7024 replies to this topic

[musicengin]

Woke up way too early, fed the cat, had an idea for yet another way to approach making a secondary holder.  

 

I was reviewing my collection of photos and builds of secondary holders yesterday, and grumbling and muttering because everyone else's secondaries are humungous compared to my dinky little one for the 4.5 inch scope I'm working, there's no SPACE for anything.

 

I was getting close to punting and just sticking it on a piece of brass that I could bend into place, and then try not to bend out of place accidentally.

 

Now I've got a two screw idea that I think will solve the two main problems (besides just being too small to exist)  -- adjustability AND stay right there no matter what.  And be buildable with my set of tools and materials.  And be adjustable with allen wrenches.  And not risk dropping said allen wrenches on the primary.  I think.  Build it and see.  If I don't get yet another idea first.

[Jeff Dunn]

Poured some dental stone pitch lap tools today for a new project.

 

 

 

 

[Pinbout]

what do you have between the glass and stone?

[Jeff Dunn]

what do you have between the glass and stone?

Seran wrap, already have the plaster off and on the patio (on a cake rack).  Going to pick up some poly tonight.

[member010719]

John aka CCD-Freak

 

Thank you !

The hub I'm using was serving  in my first 160 mm Dobsonian for about ten years.

This spider is according to recommendations of  Texereau.

I will take better pics and post them.

The central hub is machined of steel.

 

Bill

 

The bolts are too long ,they will be cut to length.

You are right , even after that , the arms including end screws are wider than tube diameter.

But the arms are made from half milimeter galvanized steel sheet , they are arching enough but do not deform during assembly.

Once the screws pushed in the holes , the tension applied by the nuts are straightening the arms.

 

musicengine

 

Have you considered the Seronik spider ,recommended also in the plans for the   Stellafane Dob ?

 

 

Thanks God , this evening I finished the assy of spider arms.

This was the last piece missing from the puzzle...

Test assembly for the balance is on the horizon !

 

 

 

Ziridava

[grtyvr]

Got some stuff done....
 
Made a secondary holder for my 'freescope".  I milled out a block for the mounting of pallet strapping to secure the mount.

 

I also got some way towards a full scale model of the design of Oberon.  That scope has had me drooling for a while, and I think I will see if I can build one, half as nice.

 

 

 

[musicengin]

More work on the drawings for my secondary holder.  I still like it, and I think solved a couple problems while still in the drawing phase, always very satisfying!

 

 

 

 

 

There is a semicircular metal vane, doubling as a shade for the secondary; the view is from above.   The oblong green thing to the left is the rear elevation of the holder, it was a convenient place to work on it.  I'm aiming to build it this coming weekend.  I'm really curious to see if it actually works!

 

The dark magenta box extending way past the 0.8 inch circle of the secondary is a thingie for testing the sanding-off of the corners of the pieces after I've glued them up, to get them inside the limits of the circle of the secondary.  There's a lot of information stacked up on top of each other, it helps me work out what is going to fit where and so on.

Edited by musicengin, 14 June 2017 - 11:40 AM.

[DivisionByZero]

I'm part-way through my dew-heater + set-point TEC upgrade system.  The dew and TEC power supply is the same unit which can put out 4.2A at 12V.  I have the P/S mounted with an old line filter from a dead microwave (why not?).  The TEC power is fused for 3.5A and will go straight to the controller and fan which will simply run full-on 100% of the time while the TEC will be controlled with a small board controller.  The dew heater controllers are just LED dimmer switches that I've opened and re-arranged onto the lid.  Since they're connectorized already, it won't have hard at all to make the pair of connections.  I'm not quite to that point, though.  That's for tomorrow.

 

I still have to do follow-up surgery on my camera to put in a heated sensor window, install the thermistor for the set-point control board, and better insulate/seal the whole camera to control dew.  It'll also be a little tricky attaching my intel heat-sink to the cold-finger... might get ugly.

 

Anyway... nearly done with the P/S and then I'll move on to the camera and making a dew strap for my autoguider.

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[PETER DREW]

Just detail finishing on a ED80 binoscope but being distracted by starting another 150mm F5 achro binoscope. Sound familiar? 

[jnanof]

Using the tripod and altitude adjustment base from my previous pipe mount post, I bought another flange and mounted my ETX 60 for use in polar mode.

I originally was going to moung the scope on a piece of wood, then that wood to the flange but I would have needed to counter sink the bolts for the scope. As I look at this thinking about what to do, I noticed that the 2" pipe flange mounting holes lines up exactly with the holes on the base on the scope. Well, they were about 2mm off so I just drilled out the flange hole.

 

http://imgur.com/a/sRqpW

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[jnanof]

another view of this. 

Now it is cloudy for the next 3 days.

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[michaeldurban]

almost finished my HG style aluminium collimator

 

6mm housing hole for small laser, 3mm hole for the protruding wires.

 

still need to tap collimation holes for the laser.

 

machined to fit the HG parallizer, the 'shoulder' sits flush in the parallizer

 

 

 

front opening -6mm- (towards secondary) will receive a fitting disc with 1mm hole

 

[michaeldurban]

or it could function as a alignment cap

[drneilmb]

Back to work on a little 12x63 finder scope. I've got the collimating lens cell done, now I need something to put the eyepiece in.

 

 

I cut a matching square of pine and drew the outline of the eyepiece holder I'm going to use. I didn't have a drill that big, so I drilled lots of little holes around the circumference and used the burr in the little dremel to get the disk out. A little cylindrical grinder in the dremel will finish the job.

 

The eyepiece holder is the top of a 1.25" drain extension. The hole was expanded to just fit and then it was siliconed in place.

