Lunar Prominences
We'll get there.
I bought a solar telescope a few months ago, a Lunt LS40. It's 40mm diameter. Solar telescopes are expensive. but we also use them in the daytime - when it's warm out (because the sun is out) and that causes the seeing (air turbulence) to be much worse than at night. so the size of telescope you can use during the day, and the magnification, is limited. It's uncommon to see a giant solar telescope unless you have the seeing to support it.
So I was curious to see how a 40mm telescope would work on something familiar like the Moon. We're quite happy with the results we got on the Sun using telescopes this size, although we always try to go bigger, so I though a comparison might be good.
First, a shot of the sun, using the LS40 and an ASI174 Mini.
I bought a solar telescope a few months ago, a Lunt LS40. It's 40mm diameter. Solar telescopes are expensive. but we also use them in the daytime - when it's warm out (because the sun is out) and that causes the seeing (air turbulence) to be much worse than at night. so the size of telescope you can use during the day, and the magnification, is limited. It's uncommon to see a giant solar telescope unless you have the seeing to support it.
So I was curious to see how a 40mm telescope would work on something familiar like the Moon. We're quite happy with the results we got on the Sun using telescopes this size, although we always try to go bigger, so I though a comparison might be good.
First, a shot of the sun, using the LS40 and an ASI174 Mini.
- Lunt LS40 solar telescope, with B1200 blocking filter
- ASI174 Mini camera, Gain=100, exposure=1 mS
- ~440 images, at 7.4 fps. Best ~50 images stacked in Registax.
- Lunt LS40 solar telescope, with B1200 blocking filter
- ASI174 Mini camera, Gain=100, exposure=7 mS
- ~440 images, at 7.4 fps. Best ~50 images stacked in Registax.
We can do some editing in Affinity Photo, and combine these two images, adjust the contrast, and add some colour. The colour of the prominences was taken from an eclipse photo from 2017. I measured the RGB values and used them here.
And now - the Moon.
The Sun is about 400000 times brighter than the Moon, and the solar telescope has several filters to make it safe to look at and take pictures. One of the key elements is the 'blocking filter' at the back of the telescope where you put the eyepiece. To get a picture of the Moon with the same telescope, I used a regular prism diagonal instead. The ERF (energy rejection filter) and etalon (magic filter) at the front of the solar telescope were left in place - this will produce a deep red image of the Moon if you use an eyepiece, and means we are using a similar wavelength of light as when imaging the Sun.
The Sun is about 400000 times brighter than the Moon, and the solar telescope has several filters to make it safe to look at and take pictures. One of the key elements is the 'blocking filter' at the back of the telescope where you put the eyepiece. To get a picture of the Moon with the same telescope, I used a regular prism diagonal instead. The ERF (energy rejection filter) and etalon (magic filter) at the front of the solar telescope were left in place - this will produce a deep red image of the Moon if you use an eyepiece, and means we are using a similar wavelength of light as when imaging the Sun.
- Lunt LS40 solar telescope with star diagonal.
- ERF and etalon were still attached to the objective, so this is basically a red filter.
- ASI174 Mini camera, Gain=200, exposure= 13 mS
- ~440 images, at 7.4 fps. Best ~150 images stacked in Registax.
This picture was taken about 15 hours before full moon, and you can see in the upper left, some craters along the edge. The moon is not quite round - it almost looks flat on that edge. In order to make this more visible, I combined the Moon image with the prominences above. I was lucky because the apparent diameter of the Sun and the Moon was the same at the time these pictures were taken (32'00.4"). I used the same process as above to line up the sun and the prominences. Now it's easy to see not all the Moon is visible.
Looks fun, but a real solar eclipse is more fun.