Canon EOS 1200D gives shaky star shots

Question

I have a Canon EOS 1200D/Rebel T5. I'm an amateur phtographer and still learning. After reading a lot about astrophotography, I tried my hand at it. I took a trip to a relatively dark place, set up on a tripod, and started taking shots using my phone connected to the USB port as a remote release/intervalometer. I took 100 shots at different places, under different conditions. Every single shot, no matter whether the stars are completely in focus or not, showed a sort of streaking in random directions (not star trailing. I used the 600 rule). Here are some examples: https://drive.google.com/open?id=0B802HQPuk5MlRTJJZEJfM2Z3REU

I have a suspicion that this shaking is being caused by the camera shutter itself. I've tried searching online for others with the same problem, but my Google-fu hasn't helped so far. Is this some kind of issue with the 1200D or is it just my camera?

P.S. Note that since I have low reputation, I can't post more than 2 links. I'll make a Google Drive folder containing a few more examples if anyone wants, and I've edited out the links in the question itself.

Answer 1

Just my opinion, but mirror slap and MLU issues don't tend to create as much motion as I'm seeing in your second shot. I'd suspect the issue to be more with your tripod or tripod technique. You may also want to check that you're not inadvertently tugging on the USB cable that's connecting your phone to your camera whenever you take an exposure.

A small, tippy four-segment tripod, like the Velbon I habitually use, sucks for longer exposure work, particularly in any kind of wind. I tend to use my Velbon for 360-pano work, because it's small, light, and portable and I'm generally shooting in daylight with fast shutter speeds or indoors without any wind. But when it comes to night-time shooting, I drag out my big heavy three-segment Manfrotto, which is far more stable, and has a ballhead that can actually lock securely and support the weight of my EF 400mm f/5.6 + 5dMkII without any bounce or drifting.

If you're using a telephoto lens that has a lens collar, use the collar. This will definitely help minimize "bouncing" of the lens/camera combination by putting the majority of the weight at the balance point.

If the lens has IS, make sure that if you turn it on, that the lens's IS version is compatible with tripod use (the first generation of IS Canon put in its lenses introduced more shake when used on a tripod).

With a tripod, the lower to the ground you want to go, the more stable the set-up usually is. Having the head extended, or the legs fully-extended may be introducing some instability. If it has a hook, add weight to the center column. If you can spread the legs out at a wider angle, consider doing that.

Also, when you calculated the 600 rule, did you include the crop factor?

Just me, but I'd say, first off, test your tripod technique indoors. If you're still getting blur/shake, then maybe it's time to look at the camera.

Answer 2

After a bit of experimentation (a couple of months after asking the question), I discovered that it was, indeed, the fault of the Canon lens. Basically, I have the older lenses with a weirdly buggy version of Image Stabilisation.

What happened is that the IS on these lenses keeps trying to correct for movement, even when there may be none. I tested it indoors by exposing for a long time in a semi-dark room and focusing on specular highlights on an object (reflections of light on a shiny surface). With IS enabled, I saw weird drift in the highlights. With IS off, there was no drift at all.

I successfully managed to take photos of the galactic center by disabling IS. They may not be great(focusing issues which can't be helped), but it was fun to take them anyway. I forgot to answer my question though. I hope anyone who is still following this question forgives me for this. Sorry!

Answer 3

From the shape of the star trails in your photos, and given the fact that you have a relatively short exposure time, I am almost certain that the problem is caused by mirror shake. With longer exposures, the "trails" caused by mirror shake will be much less noticeable. However, with short exposures (and 12 seconds is a short exposure in astronomical terms), the period during which the camera is vibrating represents a larger percentage of the total exposure time, and any star "trails" caused by mirror shake will be more evident.

One way to overcome this problem is to set a much longer exposure time on the camera and control the exposure yourself by covering the lens with something suitable and then gently removing the cover and replacing it after the required exposure period while the mirror is up. You need to allow plenty of time for any vibrations to die down. Remember that the mirror movement will cause the whole set-up to vibrate.

Do not use the lens cap as the cover. You need something that will cover the front part of the lens and that you can leave sitting on the lens. A plastic container of some sort painted matt black on the inside would be ideal. You could possibly even use a dense black cloth. All you need is something that will keep light out and that you can gently remove and replace without disturbing the camera.

Let's say that you want to make 15-second exposure. Set your camera for 60 seconds (if you can). That will give you plenty of time to do what you need to do. Press the shutter release and immediately lift the cover off the lens but keep it covering the lens. Allow 15 seconds for any vibrations to die down and then remove the cover completely. After the required exposure time, introduce the cover again and wait for the shutter to close. If all goes well, you should have a vibration-free image.

Answer 4

Stars are super distant: If an object’s distance is more than 3000 times its diameter, it appears as a point. A 10mm coin viewed from 30,000mm (30 meters / 100 feet) appears to the unaided eye as a point with no discernible dimension.

All stars thus appear as pinpoints of light. As starlight filters through earth’s atmosphere, it must pass through different densities of moving air currents. This action causes the star to appear to change its position. In other words, the light rays from a star are caused to zigzag. This is called scintillation. Scintillation plus camera vibrations and optical inaccuracies are the culprit.