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Nikon J1 for planetary imaging

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#1 prdubois

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Posted 03 July 2020 - 09:03 PM

Hello,

So I'm very new to this hobby, literally just got a Z130 650mm scope because my son got suddenly excited about planets (finally got an excuse to scratch that astronomy itch). I'd like to do planet photography but keep my initial cost low. As such I'd like to use my old Nikon J1 mirroless cam if possible.

 

It has relatively small pixels at 3.4 um but the problem is that this cam won't do 1x1 pixel in movie mode. It bins pixels. That will ruin my resolution. Is it possible to do small acquisition bursts of say, 30 images or so, wait for the buffer to empty to the sd card, and repeat that cycle a few times? I won't be getting the thousands of images I see people using for lucky imaging using that technique...

 

Will I get satisfactory results using that method or am I wasting my time? The other option I'm considering is using my even older Logitech webcam pro 9000. It's old so can only do 5 fps though so not sure it's worth the trouble.

 

Of course I know that to get best results I should buy something like a QHY cam but I'd like to get my feet wet first and get my son interest alive with a "quick win".

 

Thanks


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#2 Tulloch

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Posted 04 July 2020 - 08:05 PM

Hi there, the system you are describing is not ideal for photographing the planets for a number of reasons - the focal length is too short, it doesn't track the planets (so they will move across the eyepiece/screen) and the camera bins the pixels in movie mode.

 

However, if your expectations aren't too high, it is possible to get images of the planets with this system. My first scope was very similar to yours, a Celestron Astromaster 130EQ which is a 650mm f/l Newtonian on a horrible manual eq mount. I purchased an Orion Edge-On Planetary 3mm eyepiece and a mobile phone holder and after finding Saturn, I took some videos with my iPhone as it tracked across the screen, stacked the frames and cleaned it up a little to finally come to this result. It wasn't easy, and the resulting image cannot be described as "good", however it is something. After struggling with the scope for a little longer, I eventually went out and got a 2nd hand Celestron Evolution 6" SCT and haven't really looked back since.

 

Your plan sounds OK, you will need to get a 2x Barlow lens, a T-adapter and a T-ring for your camera (I started with this Barlow/T adapter combo) which should allow you to get images of the larger planets, but again, don't expect too much smile.gif.

 

Andrew

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Edited by Tulloch, 04 July 2020 - 08:06 PM.

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#3 prdubois

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Posted 06 July 2020 - 10:24 AM

Thanks Tulloch. I understand that my focal length is not ideal, but as long as I can somehow meet the rule of thumb of 5x between pixel size and f/ratio, does the short focal length even matter? I obviously can't use a DSLR with its big pixels but I was hoping a camera with smallish pixels would be ok.

 

I'll definitely try the eyepiece projection (or afocal?) method first because my barlow on order hasn't arrived yet (actually it's the one you proposed).

 

Once I have my barlows (2x, 3x and 5x on order), I want to to try the prime focus method. But my main issue remains: I can't use 1x1 pixel mapping in movie mode. And to use burst capture mode, I need to keep the shutter button pressed. So I'm planning on rigging an electronic shutter with a servo motor. I'm not sure that it's gonna be worth it, given that I won't be able to take thousands of frames. Hence my initial question, is it worth to even try?


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#4 Tulloch

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Posted 06 July 2020 - 05:25 PM

Hi again, don't worry about the pixel size of the camera so much, it is certainly possible to take good images of the planets using DSLRs (however the Canon system is much preferred). I've run a series of tests using a Canon 700D (with 4.3 micron pixels) and it compares reasonably well to a dedicated planetary camera such as the ASI224MC with a 6" and 9.25" SCT.

 

If you want to continue with the Nikon J1 then the optimum focal ratio is around 5x3.1 = f/15, so a 3x Barlow would give the "best" resolution. However, the main issue I see is that the planet will not stay in the centre of the frame, rather, it will drift across the sensor due to the rotation of the Earth. Depending on the magnification you use, you might get 30 seconds or up to a couple of minutes from one corner to the other, during which you will want to take as many images as you can. The planets will be small, for instance I get 300 pixels across Jupiter's diameter on my 9.25" SCT with an effective focal length of around 5000mm, and that's enough!

 

You really won't want to touch the system during recording, as any movement will cause the setup to shake and you wont get stable frames. Is it possible to set up a continuous recording mode, when the camera takes frames continuously over a period of time, or up to a certain number? Maybe the video mode (with its binning and all) might be better. It could be worth trying both methods and seeing how you go.

 

Whether it's worth even trying is up to you - you will certainly be able to get images of the planets, but they won't be the same quality as the others that appear here using larger scopes, dedicated cameras and at a price tag to match. You should be able to image the rings of Saturn, Jupiter and its moons, maybe some structure on Mars. You might want to look at the images others have obtained in the "small bore" challenge threads, designed for people with OTA's sized 6" or less.

https://www.cloudyni...er-w-6-or-less/

https://www.cloudyni...rn-w-6-or-less/

 

Have a look at these tutorial videos also, I learnt a lot from them, they should help you along the way.

http://planetaryimagingtutorials.com/

 

Good luck!

 

Andrew


Edited by Tulloch, 06 July 2020 - 05:37 PM.

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#5 prdubois

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Posted 06 July 2020 - 08:41 PM

Thanks Andrew for the tips, I'll read your thread about DSLR vs planet cam. Yes I understand that the quality won't necessarily be very great. I'm just setting a challenge for myself to try to get the best pictures I can with the gear I got, before upgrading if I catch the bug.

 

Unfortunately no way to trigger a bunch of picture frames without actually keeping the shutter button pressed. I'll probably try to rig a servo motor to press the button and see if that can keep vibrations low. It will be fun to try. I'll also try the movie mode and compare.

 

The main issue that I didn't realize before is that I can't actually take pictures without the lens on, the camera will complain. I will do some research to see if I can trick it to believe there's a lens attached. In the mean time I will try with the afocal method. Probably the worst method from what I've read but gotta start somewhere!



#6 prdubois

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Posted 08 July 2020 - 09:13 AM

I figured out how to use the Nikon J1 without a lens, you need to be in manual mode. However, I was able to score a used ASI120MC, so that changes my plans somewhat. It has 3.75 um pixels so I will need a 4x or 5x barlow. I ordered a very cheap 5x barlow from aliexpress but it's gonna take a while to come and I'm doubtful about its quality.

 

So I'm searching for an adequate 5x barlow. I'll probably create another thread about it since it's not about the Nikon J1 anymore.


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#7 Tulloch

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Posted 08 July 2020 - 04:49 PM

I figured out how to use the Nikon J1 without a lens, you need to be in manual mode. However, I was able to score a used ASI120MC, so that changes my plans somewhat. It has 3.75 um pixels so I will need a 4x or 5x barlow. I ordered a very cheap 5x barlow from aliexpress but it's gonna take a while to come and I'm doubtful about its quality.

 

So I'm searching for an adequate 5x barlow. I'll probably create another thread about it since it's not about the Nikon J1 anymore.

The 120MC will certainly make imaging easier. Since you are now heading in that direction, the planetary imaging tutorials I mentioned above will be useful.

 

I believe the GSO 5x barlows are "reasonable" quality - certainly not in the league of a Tele Vue 5x PowerMate (according to reports), but certainly good enough.

 

Andrew


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