Smaller Solar Filter for Smaller Telescope

Until recently, I've been using my usual photography-based cameras for my astrophotography.  I'm not going to get into details here but using those everyday cameras is not ideal for most astrophotography (it's okay for some things but not ideal for most) so I purchased two astronomy cameras.  One camera captures high speed video in color and the other camera captures high speed video in monochrome. 

Capturing video provides me with many frames to stack as images in a very short period of time.  Stacking the images provides a lot of benefits including less noise, more details and cumulative exposure.  With these cameras and a fast computer, I can capture hundreds of video frames (which are images) in just a few short seconds.  And that is at 6mp.  Many low end astronomy cameras are less than HD resolution, one or two are at Full HD resolution and my cameras happen to capture larger images at 6mp so I'm happy with that too.    

I have two Sony cameras that I use for my everyday photography and they are definitely class leaders.  I stuck with Sony for these astrophotography cameras too because Sony is the class leader in sensor development so I made sure the cameras I purchased sported newer Sony sensors.  

Actually, the absurdly popular iPhones that everyone thinks are amazing "cameras" actually have Sony sensors in them so, technically, these are Sony cameras, not (Cr)Apple cameras like all the iPhone fanatics think.  Just about all cellphones use Sony sensors anyway so they are all the same regardless of what anyone claims.  By "the same" I mean crappy when compared to a real, dedicated camera.  Sorry, as an avid photographer I feel confident in saying that cellphones are simply the Pinocchios of the photography world.  (Imagine a little iPhone with little arms and hands waving in the air as the iPhone exclaims, "I wish I were a real camera, I wish I were a real camera!")  If you want to shoot decent photos, get a decent camera.  Get the right tool for the job.  You wouldn't hammer a nail with radio...  to some slight extent you might succeed in somewhat hammering that nail a bit but it is not the right tool for that purpose.  The right tool is a hammer.  If you want to shoot decent photos, the right tool for the job is a decent and appropriate camera not a phone.  If you want to shoot good astrophotography photos, then you get your hands on a decent astrophotography camera.

The two astronomy cameras that I chose are on the low end of cost and features but I should point out that the high end of astronomy cameras runs into the six digit dollar range.  My disgracefully low fixed income is in no way able to support that so I chose cameras on the very low end of the spectrum.  These are still capable cameras if you use them to their strengths while avoiding their weaknesses (which is sometimes easier said than done, admittedly). 

Using astronomy cameras is a completely different experience than shooting photos with a normal photography-based camera and the learning curve is steep.  Fortunately, I have been reading up on the subject.  The entire interface between the camera and the user for these cameras is through software so a fast computer is required as is a working knowledge of a few rather odd software packages.  These software packages are nothing like most software programs though.  They tend to be more convoluted, unorganized and counter-intuitive than every other type of software out there so the learning curve is steep.  In most cases, the software is powerful but figuring out how to use it effectively can be a daunting endeavor and even a bit frustrating.

My monochrome camera was purchased specifically to use for solar imaging.  In short, the wavelengths of light that we study in solar astronomy are in a relatively narrow range (depending upon which part of the sun you are studying) so a color sensor that can see a wide range of visible light wavelengths is not all that useful on the sun.  Also, some of those wavelengths in the narrow range of solar images are not even fully visible to color cameras.  So, my new monochrome camera was purchased specifically with solar imaging in mind.  I will use the color camera for the planets and some deep space objects.  I will also continue to use my Sony photography-based cameras for other deep space objects and perhaps the moon.  For now, though, I'm focused on the monochrome astronomy camera for solar imaging.

Last week, I decided that my first astrophotography target with these astronomy cameras would be the sun.  I set everything up last week but I couldn't get the whole sun in any of my images.  I could only see part of the sun.  Capturing the whole sun was easy with my land-based cameras because of the much, much larger sensors in them but this is not so easy when using the smaller sensors in astronomy cameras.  Just to be clear, there are dedicated astronomy cameras with larger sensors but they were/are well beyond my budget.  I compromised and chose a camera with a smaller sensor. 

To compound this field of view problem, the telescope that I use for the widest views wouldn't even come to focus with my solar equipment!  I needed a new filter that was smaller because I needed a filter with a shorter optical path if I was going to be able to focus the sun with these new astronomy cameras.  I ordered the appropriate solar filter for this particular wide-field telescope and it arrived late last night.

As one would expect, I immediately opened the package and inspected this new little filter.  I was excited yet my first impression was not a very good one.  This solar filter seemed small and cheap compared to my larger Meade solar filter of the same type.  It was nothing like my larger Meade solar filter.  This new smaller filter was tiny and almost felt as though it was plastic.  It is almost toy-like and very basic!  It lacked additional filters too whereas my Meade solar filter came with more appropriate filters.  I was left feeling a bit underwhelmed by this new Lunt solar filter when I should have been excited about a new piece of gear.  As I held this new filter in my hand, I decided that in the morning, if the weather cooperated, I could try this new filter and see if it would be an acceptable compromise to capture a full disk solar image and be able to focus the sun in my small wide-field telescope.

This morning, the sky was almost completely white with haze so it would have been pointless to attempt any sort of solar astronomy.  As lunchtime approached, the sky was showing as a very pale blue but it was still closer to white than it was blue.  I decided to give the new solar filter a shot anyway.  I knew it would drive me crazy if I didn't try it.  At the very least, even if the seeing conditions were poor, I could still find out if I can focus and capture a full disk image of the sun which was the purpose of purchasing this smaller solar filter.

