Helix

[Paul Haese]

Like so many others I thought I would produce an image of this very well imaged object.

The last time I had a go at this I used my TSA102. This time I had a go with the RC12.

I have been having issues with my camera and so the image is cropped. Subs were 30 minutes long and the image contains a total integration time of 26 hours. In retrospect I should have done longer subs still as the faint outer regions hardly even showed up. I would also like to have a lot more data to help smooth the background out a little.

Click here (http://paulhaese.net/NGC7293RC.html) for larger resolution image.

[RickS]

Nice image scale, Paul, and good colour and detail. I'm surprised you didn't get more of the faint stuff in 30 minute subs and wonder if there's more going on with the camera than the problems at the edge?

Cheers,
Rick.

[Amaranthus]

Nice work Paul. I see you chose not to make a synthetic green channel?

I've also collected NB data for Helix (about 24 hours) but am still processing! It'll be ready soon, I'm sure. This is motivation to get it done...

[Paul Haese]

Yeah maybe. Looks like SBIG are intending to replace the camera, so I will soon know if I can get great depth.

[Paul Haese]

I did use a synthetic green channel, I did not mention it though. I blended the Ha with the OIII at about 30%.

[Andre27]

Nicely detailed , great color.

[Stevec35]

Nice crisp Helix Paul. It is a bit surprising you didn't get more of the outer regions though.

Cheers

Steve

[gvanhau]

Nice result Paul.

Nice color it resembles a lot like RGB images.
I also agree that with 30 min subs there should be more faint stuff.

Geert

[johnnyt123]

a little question about sub time and integration time..

I have read that integrating for example 10x 3 min subs will produce the same fain detain as 1x 30min sub. but will smooth out the background noise also.

I agree with smoothing out the noise but not about bringing out more faint detail....

is my understanding right???

John

[Amaranthus]

John, each sub has a fixed read noise that can't be removed (the bias signal can). The fewer subs you have for a given integration time, the lower this noise relative to signal. So, in an ideal world, you'd want your subs as long as possible to minimise the % contribution of the read noise.

In the real world, long subs are problematic due to need for excellent tracking, avoiding wind/satellite/plan trails, bumps etc. They are also a problem because sky background will accumulate to a point where you start losing dynamic range.

Paul was imaging here in narrowband in a dark site, so sky background will be minimal. Thus, provided he has tracking and scope protection under control, longer subs are desirable.

[Rod771]

Really nice Paul love the colours!:thumbsup:

[Paul Haese]

Hi John.

I subscribe to the idea that long subs is better than doing short subs. My thinking is that doing long subs over whelms the noise floor and increases the background ADU. Which in turn means I do not have to stretch my data as much to achieve a desired brightness. Faint detail is captured easily too. Any noise that is present in an image is always going to show up when there is heavy stretching. Besides I like to hunt down the faint dust where possible. Lots of the worlds top imagers are doing long subs. Feel free to ask any of them about why they are doing this. :)

I prefer to gather lots of photons in a single sub rather than try to increase signal via thousands of subs for any given number of integration hours. I do collect lots of subs though but only collect until that frame is relatively noise free. I don't use an arbitrary number as suggesting by a simpleton recently. My plan is to produce noise free images.

I do have a dark sky, good mounts with excellent polar alignment and don't have to be wake to collect the data. I invariably collect way more data than I use and often throw out a lot of data that does not meet my needs, simply because I can and I am not impatient and need to be gratified instantly. That is the beauty of automation.

Try some experiments for yourself and decide what you would like to do. In any event its about what you want to achieve. :D

[Ross G]

Great looking closeup photo Paul.

Sharp and detailed.

Ross.

[atalas]

Good work on the internal structure Paul...the outer shells I would of thought were attainable at 26 hrs? are they mainly hydrogen?would a faster scope have done the job?anyway still a fine image.

[Paul Haese]

Yep probably all hydrogen yet they did not show up. I note plenty of other images at F8 don't show them either. Maybe the f-ratio but could also be my processing. To hide the wide bar problem I had to dark the background quite a bit. I can see the first shell but the secondary shell is hard to see.

I might have to try this object again as some point soon.

[NOMH]

Great work Paul.

JB

[atalas]

Paul,what's the "wide bar" problem?

[Paul Haese]

Seen here (http://www.iceinspace.com.au/forum/showthread.php?t=125010) Louie. Might be of interest. SBIG are replacing the camera. Just waiting for one to come down the pipe.

[atalas]

Thanks Paul,I'll check it out....didn't have much luck with Sbig cameras myself a couple of years back!lucky it was replaced with a new one by the retailer after 12 months and three returns.

Best of luck with the replacement.