SharpCap Forums

Hi,
I have a Omegon branded Touptek 585 Mono. Since the latest SharpCap update the read mode LCG and HCG have vanished and instead I can choose from "Normal", what ever that means, and HDR. In N.I.N.A I still have the choice, but I want to use sharpCap. The latest firmware of the camera is 4.49.
How can I switch between LCG and HCG without using ASCOM?
thanks,
Matthias

Hi Matthias,

the switch from LCG to HCG is now handled automatically by SharpCap when the camera is in 'Normal' mode as part of the gain adjustment, which helps make sure that the correct choice is used for the amount of gain required. In the case of the IMX585 sensor, SharpCap will automatically switch to HCG mode when the gain control is set to a value of 1365 or greater, adjusting the normal gain in the background to ensure that the brightness of the image doesn't jump as you move past this gain level. That point of 1365 (13.65x brighter than minimum gain) seems to be the lowest total gain at which the 585 chip can operate normally in HCG mode, so there is no point in trying to switch to HCG before that and no real reason to be in LCG mode beyond that.

This approach mirrors the approach taken by a number of other brands (ZWO, PlayerOne, etc) of not presenting the LCG/HCG switch to the end user as it complicates matters without providing any significant benefit. I would imagine that a good 90% or more of users wouldn't understand the implications of switching LCG/HCG without some detailed research, so would be just as likely to set the wrong option as the right one.

cheers,

Robin

May I ask for the implications in Nina as Nina still offers the LCG/HCG/HDR-Switch ?

I did a sensor analysis in Sharp cap an saw the effect on noise at 1365 gain in normal mode. So, when I want the lowest Gain but in HCG-Mode in Nina:

What are the correct settings ?

A: HCG mode and gain 1365 ?
B: HCG mode and gain 100 ?

I am not sure if Nina uses the same gain-logic as Sharpcap or

if Nina HCG-Mode at GAIN=100 equals sharpcap in Normal mode at Gain=1365 ?

Hi,

In NINA, since you have manual control over LCG/HCG, you need to select HCG, gain 150, which is equivalent (for the 585 sensor) to gain 1365 in SharpCap.

For the IMX585, the switchover from LCG to HCG gives a boost in brightness of about 9.1 times. However, in HCG the sensor may not give good results if the gain is between 100 and about 150, so SharpCap delays the switchover to HCG until it can use a gain of 150 - 1.5 * 9.1 = 13.65.

I think the problem with low gains in HCG is similar to the one with the IMX294/492 - the sensor fails to produce fully saturated images at low gains in HCG even if the image is massively over-exposed. This can be very misleading to astronomers who are used to working with the image histogram when doing things like capturing flats - you can look at the histogram and think it is properly exposed, but it is actually badly overexposed with a sensor working outside the recommended range and your flats will just not work.

cheers,

Robin