L-Extreme chrominance noise - normal?

[RugbyRene (Rene)]

Hi all,

I've been using an Optolong L-Extreme filter with my ZWO2600MC and the images come out with a lot of chrominance noise. I'm just wondering if this is normal or is the filter (or camera) faulty? It's mount in a ZWO filter drawer and so is facing the correct way.

Rene

[Nikolas (Nik)]

images would be helpful also image train, exposure length etc

[Startrek (Martin)]

Rene,
I’ve used the same camera and filter in my 6” and 8” newts for nearly a year now
I only see abnormal noise sometimes when conditions are less than ideal and I’m imaging with short subs ( 60 to 90 sec ) with the camera set at highest dynamic range or gain 0. Other than that the cameras performance set at highest dynamic range ( gain 0 ) cooled to -10 to -15C pushing 2 to 5 minute subs at both imaging locations , Sydney Bortle 8 and South Coast NSW Bortle 3 is almost noise free ( I usually only require a noise reduction of 2 to 3 pixels
Some details may help diagnose your issue
Camera setting ( gain offset ) ?
Cooling setting ?
Exposure lengths ?
Bortle class skies ?
Seeing conditions when this chrominance noise was apparent ?
Focal length of scope ?
Do you dither your subs ?

Seeing conditions have a significant affect on noise ( see above my experience to date )

Martin

[AdamJL]

Gain 0 will introduce more noise to an image.

Are you pushing the image a bit too much where you don't have enough integration time? Are you seeing the noise after a healthy stretch of the data or at the beginning?
And what are you cooling your camera down to?

[Startrek (Martin)]

Originally Posted by AdamJL

Gain 0 will introduce more noise to an image.

Are you pushing the image a bit too much where you don't have enough integration time? Are you seeing the noise after a healthy stretch of the data or at the beginning?
And what are you cooling your camera down to?

Adam,
Only on paper
My experiences.....
I’ve used gain 100 Lowest Read Noise and Highest Dynamic Range Gain 0 with the 2600MC under different skies , different scopes , same objects , different exposure lengths and did not see any discernible difference in noise floor after a stretch in synthetic luminance using Startools. Most folk on CN have said the same thing. I just leave mine on HDR gain 0 and get fantastic results on all objects, conditions and exposure lengths ( 90 sec up to 5 minutes ) I cool mine to -10C although it can go lower to -15C but again I haven’t seen a noticeable difference between -10C and -15C as dark current is super low anyway on this camera
Lowest read noise as ZWO have suggested is best for short subs or lucky imaging under crappy sky conditions
Cheers
Martin

[RugbyRene (Rene)]

Originally Posted by Startrek

Rene,
I’ve used the same camera and filter in my 6” and 8” newts for nearly a year now
I only see abnormal noise sometimes when conditions are less than ideal and I’m imaging with short subs ( 60 to 90 sec ) with the camera set at highest dynamic range or gain 0. Other than that the cameras performance set at highest dynamic range ( gain 0 ) cooled to -10 to -15C pushing 2 to 5 minute subs at both imaging locations , Sydney Bortle 8 and South Coast NSW Bortle 3 is almost noise free ( I usually only require a noise reduction of 2 to 3 pixels
Some details may help diagnose your issue
Camera setting ( gain offset ) ?
Cooling setting ?
Exposure lengths ?
Bortle class skies ?
Seeing conditions when this chrominance noise was apparent ?
Focal length of scope ?
Do you dither your subs ?

Seeing conditions have a significant affect on noise ( see above my experience to date )

Martin

Here's some details. This is s single frame. Yes I know noise will be reduced by stacking but to be honest there wasn't that much difference.

• Date taken - 17 June so close to a new moon
• Camera setting ( gain offset ) ? gain-100 offset - 50
• Cooling setting ? -10
• Exposure lengths ? 300sec
• Bortle class skies ? Class 6 (Sydney)
• Seeing conditions when this chrominance noise was apparent ? Don't know
• Focal length of scope ? F/L550 (Esprit 100)
• Do you dither your subs ? - yes they were dithered

Rene

[Nikolas (Nik)]

I don't think it was the filter and you are only showing 1 image,
Are your subs calibrated with darks?
why is your offset so high?
Try offset of 30
Have you tried 600 second subs?

[Startrek (Martin)]

Originally Posted by Nikolas

I don't think it was the filter and you are only showing 1 image,
Are your subs calibrated with darks?
why is your offset so high?
Try offset of 30
Have you tried 600 second subs?

Nik,
I’ve never had to use darks with the 2600MC , although I have a library
I’ve processed with and without and have not noticed any significant difference in quality of image even zooming down to pixel level comparing both scenarios
Amp glow at 300sec is non existent
Cheers
Martin

[Startrek (Martin)]

Originally Posted by RugbyRene

Here's some details. This is s single frame. Yes I know noise will be reduced by stacking but to be honest there wasn't that much difference.

• Date taken - 17 June so close to a new moon
• Camera setting ( gain offset ) ? gain-100 offset - 50
• Cooling setting ? -10
• Exposure lengths ? 300sec
• Bortle class skies ? Class 6 (Sydney)
• Seeing conditions when this chrominance noise was apparent ? Don't know
• Focal length of scope ? F/L550 (Esprit 100)
• Do you dither your subs ? - yes they were dithered

Rene

Rene,
Silly question , are you capturing your subs as fits files and stacking as fits files
Do you use Deep Sky Stacker to stack ?
If your using jpegs this is counterproductive
Also are you setting your camera via Ascom or ZWO native drivers
I use Ascom and no issues at all
Sorry for all the questions
It’s great that Adam and Nik have offered advice to help
Hopefully a few more folk can pitch in for some ideas and help
You have a damn good camera there and an excellent filter too
Somethings not quite right !!
Martin

[AdamJL]

Ah, that's fine Rene

Here's an image with the same combination.

180 seconds, L-Extreme, 100 Gain + 50 Offset. Second image, you can see it processes all out anyway (I'm not done with this set just yet, still got a way to go to try and bring in RGB stars)

Your noise looks okay to me, unless I'm also doing it wrong

[Nikolas (Nik)]

As stated Offset should be lower and with the L-extreme I'd be upping the exposure time. to 10 minutes
I'd like to play with the subs and the darks. Something isnt right.

[RugbyRene (Rene)]

Originally Posted by AdamJL

Ah, that's fine Rene

Here's an image with the same combination.

180 seconds, L-Extreme, 100 Gain + 50 Offset. Second image, you can see it processes all out anyway (I'm not done with this set just yet, still got a way to go to try and bring in RGB stars)

Your noise looks okay to me, unless I'm also doing it wrong

Cool. Makes me feel better. Or we can both be wrong together.

[RugbyRene (Rene)]

Originally Posted by Nikolas

As stated Offset should be lower and with the L-extreme I'd be upping the exposure time. to 10 minutes
I'd like to play with the subs and the darks. Something isn't right.

Yeah I don't have the conditions or the mount to do a 10 min sub. The offset is what was recommended by a lot of people on the forums so I went with it.

[RugbyRene (Rene)]

I'm looking to get 10hrs + of integration time (got 7.5hrs so far) and drizzle so hopefully the noise will process out.

I'm imaging atm and while the moon is down.

[AdamJL]

Originally Posted by RugbyRene

I'm imaging atm and while the moon is down.

Ditto Good luck with your session!