ToupTek SkyEye62AM - Sony IMX455 Sensor v4 - settings

[Peter_S]

Hi Robin, hi forum,
for my Touptek SkyEye62AM (Noctutec MILAN) with the sensor v4 am trying to get data for best settings (deep sky).
As already discussed in earlier threads the ToupTek has 2 settings (LCG / HCG) which I´d like to test separately.
When choosing the ASCOM driver SharpCap crashes. Taking the native driver one gets mixed data as you described (auto switch).
ToupTek has published sensor data (of the previous version of the sensor) which show the difference in read noise:

Skyeye62AM_curves HCG.jpg (123.67 KiB) Viewed 326 times

Skyeye62AM_HCG.jpg (67.33 KiB) Viewed 326 times

Skyeye62AM_curves LCG02.jpg (127.9 KiB) Viewed 326 times

Skyeye62AM_curves LCG.jpg (67.4 KiB) Viewed 326 times

There are mainly two situations, as Stathis wrote in another thread:

- aiming for high dynamic range
- aiming for low noise (faint signals)


I image with APT and have to set either LCG or HCG (no auto switch); my exposures are 240 - 300 sec; 3 nm NB filters.
My data attached, made with a L filter.

SkyEye62AM~MONO16 (Ultra Low Noise).json

(15.26 KiB) Downloaded 20 times

2024 03 24 SkyEye62Am sensor data v2.txt

(1.68 KiB) Downloaded 16 times

Until now I couldn´t test the sky brightness due to the bad weather.

Interpreting Touptek´s graphs I´d take LCG mode in both situations due to the almost equal dynamic range but the better read noise (?)
Do you have any suggestions concerning the settings?


thanks, Peter

[admin]

Hi Peter,

the thing that I think is missing in your analysis of whether to use LCG or HCG is a consideration of the effect that the different read noise values on sub-exposure lengths...

If you pick gain 100 in LCG and compare to gain 100 in HCG (both with low noise option), the read noise values are 2.72 and 1.95 respectively. The sub exposure length needed to properly expose for deep sky is proportional to the square of the read noise, so using LCG you will need to use sub exposures twice as long as for HCG. As an example, HCG might need 60s exposures and LCG might need 120s.

That means that in an hour of imaging you would get 60 HCG subs and only 30 LCG subs. While the individual subs in LCG have more dynamic range, the fact that you have twice as many HCG subs out of the same amount of imaging time will - I think - at least compensate for this and quite likely leave HCG slightly ahead in terms of dynamic range of the final stack (the SharpCap smart histogram tool will work this out exactly). The other advantages to the shorter subs in HCG is less pressure on the guiding/tracking and less loss if an individual sub is spoiled by satellite trails, etc.

As the read noise difference between HCG and LCG is not as dramatic in this case as for some sensors, the choice of HCG is less clear cut, but still an option very much worth considering.

cheers,

Robin

[Peter_S]

Hi Robin,
thank you very much for your answer (on sunday) - now it´s clear...
as soon as I can measure the sky brightness I´ll post an update.
Peter