l had a couple of hours today to have a look at the dob wedges and have come up with a first idea, this wedge will be made as an add-on for the dob carts and will just bolt into place, it will be adjustable to any latitude from about 20-50 degrees and will then lock into place as well as be able to moved on the cart forward or backward to address any balance issues. These pictures are just to give an idea of scale with the cardboard disc being the size of a 12" base, l will brobably have it mounted to the cart tomorrow and will post some more pics.
Last edited by mick pinner; 28-08-2005 at 08:08 PM.
however I would think that the wedge would only be used for non-visual ccd work, hence does the position of the focuser matter. The dob can still be used in alt/az mode with tracking motors and you can throw in a field derotator for longer viewing. I think Mel bartels stepper system would be the best bet to use. As it can switch between alt/az and ra/dec. It also has a field derotator component.
l read and understand your concerns Geoff but what is the alternative?, my ultimate aim is to have a more rigid and user friendly dob design which l am working on at the moment such as captured bearings and tube rings to allow the scope to be balanced by shifting the centre of gravity, as for the focuser position dob owners will not suffer any more than SCT or Newt owners in this regard, if people persist in buying dob scopes as a cheaper way into astronomy then deceide to tackle photography they will need some method to achieve this and my aim is to give them an affordable way of achieving this.
Great idea, and one I have pondered (no relation Paul) myself.
The focuser position is a pain in any newt, and I have made a split cradle that surrounds the tube proper, and has the altitude bearings mounted on the outside. A suitable clasp pulls this cradle together, but when released, slightly, allows the tube to be rotated. I can then roll the tube to afford the desired eyepiece position.
Keep at it Mick.
Gary
I think that you are doing a good job Mick.
There are always good and pad points to different types of telescopes and mounts and the same goes for the dob wedge but I believe that people will get more satisfaction out of their telescope with the wedge.
The prototype will tell how useful it will be and how well it will work.
the cart itself is almost finished so l thought l would post a couple of pics with the wedge attached,it can be used as a flat dob cart with levelling adjusters and it can have the wedge added at a later stage, it can also be raised from a ground clearance of 50mm for flat ground to 120mm for more uneven surfaces the wedge is fully adjustable from 20 - 60 degrees. as with the tripod wedge the wheels are 8" pneumatic with bearing hubs and the front wheel is a greasable roller bearing. it breaks down into 8 seperate parts including the steering handle and weighs around 10kg with the largest section being only 680mm long, the wedge as a seperate section is 600mm wide and 780mm long.
Great idea, and one I have pondered (no relation Paul) myself.
The focuser position is a pain in any newt, and I have made a split cradle that surrounds the tube proper, and has the altitude bearings mounted on the outside. A suitable clasp pulls this cradle together, but when released, slightly, allows the tube to be rotated. I can then roll the tube to afford the desired eyepiece position.
Keep at it Mick.
Gary
I made such a cradle for mine as well. I also added rubber wheels to the cradle for easy tube rotation.
one day closer to completion,
pic 1. the scope can be used for visual observing when the wedge is in it's fixed flat position.
pic 2. simply raise the wedge to the desired latitude for polar alignment.
pics 3 & 4. the rear sliders can be left at the fartherest point backward or slid forward to increase the angle of the wedge and also if necessary move the centre of gravity of the scope further towards the centre.
the final fine adjustments are then made using the threaded rod and locking nut.
there are a few final touches to finish but this is basically the finished item, a top plate for the wedge will be fitted but l haven't deceided what material to use yet.
