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Hi, I ve a qhy163m and a sw 150/750PDS and n TSAPO65Q. What are your experiences for best gain and offset? I ve the original qhyccd filter - NB are 12nm. At the moment I use 90/60 for lrgb and 180/90 for nb |
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For NB you have 2 settings many use mostly 1. Unity gain = 139 / 21 2. High gain = 200 / 50 I also tried the following: A. 177 / 79 B. 200 / 21 LRGB it depends on the sky quality, if high LP then gain 0 or 10, if dark nice then Gain 75 Offset 15 is good to use. |
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Tareq Abdulla: Thx! What offset do you use for lrgb with gain 10? 0? And is it for use with a f5 Newton? |
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Bertl:Tareq Abdulla: For gain 10 i use offset 0, and for gain 0 i use offset anywhere between 10 up to 50 only. F5 is more forgiving, because it is fast but not super fast like F2-F4, so that allow me sometimes to go higher gain, it is also depending on the target and its location in the sky, and if i do use something like LP filter then somehow i can also increase slightly the gain, i am still experimenting, and this year i will but all test in use more, but i will do more of narrowbanding than using LRGB, but galaxies and clusters are around so i can always test that as well. |
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Hi, I used again 140 (Unity) under Bortle 5 skies for LRGB. That does work, but I can see no advantage over Gain 40 (Offset 50), which I use now for its much better headroom. I use G40 rather than 0 because read noise drops to 2.5e rather than 3.5 or so. At this setting, the camera almost works like to QHY9 or the Trius694 I used before (similar Dynamik Range). For Ha/OIII (7/8nm) I use Unity (140) and 600s subs. I will try 600s subs also with LRGB at Gain 40 because I do not like to have so much subs to deal with. Cheers, Stefan |
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Tareq Abdulla: hello! I saw that unity gain of the QHY 163mm is GAIN 120 OFFSET 80, where did you find this values 139/21 please? it seems to be the ASI1600 values and not QHY 163? Stefan: Hello Stephan are you sure about this 140 value? i saw unity gain is 120 with offset 80 for the QHY 163 isn't it? Cheers, Mathieu |
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Hi Mathieu, I used PI to measure the gain value at Gain 120 and that was about 1.02 e/ADU. So I increased the value to 140. Did not measure again, but that should be close to Unity. by the way, I made the last images with Gain 40/Offset 50 which provided for much more headroom and had no noticeable impact on s/n. Cheers, Stefan |
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Stefan: ok thank you very much i will try this! |
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Mathieu Guinot: From forums mainly the popular one, CloudyNights, they mentioned the unity gain for QHY163M and also ASI1600 as 139, QHY163M and ASI1600MM are the same, only color and maker name different, type and search about QHY163M unity gain and you will find out. |
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Tareq Abdulla: ok, very amazing... i know that QHY163 and Asi1600 have the same sensor, but all qhy users that i know told me that values of unity gain are not the same at all |
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Mathieu Guinot: QHY has so many cameras, i am talking about QHY163M, i have one, and if you want the truth, it is pointless to talk about unity gain, i swear if i use gain 100 up to gain 200 it will work, any value, so i tried once or twice that gain of 139 and it worked, now i ordered ASI1600MM which i hope to receive soon then i can easily test and compare both, it is not just the sensor, also the specifications are almost the same, so why they have to be different. |
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Tareq Abdulla: i have also a QHY163 and i read QHY specification and i also saw several Times some curves (astro camera shops etc...) where unity gain is 120 for the QHY163. i don’t know why it is different from the Asi1600 but it is... maybe électronic part you can read 120 here : https://www.qhyccd.com/index.php?m=content&c=index&a=show&catid=94&id=15&cut=1 and also Here : https://laclefdesetoiles.com/cameras-ccdcmos/5836-camera-qhyccd-monochrome-qhy163m-refroidie.html for the offset 80 i don’t remember where i saw it |
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Mathieu Guinot: From the first link i didn't read anything about unity gain, unless if i click that link to take me to the CloudyNights forum which i read people using 139 as unity gain unless one member is using gain 120, but in both cases i really don't see any wrong using gain 100 or 120 or 139, in fact i sometimes use the default gain from SGPro which is 174 Offset 77, and i got nice results sometimes, but most of the time i like to use gain 200 to get stronger signal with shorter exposure than 5min or up to 5min. |
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Hi, I use its unity gain, that is 120 and for the offset I use 1/4 gain, even if it all depends on the instrumentation and your histogram. Just see the dynamics of your histogram and find the right compromise to get a good signal without saturating it, but clearly, as I said before, it depends on the speed of the lens and the camera. Histogram, however, gives you a hand to determining the right contribution between dynamics and signal. |