In this photo, below, you can see the new filter...  it is the 90° diagonal in between the blue tube-like thing and the gold collar thing.  The black solar filter has some sort of perverted-looking simplistic cactus etched into one corner of it which, apparently, is Lunt's logo...  

The blue tube-like thing is one of my new astronomy cameras.  The gold collar part is a Roto-Lock adapter so I can fit this 1.25" filter snugly and securely into my 2" focuser and lock it in place with a quick turn of the gold collar.  My 2" Meade solar filter was too large for any of my 1.25" eyepieces to come to focus.  I couldn't use these new astronomy cameras either.  The least expensive option to capture a full disk image of the sun was to purchase a 1.25" solar filter so I chose the Lunt Solar Wedge.  Every other acceptable option would have cost at least double the cost of purchasing this new filter.

My first two or three attempts at capturing video clips were unusable.  Honestly, that wasn't a complete surprise but it was a bit disappointing to feel as though I wasted some time and energy.  Even at the fastest shutter speeds with the sensitivity turned all the way down (the 'gain'), the sun was still terribly overexposed.  Apparently, the camera was too sensitive and this new filter wasn't filtering enough light so the images were completely overexposed.  This was a bigger problem than it should have been because I was not familiar with the software needed for processing these video clips either so there was a bit of a learning curve there too.  

I ate lunch, thought about this problem, and then came back outside.  The sky was slightly more blue than it was just before lunch so that was good.  I decided to add a polarizer and a neutral density moon filter to the nosepiece of the camera in an attempt to cut more light to avoid overexposing the next series of video captures.  This was like putting polarized sunglasses on the camera.  This seemed to help but, in the future, I think it might be best to purchase more appropriate filters in this smaller 1.25" size.  I have all the filters I need in 2" size but none of those filters can be used in this current configuration with the 1.25" solar filter.  

Here is a shot, below, of the whole solar kit with an eyepiece inserted into the solar filter.  I should mention that looking through the eyepiece was also far too bright for my eyes so I added a polarizer to the bottom of the eyepiece to cut down on some of the light but it was still a bit too bright.  I'll need to remedy that too with more appropriate filters.  

This is a nice looking kit though!

I've covered this in previous blog posts before but I'll mention it again here.  This photo, below, shows my homemade solar finder scope.  This thing works exceptionally well.  Here is a profile view, below.  The speckled flake black paint job matches the telescope.

When looking at the rear of the solar finder scope, there is a bullseye and a dot of bright sunlight that is shining through a small hole in the front assembly of the finder scope.  When you put the bright dot in the bullseye, the sun will be in your field of view...  easy peasy...  It is very easy to use and is more helpful than you would think!

Here is another closeup of the bullseye on the back of the solar finder scope...

Below, I've swapped out the eyepiece for the monochrome astronomy camera (the blue part).  At this point, I just need to attach the USB cable and plug it into my computer.  

I had my Microsoft Surface 3 tablet (with keyboard) sitting on a small table at the base of the telescope pier.  I draped a towel over the little computer and my head so I could see the monitor in the bright sun.  This allows me to see the monitor clearly while also remaining close to the telescope to adjust focus and capture video.  Another project on my to-do list is to make a small, folding sun shade for this computer.  Although I still might need to drape a towel over my head to block out all light and cut down on reflections on the monitor screen.

As I said previously, my first attempts at capturing video earlier this day with this new camera were failed attempts.  Those first attempts had overexposed the sun so much that there was absolutely no detail in the sun.  It was just a flat, bright white disk on a black background.  After lunch, I had far more success though.  Actually, everything went very smoothly after lunch!

Below, is a full disk photo of the sun from after lunch today...

In this image, you can actually see a bit of granulation.  Granulation is convection cells showing molten plasma bubbling to the surface which is seen in the image as a texture sort of resembling the skin of an orange.  Normally, at this wavelength we would see more surface details of the photosphere but, unfortunately, the sun is still a featureless disk right now other than picking up on some granulation but this is through no fault of my own or my imaging.  When I look closely at this particular image at full resolution, however, I can see some patterns indicating that some sunspots or faculae are attempting to form.  

The fact that the sun is mostly featureless is probably good for my lousy health but it makes for some boring solar astronomy.  (I have an unproven, as of yet, theory that my health issues are far worse during periods of significant solar activity.)  As we approach 2024 or so, the sun should be hitting its peak in its approximate 11 year cycle.  As this peak approaches, the sun will become more and more active and show far more detail.  Right now, we are in the quiet inactive part of this solar cycle so there isn't much to see.

The good news is that I had success today even though the sky conditions weren't all that great.  The sky really was closer to white than blue which is not good for viewing the sky yet I managed to capture some nice detail on a full disk image of the sun using my new monochrome astronomy camera so it was a success and it is promising for days with better seeing conditions.  There is no question that I captured far more detail today than I ever have with my photography-based cameras.  

For this particular image, above, I captured about 100 frames of video in a few short seconds and I kept just the best 25% of frames to stack for a final image.  I'm pretty happy with the result.

Next, I'll need to order some smaller filters to use with this new Lunt solar filter so that I can more effectively cut down some of the overly bright light while adding a bit of contrast to bring out some additional detail.  In the meantime, when (if) we have a very clear and sunny day, I'll attempt to use one of my larger, more powerful telescopes to get some closeups of the sun.  That should provide some very interesting images!  I'll need a crystal clear day for that though.  

We'll see how long it takes for us to have appropriate weather for something like that.  And, of course, my health will need to cooperate too.