Under 3 hours of the Rosette -last Monday

[pixueto]

This is a quick processing of the Rosette I took last Monday with the ED80, the Baader modified canon 1100D and the CLS clip filter.

All subs taken at exposures of 8 minutes and ISO 1600.

I find it a bit noisy. I'm thinking about spending another night on this target, maybe at ISO 800, maybe shortening the exposures to 6 minutes.

Thanks for your comments.

[Ibbo!]

coming along nicely

Steve

[Dark Horizon]

How many subs??

Drop down to ISO400 and expose for 10 or 12 min, will mean you'll need many more exposures to help reduce noise but you'll attain a higher res image.

Good luck.

[andyo]

That's looking good, if you are dropping the iso I would increase the exposure time as dark horizon suggests

[Quatermass]

very nice pix have you got the stacked image in dropbox would like to have a go at the processing on this one.

[RikM]

That's going very well. It would improve it if you balanced the colour of the background to get rid of the blue tint from the CLS. Fairly easily done using the levels control in Photoshop. It would also allow you to add more contrast in the neb with curves and boost the red tone a bit with selective colour if you like. More data will help smooth out the noise, but a bit of a soft blur after masking the stars and the bright bits wouldn't hurt either.

e.g.

I have no idea how dropping the ISO will have any effect on the resolution. But it should allow you to increase your sub length, to catch more faint stuff, without burning out the colour on the stars. You have done well to retain the good star colour you already have though.

[pixueto]

very nice pix have you got the stacked image in dropbox would like to have a go at the processing on this one.

Thanks Mark, I'll put the link when I get home. I really appreciate it.

The stack came up with a bit of vignetting which I removed with Pixinsight Lite, by the way. However, I did take flats, darks and bias frames.

[pixueto]

That's going very well. It would improve it if you balanced the colour of the background to get rid of the blue tint from the CLS. Fairly easily done using the levels control in Photoshop. It would also allow you to add more contrast in the neb with curves and boost the red tone a bit with selective colour if you like. More data will help smooth out the noise, but a bit of a soft blur after masking the stars and the bright bits wouldn't hurt either.

e.g.

I have no idea how dropping the ISO will have any effect on the resolution. But it should allow you to increase your sub length, to catch more faint stuff, without burning out the colour on the stars. You have done well to retain the good star colour you already have though.

Thank you all guys.

Maybe someone here could be kind enough to elaborate a bit on how different ISO and exposure would affect overal noise. By reducing ISO but increasing exposure time, aren't we increasing thermal noise? 

Sorry if that's a silly question.

Thanks

[pixueto]

How many subs??

Drop down to ISO400 and expose for 10 or 12 min, will mean you'll need many more exposures to help reduce noise but you'll attain a higher res image.

Good luck.

Good luck.

It's about 2 hours, 43 minutes worth of subs so I was surprised to see the result that noisy. Maybe I have overdone a bit the processing trying to bring out more detail than what is possible for this stack.

[Quatermass]

I use an ISO of 1600 most times and find that I can reduce the noise by taking and stacking 80 sub under 50 is just about ok less than that and the noise problem creeps back up thats on my modded canon 350d though. I stack with 80 darks flats and bias shots and have been using the masters from that lot for ages with no problems.

[RikM]

Thank you all guys.

Maybe someone here could be kind enough to elaborate a bit on how different ISO and exposure would affect overal noise. By reducing ISO but increasing exposure time, aren't we increasing thermal noise? 

Sorry if that's a silly question.

Thanks

I have never found that adjusting the ISO makes much difference to the perceived 'noisiness' of the final image. I think of ISO as an in-camera pre-stretch of the data before output. However, by reducing the ISO you should reduce the tendency to oversaturate the brighter stars, thus avoiding burning out the star colour.

Yes, longer subs will lead to more thermal noise but this can be dealt with either with good darks and more subs or by software aerobatics. If you don't have the exposure time, you don't catch the faint signal and if you don't have the signal you can't show it in your final image. It is all a big compromise really.

If it's any consolation, I put well over 4 hours into my Rosette in 8min subs @ f/5 and it was at least as noisy as yours if not more so. As I said, I think you have done really well.

[dph1nm]

I have never found that adjusting the ISO makes much difference to the perceived 'noisiness' of the final image. I think of ISO as an in-camera pre-stretch of the data before output.

Yes, ISO makes no difference to the sensitivity of your camera to light, so the S/N for a given exposure time remains the same.

NigelM

[ollypenrice]

I felt the colour imbalance in the orginal was down to too much green. I thought the proposed alternatives were then too red. Personally I'd drop the green first and see how that looked. Just me, I stress.

Olly

[x6gas]

Nice work.  It's a lovely image with great data.  I too find the background in the original a bit too green.  I hope you don't mind but I've had a go at balancing the colour too:

[pixueto]

I use an ISO of 1600 most times and find that I can reduce the noise by taking and stacking 80 sub under 50 is just about ok less than that and the noise problem creeps back up thats on my modded canon 350d though. I stack with 80 darks flats and bias shots and have been using the masters from that lot for ages with no problems.

The problem is that with 8 minutes subs it's going to take weeks to get 80 subs!!!

Mark, you have here a link to the stack if you want to have a go at processing:

https://dl.dropboxusercontent.com/u/81776321/StackedRosetteEmbed2hr39min.TIF

Please, anyone else have a go if you want to.

[pixueto]

I tried a a new, slightly less aggressive processing this time attempting to keep the noise down.

[ollypenrice]

I tried a a new, slightly less aggressive processing this time attempting to keep the noise down.

Way too green.

Olly

[andyo]

Thank you all guys.

 

Maybe someone here could be kind enough to elaborate a bit on how different ISO and exposure would affect overal noise. By reducing ISO but increasing exposure time, aren't we increasing thermal noise? 

 

Sorry if that's a silly question.

 

Thanks

I believe that the ISO setting changes the way the tonal steps are allocated in the overall dynamic range.At a high ISO setting more tonal

steps are allocated to the shadow areas wheras the lower the iso the more total the dynamic range.So for really faint areas the higher the

ISO setting will help distinguish faint detail from noise but at a cost of the dynamic range dropping.

Lower ISO with longer sub lengths will help raise the signal above the noise and give a higher dynamic range.

With a DLSR noise becomes a problem because they are not cooled so the thermal signal becomes worse with longer exposures.So you may get

better results by using a higher iso with shorter sub lengths and stacking more of them.Its really a balancing act between most of these

factors.What may be the best settings for one target mey not be the best for another,in a nutshell experiment to see what works best.

[pixueto]

Way too green.

Olly

I

Not sure if this is an improvement?

Thank you for the advice.