[prev in list] [next in list] [prev in thread] [next in thread] List: kstars-devel Subject: Re: [Kstars-devel] 1e8 stars in KStars From: Jason Harris <kstars () 30doradus ! org> Date: 2008-09-09 17:34:05 Message-ID: 8401E7FD-2E10-4CE2-B3A1-3E517B877022 () 30doradus ! org [Download RAW message or body] Hi Akarsh, On Sep 9, 2008, at 12:26 AM, Akarsh Simha wrote: > What is the reason for such tiles? Are we seeing them in KStars too? > > Whenever 'V' is undefined, I use B-V = 1.6. There are many such cases, > so you might see a large density of reddish stars. But I haven't > noticed sharp edges. > I can see such an edge in the screenshot you attached. I've attached a gimp-ed version to highlight the edge: left of the yellow line, the average star color is noticeably bluer. > Are these tiles (in density / colour) a result of telescopes that > create the catalog capturing the sky tile-by-tile? Yes, exactly, they're catalog artifacts. The catalog is constructed by measuring the brightnesses of stars in images; this is a complicated, imperfect process requiring many calibrations to get reasonable results. The images were surely taken over many different nights (probably over many years), during which weather conditions and instrument properties varied in ways both subtle and dramatic. What we are seeing are the edges of these individual images on the sky. Small mismatches in the limiting magnitude of two adjacent images lead naturally to a discontinuity in the stellar density at the boundary. I'm actually surprised to see that the artifacts are so prominent in the screenshot Mederic posted. Hopefully, we will only see the subtle effect I noticed in your screenshot. regards, Jason ["nomad_edge.png" (nomad_edge.png)] �PNG IHDR � � �M gAMA �B�O� pHYs �� "tEXtSoftware QuickTime \ 7.5 (Mac OS X) ��� tIME� @�U\ \ IDATx��}��ĵ��J��xݻ�66�16���`�B�{��!?%�$/!BBh���0 54����I����z{�ۋ�i����t��� ���e- \ ���93s�sF3#�����M�ѷ�$с���O�u���h�[���O���E�I��48��K��rZ���?&P.�fS�U���8]?cZ��t� \ �>��&g��EK�/�G �MK�aB�b�Ii�MD-)��1f�C��4D=$%���h��H��(Q,qZ�L�����)_��Z) \ b�����!\W�&^.��*�~DX�n4{�v4�VJ�Nh2�s�#�������kmi���%%%���F��CCɚ�=�fj7�cQ� \ ��)���4�NM�֛U�4V�$\�pX�C4��M�:Q�%s�[��.-.K��*�fn�X�NS�"=��[F�S��$z|�a�Ȍh�g�p�?LM�A�ᴺ��!:���b����3����j� �5���"��)���o�mh��8Z? lV��X:����ڠ�**+���2D�D"-�͡p8??������C�C2�lkk���t�\���N��~�� \ `0��{�B�O8���,C��T���ح��r8���EcÆg��ѠI7�L��hG��xk�b�?v^�:�q�t�ZdSu`F�7� �Ol��K�C \ �D�0���W���im�cͪx��$��XJ`�.fsz`��$f�B�ب�9M}���6�st]���!��DKVqLu�np^wY�9�f]B]^�� ���ђO FT֣o�[C���ڝ���6�@��o�UV���'p���o��*�*A �����p���� �imm��訪���|���ݝ��h�� \ y������J����ٹ����5�*0 '��k�1��^^p�q`������B5R�$�*X P� JKKm��Q��Gmkk��{-Z�t�R���O \ �!�ꫯ�;w�A��{L�a�q�0ј�&1�9cVV���DC,]���洦��G[(?���e�k8� ���hJ$�wLW8���7����%$��� �n�la� ��Bil 9�H�.݈�`�.