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Astro Projects

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Preparing a talk on Astro-photography

Gina

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I've offered to give a talk with pictures to our local social group and thought a Blog on here would be a good place to prepare and assemble it.  Also, I would welcome any comments and suggestions.  I have a few ideas and will see how it progresses.  I will probably take me several days to get my initial ideas sorted out.

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Gina

Posted (edited)

Apart from my own DSO images I may also use some from the web such as Hubble ones though of course, I shall make it clear that these aren't mine.  I'm also thinking of describing various types of amateur telescopes and using camera lenses for widefield.  Tripods and piers should also get a mention I guess.  Then there's mounts, observatories, cameras, filters, etc.  I guess a none too detailled explanation of image processing should also be included. 

I have to bear in mind that this is a general audience probably with little knowledge of physics or maths so all explanations have to be very basic. 

Edited by Gina

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I regularly do talks on Astrophotography, and do it with Powerpoint.  I normally start at the beginning and say what kit is needed and why, and what happens if you don't use an Equatorial mount etc.

Then I have a prepared number of stacked images showing the improvement the more that are stacked. starting with a single sub, then 2, 4,8, 16 stacked, and then show the whole image 50% single sub and 50% 16 subs stacked showing the huge difference.  That always brings some Oohs and Aahs.

An example of an image processed without flats, then the stretched flat for that image showing the dust and vignetting, and then the image with flats applied.  More oohs and aahs.

I show how to focus with a Bahtinov mask, and topwards the end of the talk I show a few of my images and how long they took in exposure.

HTH

Carole 

Edited by carastro
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Thanks Carole, that's very interesting and gives me more food for thought :thumbsup:

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@carastro  Do you give your talks to astronomers or the general public, Carole.  I ask because my audience will be non-astronomers so doesn't want to be too technical.

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I wouldn't make it appear only possible with a motorised eq mount but also include a static milkyway and landscape shot.

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I plan to include some all sky camera images and probably time-lapse video.

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Do you give your talks to astronomers or the general public, Carole.  I ask because my audience will be non-astronomers so doesn't want to be too technical.

Generally photographic groups, and U3A and similar. 

Carole 

Edited by carastro
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I wouldn't make it appear only possible with a motorised eq mount

Yes I do mention simple ways of imaging too.

Carole 

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Just an idea Gina but a few mentions from history could go down well. Here's a short list of a few " Names " that might interest you. Once you have those names you can look round for their images.

http://www.catchersofthelight.com/catchers/archive#cat-History-of-Astrophotography

It's interesting to know how far we've come and that over a hundred years ago they had roughly the same problems we do with this photography lark !

Dave.

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A personal thing that occurs to me when I see a "slideshow" talk of DSOs etc.,
by an expert imager is to wonder about the *actual size* of these objects? ?

Can they be seen by casual observer? Can Amateur scopes SEE this thing?
I began my "Video Astronomy" talks with a discussion of *magnitudes*.  A
basic intro to the idea of Logarithmic scales... The visual magnitude limit.
The (rather positive) ability of technology to see things in the real world? ?

They might end up a tad disappointed in the long run, but that's science! ?

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I've also done this sort of thing to an audience of non-experts.  I tend to cover the broad principle of correcting for the Earth's rotation which leads nicely on to guiding (nothing too technical, just an explanation that you point at a star you're not imaging and movements of that star are used to correct for the movement of your target).

Then I've done a bit on the principle of digital stacking - again in simple terms pretty much as Carole suggests.

I have done a bit on narrowband imaging and I think have just about got away with explaining the physical principles behind emission nebulae with the help of a diagram or two and how that translates.

I agree that people always seem interested in how far away things are, and of course that gives the chance to say that when the light hitting my camera left this object then dinosaurs were roaming the Earth (or whatever)...

Have fun with it! 

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Some Visual vs AP examples! :)


As I started only 2.5 years ago,

I do clearly remember My Main Question was, - What actually I would be able to See from London using 10"DOB :)

 

 

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Unfortunately I'm not an observer so can really only cover imaging but that will be the title of the talk viz. "Astronomy Photography".  OTOH, I can certainly touch on observing and how you need a very much bigger telescope to see anything directly.

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carastro

Posted (edited)

I have just done another talk on Monday to a huge U3A audience (over 200 people).  I was told a lot of the photographic group had turned up too.

I did my usual talk which included what, and how to create images.  I think one or two people dropped off to sleep, or glazed over, but the majority seemed to find it very interesting.  

At the end I took a stacked image (old Horsehead DSLR image) and live processed it.  

I got some very interesting questions afterwards, and one person turned out to have done a bit of AP himself.  

I got another booking on the back of it for a Probus group.

If you would be interested I might have a PDF copy of my talk somewhere I could e mail to you for ideas, I sent it to some-one else asking a similar question, assuming I can find it.

