How I got some photos of some planets
You can do this! I used inexpensive equipment to get some reasonable photos of Jupiter (and one of Saturn). In doing so, I learned a pile of lessons, which I've listed at the end.
It's planetary season, with Jupiter just past opposition, meaning it's overhead at midnight. Saturn's not far behind.
I'm a nebula hunter and not a planet expert, so I'm really a beginner in this area. Planets are tiny little things, but they're very bright. They're about as far, technically, as you can get from nebulas, which are large and dim.
We wanted to get some photos of planets to show what inexpensive equipment is reasonably capable of in the hands of someone who isn't much of an expert.
I'm also keen on using non-premium equipment to take photos. I'm often quite pleased at the results you can get without having to shell out big bucks.
For a scope, I grabbed a saxon 127 Maksutov on a go-to mount. I could have taken a similar tube from other brands, Celestron and Sky-Watcher also brand the same tube. This telescope has a 1500mm focal length, and is f/11.8, meaning it's pretty much a planet specialist.
I could have used my own DSLR to take the photos, but I decided to use an old ZWO ASI034MC astronomical camera that was literally lying around the office. The performance of these two was probably going to be similar as the size of the pixels of both cameras were about the same. The newer CMOS cameras from ZWO and QHY are heaps better, of course.
I also used a cheap saxon 2x Barlow so I could get a few more pixels on the planet.
To get an idea of what I might expect, size-wise, from these bits of equipment, I looked up our usual field of view calculator. I've mentioned this tool before, it's very useful. It showed me a picture of Saturn in a rectangular field. I've attached a screen grab of the eventual photo next to the calculator. Pretty close!
I've got the photos below. I'm pretty pleased with what you can do without a big investment, as well as without a huge amount of experience on this type of photography. With more practice on the same equipment you will do better.
In this section I'll also talk about how I used free software to process the images.
Like I mentioned, I'm no expert in planetary photos, so this is pretty rough and ready stuff. The experts will probably be able to give me pointers on how to do better - I hope they do!
Taking the shot
Remember I had a choice of cameras, my own Pentax DSLR and an obsolete astronomical camera I found around the office, a ZWO ASI034MC, a "one shot colour" camera. This particular camera was replaced long ago by a couple of variants of the ASI120MC or the ASI290MC.
The videos my DSLR gives me are "full-HD", meaning they are 1920x1080 pixels in size. The sensor on the camera is in fact 6016x4000 pixels, but when shooting for videos, the camera "bins" pixels, (meaning it combines adjacent groups of pixels) to provide more sensitivity in low light conditions. This is fine in most situations, but in this case - trying to get as much detail on a tiny target in the middle of the sensor somewhere - it was definitely not what I was after.
So it might
be a museum piece, the ASI034MC would get more detail. This is the camera I'd use.
The camera connects to my laptop using a USB cable and a free driver off the ASI website. I actually operated the camera using another free bit of software called SharpCap 2.9.
I set up the mount and the Maksutov, aligned it using the handbox and found Jupiter through the planets menu. This was very simple - the wonders of go-to mounts. I used an eyepiece to centre the planet in the field before swapping to the camera and the Barlow.
I found that the camera I'd found under a pile of rubbish at the shop had the world's dirtiest sensor. I hadn't checked the camera before showtime - a rookie error, which turned out not to be my last.
Once the planet was in focus and used SharpCap's gain to slightly underexpose it (you can fix a bit of underexposure but not overexposure in processing). Using video capture, I took 5000 frames of about 20 milliseconds each. This saved on my computer as an SER file, which is the type you need for colour images.
Processing the shot
Back inside, I opened the file using another free bit of software called PIPP. This sifts out the poor quality frames, centres the image and saves the output as a familiar AVI file.
Then I opened this file using yet another free bit of software called RegiStax. This combines all the images I took to make a final TIFF image, which you can then sharpen using Registax's wavelet sharpening tool.
