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 Post subject: My first nebulae!
PostPosted: Mon Aug 09, 2010 4:13 pm 
Got them Sat. evening... the Lagoon & Triffid nebulae...
(Little left of center, bottom 1/3 line)
Image
35(!!) 10 sec. exposures @ ISO-200
About choked my poor laptop processing the stack in Iris - 12+ hours to do it.

To do it over, I'd probably kick it down to 5 sec. shots. I noticed that I got a bit of trailing at 10.

Floyd.


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 Post subject:
PostPosted: Mon Aug 09, 2010 4:34 pm 
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Joined: Mon Jan 18, 2010 3:52 pm
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Location: The Netherlands
Nice!
What lens/ scope did you use?

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 Post subject:
PostPosted: Tue Aug 10, 2010 12:39 am 
Ruben123-
Thanks! :)
It was taken with my Olympus E510. 50mm setting on the 150mm zoom kit lens, F/3.7 or F/4 (have to check the original EXIFs to be sure).
Edit: Just checked - it was set to F/5.

As I stated before, the next time that I do something like this, I'll probably do 5 sec. @ ISO-200 or go back to 10 sec. @ ISO-100, and set the F-stop 1 stop less than full-open (wh is F/3.7 on my lenses).

By the way...any suggestions would be welcome :)

Floyd.


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 Post subject:
PostPosted: Tue Aug 10, 2010 12:24 pm 
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Joined: Mon Jan 18, 2010 3:52 pm
Posts: 2175
Location: The Netherlands
Some suggestions:
Set iso to 800
Set the shutter to 30 sec and aperture wide open.
SHOOT RAW and take 10 pictures at least. Then, take 5 pictures with the cap on the lens with the same settings.
Download DeepSkyStacker and stack the photo's. I see you have IRIS, I dont understand that program, DSS is much simpler.
That's it!

O, before I forget to say: Have fun!

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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 Post subject:
PostPosted: Tue Aug 10, 2010 12:44 pm 
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Joined: Sun Feb 15, 2009 12:59 pm
Posts: 6009
Location: The Netherlands
I want to get started with astrophotography but the night skies aren't very clear here. I do have some processing power at my disposal (4x 3.6 GHz) so I can give the processing a shot if you want?

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 Post subject:
PostPosted: Tue Aug 10, 2010 1:29 pm 
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Joined: Mon Jan 18, 2010 3:52 pm
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Location: The Netherlands
Citruspers, I dont know if you already have read Gordon's tut, but I can say you (and others) this:
It's much more difficult than you may think. Just simple start with 30 sec and a very bright lens. Tracking nebulae, using a telescope, only start with that if you have some experiences with them.
The funniest and easiest thing to photograph is the Milkyway, point the camera to the south (there's the centre of it) and take many shots, stack them, and have fun :wink:

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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 Post subject:
PostPosted: Wed Aug 11, 2010 11:59 am 
@ Ruben123-
I'll give D.S.S. a look - anything has to be simpler than Iris :lol:.
I already do RAWs, after reading about Astrophotography on some other sites (as well as other posts here). There's just more that one can do with RAWs.
As to exposure times - anything over 5-10 secs. cause trails for me, owing to the lack of a tracking mount. My barndoor (or Scotch) mount is currently in the planning stages, but hopefully I can get it put together by the time Fall rolls around (generally better seeing around here).

A question regarding "stacking":
I know that I'm gaining quite a lot by doing so, but what effective shutter speed am I getting? I'd imagine that 35 10 sec. shots wouldn't quite add up to a 350 sec. exposure (due to loss in processing, etc.), but I'm curious about what it would be equivalent to.

Floyd.


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 Post subject:
PostPosted: Mon Aug 23, 2010 12:46 pm 
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Joined: Sat Oct 11, 2008 8:27 pm
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Location: Bristol, UK
Not a bad effort. It will take far more 'subs' to begin to bring out the nebulosity in more detail.

The key is subs, subs and more subs!!!! More subs allows an improved signal to noise ratio allowing more detail to stand out.

There shouldn't be anything stopping you adding more subs to the ones you already have, therefore over a period of time you can really bring out the detail.

To expand on what Ruben123 suggested the 5 pictures with the lens cap on allow DSS to assess where any hot pixels may exist and thus remove them from the final composite. The key is to take these 'darks' at the end of the session so the sensor it 'hot', its no good taken these at the beginning or at a different time.

HTH

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 Post subject:
PostPosted: Mon Aug 23, 2010 5:07 pm 
Digz-
Next time I go out, I'll probably go for 60+ lights, owing to the ease of stacking them with DSS (yes, it's a much simpler process - thanks, Ruben123!).
One thing I read on the DSS site - It mentioned using a large number (~30) of darks, flats, and offsets (I currently use 9-11 of each). I can see where it could help some, but is the quality gained worth the extra time and effort?

Floyd.


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 Post subject:
PostPosted: Mon Aug 23, 2010 5:18 pm 
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Location: Bristol, UK
Yes it is worth the time and effort.

Im no expert but I think the Flats and Bias frames can be taken at any time therefore, for example, you can take the flats and bias (and take a good sample) and store them in a convenient location for use in the future. Its only the darks which need to be taken at the time of shooting.

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 Post subject:
PostPosted: Mon Aug 23, 2010 5:41 pm 
That's what I've heard about the flats/offsets(bias) as well. The only things that have to be the same for them is ISO (bias and flats) and focal length (flats only). Since I use pretty much the same settings (ISO-100, 50mm), it shouldn't be hard to get them and store them away.

I'll give a go at ~50 of each (darks included, next time I go out), and see how that helps.

Thanks for the confirmation, Digz! :D

Floyd.


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 Post subject:
PostPosted: Mon Aug 23, 2010 6:04 pm 
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Joined: Sat Oct 11, 2008 8:27 pm
Posts: 404
Location: Bristol, UK
Ah yeah, I remember now.

It shouldn't be too difficult to get a set of bias for each ISO setting on your camera (then combine them into DSS for a master bias / flat). The flats will involve a little more setup, especially if using a scope but again the effort will be certainly worth it.

BTW its looking quite clear here at the moment but the wind is howling which looks like it might scupper my plans tonight. :cry: :cry:

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