 

 

 

 

It works great for holding an eyepiece

 

 

and now things are ready to check the focal length.

 

[Messyone]

Knocked up a secondary scope thingy...with WO rings and ADM V rail clamps. 

 

Black and Brass to match my 2" pillow block mount. I needed a bit of weight on this one to match the weight of another widefield scope I also use, this one is for a 70x900 Achro.

 

 

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[drneilmb]

Telescope's done, time to make accessories. This is my homebrew red LED dimmable flashlight. 

 

 

LED goes through the lid of the bottle, 10k pot with built-in on-off switch goes out the bottom, and the 3xAAA holder sits inside. It seems like it should be dim enough, but we'll have to test it and see. It's certainly bright enough when it's turned all the way up.

 

The LED needs to be "potted" onto the bottom of the battery case so nothing shorts out when you screw in the lid. Does anyone know if silicone glue like you'd use to hold on a mirror (if you're a phillistine like me) is an electrical insulator?

[DivisionByZero]

Work finally calmed down enough, and I had some time to figure out how to mount my TEC and heat sink to my camera.

 

Next: build a little box for the controller and wire up power+fan to a single input.  

After that: camera surgery part 2 to add a sensor-mounted dew heater.  

 

I hope to be done at least by full moon if not sooner.  

 

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[roscoe]

Telescope's done, time to make accessories. This is my homebrew red LED dimmable flashlight. 

 

20170628_213552-298x530.jpg

 

LED goes through the lid of the bottle, 10k pot with built-in on-off switch goes out the bottom, and the 3xAAA holder sits inside. It seems like it should be dim enough, but we'll have to test it and see. It's certainly bright enough when it's turned all the way up.

 

The LED needs to be "potted" onto the bottom of the battery case so nothing shorts out when you screw in the lid. Does anyone know if silicone glue like you'd use to hold on a mirror (if you're a phillistine like me) is an electrical insulator?

Yes, silicone is an insulator.

[jtsenghas]

 

Telescope's done, time to make accessories. This is my homebrew red LED dimmable flashlight. 

 

20170628_213552-298x530.jpg

 

LED goes through the lid of the bottle, 10k pot with built-in on-off switch goes out the bottom, and the 3xAAA holder sits inside. It seems like it should be dim enough, but we'll have to test it and see. It's certainly bright enough when it's turned all the way up.

 

The LED needs to be "potted" onto the bottom of the battery case so nothing shorts out when you screw in the lid. Does anyone know if silicone glue like you'd use to hold on a mirror (if you're a phillistine like me) is an electrical insulator?

Yes, silicone is an insulator.

 

Yes, indeed. If you have any doubt whatsoever about any material, just set a good meter to an ohm setting and apply the two electrodes to a sample with very minimal spacing between them. Resistance should remain close to infinity.

[musicengin]

I still like my secondary holder, so I'm finishing it up and planning on actually gluing the real thing together this weekend.  Then I just need to cut out the vane, which I think I've finally settle on as a semicircle of mild steel, doubling as a shade for the secondary mirror.  I've got an image for a R. Ravneburg scope that does that, and I'm curious to see how well it works.

 

Then there's the mount.  I think I like my design, but I need to do some hardboard prototyping before cutting wood, and of course I have no precedent and no idea if it will work well, and I'll probably have to build the whole thing and I'm way out on a limb, with is both fun and scary.

 

But if it works it will be pretty light, which is one of my main design constraints.  I like carrying things up a hill, if they aren't too heavy.

[member010719]

In urban environment you will not like it.

 

A Newtonian telescope need a much wider  secondary baffle than that.

A focuser baffle like that recommended by Mel Bartels will be much better.

Check your figures here :

 

http://www.bbastrode...com/baffle.html

 

I decided from now  to add focuser baffle  to any Newtonian.

Because I build by necessity only solid tube Newtonians , the secondary baffle is solved automatically by the extension from focuser to the upper end of tube.

Also the solid tube it solving  the primary mirror baffle.

So where I can act is the focuser baffle.

For secondary and primary mirrors baffles I just have to check my figures are right.

 

 

Ziridava

[musicengin]

Ziridava --

 

Thanks for the comments!  I like Mel Bartel's ideas a lot, but I'm off in a rather different direction in terms of which designs I'm building from.

 

My vane is a semi circle 2.5 inches deep -- deep enough to just reach the bottom of the secondary -- and 8+ inches, to reach opposite sides of the upper optical board/assembly/doodad.

 

I've gone around in so many circles and come back this design often enough that I think I'm up for trying it and seeing if I like it.

 

If I don't, I just unbolt the vane to put the next idea on; I like gadgets I can take apart and update, and this part strikes me as especially likely to be something I want to do that with.

 

I also like Ross Sackett's designs, though I'm going to use the same two stalk approach that I used with my 3 inch scope.

[ed_turco]

A lady called me a few weeks back and wanted me to teach her how to make a telescope. 

 

 

SHE FINISHED IT ALL TODAY !!!

 

 

I can hardly believe it but she came every day, 4 to 6 hours per day.   I wonder if there are any more like her, waiting to call.

 

Recently, I realized that my RA has crippled me to the extent that I can now longer make telescopes.  Hell, I can barely walk now.   Or observe.  It was a great 60 year run. 

 

But these new experiences have taught me this new role as a teacher is FUN!

 

 

ed

[mark cowan]

Ed that is very cool!  

[roscoe]

Good on her, and GOOD ON YOU, Ed!!  Your body may be slowing down, but your experience and knowledge is still in fine shape, it's wonderful that you are able to share that!