I recently changed my imaging and processing laptop, so have been testing the new setup. The weather has also been below average in Melbourne lately, so it doesn't really lend itself to much imaging.
Anyway, this is a quick grab of the Helix with 10x3 mins exposures, lightly tweaked in Photoshop. As expected with such short time, there was a fair amount of noise.
Taken with my FLT 110. Comments welcome.
Just waiting for cloud free nights...
Bo
Is there a way to deal with the noise in uncooled images of less bright objects?
I find I can get really good looking dslr images of the brightest targets with an hour of exposures, but helix or tarantula images end up looking very noisy.
Is there a way to deal with the noise in uncooled images of less bright objects?
I find I can get really good looking dslr images of the brightest targets with an hour of exposures, but helix or tarantula images end up looking very noisy.
I guess one way is to lower the ISO to 800 or even 400 I agree re dimmer images and increased noise.
Quote:
Originally Posted by Camelopardalis
That's a good start Bo it's surprisingly faint, but then it's also fairly sizeable for a planetary nebula
Thanks Dunk, but the clouds are having a permanent holidays here in Melbourne.
Quote:
Originally Posted by Regulus
What Dunk said. And a good basis for more data, which may help with the overall red colour cast once it is added.
But still, nice.
I've never found this an easy target - it has quite a low surface brightness for a PN. The smaller ones are often easier. Also Melbourne's night sky isn't very dark - hard to get a nice black background.
Do you have photoshop? You can use layers and masks to reduce noise a lot - if you like I can post an example. It really gets rid of the grainy look.
Faint objects are always noisier - I guess there is less signal so the noise shows up more?
I don't have much luck with faint galaxies - they need long exposures and with Melbourne's current weather there isn't much time available.
I've never found this an easy target - it has quite a low surface brightness for a PN. The smaller ones are often easier. Also Melbourne's night sky isn't very dark - hard to get a nice black background.
Do you have photoshop? You can use layers and masks to reduce noise a lot - if you like I can post an example. It really gets rid of the grainy look.
Faint objects are always noisier - I guess there is less signal so the noise shows up more?
I don't have much luck with faint galaxies - they need long exposures and with Melbourne's current weather there isn't much time available.
Tony.
Thanks Tony,
I use Images Plus for stacking and the first tweaking and then export the file as a TIFF to PS for additional works in levels, curves, sharpening and de-noising.
If you have any links for online tutes, please post them up. I am always on the look out for new tips and hints!
Bo
This is a quick go I had at this - it is never perfect, it replaces the grainy look with a mottled look. Sometime you can go further with the noise reduction to get rid of this. It is a matter of which you prefer.
Here is the basic procedure:
Open image
Layer, duplicate layer, background copy
Filter, noise, reduce noise. (for more extrme reduction you van use Median).
Then play with the sliders to get what you sort of like (you can do the procedure more than once).
Typical: Strength 10, Preserve details 15%,reduce colour noise 100%,
sharpen details 15%. This depends on the image and what you prefer.
"Ok"
Add layer mask (icon - square with a circle in it).
Click on background image.
Ctrl A, Ctrl C (select all, copy)
Alt + left click on Background copy. (should be white)
Ctrl V (Paste), Ctrl I (inverse), Ctrl L (Levels).
Slide the left pointer to right(about 80%) and the right pointer to the left.
Black objects will be protected, white will have the noise reduction applied.
When you are happy with the levels of black and white press OK.
Then click on the eye for the backgound copy. Clicking this on and off will show the before and after.
If you like it - "Layer" flatten image, deselect - save new image.
I use this method a lot - it is really good especially when the noise is fairly low.
it's surprisingly faint, but then it's also fairly sizeable for a planetary nebula 