Finally, I opened this in PhotoShop and did some final tweaks. I doubled the size of the images and then cropped them, and played around a bit with saturation, contrast and some other details.
A second try
The images I've got here was using an old colour astronomical camera, connecting it to a Barlow and hanging it all on the back of a saxon 127mm Maksutov telescope. I was pleased with them, given the equipment I had access to (remember, my telescope isn't built for planets).
A new camera - monochrome with filters
After this, I rummaged around some old equipment I had and dug up a colour filter wheel. Then I robbed my current rig of its guide scope, a monochrome ASI120MM, which has higher resolution than the one I used before. Putting these together on the Barlow lens, I attached it to the scope, which was already aligned and ready to go.
The go-to mount did have a little trouble following the planet at that extreme level of magnification, so I had to keep a finger on the handbox. I needed the slew rate turned down or the image would zip out of view.
Using SharpCap, I took three series of 1000 frames for each of my red, green and blue filters. This took a couple of minutes each and there were another couple of minutes of filter swapping and refocusing between each one, which is important, as you'll see.
I've attached one of the raw monochrome frames. This one was from the green filter. Yuck.
I put the nine 1000 frame videos into PIPP, which kept the best 90% of frames for each (cutting each film down to 900 frames each). Then I opened them in RegiStax, which aligned them, cut the frames down to 90, and stacked them. I also used RegiStax's wavelet function to sharpen the single images.
In the green filter photos above you'll notice the stack is much less speckly than the single frame. This is what stacking does for your images through the magic of mathematics!
This gave me three monochrome images like the second one - less noise and (hopefully) more detail. Then I recombined them using Photoshop to make the first colour photo. To do this, I made a new RGB image and copied the monochrome image taken through the red filter into the red channel of the new image, then did the same with the blue and green images.
Another rookie error
But Jupiter rotates quickly, and I took photos over a half hour. So what I've got here is motion blur!
I had to reprocess everything, but this time, just use the last of the three series of video I'd taken. It was a bummer having to throw away so many frames. Once I had finished, I could see a bit more detail - including the shadow of the moon near the top of the planet's disk.
This is my final composite image. I recombined three images taken through red,
green and blue filters with my monochrome astronomical camera (the ASI120MM). I normally use this camera to drive my autoguiding system.
The telescope was a saxon 127mm Maksutov on an AstroSeeker computerised go-to mount. This is an entry-level (or nearly an entry-level) go-to scope.
The final image, with help from a pro
After I'd published a couple of these photos on the Australian Amateur
Astrophotography Facebook page, I was approached by another member, Bruce
Rohrlach. He offered to take my raw data and try to process it himself. I sent
him a pile, and he came up with the three monochrome frames here.
He told me that his processing wasn't much better than mine, but I think it's fairly obvious he was being modest.
As a final follow-up of this story, this what I learned while doing it.
The important things I learned about photographing Jupiter are the following:
- you need at least 200 pixels across the planet's face, or it's just going to be either tiny in the frame or blocky because it's too blown up. You can use a telescope with a long focal length, a sensor with tiny pixels, a Barlow lens, or all three.
- colour cameras are naturally lower resolution than monochrome cameras because they use one pixel for each colour (and sometimes two for green).
- if you're going to use a monochrome camera, you need to use filters, and this adds to the expense and fiddliness.
- use video to get the raw images and get the computer to process them for you. Jupiter is bright and you'll only need a very short exposure.
- if you're going to use a DSLR, it's probably best not to use video mode as this cuts resolution down considerably, combining pixels to make the video frame.
- Jupiter rotates really quickly - so much so that you'll get motion blur and lose a lot of detail unless you confine your photographs to a very short time period.
- you learn a lot very quickly when you' re in the deep end.
- people in this hobby are really supportive and eager to help and share their knowledge.
- it's really not that difficult to start getting good images, and you improve quickly.
I'd love to see your images here!