A few questions for Wayne about SOHO bleeding effects and recent Hinode images.

[michaelmozina]

<p>I'm really trying to get a handle on the bleeding (planetary ring) effects seen in the SOHO Lasco-C2 and C3 images.&nbsp;&nbsp; It would seem to me that there is some bleeding going on in the horizontal axis that tends to resemble a "ring" of sorts around the light source.&nbsp; I've notice this effect on almost every bright object in the image, not simply planet that are known to have rings.&nbsp; I'm most puzzled by the "pulsing" nature of these image artifiacts.&nbsp;&nbsp; Can you briefly explain to me what's going on in these images, and why that bleeding occurs?&nbsp; I'm trying to understand why the bleeding seems to be restricted the horizontal axis, and why there are different pulse rates for different ring artifacts.</p><p>I'm also curious if you ever had a chance to get an explanation as to why that blue Hinode images appeared to show movement between the photosphere and the coronal loop images.&nbsp; I sure that's an image artifact as well, but I'm not sure how to explain it. </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I'm really trying to get a handle on the bleeding (planetary ring) effects seen in the SOHO Lasco-C2 and C3 images.&nbsp;&nbsp; It would seem to me that there is some bleeding going on in the horizontal axis that tends to resemble a "ring" of sorts around the light source.&nbsp; I've notice this effect on almost every bright object in the image, not simply planet that are known to have rings.&nbsp; I'm most puzzled by the "pulsing" nature of these image artifiacts.&nbsp;&nbsp; Can you briefly explain to me what's going on in these images, and why that bleeding occurs?&nbsp; I'm trying to understand why the bleeding seems to be restricted the horizontal axis, and why there are different pulse rates for different ring artifacts.I'm also curious if you ever had a chance to get an explanation as to why that blue Hinode images appeared to show movement between the photosphere and the coronal loop images.&nbsp; I sure that's an image artifact as well, but I'm not sure how to explain it. <br />Posted by michaelmozina</DIV><br /><br />Rather than me trying to explain it from memory, this is from the SOHO FAQ:</p><p>"</p><h1 class="right">What are those flying saucer-shaped objects in the LASCO images?</h1><p class="right_p">The "funny-looking spheroid" is a typical response of the SOHO LASCO coronagraph CCD detector to an object (planet or bright star) of small angular extent but so bright that it saturates the CCD camera so that "bleeding" occurs along pixel rows. There is a bright horizontal streak on either side of the image, because the charge leaks easier along the direction in which the CCD image is read out by the associated electronics. </p><p class="right_p">CCD stands for charge-coupled detector, and refers to a silicon chip, usually a centimeter or two across, divided into a grid of cells, each of which acts like a small photomultiplier in that an incoming photon knocks loose one or more electrons. The electrons are "read out" by row (fast direction) and column (slow direction), the current converted to a digital signal, and each cell or picture element ("pixel") thus assigned a digital value proportional to the the number of incoming photons in that pixel (the brightness of the part of the image falling on that pixel). This is the same kind of detector as is used in a hand-held video camera, though until recently, the analog-to-digital conversion was left out in consumer devices. </p><p class="right_p">If you point a video camera at a very bright source (say, the Sun), the image "blooms" or brightens all over --- there are so many electrons produced in the pixels corresponding to the bright source that they spill over into adjacent rows and column, perhaps over the entire detector. Better CCD's will "bleed" only along the fast readout direction (a single row), and perhaps a few adjacent rows. </p><p class="right_p">The LASCO and EIT CCD cameras include "anti-bleed" electronics which limit the pixel bleeding around bright sources to less than the full row (and usually no adjacent rows). In the case of a marginally too-bright object, the pixel bleeding will be only a few pixels in either direction along the fast readout direction. Thus, the "flying saucer" images.</p><p class="right_p">&nbsp;</p><p class="right_p">Regarding question number 2, I'll have to go back and look at them again, that was quite a while ago.</p><p class="right_p">Wayne&nbsp;</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[michaelmozina]

<p>Thanks for the info on the Lasco images.&nbsp; I'm not sure it explains the pulsing action I'm seeing, but I'm assuming that is associated with the timing between images. </p><p> If you do get some additional info on the Hinode images, by all means, share it with us.&nbsp; I am curious.</p><p>By the way, Merry Christmas, or happy holidays, whichever might apply. </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Thanks for the info on the Lasco images.&nbsp; I'm not sure it explains the pulsing action I'm seeing, but I'm assuming that is associated with the timing between images. If you do get some additional info on the Hinode images, by all means, share it with us.&nbsp; I am curious.By the way, Merry Christmas, or happy holidays, whichever might apply. <br />Posted by michaelmozina</DIV><br /><br />The pulsing is due to the point of light hitting one pixel (vertically) or being kind of in between where the light is split among two adjacent pixels. When it hits one pixel exactly, all the photons fill that bucket, so all the bleeding occurs on one row, so is longer.</p><p>When it is in between two pixels, the photons wind up in two buckets, so each one has less to be spilled along&nbsp;each row.</p><p>Therfore, while there are two rows affected, each has less bleeding.</p><p>For the largest objects (like Venus) which covers multiple pixels, it's the same effect, just split among more rows, but of course with more photons to work with as well.</p><p>MW</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The pulsing is due to the point of light hitting one pixel (vertically) or being kind of in between where the light is split among two adjacent pixels. When it hits one pixel exactly, all the photons fill that bucket, so all the bleeding occurs on one row, so is longer.When it is in between two pixels, the photons wind up in two buckets, so each one has less to be spilled along&nbsp;each row.Therfore, while there are two rows affected, each has less bleeding.For the largest objects (like Venus) which covers multiple pixels, it's the same effect, just split among more rows, but of course with more photons to work with as well.MW <br /> Posted by MeteorWayne</DIV></p><p>This seems to explain pretty much all the observations I can think of, save one.&nbsp; It seems to me that there are times when there are two or more planets in the images that seem to "pulse" at different rates, which is not something I would necessarily expect if such pulses are always simply an image artifact.&nbsp;</p><p>Would it be possible for SOHO to actually observe light that is reflected off the moons of Jupiter or Saturn (or it's rings) at times which might explain why these ring patterns seem to "pulse" at different rates? </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>This seems to explain pretty much all the observations I can think of, save one.&nbsp; It seems to me that there are times when there are two or more planets in the images that seem to "pulse" at different rates, which is not something I would necessarily expect if such pulses are always simply an image artifact.&nbsp;Would it be possible for SOHO to actually observe light that is reflected off the moons of Jupiter or Saturn (or it's rings) at times which might explain why these ring patterns seem to "pulse" at different rates? <br />Posted by michaelmozina</DIV><br /><br />The pulsing is caused by the precise alignment of each individual point of light to the CCD array rows. So for points at different positions, they will be in different positions relative to the rows. What makes the rates different for planets is that the planets are not stationary relative to the stars (which would be more likely to pulse at the same rates). The planets also have some "up and down" motion since none are at 0 degrees inclination.</p><p>As far as the moons of Jupiter, I believe they are too faint to show up on the LASCO images. I one time measured the magnitude of the faintest stars that can be seen on the C3 (blue) image and I recall it was something like 4th magnitude...I'll see if I can repeat that. The moons are far fainter than that. And the C2 LASCO images captures only the brightest stars and planets since it is surveying a region much closer to the sun itself.</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[michaelmozina]

Thanks for your help Wayne, I appreciate it. <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>