Monday, May 1, 2017

Eclipse Imaging #1 Individual images

I was reading a lot about how to take individual real-color images of a solar eclipse. But the outlook of constantly adjusting exposure time, changing filters.. wasn't too great. I want to enjoy the eclipse as much as possible and pay as little as possible attention to my gear.

So, I was delighted to learn about Eclipse Orchestrator. It does create a whole script and executes it along a very tight timeline (needs exact location and time). The only thing that it needs is to remove the filter just before the second contact and put it back on after the third. I can do that!!!

Initially, I was thinking of using my 300mm lens for my Nikon camera (I can only use the D7000 as the D750 is not supported) and mount it on top of the TOA-130 scope and use the Mach1 mount to track. But then I realized that I could also use the TOA-130 scope itself with the Super Reducer to take images. The field of view should be perfect and the non-flat image shouldn't be too bad for these images (especially considering that the D7000 isn't a full frame camera!)

So, the equipment that I want to use is:
  1. TOA-130 scope with Super Reducer
  2. Nikon D7000 (connected with DSUSB from shoestring astronomy to short the time between exposures)
  3. Mach1 mount
  4. Eclipse Orchestrator
There are a number of things to figure out:
  • I have an adapter from PreciseParts that should work (might be a few millimeters too short). Need to try it out and measure the distortion in the corners.
  • Need to spend a lot of time trying out the script that Eclipse Orchestrator generates - maybe adding some frames as possible (this turned out to be very involved and I decided to write an extra blog post about it)
  • How can the Mach1 mount track the sun over 2.5 hours?
    • The AP driver has a "sun tracking" speed. Need to try that out and how accurately it keeps the sun centered.
    • I could use APCC Horizons to accurately track the sun
    • "proper" sun guiding solutions (like LuSol) might not work as the sun will be distorted.
  • Need a new Serial-USB adapter (my old ones don't work with Windows 10)
Things I would have to do to set this up onsite:
  • Good polar alignment (not a problem as I will use the TOA scope the nights before for astro imaging)
  • Focus the sun extremely well
  • Enter exact coordinates from GPS (unfortunately Eclipse Orchestrator can't read from my GPS - have to enter them manually)
  • Keep NMEATime running while imaging to make sure that time is as accurate as possible (and disable Dimension4 - it shouldn't do anything as it won't find any internet. but better be on the safe side)
  • Exchange my normal imaging train (flattener, filter wheel, CCD camera) in the morning with the Super Reducer and Nikon camera WITHOUT affecting polar alignment or such.
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Update 05/01:
Received the new Serial-USB adapter - works. Yei!!!

Update 05/28:
1. Camera Setting
Tried to figure out what exposure time / ISO to use. Full sun with the Baader filter is best at:

  • ISO 100
  • Exposure 1/400 sec
I need to use that as the basis for Eclipse Orchestrator.

2. Adapter
The adapter that I had, was too short (to match the backfocus of the super reducer). I ordered one with the proper length - but that one brought the camera so far out that I couldn't focus ...
So, I went with the shorter one. Need to measure the aberration in the corners - hopefully it's not too bad...

3. Focusing
Focusing is surprisingly difficult. What I ended up doing:
  1. Focus on a distant object without the filter.
  2. Put on filter and slew to sun.
  3. Use Live View (Nikon Control Pro 2) to focus the sun well (zoom into outer areas or spots and focus on it).
I will have to do this early enough - hopefully the temperature difference before/during/after the eclipse won't change focus too much.