Firstly, we get asked a lot about whether “Unity Gain” should be used with the Hypercam 24CFX camera.
We believe that a unity gain setting isn’t really necessary with the 24CFX camera, because it has 14bit depth and HCG mode.
Firstly, we should explain that there is no reason to use Low Conversion Gain (LCG) with the 24CFX camera in low light conditions like astronomy if you are stacking the captured images.
It’s better to use the High Conversion Gain (HCG) setting, because it preserves dynamic range without increasing read noise, and read noise is more of a problem to overcome in low light situations.
For example, in a typical suburban sky of say Bortle ~5, with an F5 telescope, you need about a minimum of 15secs exposure in HCG mode (High Conversion Gain) for deep sky images with a good signal to noise ratio, but you would need a minimum of 2 minutes in LCG at Gain 510, and 3.5 minutes in LCG at Gain 100 which is the lowest gain setting available.
In SharpCap which has an automatic switch to HCG at 520 Gain, just choose Gain level from 520 to 1500 to switch into HCG mode automatically.
For other apps like NINA or the ASCOM driver, which do not automatically switch to HCG, set HCG to on, and use any Gain from 100 to 200 as a basic setting to get you going with your new camera. Because HCG multiplies the basic gain of the camera by about 4.3x we tend to recommend gain of 100 to reduce any chance of oversaturation of bright stars.
To summarise, most Hypercam 24CFX owners seem to be imaging with:
- Gain of 100
- 60-120 second subframe exposure time
- -5C temperature
- HCG on
- Images with 50 subs or over seem to look the most impressive, but you can just keep adding data from night to night to build up the image detail. There is no such thing as too many subs if you are using sharpening techniques in post-processing – the more the better.
These are just suggested settings which seem to work in most situations, however if you want the ultimate use of your time and to get the best possible results from your camera, it would be best to use the “Smart Histogram” feature in SharpCap PRO. This will help you trike the best possible balance between exposure time and image quality, whilst keeping the number of sub-frames reasonable.