New dobbie mount for an existing telescope.

Hi all,

With the horrid run of astro weather we have had here in Sydney, I've had to keep myself busy with other astro projects to keep my hands occupied.  So, it became the perfect opportunity to revamp a flawed little scope, and transform it into a brilliant performer!

I’ve had this 130mm Celestron Astromaster scope for a little while.  The single biggest problem with it is the poor equatorial mount it comes with.  The mount is too wobbly, and really more of a pain in the neck than what it offers.  And for beginners, this mount is the single biggest frustration that leads to this and similar scopes being put away and never used again.

The finder bracket on this scope had also broken off.  I am not too sorry about this as the original finder it came with was rubbish too.  Too close set to the tube made using it difficult, and its design is not easy to use.

So, the solution to this scope to give it a new lease on life is to ditch the eq mount and make a new table top dobbie mount for it, and install a better red dot finder to it.

I went to town on this little scope!  I had some fine materials left over from some other DIY projects, so I was able to use the following stuffs:

·      *   15mm marine grade plywood

·      *  Ebony Star laminate

·      *   Teflon bearing pads

·      *   Marine grade varnish

·      *   Stainless steel azimuth pivot bolt and washers

·      *   And a brand new 20mm red dot finder on a dovetail block.

Many dobbie mounts, including table top designs, do not have a balanced Optical Tube Assembly (OTA).  This means that if you switch between a wee little eyepiece to a very heavy eyepiece, the tube become top heavy or tail heavy when you switch back.  So these mount have a friction mechanism by which the altitude bearing is tightened, and there by making action of the altitude bearing stiffer so the tube does not drop under a heavy load.  Biggest problem with this being the quality of the action of raising and dropping the scope not only becomes harder/stiffer, but it makes tracking a target at high magnification as the action becomes jerky and very difficult to control.

Not with this little scope!

I designed the mount without any friction mechanism, but the OTA is perfectly balanced and the mount allows for the OTA to be loaded with any size of eyepiece, and the scope does not drop or rise – it stays put and the quality of the action not only remains exactly the same all the time, but it is silky smooth ALL the time!

This little scope now is a red hot, stable and very user friendly instrument.  I can swap eyepieces and the tube does not shift, even with no eyepiece in the focuser.  I can more easily locate targets because of the higher set red dot finder, and I can easily keep track of targets no matter the magnification I am using!

Alex.

Links to fellow Astro-Sketcher sites and blogs, and other astro-sketching resources

Hello all,

I've added a new links gadget to my site in the right hand side margin - Sites and Blogs of fellow astr-sketchers and other astro-sketching resources.  It is dedicated to the websites and blogs of fellow astro-sketchers and other astro-sketching resources.

I've started on a journey to find as many fellow astro-sketchers, and add their sites to the listing.  Different artists use different media, some pencil and paper, others soft pastels and black paper like myself, others work with digital processes, and many other different materials and media.  Astro-sketching though a very small niche, there is a wide variety of media, materials and techniques being used.  By adding the sites of as many astro-sketchers as I can, I aim to give exposure to all the different ways people illustrate and fulfill their passion for astronomy and sketching in its many forms.

There are a few people who cannot view into their telescopes due to physical limitations, so they use electronically assisted methods, such as video astronomy, to produce an image on a monitor, and they then make a sketch of what they see on the monitor.  Technology now provides a means of allowing a wider audience to participate in astronomy, and gives them tools by which to facilitate their own passions within astronomy and art that prior to this technology being available these people had no way of doing so.  Marvelous stuff!

If you know of a site that I have not listed, PLEASE let me know of it!

Please explore the work of these fellow astro-sketchers.  They all offer a different take on their art, different experiences and different approaches.

Alex.