Graeme

4 hours ago, Naughty Neal said:

The 4 x 2  slide off rails will need beefing up  or replacing with something far sturdier to prevent sag/bowing,  one  could add an additional central support post on both sides. 

3 hours ago, malc-c said:

I agree, the wood used to support the roll off roof needs to be  a little more substantial, or the existing supported by some cross-bracing.  Other than that I think you've done a fantastic job.  

Thanks for the input. You're both right of course, I didn't appreciate the total weight of the roof once all the OSB and roof felt was added! The calculation I did to work out the weight required under the legs to mitigate against the risk of wind lifting the roof when rolled off was done quite recently, after I added together the weight of all the component parts. And even then I thought the angle iron would stiffen the 4 x 2 adequately. Probably should have gone for 5mm angle iron but that adds a level of difficulty to the construction. 3mm angle iron is easier to work with but a lot more bendy than I imagined! So the plan now is to put in additional 4 x 2s to the underside of the two that are there now and add two diagonal braces to each one. 

Graeme

We have lift off! I got the wheels on and the cross members up then I put the steel angle iron up in the centre of the 4 x 2 but that was a bit of an error because it followed the slight curve of the wood. The first roof roll off was not as smooth as I hoped. So I had to re-fix the steels to lay them parallel. It's still a bit stiff so I'll have to put some thought into that. But otherwise smoothish and to be fair the roof does weigh about 130kg! It's a pleasing milestone, I might get the telescope in this week and start setting it up, The finishing touches, the gable ends, the air bricks and the floor can wait till next weekend!

The roof open support posts are in. My good friend Andrew tells me that the uplift on the roof is around 75 kg/sqm for a site near the Thames Estuary, 3km from the shore. So if the roof is  supported on the 4 corners that would equal 75kg x 2m x 3m / 4 = 112.5 kg per leg uplift minus quarter of the weight of the roof. Which almost exactly equates to two bags of postcrete and 8 house bricks per post.

4 hours ago, carastro said:

Looking good Graeme.  Presume you are planning some sort of roll off roof and that it is going towards the palm tree.  

Carole   

Thanks Carole. Yes, that's the plan. The palm tree and the neighbour's silver birch are my biggest horizon blockers but the dome of London light pollution is in that direction so they form a natural shield. I dug one of the post holes today and got stung by a bee, so that was fun! Hoping to get both posts in tomorrow.

Graeme

Got the felt on the roof, there was a sale on for the nice green one! Not decided yet how to finish off the gable ends. I've run out of feather edge cladding, I might use the rest of the roofing felt that I have left over. And the palm tree has 14 flowers coming on it this year!

Does anyone else think that the markings on a chop saw are confusing? If you need a simple 90° cut across a timber you have to set the cutting angle to 0°. Then if you want a 60° angle you set it to 30°. 45° is ok because it's half of 90° and the same either way. To cut the 20° angle for my roof timbers I had to wedge in an off cut that had already been cut at 45° and then set the blade angle to 25° because 20 = 90-(45+25)!

All the best for a full recovery!

3 hours ago, bwj said:

Graeme, 

Sorry if I missed it in the posts, but would you mind posting the dimensions of this build? Looks like a nice job!

Hello bwj

Yes it's 3m x 2.1m x 1.7m high. With an extra 0.5m for the roof. It's based on a 700mm radius for the telescope plus an extra 200mm for clearance with 900mm on the end for the door, desk and a set of drawers and 300mm clearance on the side where I plan on putting a flat frame light box panel. Some might say it's the width of the gap between the fence and the path less 300mm to get behind the shed and it's the length the 4 x 2 timber comes in!

I'm glad you like it, I'm enjoying the build but it's going a little slowly!

Graeme

There's a good possibility I was overly pedantic today! I cut the roof trusses to give a slope of 25°. When I put them up the overall look was too high. So I took it all down again and recut the trusses to give a 20° slope. I think it was the right call! As a result I didn't have time to put the felt on the OSB. Let's hope it doesn't rain!

10 hours ago, Mr H in Yorkshire said:

I meant something tougher than nitrile actually, 

Yes, the "rubber" is a nitrile coating. Part of my role at work is to compile the Method Statements and Risk Assessments for HV electrical installation works. Gloves have been mandatory PPE for a number of years now. The standard used to be nitrile but now we use Cut 5 safety gloves. So it's a bit remiss of me to go home and not wear any, even more so while I'm taking an anticoagulant!

2 minutes ago, Mr H in Yorkshire said:

I wear work gloves regularly these days, even two pairs on occasions. I used to tough it out, you know using my hands to remove rough wood edges! Not any more.

That's sound advice Mr H. I had nitrile gloves on today for painting and for handling 8 x 4 OSB sheets and to stop getting blood stains all over my woodwork!

Well the walls are done and I've got a door. The hinges were a pain in the rear! They're extra wide to allow for the cladding and they don't close flat. I'm taking Rivaroxaban for a DVT I had at the end of last year so there's more blood in the build now because every nick and scratch keeps bleeding! Still need the 2" trim around the top. The roof section is made up, the trusses have been cut and the steel angle iron for the runners was delivered this week. Tomorrow the roof!

1 hour ago, Ags said:

I see you bought your shed some flowers 💐 

The Missus went to the garden centre. She thought it would brighten things up!

External cladding continues. It rained yesterday afternoon so the tarpaulin roof went back on. In the morning it was important to do some stuff in the garden, apparently!  So cladding was 3/4 finished today. The missus added her contribution. I used a 4ft spirit level with a piece of roof batten tapped to the bottom edge to space and level the feather board planks and copied my son's girlfriend's fence fixing method with a hidden nail under the overlap and another single nail on the bottom edge. Except that I used a nail gun loaded with staples, banged in across the wood grain on each upright under the overlap and a single nail on the bottom edge. 

