First Narrowband Images of Horsehead and the Crab

[Ishtar]

I recently bought myself some narrowband filters and here are the first light images. Not very good but to be honest I didn't collect much data.

The horsehead nebula: 10 x 3 minutes Ha. Stacked in DSS and post processed in Photoshop CS5.

The Crab Nebula: 10 x 2 minutes Ha, 20 x 2 minutes OIII. Stacked in DSS and postprocessed in Photoshop CS5.

[jnp]

Not very good

They both look good to me, nice detail and colour. Perhaps centre the targets next time. Which scope were you using 8" F5?

[Ishtar]

They both look good to me, nice detail and colour. Perhaps centre the targets next time. Which scope were you using 8" F5?

Hi Jnp

Thank you. Yes, I was using my 8" F5 Newt.

What I didn't mention in my original post is that these images were also from my first attempts at auto-guiding. I struggled to find a nice fat guide star so that's why the targets are not correctly centred.

I am currently having more success imaging the Bubble nebula.

Nikki

[narrowbandpaul]

you will need longer subs when doing narrowband imaging. I reegualry use 15mins or 20mins. 10 would be about the min for most objects except for orion which is bright...maybe one or two minutes would be enough!

paul

[GordonH]

I agree with Paul, 10 minutes is a minimum except for the core of M42. Nice pictures though with plenty of detail, just a minor point and that is that your horsehead is back to front, it should point to the left

Best wishes

Gordon

[Tim]

Well done on you first attempts at NB, it really does open up the sky to you, and vastly increase your chance of getting more nights suitable for imaging.

Although it is tempting to use a big bright star to guide by, you might try a more subdued one. You'll get a more accurate guiding with an unsaturated star.

When you nail the guiding, do have a go at loooooong subs as mentioned above. Especially in ha. The clouds of gas start to take on a new dimension with long exposures, and lots of extra usually hidden details start to emerge, especially darker areas of gas.

Welcome to the darkest side

[Ishtar]

Thanks everyone.

Just one question: Am I right in assuming that if I take 10 minute exposures then I need less subs in order to get the same signal to noise ratio?

Nikki

[narrowbandpaul]

yep! in theory 3x20 mins is better than 6x10, which is better than 12x5 etc....despite the cumulative exp is 1 hour.

if you are read noise dominated, which the very faintest parts of every image will be. ie the stuff near an SNR of 1. The more subs you take the more read noise you add together.

for the brighter parts that are shot noise dominated, it doesnt matter. But the faint stuff will appreciate having longer single subs.

paul

[peter shah]

nice work....super detail in both:cool:

[ollypenrice]

Remarkable for such a brisk collection oif data! I love the Crab colours.

You need to be careful with polar alignment on long subs but NB does love them.

Olly

[Ishtar]

Thanks everyone

I have just ordered a SII filter so I will now be able to do the "Hubble Palette":headbang:

Nikki