�q�Y<6��/��k,��f� ���'��uN ;��M�_�U3 �AƆc��8������,�}_IEp:KJ�A����%��S4NaD���U����766��~��=hH4... \ �U�6��������<�8�- y�۳�k��<z�ѐҘi4�y�P�X,�C��4pQqQGg�<MEnnnڰa���w�u���O>���O|�� \ ��#۷o�������_����f�ʕ'NظqӔ)Sjkk!UJDII�A��uR�oS���o9�$J�|+J)92�H�J����\�x��9�a��2j�c�j����tF$9��u��`�r���B ��Kǥ�Jt̒pE���d�6�8g��1&ǔaV #G�p�y�4o�5Cb#�r���'�$�4�1��r�pcS��dCio>�.�C�ԁ� 9NτI���a�e"�Ԟ�t1-/��X�J�5� G2�H���a �YC$XA_̡���#dWK�(���W���"m���$*�����&��Y��D5�K��K"%��!V��M�r�v?�4-jUҌ�!1��H�n9���i\�c���v6s3 ��MJ��$SۘZO�*��P(� &�p ����0��~�O@Y��p8��~��7�|3D����v�\�3_��T2YPP���9r�;v�x����.�? ���vD |�TJ���{� \ If�>�<r�-��|>&_�&�N�(�La���P$�����ѣ��5��W^6l���8e��5kVWT�744̚5syo��D>���W��B \ D�mH��7��7�Zf�:ȴY$�t�Ѫ�y�Hsb�t��\��6>0γ1��5�̚����p��fh"3�4��!3��C�KL���O 0� \ �!s��q]��tB��2}�,%7F=`���P"��x�H?���YZ�$�VK߸��\���2����o:Dn�n\���ĸ>P�l�����G��OSk�&�(ȡ�dKˁf���@�)��+B \ ��b�C��,K6*��_ �|�S� O��Ѯ]�B��!p��O�\^Q�G���.��X���k֬���s��p�8N!C�{9�� \ �أ��s�>����r��2����1b�矯:j���-[�bոq����SW_u����I�C}?_���������(��������o�7o��g� \ }�5מ�y�����iii����N�>�W�����3f�Tk"���@H�x�)�B�wE��.��Ŏ��z�q�e�"�*B,�)}����u���[b��bp,'8@�Q���S�|U��] �.B%��Hs�I�h�W� v�,�Ui�#�XVYiP� \ uI��U�pI/B]�tq�[IZ��֦[S�U��r�o�L�p�"�..=���R���D�S�3�Nc���M�v�I�uΏD�TW�h��$�P��rO�~� \ ��P�=MR�;ZHi(��gTi�Oˉ��D&��͎�C�s֤ \ )a?��d���ʪ4�,]A�%�ӣ��+�F@=A������Lw �h���c90��z6)��l���tfʄ-���(BG�����{u�ˋ���������+�KKK�b�;�o��ÿ=��S�{�~�_�>����߀�>�@��%�@ �����1�o�w c� �I{�%�%O; ~����K/��u����v�G?��?�I4���'VUW�[��譗��=�̳�;�����+�|��]�ʛ����F����������k��x�W�-x�v�%���3��-� ��5��A�� \ R�T�ęra����!�%Y�kD��Ff��R�J" \ ��F���8n@U��Ġ�}��K�d��¼�NK�8�V�Gk�1.C���B��j \ A�����=� �+��+Q�s�!F�w�T���l�r�y��BM=x�ٓ��$��Fni���!0���I�1!i�f�d�0i�9G��ձ�����K.�8q�yΒTU]=�����qۖM�e%�M�}B@JfUS�Dx���loi=zT$n<�0|�H�I�&ې \ �G}4z��o��f��}^aa!y�D�����bR�O�H� \ �����&��� ���jmm �z{e�7�s��سg@rWW'������"��S�O2M�t8�1�f�'���X����b: ��t�r� \ �`fB�Y"@h�tu����4�*�h�X(+�#�N��>�,��ttZ���5S�i��z��1��qi����(�طP�cVTQ8� \ +g5���1�`\�F��w��jN�6����D����[�g�-����2�,0Ü3;`U��o�[��ߐ@&}���AS�U+�//�`��z��{v��K-o� G��; �/458��ǎ/)�����w�,x���u�\o���d2y�)7}�~��u�/:������Z ���\�fͤ��J-&��v� �д������������ae�rI/�@�-�2ρ#���$=�F��0m`�l(�.�AH�C$�u�d.��fk�dn��I ��Ѝ�AW�#��z@�եN�d��K�M2[N�$��]]�щ.�C:[C���5ks!2�Nʪ\�I��%�����ck�X���^ff[q��f��X \ K��Tb�~�!�����'�վI3}]�$����%U \ I���,. ��ƀƹ i�B�b@��z �%��%g��*aI��6��t8�60){���d�w�2M�cRVAw�|>څ \ ���--+��'W::;����Ţ�m��U5�����w\��)�7 ����k�dþ=E��/Y���ڱc�$��w�(//7�?���E�۶l)*.�/(@� �o��zb�d��f�܊r��b|\���F&^g�A�l�S�A͙�Ai^u�ap| ��D�s7�����'6���#9�E���-�0��"��+B��8ʹ��x?&9��}MZ�4T�n~� �Σ@�oJ/��fJլ���ڭD�uw \ ᦏ��UK��eV$ �<�}�:p1%I�4��-����4L����L��|�T��'���x����ܾ�vH�[�w��ښ���6��i \ p[VZ�s���>dUu-�Ļv�1j�Wy_;hf=^o4�"EŊ�]����F���;Ɂ�h�f��D<^TT���~�q����������z*�+ \ 0�J �� �,�H�9^��#tnjk�Okg#֦�a�BZ#��!���a��#�^�������<g�JձJ�a�=�\�V"�k[c3���="�gz���"�ͤ\}��S�u�s�Ȩz�2 \ ��i�GF3�D��q�ad���nL�F\L�)J7S&S�<54;I��-�����"G�l�; \ |�H0?/PRZ&�R����|�IQo����a��4 � ~pkKK,��"J��yy�d2mue}��(+���rA%�1��8mӑ)1���-d��]!tq&�rc"a/Q�ewhjM�m[4� \ �& �{�Քjd<�F�Ug�+05]n�?u�C/m'GA=�!k�����x��l������%��'2%Mh�b�ܒ��-NW�f�z�U�߀茟���e�$d�dƀƘ�>��8SImpK��E�霐DK��z��V \ 54��j��+��fV������y���^}�&