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Author Topic: Planetary imaging with Nikon 1 ?  (Read 933 times)

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Offline TeeJay

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Planetary imaging with Nikon 1 ?
« on: 09:58:40, 09 November, 2016 »
Hi guys, I was wondering if it might be viable to use my Nikon 1 J5 to capture video frames for planetary imaging
I currently have a Celestron C5, Skywatcher Star Adventurer and the adaptors required to atatch my Nikon cameras including my J5 which is a CX format (1 inch) sensor, I also have the Celestron 0.63 reducer.
The camera has the ability to record video in the following rates/modes (as well as 4k at 24fps and normal HD modes)...

 1280 x 720/120 fps.
 800 x 296/400 fps.
 400 x 144/1200 fps

It internally creates files which play back at 29.97fps giving slow motion but as long as all the frames are there that doesn't matter

I'm guessing that for most planets with my scope the 800x296 would cover it ? or maybe that's too small and I'd need 1280x720 (shame there's no 4:3 ratio in the high speed modes)

Although there is another potential trick the camera has and that is the ability to record full resolution (20.8mp) images at 60fps though the buffer can only take 20 images so 1/3rd second bursts is all it can do at that rate, it can also do 20fps/10fps, obviously it will only be able to acheive 60fps if the shutter speed is at least as fast as that so dim objects would not work

I don't want to invest in dedicated CCD cams etc, I don't have a laptop either

Any thoughts, suggestion or tips ?

Offline ChrisLX200

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Re: Planetary imaging with Nikon 1 ?
« Reply #1 on: 14:46:23, 09 November, 2016 »
No-one is going to tell you that it can't be done or, given your camera's ability to use a crop video frame, that you shouldn't try :-)  I would certainly give it a go. You will need to post-process though so I assume you have a desktop PC to hand for that. AutoStakert is a good program to use for stacking the video frames. I don't know where you reside but here in the UK the major planets are going to be poorly placed for us over the next few years, always being low and near the horizon.

ChrisH
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Offline chris.bailey

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Re: Planetary imaging with Nikon 1 ?
« Reply #2 on: 15:39:50, 09 November, 2016 »
As Chris says, give it a try!

You certainly will not want the focal reducer, though a Barlow would useful, all of the planets will be pretty small at a focal length of 1250, 2500 with a decent Barlow would be better.

800x296 would be a good starting point.

You face two difficulties, the first is finding them! At 2.5m getting them in the field of view is not without difficulty. The second and bigger issue is, as Chris says, they are very low in the sky and transiting early afternoon so by the time it gets dark, they are pretty much on the horizon if not below. Jupiter is perhaps the best bet as it rises very early in the morning so you might be able to catch it just before dawn.

Chris
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Offline Einari

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Re: Planetary imaging with Nikon 1 ?
« Reply #3 on: 16:40:36, 09 November, 2016 »
Adding to what others have said I'd like introduce another problem (or a thing to do).
Don't know the video format what Nikon makes but it might need conversion, and imo PIPP is the best tool to do the job.
Tapio

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Offline TeeJay

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Re: Planetary imaging with Nikon 1 ?
« Reply #4 on: 17:46:32, 09 November, 2016 »
Thanks guys
Yes I have a desktop PC and am familiar enough with Sony Vegas to be able to convert to AVI or there are many video convertors out there for free
Damned shame about the planets at the moment though, I'm not afraid to get up or travel to dark sky areas though so maybe Jupiter could be a possibility, I did phot Jupiter before just with two shots of my camera and 300mm lens, one for Jupiter the other for it's moons, the camera's sensor means it has a 2.7x crop factor compared to a full frame DSLR so in 35mm terms for example a 1250mm lens is in effect 3375mm, I can fill the frame with the moon with the 0.63 reducer fitted

Offline chris.bailey

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Re: Planetary imaging with Nikon 1 ?
« Reply #5 on: 18:37:40, 09 November, 2016 »
TeeJay

Forget the crop lens scenario for astro photography. A 1250 focal length is always a 1250 focal length, a bigger sensor just lets you see a bigger area at that focal length but the scale will be the same provided the pixel size is the same.

Chris
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Offline TeeJay

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Re: Planetary imaging with Nikon 1 ?
« Reply #6 on: 19:41:06, 09 November, 2016 »
The scale won't be and isn't the same, the pixel density is greater, i.e. it collects the same amount of light from a smaller area than a full frame or APS-C sensor with the same number of pixels (20.8mb in this case) so effectively it gives a higher maginification ratio on any given lens or optic than a 35mm or APS-C camera, this is tried and tested on other photographic lenses for example my 240-600mm f/5.6 lens when mounted to my Nikon J5 gives the equivalent field of view of a 648-1620mm f.5.6, the only real downside to a smaller sensor with higher density is extra noise to deal with.

