{"id":9091,"date":"2011-01-10T21:46:20","date_gmt":"2011-01-10T21:46:20","guid":{"rendered":"https:\/\/groupeastronomiespa.be\/astrogas\/gain-noise-stack\/"},"modified":"2025-06-08T22:47:39","modified_gmt":"2025-06-08T20:47:39","slug":"gain-noise-stack","status":"publish","type":"post","link":"https:\/\/groupeastronomiespa.be\/astrogas\/gain-noise-stack\/","title":{"rendered":"Gain, Noise & Stack"},"content":{"rendered":"

Bonjour,
\nHello,<\/em><\/p>\n

En observation solaire Ha, d\u00e9j\u00e0 pour des captures de protub\u00e9rances \u00e0 moyenne r\u00e9solution, les temps de pose s\u2019allongent et la turbulence devient difficile \u00e0 figer.
\nIn solar Ha observation, already for the imaging of protuberances at medium resolution, the exposure time increases and the turbulence becomes difficult to freeze.<\/em><\/p>\n

Solution: augmenter le gain \u00e0 la capture, au prix d\u2019une augmentation du bruit.
\nSolution: increase the gain at the time of capturing data, at the cost of increasing noise.<\/em><\/p>\n

Voici le r\u00e9sultat d\u2019essais d\u2019imagerie de protub\u00e9rances sous Avistack2, pour 5 captures de 60s.
\nHere, some results of protuberance imaging under Avistack2, for 5 captures of 60s.<\/em><\/p>\n

Le gain a \u00e9t\u00e9 pouss\u00e9 progressivement, permettant de r\u00e9duire le temps d\u2019exposition. Il est \u00e0 noter que des temps d\u2019exposition longs ne permettent pas d\u2019utiliser la cadence nominale de la cam\u00e9ra: 30i\/s.
\nThe gain has been pushed up step by step, allowing an exposure time reduction. Note that longer exposure times don\u2019t allow exploiting the nominal frame rate of the camera: 30fps.<\/em><\/p>\n

Avi\t\tCap100001\tCap100003\tCap100005\tCap100007\tCap100009
\nGain\t\t180(Min)\t400\t\t600\t\t800\t\t1023(Max)
\nExposure [s]\t0.100\t\t0.067\t\t0.026\t\t0.014\t\t0.006
\nExp Qty\t434\t\t594\t\t1793\t\t1798\t\t1800<\/p>\n

Une trame brute. Le bruit augmente de capture en capture:
\nOne raw frame. Noise increases from sequence to sequence:<\/em>
\n\"\"<\/a><\/p>\n

Addition de 64 trames par point d\u2019alignement. Avistack2 g\u00e8re sans probl\u00e8me 20 \u00e0 30 points d\u2019alignements sur la protub\u00e9rance, quelque soit le niveau de bruit:
\nStack of 64 frames per align point. Avistack2 manages with no problem at all 20 to 30 align points on the protuberance, what ever the noise level:<\/em>
\n\"\"<\/a><\/p>\n

Un traitement par ondelette fait ressortir les d\u00e9tails. Les m\u00eames valeurs ondelettes ont \u00e9t\u00e9 appliqu\u00e9es sur chaque image; le bruit ressurgit…
\nA post processing by wavelet help to push out the details. The same wavelet parameters are applied on each picture; noise re-emerge\u2026<\/em>
\n\"\"<\/a><\/p>\n

Le bruit peut cependant se g\u00e9rer par des softwares sp\u00e9cifiques, ici Neat Image avec des param\u00e8tres auto-calibr\u00e9s:
\nNoise can however be managed by specialized software, here Neat Image with auto-calibrated parameters:<\/em>
\n\"\"<\/a><\/p>\n

Donn\u00e9es d\u2019observation:
\nObservation\u2019s data:<\/em>
\n2010-Apr10
\nTakahashi\/FS-60C
\nPowermate\t2.4x
\nF [mm]\t355 x2.4
\nD [mm]\t60
\nCoronado SM60
\nTIS\/DMK31AF03
\nExp Qty:\tTarget: 1800 (60s x 30fps)<\/p>\n

Alexandre<\/p>\n\n\n

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\n Veuillez voter<\/span>\n <\/div>\n <\/div>\n","protected":false},"excerpt":{"rendered":"

Bonjour, Hello, En observation solaire Ha, d\u00e9j\u00e0 pour des captures de protub\u00e9rances \u00e0 moyenne r\u00e9solution, les temps de pose s\u2019allongent et la turbulence devient difficile \u00e0 figer. In solar Ha observation, already for the imaging of protuberances at medium resolution, the exposure time increases and the turbulence becomes difficult to freeze. Solution: augmenter le gain […]<\/p>\n","protected":false},"author":16,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[3],"tags":[],"class_list":["post-9091","post","type-post","status-publish","format-standard","hentry","category-astrobricolage"],"_links":{"self":[{"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/posts\/9091","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/users\/16"}],"replies":[{"embeddable":true,"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/comments?post=9091"}],"version-history":[{"count":1,"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/posts\/9091\/revisions"}],"predecessor-version":[{"id":12591,"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/posts\/9091\/revisions\/12591"}],"wp:attachment":[{"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/media?parent=9091"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/categories?post=9091"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/groupeastronomiespa.be\/astrogas\/wp-json\/wp\/v2\/tags?post=9091"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}