Olivier-Fantasy a écrit : ↑21 avr. 2021, 18:24
Super images (comme d'habitude )... Dis-moi, comment "travailles-tu" le couple gain/offset ? Tu fais plusieurs stacks à la suite et tu compares ? Ou tu vois le changement de réglage en temps réel ?
Etape 1: travail de recherche sur les forums
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Pas mal de lectures sur les forums francais et anglophones + check Astrobin
Le meilleur commentaire de synthèse pour la 183MM:
https://www.cloudynights.com/topic/6445 ... mperature/
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Regarding GAIN values :
Try to stay within the 54-178 gain range and more likely between 54 and 111 range. Below 54 gain, you could have banding issue and above 178 gain, the amp glow could become a problem despite a good calibration.
LRGB : Gain 54 and exposure of 60s, 90s of 120s.
Narrowband SHO : Gain 54 or 111 and exposures length of 5min (with short focal ratios < 5 or 6) and up to 10min (with longer focal ratios > 5 or 6)
If you need shorter exposures because of your mount quality guiding limitations, you could try a gain of 178 but ideally with exposures length shorter than 5min (like 4 or 3 minutes).
The sensor doesn't have the same behavior as the ASI1600MM/QHY163M (with its bigger pixel size of 3.80µm which seems to be easier to use) where you can push the gain much higher for shortening exposure lengths in narrowband for instance.
Though, with short focal ratio < 400mm, the smaller 2.4µm pixel size of the 183MM will give you nice details and the AR coatings on the senror will not have reflection issue on bright star contrary to the 1600MM.
Regarding TEMPERATURE Values :
It is recommended to stay within 10%-90% power range. Below 10% power you can face some issues while trying to keep the temperature at a precise value. Above 90% isn't recommended as well unless you want your camera to face death a little bit earlier than expected tongue2.gif . Who knows, better to be careful.
As the camera can "really" do -35°C below ambiant temperature it can be interesting to have 2 settings: one for summer season and one for winter season.
In my case : -15°C is the "summer" temperature setting and -25°C is the winter temperature setting.
On last thing, regarding the cool down or warm up durations. I think it might be interesting to use "safe values". Such as 15min or 20min to cool down and between 20min to 30min to warm up but probably other people will tell you not to worry regarding this matter. From my perpective, if you want that your camera last longer without frost issues, using some safety margin values can be a good approach because I remember the duration of cool down or warming up of the APOGEE (=high end CCD brand) with the older KAF8300 which was around 30min each.
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Etape 2: définir une bibliothèque de darks suffisantes
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Avant de pouvoir tester, il faut avoir une bibliothèque de darks permettant de tester différentes configurations sur une même cible
J'ai construit une matrice de configuration:
- Temperature: -10°C
- temps: 2s, 4s, 8s, 15s, 30s, 60s
- Gain: 54, 75, 111-115 (SC), 150 (pas plus haut car pas de filtres)
- Offset: 4, 8, 10, 12
J'ai fait ma bibliothèque de darks
Etape 3: Tests
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Il faut essayer de sentir les choses sur une cible
Pas assez de pêche: j'augmente le gain
Trop blanc: je diminue l'offset
Si je diminue le temps: j'augmente le gain et l'offset (et inversement)
L'idée, suivant ce que l'inspecteur le plus célèbre de notre forum conseille, ne pas laisser le petit histogramme coller à gauche.
Je démarre, donc, je tâtonnne aussi beaucoup
Pour l'instant, ce qui se dégage, c'est un gain de 115 avec un offset de 8
)... Dis-moi, comment "travailles-tu" le couple gain/offset ? Tu fais plusieurs stacks à la suite et tu compares ? Ou tu vois le changement de réglage en temps réel ?
)
... et quelques semaines après tu peux en discuter 
