<div dir="ltr"><div>But why not use an 8 or 16 bit integer with a scale factor and zero offset?<br clear="all"></div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><br><div dir="ltr" style="margin-left:0pt"><table style="border:medium none;border-collapse:collapse"><colgroup><col width="445"><col width="275"></colgroup><tbody><tr style="height:90pt"><td style="border-color:rgb(255,255,255);border-style:solid;border-width:1pt;vertical-align:top;padding:5pt"><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span style="font-size:9.5pt;font-family:Arial;color:rgb(34,34,34);background-color:transparent;font-weight:700;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Arnold H Rots</span></p><p dir="ltr" style="line-height:1.2;margin-top:0pt;margin-bottom:0pt"><span 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style="font-size:9.5pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline;white-space:pre-wrap">Newsletter</span></a></p></td></tr></tbody></table></div></div></div></div></div></div></div></div><br></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Sat, Jul 26, 2025 at 8:55 PM Barrett, Paul via fitsbits <<a href="mailto:fitsbits@listmgr.nrao.edu">fitsbits@listmgr.nrao.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">The quick answer is that most telescope backends have 8-bit A2D converters, so 16-bit floats provide sufficient range and precision to store the calibrated data. If you need extended range, then a scaling factor can be used.<div><br></div><div> -- Paul</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Jul 26, 2025 at 7:49 PM Eric Greisen via fitsbits <<a href="mailto:fitsbits@listmgr.nrao.edu" target="_blank">fitsbits@listmgr.nrao.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div>
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I am perhaps the person with the longest exposure to FITS. I expect that adding 16-bit floats would do little harm. But I have not seen a proper exposition of why it is needed. And I have 50+ years of writing radio astronomy software. At this stage I would
vote against it until a proper set of examples are described.</div>
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Eric Greisen</div>
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<div id="m_-8332966783569991369m_7732203089533686962divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> fitsbits <<a href="mailto:fitsbits-bounces@listmgr.nrao.edu" target="_blank">fitsbits-bounces@listmgr.nrao.edu</a>> on behalf of William Pence via fitsbits <<a href="mailto:fitsbits@listmgr.nrao.edu" target="_blank">fitsbits@listmgr.nrao.edu</a>><br>
<b>Sent:</b> Saturday, July 26, 2025 1:11 PM<br>
<b>To:</b> Fitsbits <<a href="mailto:fitsbits@listmgr.nrao.edu" target="_blank">fitsbits@listmgr.nrao.edu</a>><br>
<b>Subject:</b> Re: [fitsbits] [EXT] Re: 16-bit floats {External} {External}</font>
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<div>[Have had technical difficulties posting here; here’s another attempt.]<br>
<br>
Based on the discussion so far I am inclined to support adding the 16-bit floating point format to FITS, but not the 128-bit format, as a fundamental datatype in images and binary table columns. As a reminder, the numerical range of the float16 datatype is
limited to +65504 to -65504 and the precision is limited to about 4 decimal digits. That means the largest values (in the range of about 32000 to 65500) are only precise to +/- 32, i.e. the largest possible value is 65504 and the next smaller allowed values
are 65472, 65440 and so on. Based on my own experience in optical and Xray astronomy I can’t think of many applications (or any in fact) where this float16 datatype would be appropriate to use. Apparently it could be useful for some radio astronomy data
however. <br>
<br>
Bill<br>
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