Offline chris.bailey

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Re: Planetary imaging with Nikon 1 ?
« Reply #7 on: 22:30:18, 09 November, 2016 »
Mmmm fair dos. I'm not going to argue the point, it comes up here every so often from someone coming from camera lenses.

Chris

ps

https://en.wikipedia.org/wiki/Crop_factor
https://bkloflin.wordpress.com/2014/12/15/understanding-the-myth-of-crop-sensor-cameras/
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Offline TeeJay

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Re: Planetary imaging with Nikon 1 ?
« Reply #8 on: 23:23:19, 09 November, 2016 »
Mmmm fair dos. I'm not going to argue the point, it comes up here every so often from someone coming from camera lenses.

Chris

ps

https://en.wikipedia.org/wiki/Crop_factor
https://bkloflin.wordpress.com/2014/12/15/understanding-the-myth-of-crop-sensor-cameras/

With any due respect to the author that second article you linked to is ridiculous logic, if both sensors were the same pixel count then the APS-C would indeed produce a magnification factor of 1.5x, as it is he compared a print size from  36mp camera to a 12mp camera, his entire logic revolves around a false assumption that a smaller sensor must have a lower pixel count, frankly there's an irony in him calling it a myth when his own assumptions are mythical.

As for the Wiki link, that is more factual, the confusion for some is the graphic depiction of the red vs blue rectangular areas which may lead some to assume that the blue rectangle is in some way smaller than the red rectangle when reproduced on a screen or print.....
Now imagine that the red rectangle is a 20 Megapixel image and the blue rectangle is a 20 Megapixel image, which one has a greater magnification ratio ?

As soon as I get the opportunity I will create a demonstration of this for the benefit of all, it's important for people to properly understand it as there can be great benefits in using that knowledge
I have a 24mp Nikon APS-C and a 20.8mp Nikon CX, I will take identical shots at identical distances to compare, even the extra pixels of the APS-C will not make up for the sensor size difference and I will also demonstrate that by cropping the larger image to the same pixel count as the smaller one

I may be new to astro photography but I've been a photographer since the 1980's and I've always been a proper tech head

Offline Bazzaar

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Re: Planetary imaging with Nikon 1 ?
« Reply #9 on: 09:47:22, 10 November, 2016 »
TeeJay,
True magnification can only come from the optics, the sensor cannot alter the optics in any way so cannot alter the magnification.
Think about why it is termed crop factor. You get a resultant image that you would get if you printed out a full frame sensors image and then cut it down, cropped it, to the view you get on the crop sensor.
If, back in the day, you took a 35mm negative and blew it up in the dark room to give a bigger image, would you be able to claim the lens on the camera was bigger?
This is the objection, its not really magnification. Its virtual magnification, its a magnification factor. Its a shortcut to explain the resultant field of view on the crop sensor camera.
Another explanation,
you take the same picture using the same lens on a full frame and crop frame camera respectively,
you select two points that appear on both images that are the top and bottom of a feature or subject, in an astronomy image it might be the distance between two stars,
you count up the pixels between the two points an multiply by the pixel size.
The result will be the same size. The real size in millimeters, inches what ever, on the sensors will be the same.
No magnification.
Change the lens, size on the sensor changes.

Once we've explained this we can go on to show you how the ISO setting on DSLR is nonsense too :)

Baz
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Offline TeeJay

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Re: Planetary imaging with Nikon 1 ?
« Reply #10 on: 10:42:05, 10 November, 2016 »
You're wrong on your precept, magnification is not just a feature of the glass in the optical system, the receptor also has an effect on the resulting image size and angle of view
The proof is in mine and everyone else's images, you can argue with the results all you like but the results are the results and if the results do not match your explanation then I'd suggest that your explanation has flaws

Here's the bottom line
If I fit a 300mm lens on my APS-C camera and exactly the same lens on my CX camera the CX camera will give me a larger magnification for the same size (physically) image
The point you are missing is that sensors do not capture every photon that comes their way, sensor have gaps between the receptor where the photons hit there they don't register, physically smaller sensors have more tightly packed receptors so they catch the same amount of light but over a smaller area therefore giving effectively a narrower field of view but for an image which is physically the same size

As I said, when I get the time I will demonstrate this conclusively in the mean time perhaps you can explain how I can get the images below using a 300mm lens ?







