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MikeODay

Alnitak and the Flame and Horsehead Nebulae

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Alnitak and the Flame and Horsehead Nebulae ( by Mike O'Day - https://500px.com/mikeoday )

I struggled to try to significantly reduce the quite apparent noise without losing too much detail in the clouds. In the end I decided to keep the detail ( and the noise ).

Details:

Orion's Belt - centred on "Alnitak".

A 1.7 magnitute tripple star at one end of the belt.

Includes the Flame Nebula (NGC2024) and IC434 which contains the Horsehead Nebula.

RA 16h 41m 42s, Dec -48deg 48' 46".

Approx. 3800 light years away.

Skywatcher Quattro 10" f4 Newtonian.

Skywatcher AZ Eq6 GT Mount (on concrete pier).

Orion 80mm f5 guide scope and auto guider - PHD2.

Baader MPCC Mark 3 Coma Corrector, no filter.

Nikon D5300 (unmodified).

Field of view (deg) ~ 1.35 x 0.90.

300 subs in total.

63 x 10 sec ISO100.

38 x 20 sec ISO200 .

21 X 20 sec ISO800.

165 x 30 sec ISO800.

13 x 60 sec ISO800.

(14bit NEF, Long Exp. NR on).

Pixinsight and photoshop.

18th December 2015.

source:

http://photo.net/photos/MikeODay

https://500px.com/mikeoday

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Excellent shots, that area around Alnitak is one of my favorites, the Pleiades as well. I see the reflection nebulosity there at times, very beautiful.

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Noise or no noise, still a great looking image... especially for a unmdded DSLR.

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Noise where, I think this is stunning photo which shows the whole area very well indeed, it is also very useful to me as I am on a quest to find this difficult IC 434 and now at least I know I am in the right area, great shot.

Alan

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Thank you guys for your very kind words - they are much appreciated.

Cheers

Mike

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I think it looks awesome! Struggling with this one myself at the moment.

Good call on keeping the noise with the detail, I think that looks a lot better than too heavy noise reduction.

Two questions:

1. Why long exp. NR on? The stacking should handle the noise, especially if you use dithering with PHD2.

2. Why no longer subs than 60 secs since you are guiding? LP? Given your result with these short subs I think you will have a killer image with some more time on it. At least do 50-100 of those 60 sec. ones.

Again, great photo!

Sent from my phone using Tapatalk

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I think it looks awesome! Struggling with this one myself at the moment.

Good call on keeping the noise with the detail, I think that looks a lot better than too heavy noise reduction.

Two questions:

1. Why long exp. NR on? The stacking should handle the noise, especially if you use dithering with PHD2.

I presume that by using it and applying a custom dark to each image, the problem of matching a dark to all those different exposure times and ISO ratings is avoided?

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I presume that by using it and applying a custom dark to each image, the problem of matching a dark to all those different exposure times and ISO ratings is avoided?

Yes, but since it is done when taking the photos it takes twice the time! At least here in Sweden clear nights are very rare so imaging time is precious [emoji4]

Darks can be a task for cloudy nights [emoji4]

Sent from my phone using Tapatalk

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I think it looks awesome! Struggling with this one myself at the moment.

Good call on keeping the noise with the detail, I think that looks a lot better than too heavy noise reduction.

Two questions:

1. Why long exp. NR on? The stacking should handle the noise, especially if you use dithering with PHD2.

2. Why no longer subs than 60 secs since you are guiding? LP? Given your result with these short subs I think you will have a killer image with some more time on it. At least do 50-100 of those 60 sec. ones.

Again, great photo!

Sent from my phone using Tapatalk

Thanks Martin.

1. I had difficulty previously when using 'dark';I ended up with small streaks that looked like rain. I understand that dithering might solve this but I cannot get it to work. Anyway, my images greatly improved when I started using in camera dark subtraction.

2. When not using a filter, 30 sec subs @ 800iso with my f4 Newtonian produce a histogram that peaks about 20% from the left and leaves clear gap of about 10% at the far left. I'm still experimenting but at the moment I am not sure I gain much by increasing the exposure any more given that the skies have not been too dark lately ( ie. high humidity raising LP ).

Also, I lose about 10% of my 30 sec subs due to tracking errors, aircraft lights, satellites, meteors, etc. Longer subs would mean fewer good subs.

With regard to 'more time'; I'm still confused about that. Intuitively I want to agree but I read somewhere that the sub length is not important. The SNR is the same from say 50x60sec and 100x30sec - that is, it is only the total time that matters. Anyway, still experimenting and judging by results.

All the best

Mike

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Firefowx won't let me look - Flickr's security certificate has expired...

Here is a direct upload - quality is probably poor though; the uploader is reporting a file size that is 1/10 of that of the original (I presume the system is recompressing the JPEG with quality set to "poor").

Edit: yep, I was right; it looks terrible loaded directly...

post-36360-0-50241700-1450610076_thumb.j

Edited by mike005
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I presume that by using it and applying a custom dark to each image, the problem of matching a dark to all those different exposure times and ISO ratings is avoided?

Yes, but since it is done when taking the photos it takes twice the time! At least here in Sweden clear nights are very rare so imaging time is precious [emoji4]

Darks can be a task for cloudy nights [emoji4]

Sent from my phone using Tapatalk

For me it comes down to the quality of the final result - in camera dark frame subtraction seems to produces better results for me than using "darks". Could it be a temperature related factor? In camera processing uses a dark frame taken under the exact same conditions as the original, whereas post processing using a library of darks is at best only an approximation of the actual conditions. On the other hand I could be talking rubbish :). After all I have only been at this for a little over a year and I still have a great deal to learn.

Cheers

Mike

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With regard to 'more time'; I'm still confused about that. Intuitively I want to agree but I read somewhere that the sub length is not important. The SNR is the same from say 50x60sec and 100x30sec - that is, it is only the total time that matters. Anyway, still experimenting and judging by results.

With more time I meant not only longer subs but at least more of your longer ones. If you have a lot of subs and stack using sigma rejection all airplane trails etc will dissappear.

Regarding the total integration time being the only thing that matters it might be true to a degree but it's not going to work if the subs are too short. I've tried with 300 1-second subs and a single 60-second sub blows them out of the water [emoji4]

Sent from my phone using Tapatalk

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With more time I meant not only longer subs but at least more of your longer ones. If you have a lot of subs and stack using sigma rejection all airplane trails etc will dissappear.

Regarding the total integration time being the only thing that matters it might be true to a degree but it's not going to work if the subs are too short. I've tried with 300 1-second subs and a single 60-second sub blows them out of the water [emoji4]

Sent from my phone using Tapatalk

Thanks Martin, I'm stuck with the moon now for the next 10 days or so but I'll have a go at trying to grab some more longer subs when it departs.

By the way, do you have a rule of thumb for setting one shot DSLR exposure in light polluted skies? I've been aiming for a LP histogram peak of no more than 30% from the left (that would be about 60 sec @ iso 800 with the LP we have been experiencing recently due to high humidity).

Cheers

Mike

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Although my skies really aren't that light pollluted. I can do 10 minutes at ISO800 and f/4 on a good day [emoji4]

Sent from my phone using Tapatalk

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Thanks Martin, I will try pushing it that far and see how it goes.

Cheers

Mike

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