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FORUMS Photo Sharing & Visual Enjoyment Astronomy & Celestial
Thread started 27 Oct 2010 (Wednesday) 15:45
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You don't need a telescope

 
Pagman
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Post has been edited 9 days ago by Pagman.
Nov 08, 2017 17:26 |  #2116

Another try from tonight - I incresed the exposre a bit pushing the Iso to 3200 and using my lens max ap f4 and still retained the 1 sec sh speed, I was aiming for Andomeda but to be honest even using the LV screen I did not know were to find it even with using Stellarium to get a basic guide, I tried using the brightest star facing East that was Capella and using that as a guide I moved the lens to the Right and upwards to what was roughly where I thought Andromeda might be.
I dont know if you are suppost to be able to see Andromeda through a tele camera lens, I couldn't see it but wondered if it would just need the stacking and processing to bring the gases and colors out.

Anyway here is what I got after stacking 5 shots together.

P.

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Pagman
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Nov 09, 2017 17:22 |  #2117

I had another go at Seven Sisters Pleiades using the following exposure - Iso 3200 x 10 and 6400 x10 = 20 sec, 1 sec and f4, I then stacked them in DSS.
But still not seeing the gas colors just the stars, I adjusted the sliders in LR5 increasing saturation etc, but alas this is the best I could get.

P.

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Tareq
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Nov 10, 2017 06:49 |  #2118

Maybe the thred is about no need for telescope to do astro photography, but why it should be? there are telescopes which are as expensive or even cheaper than lenses, so it shouldn't be an issue.

I did this with a cheap lens, as cheap as a kit lens maybe, i think even a kit lens is more expensive, the only thing that helped me a lot is the camera type and the mount, but the telescope wasn't something expensive to be honest.


IMAGE: https://scontent.ffjr1-2.fna.fbcdn.net/v/t1.0-9/23319197_10154737376766572_2776392991731445330_n.jpg?oh=5ebdd4161c8f63243978b52b00075457&oe=5A9A1D9F

Someone processed it for me, thanks to him.

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Pagman
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Nov 11, 2017 20:55 |  #2119

How can I extract more detil out of my deep space shots as in the one above of seven sisters, I thought I gave it a reasonable amount of exposure, I use faily good equipment and im in a quite good seeing location, so all the ingredients should be there.


P.


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MalVeauX
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Nov 11, 2017 21:17 |  #2120

Pagman wrote in post #18494323 (external link)
How can I extract more detil out of my deep space shots as in the one above of seven sisters, I thought I gave it a reasonable amount of exposure, I use faily good equipment and im in a quite good seeing location, so all the ingredients should be there.


P.

There is but one way to see the secrets of the celestial heavens, and that is with signal to noise ratio.

But first, you have to expose for the night sky first. I would suggest you aim for a histogram that shows a spike at 1/3rd of the histogram from the left, and no more left than 1/4th of the histogram. Then simply acquire lots of them over time of the same spot (this requires a tracker).

The images you've seen are not how they come out from an exposure. With enough signal to noise ratio, you should end up with a nearly dark image with nothing really to see. The details are feint. And with enough signal to noise ratio, you can then start stretching, pushing, pulling the histogram around to see the minute detail buried in the signal.

An easy way to do this is stacking exposures. Signal to noise ratio increases by the square root of the number of images you're stacking.

Read about this here:

http://www.clarkvision​.com ...s/image-stacking-methods/ (external link)

Get this concept, then learn to acquire your data differently with this in mind, and then learn to process it and you'll pluck all kinds of stuff out of the sky.

For processing, this tutorial alone will send you light years forward (literally), but only if you are acquiring appropriate amounts of data:

http://www.astronomers​doitinthedark.com/dslr​_llrgb_tutorial.php (external link)

If you are only willing to continue doing short, single exposures, you need to pick extremely bright objects to do that with (such as the milky way, M42, and planets).

