M27 - my second image

[Galen Gilmore]

Here is my second real image. I originally only had 15x30 seconds exposure, but I had time to go out the next night and grab another 15 exposures.

M27

30x30 seconds exposure time.

fujifilm xt-1

Any tips/tricks welcome  

[HunterHarling]

Very nice! Much better than my second image.

[Galen Gilmore]

11 hours ago, HunterHarling said:

Very nice! Much better than my second image.

Thanks  

[Shera]

It's lovely. How did you photograph it? Did you use a camera and telescope or just a camera?  And why did you need to get more exposures? I'm learning how this all works and I'd love to capture something like that!

[Galen Gilmore]

8 hours ago, Shera said:

It's lovely. How did you photograph it? Did you use a camera and telescope or just a camera?  And why did you need to get more exposures? I'm learning how this all works and I'd love to capture something like that!

Thank you for such kind words!

I used a telescope on a tracking Equatorial mount with a fujifilm xt-1 at the prime focus of the telescope. The reason I captured so many exposures is to reduce the signal to noise ratio. If I could I would take a single 15 minute exposure, but that is limited by the light pollution and my mounts tracking ability. So I take more shorter exposures to simulate what I could get in a single 15 minute exposure. I then stack all of my frames using a computer program (such as deep sky stacker) to get a brighter, clearer image with less noise. Stacking reduces noise because noise is random, while the thing you are imaging is the same each time. So everytime you stack one image you sort of fill in the blanks that the noise left behind. This is also the reason why you can't just take one image, duplicate it, and stack it, your not just stacking your nebula but also the noise is being stacked.

Hope this helps

[bobro]

If you're using DSS to stack and not already doing this, before saving the image in DSS set the Saturation shift (Saturation tab) to about 20% before aligning the RGB histogram peaks (RGB/K Levels tab). This will bring out more colour in the image before subsequent processing. More subs too of course to reduce noise.

[Galen Gilmore]

1 hour ago, bobro said:

If you're using DSS to stack and not already doing this, before saving the image in DSS set the Saturation shift (Saturation tab) to about 20% before aligning the RGB histogram peaks (RGB/K Levels tab). This will bring out more colour in the image before subsequent processing. More subs too of course to reduce noise.

What do you mean by align the RGB histogram peaks? After the picture gets stacked I just move the stacked picture to PS for processing.

[bobro]

Colour balance can be corrected in DSS, though it's not essential as it can be done later in PS. I do it in DSS as it's easier for me than using GIMP. To do this click the central slider for each colour and move the histograms sideways using arrow keys until all 3 colours line up.

[Galen Gilmore]

5 hours ago, bobro said:

Colour balance can be corrected in DSS, though it's not essential as it can be done later in PS. I do it in DSS as it's easier for me than using GIMP. To do this click the central slider for each colour and move the histograms sideways using arrow keys until all 3 colours line up.

Ok thanks, that is helpful!

[ollypenrice]

Well done. You have the key features in place.

It looks to me as if you have used pretty invasive noise reduction, giving the background sky an 'oily' look. I would suggest letting a little 'grain' remain in the image.

Olly

[Galen Gilmore]

3 minutes ago, ollypenrice said:

Well done. You have the key features in place.

It looks to me as if you have used pretty invasive noise reduction, giving the background sky an 'oily' look. I would suggest letting a little 'grain' remain in the image.

Olly

Yea, I used the PS noise reduction. I'm not exactly sure how it works so I just used that tool about 3 times until it looked good to my eyes. I guess I just haven't learned to see when it's a little too much.

[ollypenrice]

Just now, Galen Gilmore said:

Yea, I used the PS noise reduction. I'm not exactly sure how it works so I just used that tool about 3 times until it looked good to my eyes. I guess I just haven't learned to see when it's a little too much.

Noise is proportional to signal so areas of strong signal (bright nebulosity, stars...) have a low level of noise relative to signal. Backgoround sky has a high level of noise to signal because there is not much signal. Noise reduction, at the end of the day, is blurring. So don't blur what you want to be sharp. Use the selection tools/layers to identify the background sky and give that a bit of NR but don't, under any circumstances, blur your nice sharp signal on nebulosity. This is sometimes called the 'zone system,' the zones being the parts of the image which need different processing. Some zones invite sharpening, some invite blurring. This is the life blood of processing.

Olly

[Galen Gilmore]

2 hours ago, ollypenrice said:

Noise is proportional to signal so areas of strong signal (bright nebulosity, stars...) have a low level of noise relative to signal. Backgoround sky has a high level of noise to signal because there is not much signal. Noise reduction, at the end of the day, is blurring. So don't blur what you want to be sharp. Use the selection tools/layers to identify the background sky and give that a bit of NR but don't, under any circumstances, blur your nice sharp signal on nebulosity. This is sometimes called the 'zone system,' the zones being the parts of the image which need different processing. Some zones invite sharpening, some invite blurring. This is the life blood of processing.

Olly

Yeesh! That's good to know. The nebula itself was pretty noisy, so I guess that means I need a lot more subs or darker skies as others have said.

[ollypenrice]

Yes, nobody ever had too much data!

Olly