Touptek ATR2600M Sensor Analysis in High full well mode

[giraud]

Hello,

I a running a sensor analysis on my Touptek ATR2600M. I managed to adjust the settings to analyse two configurations, the "standard" one and the "Low Noise" one that are the only two proposed in the camera selection menu.

I'd like in addition to analyse the performance of the camera in the High full well mode, but I don't see how to select this mode. Could you please advise?

Many thanks.

Cheers,
Eric.

[admin]

Hi,

SharpCap doesn't currently have a way to turn on the high full well mode for the ATR2600 cameras, at least not via the direct SDK connection to the camera that we usually recommend. You can turn on that mode if you use the ToupTek ASCOM driver to connect to the camera, but that has other drawbacks (less control available, lower frame rate, etc.)

You may find that the analysis fails to complete in high full well mode - when I tested that mode out myself using the ASCOM driver, the camera image failed to saturate at low gain in spite of very bright illumination and long exposures. If this happens to you then it will cause the analysis to fail, as several stages need to get the average pixel value to about 70%, which simply will not happen.

This sort of behaviour - the sensor failing to give a perfectly white image when overexposed - happens in other sensors when they are set to operate outside their normal recommended specifications (for example the IMX294 sensor in HCG when below 4.5x gain). I will typically not enable features that allow users to get into this sort of situation, as it often leads to serious issues when imaging (for example flat frames can look properly exposed but actually be badly overexposed and fail to work). So, until I find a way to enable the high full well setting without this problem happening, I will not add direct HFW support in SharpCap.

cheers,

Robin

[giraud]

Thanks Ribin,

That's too bad as I just wanted to check the manfucturer's data: https://www.touptek-astro.com/dso-coole ... /ATR2600M/

Indeed I was wondering if, in addition to considering HGC being already my baseline, I may also consider implementing the High Full Well (HFW) mode as a baseline as well. From the curves reading it appears that for a gain setting at 100 in HGC (in Touptek's scale of gain) the HFW would only impact the read noise of about 0.2e- while improving the Dynamic Range of 0.8 stops, which apperas very interesting.

Cheers,
Eric.

[admin]

Hi Eric,

have a go with the ASCOM driver to see if you see the same saturation issue that I do in HFW at minimum gain. Maybe my camera is an older model or needs a firmware update or something - I've had it a while now...

I think that you would still get the best result by using HCG mode - the lower read noise (~1.2e) at minimum gain in HCG compared to either LCG or HFW lets you take shorter subs (by a factor of more than 4). That means that in the same hour of imaging you would have 4 times as many subs, which would give you an extra stop of dynamic range from the stacking, outweighing the extra dynamic range in the individual subs in HFW.

cheers,

Robin

[giraud]

Hello Robin,

First, I'd like to clarify that I am hesitating bewteen using HGC or HGC combined with High Full Well (I am not considering LGC). Based on Touptek public data (and they claimed they used Sharpcap with the ASCOM driver to get the results), it appears to me that HGC+High Full Well seems more interesting than HGC only, as the impact on Read Noise is negligeable (-0.2e-) while the Dynamic Range is increased of 0.8 stops.

I then tried to run Sensor Analysis for HGC + Hugh Full Well, selecting the ASCOM driver, and it worked until very close to the end of the process.. I tried twice and got the error message attached to this post. Is there something I can do to reach the end of the analysis?

Cheers,
Eric.

[admin]

Hi Eric,

ah, OK, I wasn't aware that the high full well mode was compatible with HCG - I will have to look into that combination.

It looks like the problem in your analysis is happening on the binning check stage - there was a bug with ASCOM binning in the version of SharpCap you are using, so updating to the very latest from our download page should help. Alternatively, there is a checkbox at the start of the analysis process to skip the binning measurements, so you could just check that.

cheers,

Robin

[giraud]

Hello Robin,

So I uploaded the latest Sharpcap version and the test went very well, and I didn't deactivate the Bining test option.
Just two things to be noted:
- the Ascom input parameter window has very small text size, I had to go through the Ascom Diagnstics Software to be able to configure the camera (tetx sze was normal there)
- I had to disable/enable the Live View several times as Sharpcap got stuck on about 10 instances (that happened last night as well with the older Sharpcap version).

