Denver observing chair

One problem with a dobsonian mounted telescope, like my Apertura AD10, is it's hard to be comfortable without a good chair.  A regular height chair is ok if you're looking at objects that aren't too high or too low in the sky.  If you want to observe something near the horizon, you really need to bend down.  And if you want to view something high in the sky, you'll have to stand up.  But for someone relatively tall, like me at 6'2", you can't stand up straight to observe, you need to bend down to reach the eyepiece.

The solution to this is an adjustable chair of some sort.  There are commercially made observing chairs, such as the one from OpticsMart, but they are quite expensive.  If you don't mind spending the cash, they are a nice way to go.  Something like a drummer's throne or shop stool would probably work as well, but you need to be sure they can go as high and as low as you need for observing.  Again, they cost money...

I decided to go the cheap DIY direction.  There are many designs online for observing chairs, and they aren't hard to make.  One I was considering was an observing stool.  A nice, simple design.  In the end I ended up building a design called a Denver chair, designed by Charles Carlson of the Denver Astronomical Society.  Click here to take you to the page with the design.

Here's how my chair turned out:

The design on the page linked above is very simple to build and well described, so I won't go into details here.  Be sure to find a nice straight, splinter free 2x4.  I did deviate slightly from the design.  Instead of the non-slip tread strip, I routed some 5/8" grooves along the back that the mounting bolt can slip into.  I made the grooves 3" apart.

As you can see, I also padded and covered my seat.  For the seat, I used a scrap of 3/4" MDF instead of plywood.

Since I covered my seat, beveling the back and having it ride against the front of the leg like the original design wouldn't work.  Instead, I beveled the piece of 2x4 on the bottom of the seat at the same 22 1/2 degrees as the legs and attached it flush with the back of the seat.  I then cut some pieces of rubber and screwed them to the back of the 2x4 to protect the finish of the leg.  For the rubber, I cut some pieces from a cheap rubber bungee cord.

When assembling the seat, be sure to add a spacer of some sort so the vertical plywood pieces are a bit wider than the 2x4.  Another option is to sand the sides of the leg a bit.  This is needed so the seat can slide up and down the leg easily.

Dobsonian leveling base with setting circle

I haven't done much observing recently, mostly due to weather.  First we had wildfires nearby, so standing around outside wasn't a good idea healthwise, not to mention the bad seeing.  And now it doesn't get dark enough to see anything until close to 9pm, and around that time clouds often roll in.  In the meantime, I've been keeping busy building some things to enhance viewing when I do get out.

The first thing I built was a leveling base with a setting circle for my AD10 dobsonian base.  This design should easily adapt to any dobsonian mounted telescope with some adjustments to sizes and positions.

Link to PDF plan for my leveling base.

Link to PDF detail of foot

Link to PDF of setting circle (print at 24 1/2", not 19")

I laid out my base using a 2'x4' piece of 3/4" plywood.  They call these "project panels" at Home Depot.  The base doesn't quite fit on one piece, so I cut it off around 27" wide and glued a strip about 5" wide along the bottom edge to complete the circle.  If you've got a full sheet of plywood, you don't need to worry about this.  The way I have it laid out, the glued on strip doesn't take any of the load.  The other parts you'll need are three leveling feet, knobs, and tee nuts.  I used bolt-down swivel leveling mounts, (zinc plated, 3/8"-16x4" long, part #2531K31), comfort-grip five arm knobs (3/8"-16 insert, 2 1/4" diameter, part #61125K13), and some 3/8"-16 tee nuts from Home Depot.

Once the glue dries, draw a circle with a 12 1/2" radius with the center a little over 13 1/2" from the edge opposite the glued strip.  From the center of the circle, draw a line straight up to the edge opposite the glued on strip.  Draw a couple more lines from the center at 120 degrees on each side of the first.  These lines will locate the lobes for the feet.  Mark a spot on each line 10" from the center.  This will be the location of the holes for the feet on the AD10's stock base.  Note that I deviated from my PDF plan and put these holes in line with the leveling base's feet.  It doesn't really matter, I just figured since I'd already drawn my lines, I would put the holes there as well.  

Print out the PDF detail of the foot full size.  Cut out the pattern and trace the shape at the appropriate location based on the lines you drew on the circle.  Get them as close as possible, but the exact positioning isn't critical.  Also mark the positions of the holes where the leveling feet will be mounted.

