso.edu/ftp/HA/hag/202608/20260801/20260801000002Bh.jpg";
gongData=Import[fitsURL](*displaysthefitsimage*)
Out[]=
In[]:=
Colorize[Image[gongData],ColorFunction->"SolarColors"];
In[]:=
d=ImageData[gongData];
In[]:=
Dimensions[d]
Out[]=
{2048,2048,3}
In[]:=
img=ImageAdjust[gongData];
In[]:=
d[[1;;100,1;;600.,;;]]=0;​​d[[1;;100,1467;;2047.,;;]]=0;​​d[[1947;;2047,1;;600.,;;]]=0;​​d[[1847;;2047,1467;;2047.,;;]]=0;
In[]:=
gongData2=Image[d,ColorSpace"RGB"]
In[]:=
img=ImageAdjust[gongData2];
In[]:=
mask=DeleteSmallComponents@FillingTransform@Binarize[img,.35];
{center,radius}=ComponentMeasurements[mask,{"Centroid","EquivalentDiskRadius"}][[1,2]]
Out[]=
{{1021.4,1022.26},906.659}
In[]:=
img2=HighlightImage[​​img,​​{Red,Thick,Circle[center,radius]}​​]
Zero pixels outside of red circle:
In[]:=
redMask=ColorDetect[img2,Red];​​insideMask=SelectComponents[FillingTransform[redMask],"Area",-1];​​result=ImageMultiply[img2,insideMask]
In[]:=
b=Binarize[result,{0,.6}]
Contrast Stretching via S - Curve shape.
Increase contrast by pulling down shadows and pushing up highlights:
In[]:=
bb=ImageAdjust[result,3]
Out[]=
END OF PROGRAM

CITE THIS NOTEBOOK

Reading solar global oscillation network group H-alpha image​
by Gilmer Allen Gary​
Wolfram Community, STAFF PICKS, September 22, 2026
​https://community.wolfram.com/t/28140