So now the results. In a nutshell, the sensor analysis shows the same routcome than what Touptek is adverstising. The HGC+Low Noise+HighFullWell degrades the Readout noise of only 0.45e- (1.25e- to 1.68e-) but doubles the Full Well capacity from 15.7ke-to 34.9ke-. Consequently the number of stop increases of ~0.75 (13.61 to 14.34).

I believe the HGC+Low Noise+HighFullWell is a very interetsing mode, what are your thought?

I join the two sensor analyses. Of course, for the one performed with the native driver, one needs to look at the 300 gain values (which is 100 in HGC) and compare them to the 100 gain value in the HGConly+HFW plots obtained with the Ascom driver.

Cheers,
Eric.

[admin]

Hi,

yes, I think you are right - based on those figures the single frame SNR is improved by a factor of about 1.68x (about 0.7 stops) and the stacking SNR is improved by about 1.24x given the same total exposure times, so a win if your tracking can cope with the longer exposures needed due to the higher read noise (1.8x longer).

I will re-test with HCG, HFW, ULN and see what I see - if it looks like we are getting a clean image then I will try to add SDK support for that configuration (but probably not LCG, particularly if it gives problems with saturation at minimum gain).

cheers,

Robin

[admin]

Hi,

I re-tested on my camera and found the same problem with the image failing to saturate in all modes involving high full well depth, so I then contacted ToupTek technical support to check what was going on. Their recommendation is that the 'high full well depth' mode should *not* be used below a gain of 177 to avoid this problem with lack of saturation and poor linearity of the sensor. That requirement will obviously affect the figures for dynamic range and perhaps make a difference to how worthwhile the HFW mode is.

Now that I have this information I will look into implementing HFW mode in the SharpCap SDK version of the camera. In this case I will enforce the minimum gain of 177 to avoid users being able to set up the camera in unsupported ranges of the settings.

cheers,

Robin

[admin]

Hi,

OK, I implemented this change for testing so that you can enable HFW mode but the raw gain is changed so you cannot go below 177 as recommended. Here's the sensor data chart that results from that setup.

Screenshot 2025-11-17 223237.png (143.2 KiB) Viewed 2857 times

The key value here is at gain 531 - that's where the switchover to HCG happens in this setup (since it is going to be at 177*3, rather than 100*3). The values for that give a RN of 1.62 and a FWD of 18846, with 13.50 stops of DR. For reference, the normal HCG mode is RN 1.44, FWD ~16600, 13.49 stops of DR. Essentially there is no overall gain in dynamic range due to the fact that we cannot safely access the low gain values in HFW mode. (Note, both measurements were done in UltraLowNoise mode).

The maximum FWD in LCG mode is ~57400 - That's lower than the 71700 quoted by PlayerOne for their IMX571 camera in High Full Well mode and much lower than the 100000+ quoted by QHY. My guess is that this all comes down to how low the manufacturers are allowing/recommending you to go with the gain in high full well mode (since the sensor is the same on all cameras). QHY are letting you go all the way down to minimum gain (what we would call 100 in ToupTek measurements), Player one down to about 140 - again in ToupTek units - (which was my initial estimate of where the camera started to saturate properly) and ToupTek are recommending 177. Maybe you could argue that 177 is a bit on the conservative side and a lower value would be OK - perhaps as low as the 140 being used by PlayerOne. Anything below that does give (theoretically) a higher full well depth, it's just that you can't ever get there - the sensor will not saturate that far.

I'm still thinking that this high full well mode isn't really a killer feature - it's an interesting curiosity that lets you push the sensor a little further in certain directions, but doesn't make a big impace on deep sky imaging.

cheers,

Robin