BIG dob ready for first light

[mdstuart]

My Dob now has a new home, an insulated box. Just need to make the front door.

My son James thinks the scope needs a smile on the front

 

[barkis]

Good Man, a gem like you have is worth every effort to protect it.
I look forward to some exciting reports that are sure to come from your winter skies observations 
of 2019-2020 Mark. I can only imagine the satisfaction you will enjoy too.
Good Luck matey, and may the skies be dark and clear .
Ron.

[mdstuart]

Temperature and humidity monitor now inside the box.

I keep readings for outside so I can compare. I am particularly keen to see a slow rise in temperature in the mornings to reduce the risk of mirror dewing.

Maybe I should install a web cam with an led light that detects dew on the mirror next 😀

[mdstuart]

Update. The insulation includes thin foil and that restricts the blue tooth temp signal. I have to stand near the shed to collect the log. Well at least that shows I have made a good job of the box.

Mark

[mdstuart]

Data now coming in from inside the telescope box. Humidity seems fairly stable between 65 and 70% which is a lot lower than outside the shed which ranges from 80 to 98%.

I can also see when the temperature rises fastest so I plan to check the main mirror does not dew during that phase. 

Quite interesting actually😀

 

[mdstuart]

Update on dewing in the shed.

Just opened the box mid morning. Warm sun on shed door but very much colder in the box which shows insulation is working.

Humidity still stable from 65 to 70% despite a wet few weeks here in the UK.

No condensation on mirror at all. It seems the box is working well for me. This is good given the "that is not living inside" feedback from my wife.

Next steps. I am getting a new mirror cell from Barry at Beacon Hill scopes. I am planning on building a new minimalistic dob around it. Pics to follow 😀

Mark

[mdstuart]

Mirror cell arrived. Now I need to make a mirror cell box, learn how to cut circles in wood and how to dovetail. I am sure it will be just fine. 

[jetstream]

On 27/10/2019 at 05:26, mdstuart said:

Update on dewing in the shed.

Good solution Mark.

I took a bit different approach that seems to be working well for my shipping container. We painted it a gloss white that I'm told is 90%+ reflective  (any gloss white is apparently).

So far the 24" mirror is within 4 deg f or less of outside and with a temp gradient across its surface of 34.3 deg F on the edges to 35 deg F in the center, +/- .1 deg F. When testing the gradient the mirror was within 2 deg F  of outside the other day. It might track better in the cold than the heat.

Without the white paint the temps with the stock brown were 140F on the surface when 85F outside. With the white paint the surface was ambient + a couple of degrees.

My brother in laws seacan has massive condensation problems, and has installed large vents and fans. Vents can pull in humidity...his sits on wet ground, partially in the shade.

I put the seacan on a crushed rock pad, graded so water flows though it and it also sits on treated 6x6's. The stock sea vents are used. Zero dew so far Mark.

Sorry to ramble but I'm always interested in passive climate control for scope buildings.

Eagerly waiting scope reports and very nice cell btw!

 

[mdstuart]

I was going to make a new lighter top secondary cage for the big scope.

Then stumbled across a 22 inch resonator drum shell on eBay as you do. So I thought, I wonder if that would work? Made from laminated Burch ply so perhaps not as light as two rings and stuff but hey why not give it a try.

So £12.99 later plus postage, this is on its way.

I will not need the liner which makes the drum 18% louder apparently.

If it works it will save me time and bring something back in to use again.

Mark

[Mr Flibble]

Great stuff Mark 👍

[Whistlin Bob]

Love these types of projects. Keep us posted 😁

[mdstuart]

The insulated box is still performing magnificently. Spot my two observing sessions where I let the outside damp air in!

[mdstuart]

New mirror box and cell...getting there

Edited December 14, 2019 by mdstuart

[mdstuart]

Gradually coming along. Drilling in Teflon is fun, hard to make indentations to ensure screw heads are below the Teflon surface. Give me a spreadsheet any day.

Yes I know I should have used ice pucks but I like to be unique in my approach.

Truss poles also arrived today.

Now cutting these to length will be my next challenge. In fact cutting these without getting bent ends or non level ends will be an achievement for me.

I do really enjoy the challenge and when the scope is complete it will be immensely satisfying. 

I also hope it will inspire others to have a go.

Mark

[mdstuart]

Not ebony star...an offcut of some textured laminate. Seems to work ok.

[mdstuart]

Summer has arrived so we continue. Making a focuser hole!

[mdstuart]

Perfect..

[mdstuart]

Spider painted and phew it fits.

The secondary mirror was literally held by three clips all touching the surface...eek. I am going to make an oval shaped piece of wood so I can do the silicon blob plus epoxy resin emergency cord attachment approach..

All this is tough for a non practical person but I am getting there.

[FenlandPaul]

On 07/06/2020 at 18:31, mdstuart said:

 

All this is tough for a non practical person but I am getting there.

 

You seem to be getting on just fine, Mark.  But I’m glad I’m not the only one who feels a little under-skilled in the presence of some of the engineering genius on here!!

[mdstuart]

Tidied up the secondary holder today. Epoxy and silicon to add and then I can reattach the mirror.

[Pixies]

As an aside... from a Premier drum fan.

The Premier Resonator  was produced from mid-late 70s to the 80s. The shell is 3-ply birch (with reinforcement rings) and used a thin inner liner (separated from the main shell with a air-gap). Any pre 80s drum shell will likely be 3-ply with reinforcement rings. More modern shells have many more ply without reinforcements and are generally heavier. So if you are looking for lighter shells, then earlier drum kits are what you would be after.

Anyway - a Premier Resonator dob. Clem Burke would approve! 

[mdstuart]

Varnish and internal black Matt paint added.

Looking good now.😀

[mdstuart]

Top cage down from 8.2kg to 4.5kg.

My spider is not quite square 😞 despite measuring things many times, however the mirror holder is central so it will be fine optically. I will say the spider shift is a design feature to help spot the Sirius pup star 😉

This makes me appreciate the work of professional telescope builders!

 

[mdstuart]

Well that looks ok and the mirror has not fallen off the holder...yet😱

[mdstuart]

Mirror cleaning underway. Yes too much washing up liquid!