Pixel size

[bomberbaz]

Just checking my understanding here of colour to mono! 

The zwo 183mc has a 2.4 pixel in RGGB, if I want to use it for mono purposes it it then 2x2 giving a pixel size of 4.8?

Is this correct and in simple terms what is the net effect please!

TIA

Steve

[vlaiv]

Was there ever such thing as astrophotography in simple terms? (or is it just me )

Depends on how you want to use it for mono purposes. I'll give you some examples:

1. You want to use color camera for "mono" purposes - size of pixel is the least of your concerns

2. Say you want to use it for Ha - then only red is really sensitive in Ha. In terms of resolution - pixel size will be effective 4.8um (it will be able to resolve as if pixel is 4.8um large), but as far as sensitivity goes - pixel is still 2.4um in size

3. Maybe you want to use it for OIII - things get complicated here as both green and blue pixels are sensitive in this wavelength - but to a different degree.

4. You want to bin your data 2x2 to actually get mono image (there are better ways to do this) - pixel size as far as both sampling and sensitivity go - will be 4.8um but effective QE will smaller than any of individual components.

5. You want to use some sort of duo band filter that captures both Ha and OIII at the same time - things get progressively complex here - so no easy way to describe what is going on.

In the end - I'd like to point out that with OSC - pixel size is never really that pixel size (unless you do bayer drizzle)

[bomberbaz]

48 minutes ago, vlaiv said:

Was there ever such thing as astrophotography in simple terms? (or is it just me )

Depends on how you want to use it for mono purposes. I'll give you some examples:

1. You want to use color camera for "mono" purposes - size of pixel is the least of your concerns

2. Say you want to use it for Ha - then only red is really sensitive in Ha. In terms of resolution - pixel size will be effective 4.8um (it will be able to resolve as if pixel is 4.8um large), but as far as sensitivity goes - pixel is still 2.4um in size

3. Maybe you want to use it for OIII - things get complicated here as both green and blue pixels are sensitive in this wavelength - but to a different degree.

4. You want to bin your data 2x2 to actually get mono image (there are better ways to do this) - pixel size as far as both sampling and sensitivity go - will be 4.8um but effective QE will smaller than any of individual components.

5. You want to use some sort of duo band filter that captures both Ha and OIII at the same time - things get progressively complex here - so no easy way to describe what is going on.

In the end - I'd like to point out that with OSC - pixel size is never really that pixel size (unless you do bayer drizzle)

Ever wish you hadn't asked a question 🤣

Actually thanks a lot vlaiv, I had not given consideration to HA and OIII data capture but glad you pointed all this out for when I get around to imaging again. 

I actually want to try capturing some data in mono for sampling spectroscopy and it is the data capture method that needs testing as much as the actual data before i even think to commit to purchasing a dedicated mono camera. 

I am really not sure what I am doing but getting there albeit very slowly. 

Come to think of it, I never did check if the rspec software automatically converts colour to mono, doh!. More research needed.

Cheers

Steve

Edited April 23, 2022 by bomberbaz

[vlaiv]

If you are interested in spectroscopy side of things - it is pretty "easy".

It is best to treat pixels as having double the size - but you will have lower QE as you spread spectrum more.

After you debayer your image (in above case it is best to split debayer) - you will have three channels - and all you need to do is "stack" them using max - highest of the three value.

This will produce "mono" sensor with somewhat strange QE curve - but you don't really care about that as you will remove instrument response from your data (by capturing known spectrum).

By using max - you will get sensor with above outlined response curve (it will have response of the highest component for each wavelength).