Equipment
I found it really helps to be very light, able to set up and get out in a matter of minutes. So I do not carry any of my equatorial mounts. Just a tripod, my Sony A7RIII with a 100-400 lens and focal doubler. For solar I have a Baader solar filter on a ring of wood set on the the sun shield.
For accurate timing I use my phone with an app called Atomic Clock. It needs signal to synchronize with a time server, however, which can be a curse if signal is weak.
I also trigger the picture with a cabled remote, so triggering does not cause any shake.
Planning
Transit finder is the place to go. I choose only transits happening close to the zenith. For the sun it means transits close to noon. Those transits are the one where the ISS has the biggest angular size, and where there is least air mass to image through.
I plan my trip to be dead on the centerline of the transit if possible. This is where the transit is the longest, and just a few 100m makes a big difference. Don’t hesitate to drive and take advantage of the opportunity to discover unlikely places.
Camera settings
For the images above and below, here are my EXIFS :
- Camera: Sony ILCE-7RM3
- F-stop: Sun=f/13, Moon=f/11
- Exposure time: 1/4000s
- Iso: Sun=500, Moon=800
- Focal length (35mm reference): 800mm
- Metering: pattern
- Picture: JPEG, Quality: Extra Fine (Avoid RAW as it slows the fps)
Taking the picture
As I usually do not carry an equatorial mount, I track manually. I stop tracking 30s before the transit, letting the sun/moon drift in the frame. At that point I focus on the clock in one hand, the trigger in the other. About 3s before the transit I trigger. The A7SIII can burst for 8.2s at about 9.9 frame per second. Then it takes a minute to clear the buffer and write to card (so wait before you shut it down!).
Advice
Disassociate the focus from the trigger, so the camera does not mess with focusing before triggering. Do focus minutes before the transit. Take regular pictures as the transit is approaching to prevent your camera to auto shutdown due to inactivity.
Moon
At 1/4000, f/11, ISO 800 the moon is under exposed, which is fine. After the transit or when setting up, also take some fully exposed pictures of the moon as seen on that day for compositing.
Processing
I composite the images using layers in the Gimp.
Good luck, and have fun!
