The addition of altitude and azimuth setting circles so you can tell where the telescope is pointed is a very important consideration that seems to be lacking from all Dobsonian telescopes. I didn't want to spend hundreds of dollars on digital setting circles (which also require careful modification of the mount), so I started fiddling with building my own manual ones. What's more since I've used adhesive tape and stickers here none of these changes are permanent. If I wanted to sell the telescope to someone who didn't like any of these changes I could simply peel them off right in front of them.
For starters all that is required to add an altitude circle to your telescope is a large protractor placed by the base and something on the telescope body to point at the protractor to an angle corresponding to the altitude of the telescope. I took a scan of a protractor, printed it on a sticker and stuck it to the base and covered it with contact (to protect against weather) as you an see below. I then added a pointer on the telescope using a triangle of PVC tape. The system seems to be accurate to within about 3 degrees when the telescope base is placed level.
(I initially started fiddling with hanging a protactor and a weighted string off the body of the telescope but this didn't look very nice, and also meant that you had a weight constantly crashing into the telescope as you moved it and which therefore needed securing. This still may have been more accurate than what I have settled on, since it would not have required the base to be placed level on the ground. My current system requires that you place the base on level ground or you end up having to estimate the angle between what you read and what you read plus the tilt of the base.)
An azimuth setting circle is more time consuming but also quite cheap and easy to make. Dobsonian mounts are most often already circular. All that needs to be done is to accurately add markings to bottom part of the base with degrees marked off, and a pointer on the top half of the base. To make the marks removable, I first covered the bottom half of the base with white PVC tape. Accurate markings can only be made if you first use a tape measure to measure the diameter of the base and then divide by the number of markings you make. (I recomend 36 markings at 10 degree intervals). I also added a compass to the base (attached using only heavy duty sticky tape) to make alignment easy.
Ever since I started using a Telrad to point the telescope, I wouldn't choose to use a telescope regularly without one. A Telrad consists of a pane of glass oriented at 45 degrees to the telescope onto which is projected a target for siting objects which the telescope is pointed at at night. You can adjust the brightness of the red target, which is only visible when you view at the correct angle to point the telescope (once you've initially aligned it, which is relatively painless) and you point using an unmagnified and almost unobstructed view of the sky. They cost you less than a good lens, and using this even my mother who knows nothing about astronomy finds it dead easy with no practice to point the telescope at the moon or a bright star. If you speak to most astronomers they either love or hate Telrads. I love them. They won't completely replace a traditional finder, and it's worth learning to use both, but my choice to locate bright objects is a telrad.
As you can see I've also added a trolley to my setup. I'm still quite ambivalent about this since it does make the scope noticably less stable. However most of my viewing sessions are quite quick and the trolley saves a lot of back ache. If I need the stability I can wheel the telescope close to its final location and then move it off the trolley. Still a lot better than lifting and carrying it long distances. The only modification made to this trolley is that the handle has been reversed so that it folds out away from the telescope (allowing the telescope to be used while on the trolley) Note the strap used to secure the telescope to the trolley. Finding a suitable trolley was quite painful. Large wheels are a must have. This one doesn't have locking wheels (which it turns out are quite expensive) but that would be a useful addition. Regardless I wouldn't want to try to use this trolley on a hill. If you do buy a trolley make sure it can support the weight of the telescope and is relatively stable. I've been able to turn my Dobonian into a true "sidewalk" telescope using this setup since I've taken it down the street on the footpath to view objects that were obstructed from my house.
There you have it. A much more usable Dobsonian.
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