+++++++++++++++

For reference, a very bright object such as M42, can be acquired in a single exposure because it's just so big and bright. But, to get the detail around it, and see that the sky is rarely black and actually just lots of feint dust lanes, you have to have high signal to noise ratio. You can get a lot of it by having long exposures and lots of them. Again, M42 is bright, so you can practice on it easily night after night in terms of acquiring data and processing it. You can even capture data SEVERAL nights in a row, and eventually stack ALL of it to get high signal to noise ratio. Here's the amount of signal I was able to collect in 90 minutes (180 seconds x 30 exposures) with a Canon T4i at F6 and ISO 800 with a histogram around 1/3rd from the left:

IMAGE: https://farm1.staticflickr.com/629/33104332301_b5fc062350_b.jpg
[IMAGE'S LINK: https://flic.kr/p/Srjm​E2] (external link)M42_02282017 (external link) by Martin Wise (external link), on Flickr

Very best,

My Flickr (external link) :: My Astrobin (external link)

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Pagman
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Nov 11, 2017 21:33 |  #2121

MalVeauX wrote in post #18494332 (external link)
There is but one way to see the secrets of the celestial heavens, and that is with signal to noise ratio.

But first, you have to expose for the night sky first. I would suggest you aim for a histogram that shows a spike at 1/3rd of the histogram from the left, and no more left than 1/4th of the histogram. Then simply acquire lots of them over time of the same spot (this requires a tracker).

The images you've seen are not how they come out from an exposure. With enough signal to noise ratio, you should end up with a nearly dark image with nothing really to see. The details are feint. And with enough signal to noise ratio, you can then start stretching, pushing, pulling the histogram around to see the minute detail buried in the signal.

An easy way to do this is stacking exposures. Signal to noise ratio increases by the square root of the number of images you're stacking.

Read about this here:

http://www.clarkvision​.com ...s/image-stacking-methods/ (external link)

Get this concept, then learn to acquire your data differently with this in mind, and then learn to process it and you'll pluck all kinds of stuff out of the sky.

For processing, this tutorial alone will send you light years forward (literally), but only if you are acquiring appropriate amounts of data:

http://www.astronomers​doitinthedark.com/dslr​_llrgb_tutorial.php (external link)

If you are only willing to continue doing short, single exposures, you need to pick extremely bright objects to do that with (such as the milky way, M42, and planets).

+++++++++++++++

For reference, a very bright object such as M42, can be acquired in a single exposure because it's just so big and bright. But, to get the detail around it, and see that the sky is rarely black and actually just lots of feint dust lanes, you have to have high signal to noise ratio. You can get a lot of it by having long exposures and lots of them. Again, M42 is bright, so you can practice on it easily night after night in terms of acquiring data and processing it. You can even capture data SEVERAL nights in a row, and eventually stack ALL of it to get high signal to noise ratio. Here's the amount of signal I was able to collect in 90 minutes (180 seconds x 30 exposures) with a Canon T4i at F6 and ISO 800 with a histogram around 1/3rd from the left:

QUOTED IMAGE
[IMAGE'S LINK: https://flic.kr/p/Srjm​E2] (external link)M42_02282017 (external link) by Martin Wise (external link), on Flickr

Very best,

Hiya martin,

The last shot I showed was the result of 22 stacked frames in DSS they were all 1sec shots from my 300mm on the d7100, all at f4 and split between Iso 1600 and 3200, then after leting DSS do its work I opend the Tiff up in LR5 and moved the sliders around, but nothing was going to show the colourful gases that seven sisters has.

P.


Nikon D7100, Nikkor 300 f4 IF ED :-)

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MalVeauX
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Post has been last edited 6 days ago by MalVeauX. 4 edits done in total.
Nov 11, 2017 21:45 |  #2122

Pagman wrote in post #18494339 (external link)
Hiya martin,

The last shot I showed was the result of 22 stacked frames in DSS they were all 1sec shots from my 300mm on the d7100, all at f4 and split between Iso 1600 and 3200, then after leting DSS do its work I opend the Tiff up in LR5 and moved the sliders around, but nothing was going to show the colourful gases that seven sisters has.

P.

You had 22 seconds of data. While you had 22 exposures, they had such limited exposure time that the signal gained from stacking remains minimal. You'd probably have gotten more signal from a single 22 second exposure (I realize you can't do that with a telephoto lens here without a tracker). M45 is bright, but the nebulosity is feint and to see it, you will need a lot more data. A lot more. I would suggest you actually use a much wider lens, something that will allow 20~25 second exposures without star trails, and practice getting exposure correct and allow you to get a ton more exposures over the night to stack so that your data is measured in several minutes, and not just a few seconds. You'll get a lot more data that is usable that way.

Also, your 22 seconds of data, was probably very under-exposed. But I wouldn't know for sure unless I saw the histogram of a single exposure. But you really need to make sure your exposures are correct (the sky is not black) before committing time to lots of exposures.