Uncropped, unedited version of the Jupiter shot for reference, taken using the Nikon 1 J5 CX camera with 70-300mm lens set at 300mm


Exif data for above

Offline Einari

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Re: Planetary imaging with Nikon 1 ?
« Reply #11 on: 11:15:38, 10 November, 2016 »
Magnification has no real meaning in ds imaging.
What counts, optics focal length, camera pixel number, sensor size and pixel size which makes the field of view you get.
Tapio

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Offline TeeJay

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Re: Planetary imaging with Nikon 1 ?
« Reply #12 on: 11:37:20, 10 November, 2016 »
Magnification has no real meaning in ds imaging.
What counts, optics focal length, camera pixel number, sensor size and pixel size which makes the field of view you get.

Exactly, a narrower field of view but with the same number of pixels as a wider field of view yields what is effectively a magnified view regardless of what people prefer to call it, the end result is the same. so therefore a "crop sensor" (and I do disagree with that term) gives a narrower field of view than a full size sensor producing a physically larger object image

Without quoting sensor size or "crop factor" when asking for advice people have to run off to Google/Bing to research the sensor size and pixel density before they can give accurate advice on reproduction ratios of planets/objects, of course some like to give advice without actually doing that but that's down to me to filter that out

Really the biggest downside to the smaller sensors with tightly packed pixels is the inherent noise on long exposures but maybe with planetary images I won't need such long exposures but I will experiment with bias more as I have yet to use those

Offline chris.bailey

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Re: Planetary imaging with Nikon 1 ?
« Reply #13 on: 13:51:26, 10 November, 2016 »
Really the biggest downside to the smaller sensors with tightly packed pixels is the inherent noise on long exposures

Actually the biggest downside is that you very soon reach the point where you are diffraction limited so smaller and smaller pixels resolves no more information.

All optics have a limitation on their resolving ability relating to the size of the Airy disk. Using the Dawes formula the limit is 115.8/Do where Do is the aperture of the objective lens. For your 70-300 Do is around 60mm wide open so the lens has a limit on its resolving power of the order of 2 arc seconds and that is assuming diffraction limited optics, in truth it is probably considerably lower especially with a zoom lens/

Your 1J5 has a pixel size of 2.3 microns (as far as I can find) which on a 300mm lens gives a pixel scale of 206x2.3/300 = 1.6 "/pxl BUT your lens can only resolve to 2 arc seconds so smaller and smaller pixels would gain you nothing. A lot of high megapixel cameras are now diffraction limited by the optics used.

Now add in the effects of seeing i.e. the limits on detail resolution imposed by the 50 miles of atmosphere turbulence light has to pass through. 1.5 arc second seeing in the UK is quite exceptional and it is more typically in the 2.5 to 3.5 range. Video imaging of planets tries to 'capture' the very brief 'lucky" periods of best seeing. These periods can be in the millisecond range so high frame rate cameras 'can' give the best resolution but on some nights even this is not achievable. For deep sky work seeing of 2.5" is a good night.

If we take that 2.5" seeing and convert that to an ideal pixel we get 2.5x300/206 or 3.65 microns. Pixels smaller than this are wasted or oversampled. You may get a 'bigger' image with a smaller chipped high pixel density sensor but that larger image will yield no additional detail as it just is not resolvable.

Now lets put that 1J5 on a telescope with a focal length of 450mm. Your pixel scale now is 206x2.3/450 =1.0. Its a very rare night that could ever hope to take advantage of that. On my FLT110 that would drop further to 206x2.3/770 = 0.6 "/pxl and on my big RC it would be 206x2.3/2000 = 0.23.

Now bigger pixels capture more of the available photon flux (they have a bigger area so 'see' more light) so you might at well use a bigger pixels and take advantage of the increase in sensitivity. This is the whole reason why there are astro cameras with 9 micron pixels, they work best with long focal length scopes!

The key to astrophotography is balancing focal length, pixel size, field of view and seeing and more importantly knowing the effects of compromising one of them to get what you want to achieve.

Chris
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Offline TeeJay

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Re: Planetary imaging with Nikon 1 ?
« Reply #14 on: 15:08:56, 10 November, 2016 »
Thanks for that
Some explanations of astro specific potential issues is very useful
Yes I'm aware that a smaller sensor yields lower quality results over all and the frame rate for seeing is very useful, best I can do is 400fps, so I'll maybe have a go with that one clear night but with Jupiter being so low it may simply be unfeasible

The scope is useful to me with the J5 for terrestrial use too as it can focus as close as 20ft and isn't too bulky to haul around

Of course I can also use my Nikon D5300 which does give better low light images, though with standard DSLR lenses it simply cannot compare to the 70-300 on the J5 as that is probably the sharpest lens I have ever had the pleasure to use (hence being able to resolve Jupiter with a single shot), it really is a fantastic lens and in most situations actually allows the camera to produce superior images to the D5300 even when that has my 120-300 f/2.8 APO DG EX lens on it

 

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