I used a jigsaw to cut the perimeter of the base slightly outside the line, then a random orbit sander to take it down to the line.  I also used the RO sander to round over the edges slightly.  Using a drill press, I drilled 1/2" holes for the leveling feet and 1 1/8" holes for the AD10's feet.  I also drilled a 7/16" hole about halfway through at the center to give clearance for the center bolt of the AD10's base.  I set the AD10's base on top and used a rat tail file to adjust the large holes to fit the AD10's feet.  I worked a little bit at a time until the feet slid snugly into the holes without any play and the AD10's base sat flat on the leveling base.  I made a mark with a silver Sharpie on the leveling base by one of the holes and on the bottom of the AD10's base by the corresponding foot so I could be sure to always get it in the same position.  I finished the base with spar varnish.

I found the setting circle PDF on the Cloudy Nights forums.  Unfortunately, I don't know who originally generated this PDF, or I'd happily give credit here.  I took the original and trimmed the white space around it.  The original is for a 19" setting circle, but for my design it needs to be a bit bigger.  I took it to Kinkos and had them print it at 24 1/2".  After printing, I used a black marker to touch up a few spots that didn't print well, then I carefully cut out the circle.  I had Kinkos laminate it, trimmed the lamination about 1/8" larger than the printout, and made oversize cutouts for the AD10's feet and central hole to allow for positioning adjustments.

Note that I positioned it with the 270/90 degree position by the foot I had marked.  This puts the 0 degree position on the left side of the scope.  By doing this, I can have the pointer on the side by the eyepiece instead of directly under the scope.

I placed the setting circle on the leveling base and the AD10's base on top of it.  I shifted the setting circle until I had it as evenly positioned around the base as possible.  It may not be perfectly centered on the leveling base, but that doesn't matter.  The important part is that it's centered under the AD10's base.  Before removing the AD10's base, I used masking tape at several positions around the outside to hold the setting circle in position.  After removing the AD10's base, I flipped back half of the setting circle and glued it down with contact cement.  When that was secured, I flipped back and glued the other half.

To complete the base, I pressed the tee nuts into their holes from the bottom of the base, using a vise to squeeze them tight.  I ran the leveling feet up through the tee nuts, ran a nut down the threaded shaft a ways, screwed the knobs on as far as they would go, then ran the nuts back up against the bottom of the knobs, using a wrench to jam them as tightly as I could against the knobs.

For the pointer, I bent a piece of .064 music wire from the local hobby shop as needed and epoxied it into a 1/4" coupling nut.  To hold it on the base, I put the AD10 base on the leveling base and centered it at 0 as closely as I could and attached several rare earth magnets (from Home Depot) along the edge of the base around the position where the 0 degree mark was.  I can adjust the pointer to exactly where it should be without worrying about exactly alignment of the base.

When I take my scope out, I can plop the leveling base down, point the 270/90 degree mark roughly at North, use a torpedo bubble level to adjust the base, put the AD10 on it, point at something in the sky, check the current azimuth using a cell phone app, and position my pointer at the objects position.  

This should work great for the azimuth, but what about altitude?  People have done pointers on the sides of their dob's bases for that, but I decided to go the easy and hopefully more accurate way and got an Alti Gauge from OpticsMart.

This is just like the Wixey digital level many people use, but with an astronomical enhancement.  The Alti Gauge has a dim red backlight.  The unit has a magnet in the bottom that attaches to the scope's tube.  You turn it on it and tells you the altitude you're pointing at to 0.1 degrees.  

I'm looking forward to making use of my setting circles, as star hopping in my light polluted skies is pretty difficult.  I hope this information is of use to others as well.

UPDATE: 

I was able to get out with my scope and use the setting circle.  It worked pretty well.  I was able to navigate to a few objects, although not dead-on.  I found that it worked best to point at something I could easily see near where my target was, adjust the azimuth pointer to that object and note the altitude of it, then slew to the coordinates of my target.  This would get me close and I was able to find my targets by panning around a little bit.

The azimuth worked quite well, but the altitude is off a degree or two.  I think I need to zero my Alti-Gauge. Due to it being off a little bit, I had to subtract the difference from what SkEye on my phone told me the altitude was. I'll try zeroing my guage the next time I'm out.

Overall, I'm quite happy with the results.