+++++++++++++++

I realize you're not going to buy a tracker, so, you will always be limited to what you can do with exposure time. So, the alternative is to up the numbers in your favor that you can effect, without buying something. And that's number of exposures to contribute to the stack.

You could get away with 1 second exposures, but you would need a TON of exposures to stack to make it meaningful (literally on the order of 1 second x 2,000 + images to get about 33 minutes of data, or double that for an hour). That's the kind of data acquisition it takes, to really get the details out, especially with short exposures. The only way to get away with few exposures, is with really long exposures.

So, to do that, you may want to get a few thousand 1 second exposures, and do it over a few nights so that your image count is as high as you can tolerate without going mad, and you might just get enough signal to noise to extract significant details.

+++++++++++++++

Also, to process, you will not be using sliders. You need a pixel editor because you will need to learn how to use Curves & Levels primarily. Refer to the tutorial link I posted with the video. It's an hour, but well worth it (and save it). I use those techniques to extract detail from high signal images.

I took 31 minutes of data time captured in 31 exposures x 60 seconds each, at F7.5, ISO 1600 with a Canon T4i. Because of the signal to noise ratio from the longer exposures (even though I only stacked 31 images), I was able to get the feint nebulosity of M45:

IMAGE: https://farm1.staticflickr.com/256/31531918780_7c1d5211e3_b.jpg
[IMAGE'S LINK: https://flic.kr/p/Q3nj​U5] (external link)Pleiades_12262016 (external link) by Martin Wise (external link), on Flickr

Very best,

My Flickr (external link) :: My Astrobin (external link)

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Pagman
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Nov 11, 2017 22:02 as a reply to MalVeauX's post |  #2123

I have realised that I took three days worth of of shots amounting to about 45 frames, as we speak I sorted then and just putting them through DSS, hopefully 40 secs will be better than 22.

P.


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Pagman
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Nov 11, 2017 22:04 |  #2124

I have PS2 also for editting will taht help? and whats the best way to work with DSO objects in PS2?

P.


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MalVeauX
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Post has been last edited 6 days ago by MalVeauX. 2 edits done in total.
Nov 11, 2017 22:06 |  #2125

Pagman wrote in post #18494355 (external link)
I have realised that I took three days worth of of shots amounting to about 45 frames, as we speak I sorted then and just putting them through DSS, hopefully 40 secs will be better than 22.

P.

40 x 1 second exposures will give you approximately 75% more signal than the 22 x 1 second exposures provided. It will help. But you really need a LOT more than that. Again, at 1 second, I would push towards getting several hundred, if not a thousand, if you really want to extract nebulosity.

Also, you need to expose the histogram appropriately. I would suggest you try it with the data spike at 1/3rd of the histogram from the left, or close to it. Can you show a histogram of one of your exposures without editing?

Very best,


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Pagman
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Post has been edited 6 days ago by Pagman.
Nov 11, 2017 22:09 |  #2126

How can i show a screen shot of the histogram?

Would adding possitive EC help.

P.


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MalVeauX
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Nov 11, 2017 22:11 |  #2127

Pagman wrote in post #18494360 (external link)
How can i show a screen shot of the histogram?

P.

Open one of your basic unedited exposures that are involved in the stack (not the results of the stack) in any RAW or image editor and open levels or histogram and screen shot it.

Very best,


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Pagman
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Post has been edited 6 days ago by Pagman.
Nov 11, 2017 22:13 |  #2128

MalVeauX wrote in post #18494361 (external link)
Open one of your basic unedited exposures that are involved in the stack (not the results of the stack) in any RAW or image editor and open levels or histogram and screen shot it.

Very best,


Screen shot - how? just cant remember how to do it.


P.


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MalVeauX
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Post has been edited 6 days ago by MalVeauX.
Nov 11, 2017 22:16 |  #2129

Pagman wrote in post #18494363 (external link)
Screen shot - how? just cant remember how to do it.

P.

Press "Prt Sc" on your keyboard (Print Screen), it will be near scroll lock, home, insert, etc. And paste it into a blank image and save it. You can use MS Paint even. It's that simple.

Very best,


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Pagman
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Nov 11, 2017 22:24 |  #2130

MalVeauX wrote in post #18494364 (external link)
Press "Prt Sc" on your keyboard (Print Screen), it will be near scroll lock, home, insert, etc. And paste it into a blank image and save it. You can use MS Paint even. It's that simple.

Very best,

its a laptop on top row of small keys there is a key next on the right from f11 called PRTSC SYSRQ but it does nothing, cant find it anywhere else.

P.


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