VdB 142 Elephants Trunk in Ha

[narrowbandpaul]

Hi all,

We managed to get out for about an hour to collect 3 subs of 10, 15, and 20mins. They have been darked and bias subtracted for a total exposure of 45mins.

Taken through Takahashi Sky 90 with FF/FR to F4.5 with an SXVH9 on top of an AP900GTO.

Could be doing with more subs, but clouds came in...

Hope you like

Paul

(click to enlarge)

[Aza]

Looking good Paul! Great contrast in the image

When you have 3 subs of different lengths, do you simply stack them and process the stacked image?

Or do you go more in depth with the layering of the different subs?

Cheers

[narrowbandpaul]

just added them together to increase signal...dont bother with all that fancy photoshop guff...

paul

[Aza]

Ah right cool

Do you get a much better range this way?

As opposed to 4x10 or 3x15 etc....

[narrowbandpaul]

it is best to take equal length subs...that way you only need one set of darks.

the 10 mins was a test, the 20 mins was good, and uninterrupted with cloud. We tried for a second 20 min exposure, but cloud came in after 15 so we capped the scope. This resulted in an image with 15 mins signal and 20 mins of dark current. So the exposures we luck, and not planned.

The normal is 15 min subs or 20 min subs with the NB filters.

Hope that explains the exposures

Best Wishes

Paul

PS photoshop will need used for HDR objects like andromeda and orion, but for most nebulae, there is no need to layer, unless thats how you chose to do an LRGB combine, which is popular...

[Aza]

Thanks for the info Paul

Thought it was more of a planned thing

[narrowbandpaul]

no, im far more random than all that. There's not always method in my madness

[glennbech]

Excellent image! What kind of Ha Filter do you use? I'm curios about Narrowband imaging and have a 2" OIII filter laying around. Do you have any ideas on good targets for OIII imaging?

[narrowbandpaul]

we have an astrodon 6nm 1.25" Ha and S[iI] and 13nm O[iII] also from astrodon.

The O[iII] wavelength is 500nm, which lies on the border of blue and green. The best targets therefore are hot objects or objects illuminated by hot stars. Planetary nebula are the best targets for O[iII], especially to begin with, as their O[iII] flux is higher than their Ha flux. Just now M27, and M57 are good targets, especially M27. Other good objects are diffuse nebula/supernova remnants, but sometimes the O[iII] flux can be small. Wolf Rayet nebula also make good targets, as they are illuminated by very hot stars. Examples include Bubble and Crescent nebulae. But there is variability in these objects too. The best objects are probably planetaries, but the North American also makes a decent target.

The funny thing is some objects of the same type have very strong O[iII] emission and others have none...it is very dependant on the object.

There is a narrowband imaging discussion in the Imaging Discussion part of the forum.

You will require longer exposures, but that isnt much of a problem if you are already guiding. The longer the better. And the images look seriously cool

As a benefit you get much less light pollution and moon glow...you can absolutely image at full moon. Narrower bandwidth helps here.

I hope this helps you embark on a wonderful journey down the narrowband road.

If you need anymore assistance feel free to ask

best Wishes

Paul

[GordonH]

Hi Paul

Very nice image, very moody

Best wishes

Gordon

[narrowbandpaul]

thanks gordon