Monday, July 31, 2017

A 12.5" Kit for Mike in

The OTA components for Mike's kit are coming along. Included is a
Baltic birch 6-point non-flotation mirror cell for Mike's full-thickness
primary mirror. Note the Destiny spider and Moonlite focuser.
 
Rear of the mirror board detail. There's plenty of "ventilation" to
help when the primary mirror is cooling.
Always beautiful work by Destiny and Moonlite. This focuser
is a "single-speed" with 2" to 1.25" adapter and compression ring.



Peter's "Adjustable Struts" ....

Here's a photo of Peter's 14" telescope
he's using adjustable "upper" struts
to finalize the strut length. Great idea.
One of Peter's specifications was that
the telescope would fit into his RV

Here you see it "under the bed"!!
The fit is juuuust right!!

Friday, July 28, 2017

Tom's 12.5" F3.92 is Completed....

Tom's short focus telescope is a dream to use. Easy to manage, easy
to setup and move around The struts are only 42" long in total

Note the eyepiece tray in the front of the rocker box.

The altitude bearings are 21" in diameter. When changing eyepieces the
telescope stays in position. Note the dew shield.


The 6-point flotation mirror cell design and optimized
with Plop. The struts are all black powder coated.

A 3-vane curved-vane spider and Moonlite 2-speed focuser..

There are two clamps for Tom's Telrad. Note the sliding 1.25#
counterweight just in case it's needed for different eyepieces.
An "afocal" shot of the moon with Tom's telescope
using a 17mm Nagler and Nikon point 'n shoot camera.

Not too bad!!!!

Eyepieces Anyone? ? ?

Putting the finishing touches on Tom's 12.5" telescope. Here an
eyepiece tray for his 2" eyepieces. All Baltic birch construction.

Wednesday, July 26, 2017

John and his 7" Refractor....

Last April I made a "mount heat" for John's big 7" refractor.
I'm glad to hear from John who says "the mount works great"!

John lives in Richmond, Virginia.


Find the Center of a Circle ...

I've had some questions and comments about finding the center of a circle -- your mirror in this case. Here's some interesting examples I found on the Internet. They're pretty self explanatory, so have a look.

You can also look at my website for another method I like to use for the front of the mirror. ==> http://dobstuff.com/mountmirror.htm







Tom's 12.5" Telescope Almost Complete....

Tom's 12.5" strut telescope is just about complete. I'm having
the struts powder coated. 

Note the dew shield.

Peter and his 14" Strut -- Center.....


Hi Dennis: Here's how I placed the center mark for the mirror cell:

Put the carpenters square on the mask so that each end of short side of the square touches the side of the circle. Draw a line along this side and mark the middle of the line. This draws what mathematicians call a bisected chord.

Move the square so that the corner lines up with the middle mark and the short side is on the line you've drawn. Draw a line along the long side. From geometry we know that this line passes through the center of the circle. This effectively mimics a carpenters centering tool. 

Do this twice and the intersection of the long lines is the center of the circle. I did it multiple times to get an idea of the error in the method (from sloppy measuring etc)

Peter

Monday, July 24, 2017

Peter and his 14" Kit . . .

Peter, in Canmore, Alberta, Canada is assembling one our kits. This one is a 14". Here's what Peter has to say so far (Note: Looking greater Peter):

Hi Dennis: 

Here's the assembled rocker box. The sides weren't quite square after I put them together so I lined up one of the sides to the bottom board, screwed in that side and used my large clamps to square up the other sides with the bottom board. I then put the rest of the screws in and all is now nice and square. 

Peter....

Tom's OTA -- Almost Complete . . .



The mirror box. Note the black anodized struts. All aluminum, except
for the mirror cell, will be black anodized or powder coated.
This telescope has the Easy Transport Telescope option
Note the bottom half of the struts, about 21" long for
this F3.92 focal length. Nice 'n small!!

And with the Intermediate Ring in place. This
not only allows the struts to be one-half the length
but adds some rigidity to the assembly.

The "top half" of the struts.
Add the top ring, with focuser, spider and
secondary, and the OTA is virtually complete.

The total strut length is 42.5"









Sunday, July 23, 2017

Star-B-Que and More ...

Your truly and Linda with my 13.1" F4.5
with Swayze Optics mirror.
 A delightful evening of bar-b-que and astronomy at Ostahowski Optics in Anza, California. In case you may not be aware, Terry Ostahowski was the optician behind Discovery Telescopes for many years.

Check out his website here.

OTA for Tom's 12.5" F3.92....

Tom's OTA components are nearing completion. 

The spider is a Destiny 3-vane curved-vane, Moonlite 2-speed focuser
and Dobstuff 6-point flotation mirror cell. Nice!!

Will and his 13.1" Telescope . . .

Hi Dennis: 

Here’s a glamour shot of the scope at Pinnacles National Park.  We actually moved to a less scenic location, but with better horizons, for observing.

