Made Some Progress This Morning

I did some more work on the custom spectroheliograph yesterday but I seemed to only make things worse.  It was definitely one of those days!  I had started over with the entire process of assembly in an attempt to eliminate the little problems I was still seeing but I seemed to introduce even bigger problems than the ones I was trying to resolve.  

I think part of my problem and the one that was the most time consuming of all the problems was a software problem.  At some point, a red box was moving around on the screen as you can see in the image below.  The box would scroll right...  then left...  then up...  seemingly for absolutely no reason at all.  At first, I was wondering if it was some border around the holographic grating to indicate my alignment was way off.  I swapped cameras and the problem disappeared so I then knew it was not a problem with my instrument.  I then tried the original camera using different software and I had no problems.  At this point I realized that the problem had to do with the software.  

The only thing I could think of is that the box was somehow related to a Region of Interest (ROI) selection box but there were no resizing "handles" on this box.  I decided to select a ROI and then change back to the full capture area but the red box remained.  And, it seemed to be moving around the screen on its own!

I disconnected the camera and then reconnected...  the red box remained.  I disconnected the camera and then shutdown the software then restarted everything...  the red box remained.  I went through this process a number of times.  Eventually, the red box disappeared but I have no idea of its purpose, why the red box was plaguing me, or how I eventually removed the red box.  What I do know is it wasted an incredible amount of time.  

You can see this red box around my Order #0 slit in the photo below...

So, this morning I started at the beginning again.  I acted as though I had not previously assembled the instrument and did all the steps necessary for assembly and adjustment.

When I first connected the camera, I noticed had a shimming issue on the wavelength selector and holographic grating so I had to resolve that with layers of aluminum tape.  Once again, I needed about eight layers of this tape on the entrance side of the wavelength selector/holographic grating.  This still seems like an awful lot of shimming to need to do but that is where I ended up again.  (EDIT:  I found that I needed to remove one layer so I am left with seven layers.) 

After centering the spectral lines by shimming, I noticed that I had tilted spectral lines on the screen as seen in the photo below (left side higher than right side).  The ends of the spectral lines on the right are lower on the screen than the ends of the same lines at the left.  I needed to carefully and slightly rotate the slit to the correct angle.  As I've mentioned many times before, there are no fine adjustment screws for any of these adjustments so each adjustment becomes a very tedious process.  

After some fussing with getting the slit level, I ended up with even spectral lines (photo below).  Now the ends of each spectral line were at the same level on the screen which is what we want...

I seem to have nice sharp sides to the view...  and sharp spectral lines...  and each side appears to be perfectly vertical...  all of which can be seen below.  I think that boldest line in the photo below might be the Sodium spectral line...

This image, below, is at the far end of the ultraviolet range near the CaK spectral line...

Then I went back to the Order #0 part of the spectrum to double check the slit (photo below).  It was still nice and sharp and it was still nicely centered...

Here is the whole instrument full assembled and adjusted...

Now I need to decide on a way to filter the solar energy so the heat of the sun does not melt any of this instrument's parts.  The sun, magnified by my telescope, will be far too hot for this instrument so I need a way to cut down the intensity of the sun.  I could use a very high quality neutral density filter...  probably around an ND4 or ND8 in strength.  I'll continue to use my IR/UV Cut filter on the front end of the instrument which will also add some protection from heat but I will also need a neutral density filter.  I'm still not sure which density would be more appropriate for my situation though.  Also, I'm having difficulty finding a high quality ND4/8 in stock.  Regardless, I'm not yet sure which one I should use so, since they are not in stock, I have some time to decide which one to get.

Another option I have to filter the solar energy reaching the instrument is to use one of my solar wedges.  The solar wedge is supposed to provide better images with this instrument but it is more difficult to set up on the mount.  It hangs off one side and it must be at a perfect 90° to the scope yet level with the horizon when Polar Aligned in the Home position.  I think I can perfectly align it but I'm not sure about all the weight hanging off one side.  That could be a problem.  I guess the thing to do would be to test it.

I also need to figure out the distance this instrument needs to be behind my telescope focuser.  It needs to be perfectly at infinity.  I know some people have had great difficulty in finding this distance but others have not.  Again, I suppose I need to simply try it.  I know I'll need an extension tube but the question is, "What size extension tube do I need?"  And then, "How far do I need to extend my focuser to come to perfect focus?"  

After writing about and thinking about finding the focus point, I'm thinking that I should start with a 40-50mm extension tube.  The instrument is already set up for good focus at infinity so then I would just need to rack the focuser out until I get a good focused image on the screen.  I don't think it will be too difficult.

So, I suppose I have the gear I need.  I can use my Lunt solar wedge to filter the solar energy.  Then I can test my telescope to see if I can hang this instrument off my telescope's focuser sideways without it slipping in any axis.  

I think I'm making progress.  The data I get from all of this work better be worth it!