Gina

Here is the fork with RA drive disc. I plan to print this on my Giant printer when it's back in action since it's too big for my Titan printer.

Been out to the big shed and found a number of pieces of timber that I could use for a 4ft x 2ft pond a foot deep. All sorts of sizes. I might also make some raised beds for planting. That timber has been in there for 10 or 15 years - maybe more. We used to buy job lots of timber for making sheds from local sales. These were mostly roof timbers from large barns. I still have some 8" x 3" like I used as the foundations for my observatory and there are even bigger ones. Only problem is... I can't lift them! There's plenty of smaller stuff though such a 2" x 8" and 2" x 6" as well as what might be used as cladding. My bench mitre saw can take up to 12" x 3" so I don't need to saw by hand.

I have a fair sized heap of timber of various sizes and should be able to find something to enclose the bath as a raised pond. It's only 1ft deep so won't need very much timber. I have Ronseal Total Wood Preserver (green) from coating my observatory that I can use to preserve the wood.

At present I'm concentrating on the small garden area. I've moved the big tarpaulin to the next area as far as the observatory and up the slope a bit (northwards) covering grass and nettles 3-4ft high. It can defoliate that area I don't think I shall be moving any more large concrete slabs. They're not very pretty anyway.

WOW! That is some pond ? I don't envisage digging anything like that!!

Found something that I think would be better for an ornamental pond and more ambitious water feature. The idea would be a raised pond cased in timber (probably). Being raised with vertical sides, things like hedgehogs would not be able to get in it - they can use the ornamental pond. Faithfull BATH Plasterers Bath 4ft x 2ft x 1ft

Probably the easiest thing to do with four of those slabs is a pond with a liner to hold the water. Not so far to trundle them ? I'm thinking gravel would be better for a path to the observatory and easier to do.

Thank you both I'll be careful.

I think you're right, Louise! I'll see how things go. I'm thinking along the lines of an area of grass interspersed with stepping stones. I do like the irregular slate ones and I think I shall get some more of those. Problem ATM is that the ground has dried out now and is hard to dig or level. I can put lumps of turf into the hollows and let the higher areas self seed - it won't take long if we get some rain. I have half a dozen concrete slabs about 4ft x 18" x 1½" (1300x500x40mm). I'm thinking they might make a path from the garden area to the observatory. I need to loosen the soil before laying though - or get some sand. So far I've moved one from the back of the house to the front with my sack barrow.

I'm debating with myself whether to buy a whole heap of lightweight concrete blocks from Wickes - 90 @ £180 each plus £30 carriage. I can probably still do concrete work so I'll get some cement, aggregate and sand too. OTOH I guess there's no need to spend a huge amount in the first year (not that a few hundred pounds is much compared with astro stuff). Also I think I've decided I don't want too much concrete and stone though and I can have some lawn. Trouble with me is that I get an idea for a project and want to go full steam ahead on it. This is not really the idea of a garden - I must learn to pace myself and not try to do everything immediately.

Belt tensioning wheels.

For a second pond I have two choices (or more). Expend a lot of energy and dig a ruddy great hole (yes ruddy as this is Devon and the soil is reddish) and puddle the clay round the sides or use a pond liner and build a raised pond with concrete slabs and stakes.

A bit more detail of the reduction drive with pulleys, belts, bearings and stepper motor. Belt tensioners still to add probably on the motor side. Top view diagram showing the internal workings. Top view showing the output shaft and ball bearings. Bottom view with motor and bearings.

Now that I have confirmed the calculations I can continue with the design. The RA reduction drive first. There isn't room to have it in a line so will have to be folded back. This is more compact and needs a smaller container too. Here is a drawing of the pulleys and belts plus stepper motor.

Done a bit more clearing and planting turf round the pond.

Pump for water feature arrived this afternoon.

