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Why does my iPhone take good Moon photos, but poor planet photos?

Planet Beginner Astrophotography
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#1 shkeller55

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Posted 05 August 2022 - 02:36 PM

I’m pretty new to both astronomy & astrophotography. I’m mostly into visual astronomy but I want to take iPhone pictures of what I see to send to my grandkids to spur their interest in science.  I have a used C8, on an iOptron AZ Pro mount, and I have an iPhone 12 Mini.  I'm in Bortle 7 suburban Atlanta. I can use the phone’s night mode (time exposures) to get fuzzy but cool (to a 6-yr-old) photos of nebulae, and I can get fairly good snapshots of the Moon (using a polarizing filter), but I can’t get a good photo of a planet that looks near as sharp as the Moon, even though it looks fairly sharp (but all white) to my eye through the telescope.  I’ve seen lots of articles and videos that say you have to take multiple shots, or videos, of planets, and use software to stack and sharpen them, but my question is: why is that?  Why is a planet so much harder to photograph than the moon?  I've attached a couple of examples.  I used a light pollution filter for Saturn (without one it was too bright, so it's not like the camera's not getting enough light).

 

Scott

IMG_7100 (2) resized.jpg

IMG_7113 reduced size.jpg


Edited by shkeller55, 05 August 2022 - 04:18 PM.

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#2 gordtulloch

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Posted 05 August 2022 - 02:47 PM

Planets are hard - they are very prone to distortion due to seeing and since they need high magnification, need very careful focusing (normally with a batinov mask on a nearby star). Taking pictures of planets is an exercise in "lucky" imaging, where you take a massive number of frames of the planet and eliminate the fuzzy ones leaving the frames with brief moments of clarity which you can then stack and adjust. For example I use a C8 with 2x barlow and a ZWO ASI224MC camera (150+ frames per second, 6000 frames total used probably 20%) and I still haven't really gotten good photos with my setup due to bad seeing when I have had time to try.  So your phone is not a great tool to make good planetary images unfortunately. Your image is overexposed as well so you need some way to control the exposure.

 

jup.jpg


Edited by gordtulloch, 05 August 2022 - 02:54 PM.

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#3 Kiwi Paul

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Posted 05 August 2022 - 03:30 PM

I have run into these issues in the past and I would say it is due to the size differences of the two targets. The moon is a large and bright extended area that the camera can adjust its exposure and focus to. Whereas although the planets are bright, it is difficult for the phone to ‘lock on’ to them to get the answer right. I think has to do with the size of the sensing area of the camera. If you use eyepiece projection to enlarge the size of the planetary image, you will probably find you have a better chance of your phone locking on. I think you will see the image change when it does. My experience comes from a Nikon Coolpix camera with which I learnt how to use eyepiece project to overcome this problem.
Best of luck, Paul
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#4 spereira

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Posted 05 August 2022 - 03:52 PM

OP:  Planetary images and questions are allowed here, but please cool it on the Lunar images.  Those belong over in Lunar Observing & Imaging.

 

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#5 RedLionNJ

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Posted 05 August 2022 - 04:24 PM

As Kiwi Paul says, it's mostly a matter of image scale.  The large moon with a high-contrast, curved edge is ideal for an iPhone's auto-focus functionality. And there's a ton of light available for it to work with.

 

Saturn appears tiny compared to the moon. This not only grossly exaggerates fluctuations in seeing, but doesn't cover very many pixels and has no sharp edge for autofocus to lock onto.

 

Planetary photography IS possible with an iPhone, but you're going to need to employ some very careful techniques (see the FAQ at the top of this forum, for example).

 

And there is no point in focusing on a nearby star - that's no way to obtain the optimum focus for planetary detail.


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#6 Kiwi Paul

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Posted 05 August 2022 - 05:01 PM

I found that as the CoolPix camera hunted in and out on a planetary target sometimes it would dwell on the right setting (focus and exposure) I was able to press the capture button to freeze these settings and then take the exposure.
Cheers Paul
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#7 dcaponeii

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Posted 05 August 2022 - 06:45 PM

I think it’s general lack of definition of what a good Moon picture is.
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#8 shkeller55

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Posted 06 August 2022 - 11:55 PM

Thanks for the explanations and suggestions, everyone.  I have a better understanding of what’s going on now.  That photo of Saturn did still look overexposed even though I used a filter.  I need to experiment with my exposure settings to fix that.  And I need to try to enlarge the image.  I did read the FAQs before posting, and I generally understood what they were saying, I just didn’t see anything explaining the camera limitations.  Now I just need some clear skies so I can try again.  We haven’t had many here this summer.  


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#9 Kiwi Paul

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Posted 07 August 2022 - 01:06 AM

Just one more thought, when I used a Coolpix camera as I mentioned above, I used the zoom on the camera to get that enlargement of the planetary image. You may be able to use the zoom on your camera to do this too.
Cheers Paul
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#10 shkeller55

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Posted 07 August 2022 - 01:23 AM

Thanks Paul.  Yes, I was thinking I could try that.  I’ve only used the native camera app so far, but I downloaded NightCap Camera recently and will try it there too.  I used an 11 mm eyepiece to take that photo.  I have a 6 mm eyepiece I could try as well.  I don’t have a Barlow though.




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