Wanderer astro flat panel V4 - weird numbers with NINA WandererAstro WandererCover V4-EC · Leonardo Landi · 6/13/2024 · 6 · 394 · 1

Hi guys. Recently I bought a Wanderer astro flat panel V4 for my FRA 400 that will go remote in september. Last night I finally installed it and got a chance to put it to work with NINA. I obtained some strange exp time / brightness numbers and I'd like your opinion. 
Before starting, I'll make a premise: my previous flat box was an Artesky, manual model. Over the years I have had the opportunity to observe its excellent quality with various OTAs. I purchased the wanderer flat panel from Artesky too, and Luca had told me in advance that these panels were not at the level of theirs. 
Below is a screenshot of my trained exposures with NINA. The setup consists of an Askar FRA 400 reduced to f3.9, ASI 1600mm with Antlia LRGB and HSO 3 nm PRO filters. Gain 75 (half unity) for broadband, while gain 139 (unity) for narrowband. Offset 50 as per default. For the flats I set the histogram value to 40% of the maximum ADUs with a tolerance of 5%

Firstly, I feel like the panel is too bright. For broadband I have to use exposure times of 0.15s which from what I know are really too short and risk revealing panel flickering. Obviously, for the filter L brightness set to 1. 
Second doubt: with the same exposure times (0.15s) for the G and B filters I have a brightness of 8 and 6, while for the red I have to set the brightness to 35. Which makes me think that the panel is not very "white" .
Another doubt, but which confirms this for me, are the values ​​for the narrow band: with exposure at 3s I have brightness of 32 for the SII and 20 for the Ha, but for the OIII I have to go down to 5.

All this makes the panel almost unusable for flats: from a bortle 2 sky, in fact, I would always like to shoot at unity gain even in broadband, but I can't do it because I can't shoot flats with these settings.

Thank you Andrea. My perplexity perhaps comes from the comparison with the Artesky flat box, with which I was able to make 1.5s flats with each filter varying the intensity of the panel. With this it seems it is not possible, and it has to make very short flats at least for broadband. Unfortunately, due to clouds, I have no data to calibrate with the flats taken, in order to test them, but I think that 0.15 s is too little for a CMOS sensor. For as long as I remember, with this sensor (and with the 492 that I will use) they recommended flats of at least 3s.

Leonardo Landi:
Thank you Andrea. My perplexity perhaps comes from the comparison with the Artesky flat box, with which I was able to make 1.5s flats with each filter varying the intensity of the panel. With this it seems it is not possible, and it has to make very short flats at least for broadband. Unfortunately, due to clouds, I have no data to calibrate with the flats taken, in order to test them, but I think that 0.15 s is too little for a CMOS sensor. For as long as I remember, with this sensor (and with the 492 that I will use) they recommended flats of at least 3s.

There is no such thing as a minimum exposure time nor I can recall where this came from, unless we are talking differences between milliseconds exposures and fraction of second exposures. AFAIK, the IMX492 is perfectly linear up to 90% of the FWC but I think you mean the IMX455, don't you?

andrea tasselli:
While I don't understand what those numbers mean in term of absolute flux most modern EL panels tend to err toward the B end of the spectrum so no surprise there. As for the exposure times they seem in line with my expectations and experience, albeit wit a better EL panel in terms of chromatic balance. So you can take flats (or you can use the sky for free).

Agree, they look right to me, although I never use the so-called wizard. Just looking at the histogram when setting up the flats sequence has worked fine for me for decades. Never used the wanderer, mine are all DSD and (for the large scope) Optec, but the color of the panels is similar.