Looks like I'm going to have to paint the fence!

On 16/04/2023 at 00:36, kbrown said:

I'm in a process of making an all sky camera using a RPi 3B and an IMX219 based arducam camera module with motorised IR/UV cut filter and CS mount. A long time ago I bought this Fujinon zoom lens cheap off fleabay. By specs it should be okay but I feel it draws a bit soft especially at full aperture. It's a bit better if I close the iris a bit but I'm not sure I want to do that... That said, can anyone recommend a good quality CS mount prime lens for all sky purposes?

 

The Pi Hut do Raspberry Pi is compatible CS-mount lenses. Don't know if one of those would be compatible with your arducam camera module.

I've got a ZWO ASI 224MC camera that came with a 150° wide angle lens, I'm hoping to use with my Raspberry Pi.

On 18/04/2023 at 09:00, Tomatobro said:

After building the camera (as above) I discovered an organisation called UKMON.

 

I've just subscribed!

Hope your sky is clear for the Lyrids.

Graeme

51 minutes ago, kbrown said:

I've been meaning to do some experiments with one of these I have in my random electronic components box: https://www.onsemi.com/pdf/datasheet/qrd1114-d.pdf

They don't cost much but would require supporting electronics and a well designed enclosure. One of these days I'll get to it

Thanks, this could be a way forward!

Graeme

So here's a link to a zip file containing the the code, schematic and Ascom driver etc. The text file lists the files included..

https://drive.google.com/file/d/1pdDf8cYwVrWxIS_OOSnR1XC3yR_tG6TO/view?usp=sharing

Graeme

12 hours ago, EarthLife said:

The way it's normally done on say a car is to use an IR LED and monitor the reflected/refracted light in the window screens glass, if it changes then you have water on the outside of the glass (due to blobs of water changing the reflection/refraction direction). It's very simple and reliable.

https://cecas.clemson.edu/cvel/auto/sensors/rain-sensor.html

But to stop copper from corroding just coat it with something like conformal PCB coating or pot it in silicon sealant (local DIY store) etc ?

Thanks for that. I'll have a read of the information in the link and see if I can improve the sensor to a refractive type. But I can't coat the strip board with an insulating material because it won't change it's resistance when it gets wet.

11 hours ago, skybadger said:

You can move from resistance to capacitance measurement using an AC signal , water will change the capacitance. The AC current reduces corrosion.

And thanks for that too. Again, I'll have a read up. We use sacrificial earth electrodes on the railway because of the stray dc currents. They get very corroded!

Graeme

Feather board cladding 50% done. The wood stain looked too red when it was wet but it's dried to a nice shade of oak. With the insulation done more carefully and the Correx board holding it in place, the cladding is going on ok. There's a narrow 12" gap to the rear but the fence panels come out ok. Looks like I'm going to have to put a 2" trim around the top!

Finished the insulation and boarding today. Much happier with the finish and I think the feather board cladding will go on a lot more securely now.

That's a fair point. My situation is that I have been controlling the equipment from indoors for a couple of years now so I'm close to where it's operating. For most of the session I'm monitoring what's happening. But now, with my observatory build I'm hoping to get a lot more all night sessions and there's a good chance of me falling asleep on the settee! I think the Arduino control and the NINA notification are as reliable as any system and although the sensor would be a weak link if not properly maintained, it is easy to keep clean and easily replaceable. 

1 hour ago, Tomatobro said:

I tried this a while ago and the problem I had was the change is resistance on the stripboard sensor due to oxidation of the copper strips.  

Hello Tomatobro

Yes, I did wonder how long the copper would last before it started to oxidise and what level of oxidisation it would have to reach before a rain drop fails to allow a change of voltage between the copper strips. A regular wipe with a gentle non abrasive acid like vinegar (or tomato sauce!) would keep it clean. The other problem would be deterioration of the board under the copper strips due to exposure. The MkII version will need to have Nickel-Chromium heating wire under it. 

Either way, Vero board is quite cheap on Ebay and if you're handy with a soldering iron a new sensor plate can be knocked up with ease.

Thanks for the feedback. Did your sensor effectively operate the Safety Monitor before the copper strips became corroded? And how long did it take before that happened?

Graeme

1 hour ago, Ags said:

Beautiful photography work - so clear. Please keep up the posts!

Cheers Ags.

I did like the shadow of the Silver Birch that blocks my Western view on the black sheet!  Not too much of a problem, there's just London light pollution in that direction.

Graeme

The weather has been too wet to be out working on my observatory build so I've been working on my Arduino rain sensor instead! I saw a thread by tosjduenfs on Cloudy Nights which uses an RG-11 rain sensor. But it occurred to me that if you put the sensitivity settings dip switch for sensitivity adjustment on the same circuit board as the Arduino then you could just use a piece of vero strip board as the sensor. Tosjduenfs has written the Arduino sketch and the Safety Monitor Ascom Driver and made it available for all to share. So I have rewritten the code to include sensitivity calculations. A control wire from the sensor is read by an Arduino analogue input. The original code looks for a change of state on D2 and when it sees that it tells the Ascom driver to change from Safe to Not Safe. I use NINA for Astrophotography, the NINA advanced sequencer can use the Safety Monitor to send notifications to a mobile phone, so I have installed Pushover to do this. I've not used it in anger yet because I haven't finished my observatory! But when I do, the plan is, if it rains, I get a notification on my phone and it wakes me up so I can park the telescope and close the roof. This can be automated too, but that's the next step!

When the code has been tidied up I will post a copy here if anyone would like to have a look and comment and point out any school boy errors.

This is the schematic:

The sensor plate will need a small heater to stop condensation forming and giving false readings.

Regards

Graeme