Rusted

Whats this "solar energy" you're on about? We don't all live in perpetually sunny Oz! Once we get any sunshine [at all] I shall be measuring temperatures furiously after both D-ERFs with the tools available to me. A laser guided, handheld, thermal "gun" and an inside/outside thermometer on a lead. I wondered if I shouldn't bond the "outside" sensor to a scrap of blackened copper foil. I suppose it's only a matter of time before any thin piece of metal heats up in the focused beam. The sensor is encapsulated in plastic so won't tolerate direct heating. I can live with losing the 120MC to the eternal sunshine but losing the ASI174 would be too heavy a loss. Perhaps it is only the protective filter which is causing the mask effect on the ASI120? I'll have to look into that.

A fool and his "Go Fund Me" sponsors are soon parted. If "The Aeronauts" is to be believed: In 1861, two people ascended rapidly to 37,000 feet in a hydrogen balloon and lived to tell the tale. Of course it didn't set any records because one of them was a woman. Wealthy, as she may have been, it still didn't count at the time and still doesn't in many societies. The other was as mad as a hatter because He believed he could predict the weather from making direct observations. As barmy as a chocolate teapot! They still can't predict yesterday's weather with any degree of accuracy!

I remember burning my hand when left in the red focused beam emerging from the empty focuser. The D-ERF was obviously not blocking the heat as expected. If that was true then the unprotected etalon was being heated by the beam. I double checked the arrow on the edge of the D-ERF but there was no error. Perhaps it was fortunate that I stopped observing visually and concentrated entirely on imaging. I never felt any discomfort but the retina has no pain sensors.

It is good to hear you were so careful and avoided testing it visually before confirming the temperatures involved in your mod. The image looks very promising if you don't push it so hard in processing next time. It is grossly over-sharpened. Just as a gentle warning that you should never, ever take solar viewing for granted: In my last 6" PST mod the emerging beam at the focuser was HOT after the 90mm internal D-ERF! I had serious problems with my ASI 120MC camera using my old 6" Celestron PST mod. It may even have permanently damaged my camera from tracking the sun for hours on end. There is a persistent, translucent "mask" superimposed on the camera's video image. The "mask" looks just like solar surface texture at the same scale I see on the monitor! I had no plans to ruin another camera. So I have just built a new 150mm H-alpha OTA using the PST etalon and a new iStar f/10 objective. Not only did I use a full aperture Baader D-ERF, this time, but I added a 2" KG3 filter from Beloptik and a 2" Baader CCD. Both filters are placed before and intended to protect the PST etalon from UV/IR overheating with the 150mm clear aperture. The sun is sulking behind the clouds so I have nothing to show for all my efforts and expense so far. Take nothing for granted with solar telescopes! Let's be very careful out there!!

Wot he said. I pray they will remain in their present condition without noticeable change! I tried some "big name" hiking boots and they were incredibly comfortable as new. But they leaked enough for free replacements within the guarantee period and they leaked.

Mine are similar but taller to cope with deeper snow. Though I imagine they are all very similar. My feet used to freeze when I spent all day solar imaging in the observatory. My wife soon became bored with hearing about it and bought me some "proper" boots. The amazing thing is how easy they are to slip on and off despite being "fur lined." Skip-on sandals are more difficult to put on than these. Walking in them is akin to putting slippers on a dog.

Re: Durability test? I'll save you the bother and complain bitterly if it falls to pieces within a decade. Re: Boots? -50C rating, unsinkable and self-righting! Guaranteed to cause global warming by default. Re: Telescopes unbalanced? They wouldn't dare! Thanks guys.

Thanks for all the suggestions. I was trying to avoid tape because of doubts over longevity in an unheated observatory. The cosplay references about sticking foam together popped up in my searches. All [presumably] without major consequences or [unintended] public nudity. That said, they are unlikely to spend much time out of doors, overnight in cold and damp conditions. 🥶

Thanks Olly. The problem with laminating two tubes at 180° is the final 20mm thickness!

Indeed. The cut edge of the foam in the illustration looks similar to some black foam I have here. It will take a few days to arrive but I'll post an update when I have it here.

Excellent! Thank you Peter. The Bison range is available over here in the usual DIY outlets. I was going to use 1cm thick foam myself. Though thinner foam is available. Some have suggested mitering the contact edges for more surface area. This seems to be unnecessary if the joint is as strong as you suggest. Thanks again. Update: I have just found Campz, aluminium coated, black foam, sleeping pads. CAMPZ Liggeunderlag Single-Layer 180x50cm, black | Find outdoortøj, sko & udstyr på nettet | CAMPZ.dk Cheap! Alu. coating blocks thermal radiation to the night sky and foam insulates against convection. Pretty too! Rough foam helps blocks grazing reflections. Could even be given a quick matt black spray inside if needed. Seems ideal. So I've placed an order.

