ASICap RAW8 vs RAW16

[rob_r]

Hi, I'm after some advice please. I recently got an ASI224MC and I've been using ASICap to so far, capture some videos of the Moon with some decent results.

But, I'm a little puzzled as to what the difference is between the two options of capturing data, RAW8 and RAW16, other than the type of file it is saving. I notice that depending on the option selected it will save the video as either an AVI or SER files. SER is the preferred option as it cuts out having to convert the AVI (using Siril) into SER anyway so I can use AS!3 to stack the captures. In the ASICap manual, it states:

Quote

Raw Data: When the displayed image is a color image and you want to save the original (black and white) image, please check this box. If it is not checked, it will save the color image. This can be set only for color cameras and when the data format is set as Raw8. The black and white camera or when Raw16 format is selected, it can only save the original data.

So my question is say I want the black and white image, is it a true monochrome image that would allow me to use filters to capture separate RGB channels if so desired? Is one RAW option better quality (i.e. more data captured) than the other? What is meant by 'original data'? And so leads me to my next question about filters. I have a manual filter wheel and since the camera is colour, do I need a set of RGB filters or would I be better off just capturing in colour? Would an ADC help? I have my eye on the Baader LRGB set of filters along with a Baader IR 685nm pass filter as I know that the 224MC is particular sensitive to IR.

Apologies for so many questions, feels like I'm going down a rabbit hole. So, thanks for any pointers.

[vlaiv]

Use SER file format for capture.

1 hour ago, rob_r said:

So my question is say I want the black and white image, is it a true monochrome image that would allow me to use filters to capture separate RGB channels if so desired?

Every sensor is monochromatic sensor. Color comes from smart handling of filters imprinted on individual pixels. This is called Bayer matrix for OSC cameras - for details, look here: https://en.wikipedia.org/wiki/Bayer_filter

You can use color filters with color camera - but results won't be the one you expect - it will not behave as mono sensor + filters.

You are still capturing R, G and B data and you can separate them (see that Bayer filter thing).

Raw8 means that you are capturing 8 bit of information, Raw16 means that you are capturing 16 bit of information per each pixel.

Original data is data prior to debayering - while red, green and blue pixels are still separated. If you plan on stacking with AutoStakkert!3 - leave data original as this software knows how to deal with it to exploit it fully resolution wise.

As for filters - you'll need UV/IR block filter. You can get IR 685nm pass filter if you want to do IR astrophotography. Maybe better solution would be ZWO 850nm pass filter - as camera response is uniform above 850nm and it will behave like true monochromatic sensor in this band.

Don't get LRGB set unless you are planning to get mono camera later on.

ADC helps when planets are lower in the sky to fix the fact that atmosphere acts as prism and slightly separates colors. It has nothing to do with how you capture and process your data.

[rob_r]

Thanks @vlaiv. This is exactly the understandable explanation I was looking for.

I was looking for the IR pass filter for lunar photography mostly as I believe it can make the images a little sharper. Have I got that thinking right? So for planetary, I'm only interested in visible light by utilising the IR cut.
I'll hold off on the LRGB filters for now in any case.

Thanks again.

[vlaiv]

55 minutes ago, rob_r said:

Thanks @vlaiv. This is exactly the understandable explanation I was looking for.

I was looking for the IR pass filter for lunar photography mostly as I believe it can make the images a little sharper. Have I got that thinking right? So for planetary, I'm only interested in visible light by utilising the IR cut.
I'll hold off on the LRGB filters for now in any case.

Thanks again.

As far as lunar with IR filter - it is tradeoff.

Longer wavelengths are much less affected by atmosphere than short wavelengths (blue light bends more than red in both glass and atmosphere) but longer wavelengths suffer more from diffraction effects - larger airy disk pattern.

IR is probably better suited for large aperture scopes that are more affected by seeing and lower wavelengths for smaller scopes (like Baader Solar Continuum that is centered around 540nm). In bad seeing - use IR of course, but in excellent seeing - it can actually produce less sharp image then otherwise possible due to airy disk size.