Sun funnel done

To get the size of sun funnel I wanted, I had to join two different funnels.  But it works!

More sunspots

I was handholding the projection screen material in front of my scope for a 4-5" image.  Wow!  Today's sunspots were really impressive.

I noticed that they were very much in pairs.  Apparently sunspots come in pairs with opposite magnetic polarity.

Sunspots today

A kind soul sent me a 25mm Kellner eyepiece for solar projection purposes for the cost of shipping.  A nice thing about this eyepiece is that the field stop extends quite far from the lens, and will dissipate any sunlight if the sun goes to the edge of the field.

I played with it today to see how far away from the eyepiece I'd need to get to have a 4" image in my 8" F/4.5 (stopped down to two 3" apertures).  Answer: ~26cm.  When I projected the sun on a piece of cardstock, at that size, I was blown away by the richness of the structure of the sunspots today.  And the sun was quite low, as it was shortly before sunset.  Here's today's LMSAL photo.  I saw the two larger groups but somehow missed the smaller group that's down from center.

It's time to build a sun funnel as soon as my projection material comes.

Venus

Afocal, Coulter 8" F/4.5, TMB/BO Planetary 6mm eyepiece, with my son's Sony P100 camera.

Mars

I've never done very well with Mars, and my best views--never that good--have been with an aperture mask.  With full aperture, I just get a red and white blob of chromatic aberration.

I had a 75mm single-hole aperture mask that I was planning to use in my 8" F/4.5 Coulter for solar projection, but tonight I added another hole to it.  Both holes miss the two-vane spider.  The views of Mars with the aperture mask and a 5mm ortho are great--best I've had.  Two dark areas (one was probably Mare Acidalium) and a bit of polar cap.  I don't know if they're better with two holes than with one--there may be better contrast with one--but they are a bit brighter with two, and I love the easy focusing (with the mask, you see double and you focus by merging the images).

Lightening my Coulter 8"

I've been using my 8" F/4.5 scope more, because I just haven't been having the energy to pull my 13" out.

The 8" weighs in at around 40 lbs. I wish it was lighter. I shifted the bearings a couple of months ago so it wouldn't need a counterweight at the bottom of the tube.

And today I finally cut out big triangular holes in the sides of the rocker box.

I sketched out a template in Inkscape, and printed it out in three pieces (it didn't fit on an 8.5x11 sheet), glued them together, and transferred the locations to the wood with a punch.  I used a 2.5" hole saw for the corners of the triangle, and joined them up with a jigsaw cut. It was my first time using my fancy (reconditioned) Bosch 1590 jigsaw. I was pretty pleased. I used a Bosch T234X blade. It cut the tough OSB very nicely, and pretty smoothly (though the hole saw smoked a lot and there was a lot of tearout). The dust blower wasn't strong enough to keep the cut line clear, which was unfortunate (since I was wearing a dust mask, I couldn't blow dust away). Then I painted the exposed wood (with an approximately 1:1:1 mix of acrylic black paint, Titebond II and water). The cut out portions weighed in at a total of about two pounds. Not a big difference, but I find that at around 40 lbs, every pound makes a difference.

Wooden helical Crayford focuser

I've done this project a while back, but in case anybody is interested, I am documenting it.  My Coulter 8" scope came with a friction focuser made of pipe fittings that Coulter described as "helical", I think because you aren't going to do very well just pushing the focuser tube in and out unless you give it a twist as well.  With practice, the focuser was usable for light eyepieces, but it really didn't work for something as heavy as a Hyperion 13mm (and there are eyepieces heavier than that).  So I decided to make a helical Crayford focuser, because I was too cheap to buy a KineOptics one.

The idea behind a helical Crayford is that you have ball bearings against which the draw tube rotates.  However, the ball bearings are slightly twisted so that their axes make a small angle with the angle of the tube.  Consequently, as you rotate the draw tube, it moves in and out.  If the ball bearing angle is larger, the movement is faster, and if it's smaller, the movement is slower.

I mounted the ball bearings on two T-shaped supports made by taking a #12 flat-head screw for the stem of the T, and JB Weld'ing a segment of 1/4" square rod to the head of the screw for the line.  I then JB Weld'ed a  skateboard ball bearing (I expect from VXB's ebay store) at each end of the T's arm, trying as best I could that everything would be square and the arms of equal length (not that I am very good at that sort of thing).  I then took a piece of 3/8" particle board (Baltic Birch plywood would have been better, but I was being cheap) and mounted three posts on it.  Two of the posts would sport the ball bearings, with the stem of the T going through the post, and with various nuts and spacers to hold the bearings in place.  The third post had a little flap adjustable with a thumbscrew.  The flap was made of a piece of bondable PTFE JB Weld'ed to a piece of metal, with the thumbscrew bearing against the metal, all as in my push-pull Crayford.  For the draw tube, I used the aluminum draw tube from the Coulter.  In the picture, the hole for the focuser tube wasn't cut yet.

Here's another picture, with a better view of the T-shaped ball bearing supports.  You can see the gray JB Weld all over the  place.  Two things to be careful of when gluing are (a) don't get any JB Weld on the bearing surface, because then movement will be bumpy and (b) ensure that the JB Weld stays on the inner ring of the ball bearings, so it doesn't stop the ball bearing from moving!  Note also that the posts are located in such a way that the focuser tube would fit snugly in.  At this point in the process, the posts are, I think, screwed in place.

Eventually, I unscrewed the posts, cut a hole of the focuser with one of my trusty cheap Harbor Freight hole saws, sanded the faux veneer off the particle board, glued the posts with JB Weld to the particle board, with screws for added strength.  Or something like that--I don't remember all the details.  (It's possible that at some point the posts were weakly affixed with craft glue to help with layout and then pushed off.)

I did have one worry, and that was that the posts might bow outward with time, thereby decreasing tension, and generally making the focuser not work too well.  So I JB Weld'ed some strips of hardwood that I had lying around in my scrap pile, joining the posts as if with a fence between fence posts.  I was generous with the JB Weld.

Finally, I cut the particle board down to size, removed the old focuser (cutting the sonotube around it, ripping it out, etc.--it was a messy procedure), and attached the particle board with screws and some hardwood rails to fit to the curvature of the tube.  I also painted the wood and JB Weld black.  It's pretty heavy, but somehow fits the home-made styling of the Coulter scope.

The focuser has had a bit of image shift, which has increased with age.  Lately, it wasn't doing too well, so I had a closer look at it.  It turned out that the T-shaped supports, under pressure, had rotated further, so that the angle between the axis of the ball bearings and the draw tube was too big for good movement.  I made the angle smaller, added washers under the nuts (did I forget? or maybe I just ran out of washers?), and tightened it up.  I am guessing they'll rotate away again.  If they do that, and maybe before that, I may replace the nuts with locknuts, and/or add some toothed washers.

The focuser weight is an issue--I've had to increase the counterweight--but that's part of the price of making stuff out of wood.  And the price is hard to beat: a couple of bucks for the bearings, and then some screws, washers, nuts, square rod, and various pieces of scrap.