Iris Nebula - NGC 7023 How long for the subs

[johnb]

Hi

Im planning some sessions on the Iris Nebula and i can now do 10 min subs. Given my kit (in signature) what sub lengths should I go for, is longer always better ?

Regards

John B

[Whippy]

I think 10 mins should be alright, I did 10 mins subs when I did it a couple of years ago. One thing you have to watch out for is the central star, saturate or overcook it during processing and it does make life difficult.

HTH

Tony..

[johnb]

maybe i can do a number of 10 min subs and then a number of shorter ones and combine so as not to burn out the central star ?

John B

[ollypenrice]

maybe i can do a number of 10 min subs and then a number of shorter ones and combine so as not to burn out the central star ?

John B

I would say so. You won't need too many of the shorter ones because ipso facto you will only be keeping the strong signal bits.

I used 10 mins in the OSC CCD at f7 and didn't cook the core. It was hot and needed a shorter stretch of its own to layer into the deeper stretch but it came out fine.

What you do need, if you want to catch the outlying brown dust, is HOURS of data!!! I will be dropping at least the same again onto the 6 hours I got last season.

Olly

[swag72]

I tried this target when I had a little time left over. The subs went in the bin!! 5 min subs on a modded dslr gave me a terribly burnt out core and not an awful lot else!

[johnb]

I was thinking of plenty of 10 mins subs to get the detail then some really short subs Ie 2 mins for the core and then merge. John b

[Whippy]

I tried this target when I had a little time left over. The subs went in the bin!! 5 min subs on a modded dslr gave me a terribly burnt out core and not an awful lot else!

Really Sara? I'm surprised at that. I imaged it on a quick-ish scope (FLT98) with my Atik and no LP filter and the core wasn't burnt out at 10 mins. See here: Stargazers Lounge - Whippy's Album: DSO's, not UFO's.... - Picture .

Tony..

[swag72]

I think that the moon may have had some influence in this, as it was almost half moon, although I was pointing in the opposite direction. Perhaps if I'd had more subs, think I ended up with 5, it may have been better, but I was rather disapointed. Your pic is showing some great detail that I just didn't have.

[Whippy]

Interesting! The moon wouldn't have had any real interferance and as it's a reflection nebula it doesn't matter whether your camera has been modded or not. Sounds like an excuse to have another go Sara ...

Tony..

[swag72]

Do you know, I think you are right!! My moonlite focuser is en route (in Paris at the moment according to Fedex!) and I've got a couple of books coming too. I am really meaning to sit down and try to plan my sessions better. At the moment I just go from one whim to another, probably imaging it for less than a couple of hours. I must try harder!!

[AndyUK]

Hi Sara - I concur with Olly and Tony - I've had two nights on this to date and decided that I desperately need some more subs (here). However, as you know, I'm suffering from noise with the DSLR on 600s subs, so I'm stretching VERY carefully and intend taking LOADS of subs - Getting the detail in the the brown dust is a real devil though, especially when there's noise about...

[ollypenrice]

Here is a pic taken by a guest with his own TEC140, so F7, with a DSLR. Ten minute subs.

Olly

Deep Sky Astrophotography by Frans Kroon NGC7023

[3ggman]

This is where I am currently at with the Iris Nebula. Its 6hrs of data, 2hrs in 5min subs and 4hrs in 10min subs all at ISO400.

It was only in the last session (2hrs collected) that any real detail started to show up in processing but as Olly already stated and I think I will be doing the same, another 6hrs is needed to add to this.

This image here is a little bit over stretched.

[AndyUK]

Looking very good! I got a few hours on this too, but (like you) have decided that it probably needs another 10 odd hours.

My framing isn't quite the same as yours, but I'd be happy to let you have a copy of my subs/callibration files if you'd like them for a collaborative effort...?