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Interview with a Smartphone Astrophotographer: Grant Petersen

Often, the best camera is the one you use the most…like the one in your pocket.

I’ve been watching Grant Petersen post his work on Twitter for a while, from the first time he tagged me (I think). I see a lot of astrophotography every day, and what really caught my eye about Grant’s work is the fact that he does his best stuff with his Samsung smartphone.

And it’s GOOD work. Insane.

Here we are spending hundreds (sometimes thousands) of dollars on fancy astrophotography gear and cameras, and he’s putting out stuff that’s not far off with his phone, that you can get free on contract with your local mobile phone provider.

I had to catch up with Grant on a more personal level because who the hell does he think he is creating such great stuff without spending the cash to do it?! Damn you, Grant! Argh! What a jerk, right?

Turns out he’s a super nice dude, and he shares that same passion that got us all into staying up late to get our nerd on and take some photos of space.

Here’s what Grant “Got a smartphone? Hold my beer.” Petersen had to say

[PhotographingSpace.com] What is your favorite part of astro imaging? Why do you like it?

[Grant Petersen] I think just the concept of seeing a spot of light in the sky, pointing a telescope at it, that light then being projected on to my camera with incredible detail from an object like Saturn 1.2 billion kilometres away, just absolutely blows my mind.

Saturn with a smartphone, Grant Petersen

[PS.com] Where are you located? Where do you shoot from? 

[GP] I am based in Johannesburg, South Africa, born and bred. I shoot in my backyard on a base made for my Dobson.

[PS.com] How portable is your setup? How often do you travel to shoot? Give us a rundown of the gear you use to capture your images, since that’s the big deal here!

[GP] My set up is pretty mobile, a Dobson is 2 parts and I use a smartphone. My family and I travel a bit in SA, mostly trips to the Kruger National Park, so I guess lucky that the destinations we chose have dark skies. I traveled to darker skies for the eclipse on 27 July, 2019, which was my first astronomy dedicated trip.

Grant Petersen’s SkyWatcher 8″ Dobsonian

My gear is pretty basic, I followed the guidelines with videos on YouTube for purchasing your first telescope. I use a Sky-Watcher 8-inch Dobson [Newtonian telescope] that I picked up 2nd hand, a Samsung Galaxy S8 smartphone, a Solomark Smartphone adapter, a Celestron Xcel LX 7mm eyepiece and a 2x Barlow (for planetry imaging), 25mm Plossl (for lunar imaging). 

[PS.com] How do you plan your imaging sessions? What kind of time is involved? 

[GP] My planning starts during my lunch break while at the office. I check on my weather apps and Mobile Observatory app, firstly looking for conjunctions, moon position and phase or any other interesting events. I then check on Jupiter’s projected moon and GRS position, just because Jupiter commands all of the attention. 

Above image, planetary images with a smartphone, by Grant Petersen.

With smartphone imagery, I can put the scope outside to cool, take some footage, process and be done within an hour. 

[PS.com] What’s your acquisition process? You use a smartphone camera — what kind of special tricksy things do you do? What if you get a phone call? 

[GP] As I am manually tracking, I try to position my phone in the direction the planet is moving so I can get as much footage per track. Very important is to find a point on my finder scope that is aligned with the smartphone for quick tracking.

The ISS with a smartphone, Grant Petersen

Until recently I could only get about 15 seconds of footage as that is the amount of time the planet is visible in the eyepiece. My trick to acquire more footage was to simply pause the recording, re-track, un-pause, pause, repeat until I get 2 minutes of footage.

The Samsung smartphone cameras come with a pro mode setting where you can manually adjust exposure, ISO, white balance etc, I also use the zoom function to try get more detail. 

I usually put my phone on to airplane mode while recording, but, I forget and yeah I’ve had times where I get a call while recording. 

[PS.com] Are snacks involved in your acquisition process? 

[GP] I am a tea and coffee addict, so usually a flask with hot tea or a nice cappuccino.

[PS.com] When do you decide that you have enough data to create a final image? 

[GP] I have learnt to not obsess about getting too much footage and rather concentrate on getting better quality, I try get about 3 sets of footage with different exposures. 

[PS.com] What post-processing methods do you use to create your images? How do you deal with the smartphone video? 

[GP] This is why I love the Twitter astronomy community, I was stuck and didn’t know how to convert my MP4 smartphone format to an AVI so I can use it with stacking software. I put out a question and someone suggested I try PIPP. This was revolutionary for me, PIPP takes my moving target, breaks down all the frames and then re-aligns the frames in AVI.

One of Grant’s Registax sessions

I then use Registax to stack my images. From 2 minutes of footage at 30 frames a sec I get 3600 frames and then I stack the best 10% of frames. I adjust the histogram and the the wavelets and touch up the image with Lightroom for Android on my smartphone. 

[PS.com] What was your path and learning curve? How long have you been an astrophotographer?

[GP] I have been imaging the night sky for about 3 years now. My interest was sparked by the amazing images astrophotographers posted on twitter and a Nikon P600 camera I purchased for my wife. I was playing with the settings and I came across a Moon setting, I pointed it at the moon, zoomed in, zoomed in some more and I was astounded that I could see craters on the moon with a digital camera.

There was a Lunar eclipse in September 2015 and this got me totally hooked. I then set out and researched and purchased my first telescope which I received in December 2016 (this was obviously when the great drought ended, and it rained for a solid 3 months). The telescope I got was not geared for astrophotography as this was not my intention and not within my budget.

Total lunar eclipse with a smartphone, Grant Petersen

As soon as I had my scope set up and pointing at the moon, I put my phone to the eyepiece and thought “I can take some decent pics of the moon, planets, and Orion nebula, and I can wow my family and friends”. It did the trick, but I wanted more.

I then purchased an Orion USB Starshoot camera 2 and this got me into learning imaging, stacking and processing techniques. After trial and error and my current set up, I now only shoot with my smartphone.

I would like to eventually get into DSO astrophotography, but that just looks intimidating. Before I started this, my PC was used for invoicing, excel and watching YouTube videos. This has all been a massive learning curve and it’s a passion and a hobby I will invest in. I get so much out of this. 

The ISS transiting the moon, with a smartphone, by Grant Petersen

[PS.com] Why do you do astrophotography? 

[GP] I don’t know why I do it other than I enjoy being out under the stars. It has pulled me away from my old routine of finishing work, coming home, and watching TV. It has become a personal challenge and I enjoy the fact that I can image an object, process it, and within an hour share it with my family and Twitter

[PS.com] Where can we see more of your work? 

[GP] I am only posting my pics on Twitter at the moment.

Some of Grant Petersen’s smartphone astrophotography images

Connect with Grant on Twitter, click here for his profile.

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About the author

Cory Schmitz

Co-founder of PhotographingSpace.com, co-owner of several telescopes and mounts, too many cameras, and not enough hard drives, Cory is an American expat living in South Africa with his wife, Tanja Schmitz.

An avid astrophotographer for timelapse, deep-space imaging, lunar, planetary, and star trail imagery, he is an all-around jack-of-most-trades for night-sky photography.

He is also an internationally published and commissioned astrophotographer, where his photos have been used in multiple online and print publications.

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