Where's the nebulae?

[groberts]

On Friday night I set out to image NGC 2264 using a Canon 700D (unmodified) + Astronomik CLS filter, William Optics GT81 + field flattener, x30 x120 secs @ ISO800 + x10 darks,bias and flats.  I was quite pleased with the initial outcome and was expecting the nebulosity to become apparent post processing in Photoshop.  However, whilst 15 Moncerotis and the other stars are clearly present, the related nebulosity I was expecting is barely evident after stretching etc.

Looking across the stacked image and also the original subs the background seems unusually flat / dark, registering no more than 10 to 30 values. What's happened to the nebulae?  I have successfully used this set-up and the same DSS settings before with good results, so cant figure this out: is the target too much for my set-up, does the nebulae require longer exposure or higher ISO setting or have I done something wrong?  Thoughts and advice appreciated. Thanks.

x30 subs + calibration, stacked + Levels and Curves 

Original Sub before stacking and processing (blue tint comes form CLS filter, later removed in processing)

  

[Thalestris24]

Hi

Yeah, I think you probably need much longer subs - maybe minimum of 10mins or longer if you have a lot of light pollution. Also you're up against it with an unmodded dslr. I'm no expert but I struggle to pick up nebulosity even with a qhy8l which has high sensitivity in the red. That's because of city lp .

Also, I'd say your stacked image has the black point too low i.e. it's too black. Maybe try reprocessing it - you may be able to reveal more detail.

Good luck

Louise

[groberts]

Thanks for your comments Louise.  I'm slowly gearing up for autoguiding, hopefully early in the New Year, until then 120 to 180 seconds subs is about it!  Notwithstanding, I have previously been successful with other similar nebulae and at +3.9 magnitude (if that's correct?) thought there would be more than enough light?  Agree with the black point, though as I said the pre-processing original image already seems quite dark across the whole image, which made me suspect something else. Still the Xmas tree is clearly there! 

[Thalestris24]

I think with nebulae (and galaxies) you have to go by the surface brightness... q.v. on Stellarium :}

Louise

[AndyKeogh]

Thanks for your comments Louise.  I'm slowly gearing up for autoguiding, hopefully early in the New Year, until then 120 to 180 seconds subs is about it!  Notwithstanding, I have previously been successful with other similar nebulae and at +3.9 magnitude (if that's correct?) thought there would be more than enough light?  Agree with the black point, though as I said the pre-processing original image already seems quite dark across the whole image, which made me suspect something else. Still the Xmas tree is clearly there! 

Been there and got the tee shirt but no nebulosity

I currently use 5 min subs  and guiding. it is only now that I have good polar alignment that I am now seeing some nebulosity.

Andy

[DaveS]

Another thing to remember is the very low sensitivity to Ha of an un-modded DSLR. and I think the nebulosity there is almost all Ha. You need much longer subs.

[Owmuchonomy]

The nebula (as opposed to the cluster) itself is a faint Ha emission given shape by the dark hydrogen gas silhouette. You will need lots of data in Ha to get close to it. Not really a suitable target for a standard DSLR.

[groberts]

Well I have played around with the image more and although it is a bit noisy, the Cone Nebula etc has appeared     

Would a Ha filter help with this type of feature or are longer exposures and an modded camera the only real answer to a better image? 

[D4N]

The Ha filter won't be very helpful on an unmodded DSLR, the cameras IR filter will block out most of the Ha and the Ha filter will block out everything else.

You would need very long subs to see anything other than noise.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

[DaveS]

Astro modding is really the only way to go without going to CCDs.

[groberts]

The nebula (as opposed to the cluster) itself is a faint Ha emission given shape by the dark hydrogen gas silhouette. You will need lots of data in Ha to get close to it. Not really a suitable target for a standard DSLR.

Is there a definitive list of which objects are Ha and which are not? 

[Owmuchonomy]

You can refer to Planetarium software if you wish. I always research my targets before committing valuable imaging time. Sky Safari is my first port of call.

[groberts]

The Ha filter won't be very helpful on an unmodded DSLR, the cameras IR filter will block out most of the Ha and the Ha filter will block out everything else.

You would need very long subs to see anything other than noise.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

So the solution to Ha objects is a modded camera?  Or is a Ha filter also needed?

[groberts]

You can refer to Planetarium software if you wish. I always research my targets before committing valuable imaging time. Sky Safari is my first port of call.

I already do this using Cdc but don't see anything specifically relating to Ha, what should I be looking at?

[carastro]

No you don't need an Ha filter for a modified DSLR, modified will enable the Ha data to show up.  

Carole 

[groberts]

Thank you Carastro, too late for Father Christmas but I'll put it on the 2015 shopping list.

[lensman57]

Well I have played around with the image more and although it is a bit noisy, the Cone Nebula etc has appeared     

NGC 2264 Xmas Tree Stacked1LCLCGXDcropped.jpg

Would a Ha filter help with this type of feature or are longer exposures and an modded camera the only real answer to a better image? 

This is the proof that you do not have enough signal, whatever there is now is buried in the noise. All the previous posts are correct, you need a modded DSLR, auto guiding and much longer subs. DSO imaging is difficult with a very steep learning curve so be patient and it will happen.

A.G

[D4N]

If you are technically minded it is fairly easy to mod a DSLR yourself at no cost.

If you continue with an unmodded camera look for things that don't emit Ha.

This can be galaxies, reflection nebulae (like Pleiades) and nebulae that are strong in OIII, your camera will pick those up fine. Some targets will look a bit odd if they also have Ha present as this part will appear quite dark.

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