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<p>Dear Akarsh, dear Jasem,</p>
<p>As a simple user, I can add that the feature still exists and
works in my installation KStars 3.7.5. The corresponding option is
in the settings window, under the "advanced" menu and in the
"general" tab (just below the "Correct for atmospheric refraction"
option). Turning it on visibly applies a radial distortion to the
stars next to the Sun, which is the expected effect.</p>
<p>However, If I take the star HD207520, which Kstars shows as
grazing the limb of the sun at 7UT of today, its distance (as
measured by Kstars) from the center of the sun is 15'54'' without
the GR effects and 15'58'' with it. But:<br>
</p>
<blockquote>
<p><font face="monospace">In [1]: import astropy.units as u<br>
In [2]: from astropy.constants import M_sun,c,G<br>
<br>
In [3]: impact_parameter = (16. /60 /180*np.pi) * 1 * u.AU<br>
In [4]: impact_parameter = impact_parameter.to(u.m)<br>
<br>
In [5]: schwarzschild = 2*G*M_sun/c**2<br>
<br>
In [6]: angular_delta = 2*schwarzschild/impact_parameter<br>
<br>
In [7]: angular_delta.value<br>
Out[7]: 8.483180496594135e-06<br>
<br>
In [8]: angular_delta.value*180/np.pi*3600<br>
Out[8]: 1.749781581489136</font><br>
</p>
</blockquote>
<p>So the deflection as measured by Kstars is ~twice as large than
the actual one. I could not check if this is an issue of the
distance measuring algorithm and the presented view is correct, or
if the view itself is off by that amount.<br>
</p>
<p>Best regards,</p>
<p>Giovanni<br>
</p>
<div class="moz-cite-prefix">Il 14/02/25 07:07, Akarsh Simha ha
scritto:<br>
</div>
<blockquote type="cite"
cite="mid:CA+9k5ty4ERJupDdWFRF2q9AgCnU7gSsQuwhg+sKZ8YA0GZpp0A@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">
<div>I implemented this feature, but I did not verify it, nor is
it maintained properly at present. The main source of
computational errors isn't so much calculating the lensing
itself (the formula is fairly straightforward), but in
ensuring we have the correct position of the sun, if I recall
correctly. I wouldn't have the time to look into it, but I
would assume that it is unmaintained and therefore not
functioning as intended.</div>
<div><br>
</div>
<div>This correction is explained in the Explanatory Supplement
to the Astronomical Almanac, and one could take up
re-implementing it according to that book.</div>
<div><br>
</div>
<div>Regards</div>
<div>Akarsh</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote gmail_quote_container">
<div dir="ltr" class="gmail_attr">On Thu, Feb 13, 2025 at
8:39 PM Jasem Mutlaq <<a
href="mailto:mutlaqja@ikarustech.com" moz-do-not-send="true"
class="moz-txt-link-freetext">mutlaqja@ikarustech.com</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">
<div>Hello everyone,</div>
<div><br>
</div>
<div>I'm forwarding an email I received from Dr. Lorenzo
regarding the "Gravitational lensing effects around the
Sun" feature in KStars. I actually never used this at all,
anyone has any ideas?</div>
<div>
<div dir="ltr" class="gmail_signature">
<div dir="ltr">
<div>
<div dir="ltr">
<div>--</div>
<div>Best Regards,<br>
Jasem Mutlaq<br>
</div>
<div><br>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">---------- Forwarded
message ---------<br>
From: <strong class="gmail_sendername" dir="auto">Lorenzo</strong>
<span dir="auto"><<a href="mailto:bzzlnz@unife.it"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">bzzlnz@unife.it</a>></span><br>
Date: Fri, Feb 14, 2025 at 12:24 AM<br>
Subject: KStars gravitational lensing<br>
To: <<a href="mailto:mutlaqja@ikarustech.com"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">mutlaqja@ikarustech.com</a>><br>
</div>
<br>
<br>
Dear Jasem,<br>
<br>
I am Lorenzo, a post-doc in astrophysics at University of
Ferrara, <br>
Italy. I'm preparing a lecture for high school students on
gravitational <br>
lensing, and I just found out KStars. In particular, the
website <br>
mentions: "Switch on and switch off gravitational lensing
effects around <br>
the sun to understand Eddington’s experiment". I am trying
to visualise <br>
the deflection of starlight caused by the Sun on May 29,
1919, from <br>
Principe Island (i.e., Eddington’s experiment), however, I
am unable to <br>
observe the expected deflection of nearby stars. Could you
please <br>
clarify if this feature is functioning as intended, or if
there are <br>
specific settings I need to adjust? I've already
downloaded some extra <br>
stars catalogues. Do you confirm that I just have to press
the "R" key <br>
to activate the lensing effects?<br>
<br>
Thank you for your time and assistance.<br>
<br>
Best,<br>
<br>
Lorenzo<br>
</div>
</div>
</blockquote>
</div>
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