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Foto Fair Post your photos for friendly, non-critical feedback. This is the place to show pictures if you aren't yet ready for full-blooded critique, or simply want to share an interesting picture with other e-group visitors.

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  #121  
Old 29th May 2018
MikeOxon MikeOxon is offline
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Re: Communal Night-Sky Photography Thread

That's a good step upwards! I'd be interested to know more about the exposure details and how you attached the camera to the scope. I assume you 'dodged' the areas around the moons, to make them more prominent, but it rather distracts from the main image
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  #122  
Old 29th May 2018
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Re: Communal Night-Sky Photography Thread

Yes I did us PS to increase the exposure on the 3 moons which were very feint. They were distorted as well due to the stacking. It was a very warm night last night and there was some atmospheric disturbance due to the heat haze. It was also a full moon. To get even more detail it needs to be clear and crisp with no moon. When conditions like that happen again I will have another go. At least its better than my 1st attempt which is a bit embarrassing.

I terms of exposure I set the camera in manual. ISO 200, then used Olympus capture to take a series of 12 shots at 1/100th sec each. The scope has a fixed Focal length of 550mm and a fixed aperture of 100mm. So getting the correct exposure is a bit of trial and error your only variable is shutter speed. Live view on Olympus Capture is a great benefit and helped me choose the right speed 1/100th sec
Also the scope was on a sturdy equatorial mount that was tracking at sidereal rate.

You can attach the camera to the scope in two ways.
1. Get a M4/3 to T-Adapter and a T-Adapter to 1.25" adapter and simply plug in to the standard 1.25 mounting hole. T-Adapters are a common standard used for astrophotography. They work but can be prone to wobbles due to the weight of the camera hanging on the end. Also for wide field shots the stars end up being stretched around the perimeter of the frame when using a refractor scope.

2. Get a field flattener for your specific refractor scope to solve the star stretching. The field flattener creates a perfectly flat image field at an exact distance from the flange face, in my case its 63mm, but all scopes are different. The challenge is to use adapters / extensions to get the camera sensor exactly 63mm from the flange. This took a bit of research but I got there in the end using this combination.

The flattener for my scope has a M48 thread. I used a M48 to Nikon F-mount adapter which screws on and then a Nikon-F to M4/3 adapter and finally the Em1mk2. The thickness of this combination happens to work out at 63mm.

This is a much more rigid solution and ensures the field at the sensor is perfectly flat.
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Last edited by wornish; 29th May 2018 at 04:05 PM. Reason: reprocessed original to improve moons
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  #123  
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Re: Communal Night-Sky Photography Thread

Another appeal to any mods that look in. Could you make this thread sticky, please. It would be good to collect the various night-sky pics scattered in different threads here.

I've been having a go at photographing Saturn, which is low in the Southern sky, at around 10:30 pm at present. Viewing conditions are far from ideal, with the sky still quite light and, from my house, there are street lights near the line of sight as well.

I used my E-M1 Mk ii with Pan/Leica 100-400 at the 400 mm end, wide open (f/6.4) The camera was tripod mounted with a remote release. I also used an EE-1 dot-sight, which makes it very easy to locate the subject quickly.

I viewed the subject on the rear screen (tilted to a convenient angle) and, with 14X magnification, set the focus manually.

I shot three bursts on high speed continuous, the first with mechanical shutter and the others electronic. 95 images in total

Examining the results showed there was considerable variation in sharpness between images, presumably due to atmospheric turbulence, although the mechanical shutter images seemed a little more variable.

I selected the single 'best looking' raw image for processing by means of the Raw Therapee converter, cropping and using LR de-convolution to minimise blurring. I also adjusted brightness/contrast, to separate the subject from the background.

My conclusion is that the image is pixel-limited, in terms of detail. The lens itself produced an excellent result, with negligible colour fringing, but there are simply not enough pixels across the disk to show any real detail.

I intend to try further processing on the batches of images but do not expect to change things much, except perhaps for a little extra smoothness overall.


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  #124  
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Re: Communal Night-Sky Photography Thread

Quote:
Originally Posted by MikeOxon View Post
Another appeal to any mods that look in. Could you make this thread sticky, please. It would be good to collect the various night-sky pics scattered in different threads here.

I've been having a go at photographing Saturn, which is low in the Southern sky, at around 10:30 pm at present. Viewing conditions are far from ideal, with the sky still quite light and, from my house, there are street lights near the line of sight as well.

I used my E-M1 Mk ii with Pan/Leica 100-400 at the 400 mm end, wide open (f/6.4) The camera was tripod mounted with a remote release. I also used an EE-1 dot-sight, which makes it very easy to locate the subject quickly.

I viewed the subject on the rear screen (tilted to a convenient angle) and, with 14X magnification, set the focus manually.

I shot three bursts on high speed continuous, the first with mechanical shutter and the others electronic. 95 images in total

Examining the results showed there was considerable variation in sharpness between images, presumably due to atmospheric turbulence, although the mechanical shutter images seemed a little more variable.

I selected the single 'best looking' raw image for processing by means of the Raw Therapee converter, cropping and using LR de-convolution to minimise blurring. I also adjusted brightness/contrast, to separate the subject from the background.

My conclusion is that the image is pixel-limited, in terms of detail. The lens itself produced an excellent result, with negligible colour fringing, but there are simply not enough pixels across the disk to show any real detail.

I intend to try further processing on the batches of images but do not expect to change things much, except perhaps for a little extra smoothness overall.
Great image. You are absolutely right it is pixel limited. Even with a 2000mm lens you will have the same issue. Its simple maths. To get the best images of planets people switch to using video where they can easily capture say 1000 or more frames and then use software to select the best ones and stack them. Using this approach with a small sensor like a webcam makes a huge difference. M4/3 sensors are just too big unfortunately, and its even worse for Full frame.
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  #125  
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Re: Communal Night-Sky Photography Thread

For anyone interested in night sky photography, I strongly recommend Roger N Clark's website http://www.clarkvision.com/


See, in particular, his article about the characteristics of digital cameras : http://www.clarkvision.com/articles/...o-photography/


Apart from lots of inspiring photos, his site is a mine of technical information. One point he makes is that: "Contrary to popular internet belief, larger sensor cameras have little to do with sensitivity. We often read on the internet that full frame cameras are more sensitive and that they are better at low light photography. This is a misunderstanding of the light gathering of lens and sensor. A larger format ENABLES one to use a larger lens. It is the lens that collects the light; the sensor is just a bucket to collect the light delivered by the lens"


This is why webcams are often used with telescopes for planet photography. If the image does not cover the sensor area, you are wasting most of the pixels.
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Last edited by MikeOxon; 6 Days Ago at 11:57 AM. Reason: additional information
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