Filters - A worked example

[PKay (Peter)]

Hi Brainy Ones :-)

This example is using a colour camera.
I am ignoring using RGB filters.
When stating RGB below, it is straight from the camera (no filter).

After looking at images in Astrobin and IIS, there seems to be a few ways of taking the images (that I can use):

1: RGB
2: RGB and Ha
3: Ha, OIII, SII
4: RGB, Ha, OIII, SII

Worked example:
We have 2 nights (3 hrs/ night) to image Andromeda (guided).

My plan (method 2):
3 hours Ha. 3 hours RGB

Exposure times:
20 of 5 minutes, 20 of 2 minutes, 40 of 1 minute

Sooo... what would be your plan?

[rustigsmed (Russell)]

for a OSC (colour) camera it would be as many subs as you can get.
I wouldn't bother with any other filter except for Ha (maybe), but im not sure how much Ha M31 has. i would recommend spending way more time on the "rgb" capture than Ha.

the best way to process OSC data is to extract the luminance and blend it back in a LRGB manner (your options don't consider Luminance which is the way more important than 'colour' - as the colour data can be terrible and it it will still produce a good image if the luminance is good).

[PKay (Peter)]

Thanx for replying Russ

Using PI:
Yes I do extract illuminance and then use LRGB combination.

Regards to how much Ha in M31:

I just looked at images found in Astrobin and there seems to be a lot of detail gained by using Ha.
Also there are a few PI tutorials (M31) that include Ha.

The process for extracting the Ha (using OSC) is a bit tedious and highly inefficient, but there seems to be a usable result.

In summary, I have to debayer, and then use channel extraction and throw away the G & B channels. The R (or Ha) channel is then combined with the R channel extracted from the RGB images.

I am in the process of designing a PI work flow that at this stage, has nearly 100 steps

When tested and I have a result, I will post it if anyone is interested.

[rustigsmed (Russell)]

What camera are you using Peter? Is it a dslr?
I’m afraid I can’t help you too much with a PI solution I have done it a few times with a dslr and Ha (and OIII) but in DSS and Photoshop and it was capable of obtaining parts not visible otherwise (eg O3 shock wave around NGC 6164).

If it is a dslr you can always set it to black and white mode when capturing Ha – sometimes extracting the red channel after debayering can result in an image ¼ the size of your regular RGB (only red pixels) – again depending on settings.

There are different ways to layer in Ha into an image. As in using it as Luminance but this won’t really work for a galaxy - as you have suggested.
with Ha and R channel blending. But sounds like you’ll have a bit of experimenting to do! Looking forward to seeing how you go.