It was a fun night.  Even though it’s a bit past prime time for spring galaxies, my first target once it was sufficiently dark (after some nice views of Jupiter and especially Saturn) was M51.  Interesting coincidence, the “pinnacles” that give Pinnacles its name come from a volcano that erupted 23 million years ago…just about the same time the light we’re seeing from M51 started its journey.  The arms were apparent, but the northwestern sky at Pinnacles is the worst direction to look in terms of distant light domes.

I spent the rest of the night revisiting favorites among the milky way from Scorpius and Sagittarius up through Cygnus.  Nebulae looked bigger and brighter, and clusters richer with stars, than I’d ever seen them.  I spent a fair bit of time just panning around with a nearly 1.5° field of view provided by a 31mm Baader Hyperion Aspheric, with more detailed views provided by 20 and 11mm eyepieces.  My highest power eyepiece is a 6.7mm yielding about 223x, which I used on the planets, tracking was very easy at that power and I’m sure it could have done well at considerably higher powers if conditions and targets warranted tracking down a Barlow.

Incidentally, I have somewhat figured out the meaning of the circled “-2” on the side of the Coulter mirror.  It definitely has to do with the actual (as opposed to nominal) focal length (http://www.askmisterscience.com/coulter/odyssey-sales-pg10.gif), although it’s not clear to me what the units are…definitely not inches but might be % (http://www.askmisterscience.com/coulter/).

Take care,
Will

Bob's 16" . . .

Bob, from Princeton, New Jersey, sent along a photo
of his 16" telescope (ETT with strings) setup in
his garage. Now, to get the telescope under the stars!!

Friday, July 21, 2017

Will's 13.1" Telescope with Travel . . .

Hi Dennis,

The storage/travel struts arrived today.  Now I have a 13” telescope that is very stable and smooth but easily packs away into a small hall closet, pretty nice.  There’s even room for jackets to hang above the telescope.  The full length struts are on a shelf above.

The forecast for Saturday’s dark sky trip is looking good, too.  :)

Take care,
Will

Thursday, July 20, 2017

More on Tom's 12.5" F3.92 . . .

Tom's mirror board, mirror cell and cover are complete.

This mirror board is for a "strut" telescope. The larger 2" washers
protect the wood with the struts in place.

Tuesday, July 18, 2017

Tom's 12.5" Strut Telescope -- A Cell . . .

A 6-point flotation mirror cell for Tom's 12.5" mirror. These
mirrors cells are designed  and optimized with Plop.

Easy to collimate with knobs, vent holes for cooling.
Here, the mirror cell is affixed to the back of the mirror with silicone.
Once the center of mirror is "center marked" the cell is lined up using
its center  hole. I use the plastic "sight" to be sure the alignment is right on.


I give the silicone 48 hours to "cure".

Sunday, July 16, 2017

More on Tom's 12.5" Telescope....

The rocker box sides and altitude bearing are taking shape.
The alt bearings are 21" in diameter. Just right for a telescope of this size.

Saturday, July 15, 2017

Will and his 13.1" Telescope.....

Will, from Scotts Valley, California, sent along a photo and some comments about his telescope:

Hi Dennis:

Here it is fully assembled, with an Astroscan for scale.  After playing around with the clamps a bit I decided to try just zip-tying the Tetrad base directly to a strut (I had to drill a few holes in the Tetrad base) - it actually seems to hold pretty well but I may end up going the clamp route after all, maybe with a Rigel Quikfinder instead of the Tetrad if it gets too bulky.

Not shown in this picture, I’ve rigged up a dew shield for the primary, should it prove necessary.  The 15” opening equates to a diameter of 47.1”, so a pair of 24x12” Kydex sheets are enough to completely encircle the mirror.  Rather than trying to form them into a single piece I just cut short slots to accommodate the wingnut for the altitude bearing and form each sheet to one half of the cage, their inherent tendency to try to spring flat again holds them in place nicely.

Take care,
Will

A 12.5" for Tom . . .

The start of a 12.5" F3.92 for tom in Davis, California. Note the
eyepiece tray for three 2" eyepieces.

Friday, July 14, 2017

Peter Begins Assembly....



Hi Dennis: I don't know if you wanted construction pictures for your blog, or just finished product, but here one of staining in progress. The gel stain seems to go on well. Wipe it on with a rag and wipe off the excess with another.

Peter lives in Canmore, Alberta, Canada.

Thursday, July 13, 2017

A 16" Kit for Howard . . .

Except for mounting Howard's spider and focuser (the spider is yet to be
delivered), I've complete his 16" kit for a Hubble Mirror. Note
the 6-point flotation mirror cell. Howard lives in Salem, Oregon.

Monday, July 10, 2017

An Eyepiece Tray....

I don't to make these very often, but here's an eyepiece tray for Will's
13.1" telescope. Plenty of room for two 1.25" and two 2" eyepieces.

Howard's 16" Kit -- A Rocker Box....

Howard's rocker box assembled with clamps to check "fit". His
kit is nearing completion. just a few more items and hardware to add....

Thursday, July 6, 2017

A 16" Strut Kit with ETT . . .


Under construction is a 16" kit for Howard in Salem, Oregon.
An Easy Transport Telescope (ETT) and 6-point flotation cell is included.

The "beginnings" of the 6-point flotation cell and focuser bracket.