• Stephen Strum

Observing the Sun in White Light


White imaging the sun with a dedicated hydrogen alpha telescope can produce spectacular images, viewing or imaging the sun in white light is a lot less expensive and something you can do with your existing telescopes with the addition of a filter or solar wedge for a modest amount of money.


My main telescopes are a Celestron Evolution with an 8" EdgeHD telescope, a Unistellar eVscope2, and a TV 60. I also have a Celestron C90. I have filters available for all my telescopes so I can observe sunspot activity on the sun, or use them to watch the partial phases of a solar eclipse.



For my 8" Edge HD, I have a snap on solar filter made by Celestron that fits over the corrector plate the same as the dust cover. This is the most compact solar filter for the 8" SCT you can get, and is why I have it. Others fit around the outside of the telescope tube, and are thus much larger, making them harder to store.



For my Unistellar eVscope 2, I have an Astro zap solar filter that uses Baader solar film and which fits around the outside of the telescope tube. This filter is designed to fit around a Celestron C5, which is also a great scope and one that I might pick up again at some point. The eVscope 2 has a field of view that is just large enough to fit the entire sun or moon in the image. I've also added a Baader solar continuum filter in front of the camera sensor to help produce a sharper image. I use this same filter with all my scopes when imaging since it only allows light around 540nm in wavelength to pass through.



This limitation helps to produce a sharper image, especially with refractors as both the atmosphere and telescope lenses will refract light differently at different wave lengths. This can make it hard to keep all wavelengths in focus at the same time. Since camera sensors are sensitive over a larger range of wavelengths than the human eye, this effect is magnified when imaging. By limiting the light passing through to the sensor to around a single wavelength you don't have to worry about near infrared wavelengths being out of focus relative to the other end of the spectrum, and blurring your image. You don't need to add this filter, and it doesn’t make a big difference, but it can help you to see a little more detail in white light, especially surface granulation. Here are two images, with and without the Baader Solar Continuum filter. It is hard to see the difference without having the full resolution images, but it provides just a slight increase in image detail. These were taken with a monochrome camera so the sun is white, but visually it makes the image green.



The downside to using the filter, of course, is that the filter makes the sun green in color as it only allows the peak of the green part of the spectrum through to the sensor. You can easily adjust that when processing any images you take, but it can be off putting when using the telescope visually. So, you may not want to use the solar continuum filter if you don't want to see a green sun in the eyepiece.


Below is a screen shot of the live view of the sun with the Baader Solar Continuum filter as seen through the Unistellar app.


For my Televue 60, I'm using a Lunt Solar Wedge. I highly, highly recommend purchasing a solar wedge if you have refactor telescopes for two main reasons. First, it will almost always produce a slightly sharper image than any filter placed over the aperture of the telescope. Secondly, you can use it with any refractor. So, if you have multiple refractors, or if you upgrade your telescope, you won't need to buy another filter. The only limitation is that you can't use these with a telescope of more than 4" in aperture unless you have an aperture mask on the front of the telescope to mask it down to 4". The solar wedge won't be able to handle the additional heat of the light coming in from a bigger telescope and the image will likely be too bright to view comfortably. But, for 4" and under telescopes, the solar wedge is a great option.



You can see a comparison here between the live view of the sun on my eVscope 2 using the baader film on the front and the baader solar continuum filter in front of the camera sensors and the Televue 60 using the Lunt solar wedge, an ASI 290mm camera, and with the baader solar continuum filter in front of the sensor.



The eVscope 2 view is just a screen capture on my cell phone, so the quality shown here isn't as high as what the telescope is actually producing as I'm not getting the full resolution with the screen capture. But, it gives you a general idea. The Televue 60 puts up a better image with the ASI 290mm camera, but I can't quite get the full disk of the sun. I'll need to pick up a camera with a larger sensor or use a focal reducer, which I have, but completely forgot about until putting this video together.



This animation of the sun was created by taking images of the sun on five consecutive days, and then making a video loop out of those images. I created each image by recording two videos on my ASI 290mm camera, one of the top two thirds of the sun, and one of the bottom two thirds of the sun since I couldn't fit the whole disk in the field of view. I then processed that data in PIPP, AutoStakkert, and then Registax, and then stitched the two parts of the sun together in Pixelmator, but any photo editing software will do. I tried to rotate each image so it would be in the proper orientation relative to the other images in the animation, but don't have them quite right. Since there are no strong east-to-west features on the sun like Jupiter's cloud belts, and the sunspots move quite a bit from day-to-day, it is hard to get the orientation exactly the same with each image. But, the animation does give you a good idea of what speed the sun rotates at, and how much sunspots will move and change from day-to-day.


Anyway, the sun is heading towards solar maximum and so activity on the sun will be ramping up during 2022 and 2023.


Plus, there is the big annular eclipse across the southwestern US during 2023, and another big total solar eclipse across parts of the central and eastern US during April 2024.




Solar observing gear will be selling out in advance of those two eclipses, so you might think about picking up your solar filters this year if you plan to observe those eclipses. Adding a solar filter or solar wedge is a great way to get more use out of your telescope. The nice thing about solar observing is that you can do it during the middle of the day instead of having to stay jump late at night or get up early in the morning to catch a specific deep sky object. So, if you haven't tried viewing or imaging the sun, give it a try.


Here are links to the products referenced in this post.


Filter for Celestron C8: https://amzn.to/3rbxqzf


Filter for eVscope or C5: https://bit.ly/3r5qSly

(measure the outside diameter of your telescope to make sure you are buying the correct size).


Lunt Solar Wedge: https://luntsolarsystems.com/product/white-light-solar-wedges/


Baader Solar Continuum Filter: https://bit.ly/3LMBtK1


Polarization Filter: https://bit.ly/3LJDxCE


As an Amazon Affiliate, I earn a small commission on sales of products made through links to amazon.com.


You can watch the video version of this post below.



25 views0 comments

Recent Posts

See All