M57 Ring Nebula

Post by **VinSnr** » Sun Jun 10, 2007 5:57 pm

acc wrote:wah very nice. wish we could see such colour live... Is that a hint of the central star in the second image?

I saw the same thing using video. Same colour too. Not as big as the second picture, probably closer to the first picture. And the video could see a hint of the central star. That's at 7 seconds integration.

Post by **weixing** » Sun Jun 10, 2007 5:58 pm

Hi,

Nice. Can see IC 1296 at the 2 o'clock of ring neb.

oh... I didn't notice that...

I'll check the image again.

Have a nice day.

Post by **VinSnr** » Sun Jun 10, 2007 5:59 pm

weixing, is that a single shot of 1.5 minutes exposure or a combination of stacks?

Post by **weixing** » Sun Jun 10, 2007 6:05 pm

Hi,

weixing, is that a single shot of 1.5 minutes exposure or a combination of stacks?

A combination of 30 x 1.5 minutes exposure.

Have a nice day.

Post by **VinSnr** » Sun Jun 10, 2007 6:13 pm

weixing wrote:Hi,
weixing, is that a single shot of 1.5 minutes exposure or a combination of stacks?
A combination of 30 x 1.5 minutes exposure.

Have a nice day.

wah...you very patient sia....

I am curious...at 45 minutes of total exposure, wouldn't the sky be brighten up as well? Your contrast on the object vs the darkness of the sky is very good. Was there processing done on the sky?

Post by **weixing** » Sun Jun 10, 2007 6:40 pm

Hi,

wah...you very patient sia....

Ya... it's a bit boring doing nothing while waiting 45 minutes for DSLR to capture the series of images and later another 30 minutes for the flat...

But will get excited by thinking that I might get a nice image

May be will learn constellation next time while waiting... ha ha ha

I am curious...at 45 minutes of total exposure, wouldn't the sky be brighten up as well? Your contrast on the object vs the darkness of the sky is very good. Was there processing done on the sky?

By adjusting the level of the image, you'll get a decent black background. Anyway, still learning how to do image processing using photoshop.... hope to make full use my old photoshop.

Have a nice day.

Post by **VinSnr** » Sun Jun 10, 2007 6:44 pm

weixing, how do you get flat without a lightbox?

Meng Lee · Post by **Meng Lee** » Sun Jun 10, 2007 6:59 pm

Oops don't push the black triangle too much to the right at the Levels. Otherwise will incur data loss.

Er, I chip in here, you can use Photoshop to artifically create a frame that contains flat field details and gradient details (but can't create dust donut profiles.) So you can remove flat and sky gradient in a "lazy man's" way in Photoshop.

Post by **weixing** » Sun Jun 10, 2007 7:20 pm

Hi,

weixing, how do you get flat without a lightbox?

Err... I use the light pollution... :oops: :oops:

I point my scope at the light pollution, turn off the motor drive and shoot 20 of them. All the shot are taken with the same exposure and ISO as my image frames, so that I can reuse my dark frame. After dark frame subtraction, I median stack it and get my flat. Also, will move the scope to point at different part of the light pollution at every few shot, so that the light pollution gradient is not present after the median stack. Below is what the flat frame look like for the M57 image:

Have a nice day.

cataclysm · Post by **cataclysm** » Sun Jun 10, 2007 10:30 pm

weixing, how do you get flat without a lightbox?

I use the light pollution

After dark frame subtraction, I median stack it and get my flat.

Interesting Weixing! You killed 2 birds with 1 stone!
I obtained my Flats with the 'White T-shirt trick' in daylight. Simply cover the scope's obj with a white cloth or T-shirt and point it up the sky. Search for a patch of sky that is overcast to provide even illumination. The exposure will be really short, something like 1/3000 to 1/4000 for ISO800.