Hard to believe that in just 1 week I will have the opportunity (weather permitting) to witness arguably the most compelling astronomical event an Earthling can witness! I am truly blessed to have this opportunity!
And so…Live from Talavera….it’s preparation for the Great American Eclipse of 2017! Our first live Sun imaging session! We need to accomplish these goals hopefully:
- Find the Sun and be able to center it in the field
- Focus on the Sun
- Track on the Sun and get a sense for how long it remains in the field
- Image the Sun. What are the appropriate exposure times for the live whole Sun. These will be basically the same as the partial phases and provide a framework for other phenomena
- Check our battery situation. How does it hold up in the intense day time heat.
- Test removing the filter and putting it back on and see what effect this has on image position.
A couple of points. First thing is, it gets hot out there! That’s probably why I stopped doing Solar on a regular basis. Second is you need to be able to see what you are doing. Since we have decided a laptop is going to be necessary you need a cover for it so you can see the screen. Very important! I have learned from experience imaging the Venus transit. We fashioned on old Amazon box which fits the laptop perfectly. Remember you need to cut a whole where the fan is to allow for venting and you need to cut a hole on the other side for your usb cable.
Here is our eclipse setup. I forgot to point out the glass filter on top of the scope! You will need this! I have a small fold up table for the laptop. There is enough room on the side for the mouse. I really hate the scroll pad. Can’t use that thing for beans!
Don’t forget to vent the cardboard box so your machine is less likely to overheat
Here we are inside the box! This is indispensable for reducing glare. The additional sheet on top over my head does add to the shielding!
Ok so we did our compass alignment to the pole, then did the mount’s routine for synching on the Sun, then slewed to the Sun. It was a fare way off! So we just used the hand pad and our trusty solar finder to get the image into the field. I cannot emphasize the solar finder enough. You MUST have this or you will be DOA! It took about 10 minutes to locate the Sun even with the finder. Note also that the position of the Sun in the finder corresponding to the center position in the scope may NOT coincide. You just have to figure out where the correct finder position is that translates to the center in the telescope’s field
When the Sun’s projected image was located here in the finder we knew the Sun was now in the center of the field
To center and focus the Sun you need to utilize the “live view” feature on your dslr. This is indespensable. You cannot do it any other way. For this part of the project I use the Canon Eos Utility program on the laptop exclusively. The memory card is not being used. You cannot possibly see squat on the tiny view screen of the camera in the glare of midday so don’t try. This is the best way. Open the live view function and first center the Sun.
Here is the Sun in live view for the purpose of centering with the handpad
Now for focusing while in live view mode click on the magnifying glass and this goes to about 200% magnified. Have your friend or partner, in my case my wife was kind enough to make the adjustments in the hot Sun, and focus until the Sun’s limb is as sharp as you can make it.
Here is the result of focusing on the limb at 200% mag. If you do this you will be GUARANTEED to be in focus!
And now the results:
Sun at 1/3200 ISO 400. Slightly dim
Here is the Sun at 1/2500. A little better. At the bottom it looks like there is some odd reflection or something. This is eliminated with a histogram adjustment. I think it may be some background reflection
1/2000 exposure with the histogram properly adjusted. I think this is a winner! And interestingly it is the recommended exposure for f/8 ISO 400! Yay! By the way those are NOT sunspots but “screen spots”. I will have to make a point of cleaning them off ! There are virtually no spots on the Sun right now
So I think the first test run was a success. Let’s see what we accomplished:
- Find the Sun and center- CHECK however again this is not trivial. Daytime polar alignment is not going to be that accurate and you will HAVE to anticipate at least 15 or so minutes to accomplish this. You MUST have a solar finder. See this post on how to make one
- Focus on the Sun- CHECK- the live view function is the key!
- Track on the Sun. CHECK- this actually worked very well. It took at least a half hour for the Sun to leave the field! We were able to determine where the drift was and could easily correct for that. This will be useful on Gameday 🙂
- Image the Sun CHECK. the published exposure times are accurate!
- Battery life- CHECK. Plenty of battery life. We tested the rig for a solid hour and a half and still had plenty left. No issues!
- Removing filter test. CHECK. The amount of drift following removal and replacing filter was barely detectable. I did adjust the 3 set screws on the filter so it can easily be removed. This eclipse the Sun will be pretty much overhead so the filter is not likely to be dislodged by wind
Looks like our first run was a success! Tomorrow is Deployment Day!
Thanks for reading!