Now to check the Dec again which just doesn't seem right. 28BYJ-48 stride angle is approximately 5.625° / 64 = 0.089° The Dec drive disc can be up to 150mm diameter so let's make the calculations easier by choosing a ratio of 10:1. Drive pulley is GT2 20t so the disc wants to have a circumference of 400mm (10 x 20t x pitch of 2mm). A circumference of 400mm gives a diameter of 400 / π = 127.3mm. That's fine. Could be bigger if desired. Angular resolution of 28BYJ-48 and 16x microstepping gives 5.625 / (64 x 16)° = 0.0055° From calculations above, one pixel corresponds to 1.2 x 10^-4° for a 200mm lens. We have a resolution of 0.0055° = 5.5 x 10^-3 (or 55 x 10^-4) which would therefore correspond to 55 / 1.2 = 46 pixels. Sensor height = 3520 pixels so 46 pixels is 46 x 100 / 3520 = 1.3% of the height. Since the Dec axis will only be used for slewing to the target, this is quite adequate. With guiding it wouldn't be.

Think I shall re-check the calculation of the angular resolution at the imaging rig. NEMA17 (or smaller) stepper motor with 1.8° stride angle will be used as reference. With 16x micro-stepping this gives 1.8 / 16 = 0.1125° Final drive is a 20t GT2 pulley and over 300mm drive disc (derived from the size of the fork) If the drive disc is 1000 / π mm diameter = 318.3mm, the circumference is 1000mm. (Circumference = π x D.) Pitch of GT2 timing belt/pulley = 2.0mm so disc represents 500 teeth. Ratio is hence 500 / 20 = 25:1 The reduction ratio overall is 8 x 8 x 25 = 1600:1. Angular resolution at imaging rig is therefore 0.1125 / 1600 = 0.000070312° = 7 x 10^-5. I'm now going to re-check the angular resolution needed to resolve the image to an accuracy of one pixel. Pixel size for the ASI1600MM-Cool camera is 3.8µm. Focal length of longest lens I have that I could use in a dual imaging rig is 200mm. By geometry, 1px subtends an angle given by tan(A) = 1px and for these very small angles tan approximates to the angle in radians. So angle in radians = 3.8µm / 200mm = 3.8 / 0.2 x 10^-6 = 19 x 10^-6 A radian = 2 x π degrees so angle in degrees = angle in radians x 2 x π Angular resolution required = 19 x 10^-6 x 2 x π = 119.4 x 10^-6° Since we are only thinking rough values we can call this better than 100 x 10^-6 = 10^-4 or 0.0001 degrees. Conclusion :- Resolution is better than required. In fact resolution with a 200mm lens is about 0.6 of a pixel. For my starting point of 55mm lenses it will be a sixth of a pixel.

The pulleys and belts for the 64:1 reduction drive arrived in the post this morning and look the business. Next job is to design and print a box to contain it. Plus to see how it will fit in with the main mount frame.

The image field of that Fujinon fish-eye lens is around 6mm diameter so you would only get a small circular image in your large rectangular frame. The ZWO camera covers all but a tiny bit of the whole 185° view of that lens. It easily covers the whole of the Milky Way. This image was taken last year and captured a rare occurrence of the Aurora Borealis this far south as well as the Milky Way.

That lens works rather well with a ZWO ASI185MC camera. Just slight cropping of the full view at top and bottom but unless you really have views to the horizon all round it won't bother you. That is what I am using in my ASC. The camera will work in the daytime as well as at night except in full sunlight when it does overload at minimum exposure. A DSLR has far too larger a sensor.

Got up at 7am with the idea of getting some gardening in before it got too warm but it's raining. Pretty cool as well so no need. The rain is forecast to stop before long and the sun come out later so the garden can have a rest for a few hours. I'll clear up indoors instead

There is clay about a foot down in the soil here so it would be quite possible to dig a deep pond and puddle the excavated clay round the edge to seal a pond.

I could "plant" the trumpet shapes I've 3D printed as a water feature as surreal giant plants. The scope of things is only limited by imagination When I've got my Giant printer working again I can print some giant leaves to go with the trumpet flowers.

It can do that And I can make it do that... Sounds like a plan Thank you for the suggestion. I was thinking I might do that with the available running water at a later date but I could do it now on a smaller scale with the present pond.