Carole 

Edited by carastro
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I would indeed be very interested Carole, thank you very much.

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Ah, missed this reply, and just messaged you.

Will need your e Mail address Gina, can you PM it to me.

Carole 

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Gina

Posted (edited)

Introduction.

This talk is about Astronomy Photography or more commonly called astro-photography or astro imaging but before going into the main subject I shall describe how I got into it and also a few general principles that govern the whole process.

I have been interested in astronomy from a young age having been introduced to it by my grandfather.  Over the years I have looked at the night sky with binoculars and indeed, this is a good way to start observing.  Most of my life I haven't had very good night skies for astronomy due to light pollution but when we moved here, away from towns and cities the night sky appeared awesome with thousands of stars visible.  (All sky camera image of night sky with the Milky Way.)  With such skies I felt I had to take more advantage of them than I had to date and bought a relatively cheap telescope from Amazon.  (Picture of the Celestron whatever it's called.)

I used this to get a more detailed view of the night sky using various eyepieces that allowed various angles of view.  But having been interested and practicing photography since I was a child with a Box Brownie. it was inevitable that I would want to go on to astro-photography.  I started with a webcam but moved on through an ordinary DSLR as used for standard photography to much better and more expensive dedicated astro cameras.

After a few months I discovered a very active astronomy forum online called Stargazers Lounge, from which I have learnt a lot.

Edited by Gina

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The Stars, Planets, Moon and Sun.

Everyone knows that the sun and moon appear to move through the sky by day or night.  In the beginning it was believed that the Earth was the centre of the universe and that sun, moon and all the stars rotated about the Earth.  With the exception of Flat Earthers, it's now known that the earth isn't the centre of the universe and nor even is the sun.  Most people now know that the reason everything in the sky appears to traverse the sky from east to west is that it is the Earth that is rotating.  This rotation is a major concern when trying to photograph the night sky or indeed, even observing.

If you take a photo of the sky with a long enough exposure to show the stars you will get start trails (photo of star trails).  Now whilst this gives an interesting picture in itself, this is now what we really want.  Even with observing there is a problem as a telescope has to be moved to follow the stars. 

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Gina

Posted (edited)

Photography Terms.

Before going on to astro-photography I think I should explain a few photographic terms for those of you who don't take photos.  Those who do please bear with me.

Firstly, image or photo are used interchangeably.

(Diagram of a camera.)  The main thing you will notice about a camera are that there are two parts - the lens and the body.  At the back of the body is what is called an image sensor.  It used to be film but nowadays it's an array of light sensitive elements called pixels of which there are thousands.  Light coming in through the lens is focused onto the sensor to form an image or picture.  The image collected by the sensor is converted to data which is then stored on a card.  The card may be plugged into a computer to see the picture using software.

Within the lens are two mechanical components that need mentioning.  One is the shutter which determines how for long light is allowed through to the image sensor and the other is called aperture, which determines how much light gets through.  The aperture is often called the iris, like the iris in the eye and preforms the same function.  The time the shutter is open is called the exposure.

In daytime photography the exposure is very short as the light is very bright also the aperture may also reduced to avoid overloading the image sensor.  When taking photos at night the light is very much less and a longer exposure and a wider aperture is used to collect enough light to form a photo.  Unlike a camera that is generally used during daylight, a telescope does not have an aperture as we always want to catch as much as the available light as possible.

Edited by Gina

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Hi Gina,

I did a lot of professional public speaking in my career and have couple of thoughts based on what you have said so far.

 Given this audience is not astro people - I think I would first engage their interest by first talking about something they will understand - terrestrial photography. Hence, describe how a DSLR camera works first. Hence; reverse thes two slides

Explain how terrestrial images are typically done with short exposures and how that works fine. Then explain that longer exposures and adjustment to ISO are necessary to capture enough light for evening pictures. Then it is natural progression to quickly explain  how more extreme long exposures (or stacked long integration time short exposures) are needed to do astrophotograpy .  Then mention how daytime images can get blurred if you are trying to capture an image of a fast moving car. Then, only after people have grasped these essential camera basics, explain the rotation of the Earth and the impact that has on long term exposures and the need for tracking and or guiding.

If you offer this same information the other way round, I don't think many in a broad audience will adequately make the link between exposures, earth's rotation and 'star trails'. However, if you reverse this, it becomes a far more logical progression of information. Just my two-pence worth....

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Gina

Posted (edited)

Interesting thought - thank you.  Yes, explaining daytime photography then going on to astronomical photography is definitely better.

Edited by Gina

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Hello Gina

I did a presentation to a Scottish Photographic Society a couple of weeks ago - Powerpoint based. Its attached - feel free to bin it, rip it shreds, do anything you want with it. I dont get prissy about copyright of my images etc - feel free to use any images you might want etc etc. All the astroimages are mine and the none astro ones are all copyright free.

 

Astro Imaging presentation.pptx

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