Well done and a nice image! They used to cool photographic film to make it more sensitive. I have only once tried to set up at similar temperatures. -23C. The extension cable became as hard as rock in the form of a huge, spiral spring! Does PVC have a memory of being coiled? It had to sit out on the lawn for a week before it was finally warm enough to put away safely. I bought a "rubbery" extension cable intended for building sites after that. Though I haven't tested it at very low temperatures.

Has anyone had reliable success with gluing camping mattress foam edge to edge? The dense, closed cell foam type. Which glue did you use? I have found neoprene glues for repairing diving suits but am not sure this is the same material. I want to make foam dewshields to reduce overnight heat loss and avoid morning dewing. My thinking is that a foam tube will be far better than a conventional metal dewshield for observatory refractors. I am losing hours of precious solar imaging time to external and internal dewing of the 6" and 7" objectives. A plug of similar foam material can close the front of the dewshield tubes like a lens cap between imaging sessions. Enclosing the dew heater bands will reduce heat loss and should avoid morning dewing at lower settings. I shall be monitoring the temperatures involved with digital, thermometers to avoid any risk of fires! EDIT: Using different search terms I found an old thread on here. Evo-Stik, UHU, hot glue, gaffer tape and self adhesive Velcro were all mentioned.

No need to go over to the Dark Side once you've seen the [sun] light.

Probably not, but an on-axis camera needs quite a fat cable to run it. Major diffraction spikes! A tensioned wire spider to carry the signal and power via insulated strands might just be possible?

The OTA would also need to be considerably longer. Not a trivial matter with an 800mm aperture.

Thanks. That's very kind of you to say so.

Superb! Thanks. That was a far more interesting story than saying you bought it at IKEA. I tried suggesting a cushion, made from one of my old tweed jackets, but my wife says no. It has to be easily washable and preferably two of them. To allow for regular rotation through the laundry system. I'm just using a square of closed cell, camping mattress at the moment and it's totally "unsympathetic!"

Where can I get a superb, tweed cushion, like that, for my own IKEA observatory chair?

Remaining seated always seemed more relaxed and provided better views of fine detail. Probably because my other brain cell wasn't being used just to remain on a wobbly stepladder. Nowadays I spend most of my time seated comfortably at my computer desk imaging the sun in my home made, two storey observatory. My 25" monitor provides unbelievable views in H-alpha and white light of [sections] of the magnified solar disk, several feet across. My homemade 6" and 7" iStar refractors sit on my massive, home made, German equatorial mounting with planetarium control. The eyepieces are usually ideally placed, for height, for visual observing from a seated position, except in the very depths of winter. I nearly always use a solar prism or star diagonal as appropriate. Though mostly a camera. The monitor allows me to choose moments of good seeing for rapid imaging with a fast ZWO camera. For occasional exercise, I turn my home-made, 10' /3m dome via a hand crank deliberately placed close to my desk. I have all but given up on night time observing, or imaging. With only occasional imaging sessions on the Moon. Yet spend most sunlit hours busy in the observatory. More daylight hours, in some weeks, than I did in several years on the night sky. I am in now my early 70s but remain fitter than most through constant physical and mental activity after years of [excessive] cycling. There is always something which can be improved upon. Or built from scratch, or scrap, to make observation or imaging easier or more fun. I blame all of this on Peter Drew! His inspiration has filled all my waking hours with new [astronomical] purpose! There are no valid excuses for this sort of behaviour!!

Tar based, roofing felt is a known solar absorber, heavy and with a limited lifetime. Rubber pond liner is usually said to be good for half a lifetime. I have a dome skirt of the heaviest rubber liner I could find online to stop the rain blowing in. Somebody ought to check the temperature of pond liner when directly exposed to the sun. First find some sunshine!

Thanks for the clarification. Understood.

In theory you can invert the hobbed wheel still on its accurate spigot. To run the tap against it again. Which should smooth out the sharp edges. There are always burrs when you cut metal from one direction. So reversal of the cutting action should smooth things nicely. It should also halve any errors in the tooth form.

I'm afraid I haven't a clue about local regs because it isn't a hardwired set-up. There is no metalwork to speak of. Just the big mounting on the first floor of my two storey observatory supported entirely on dry timber. It always seemed to me that deliberately earthing metalwork gave faults a path to injure people. Though the theory is probably that electrical faults will be directly earthed. Rather than be earthed by human bods.

Thanks Simon. I'll give that a try to see if I can isolate the culprit. The AWR drives PS is not remotely a budget wallwart. It has a standard 2 pin plug and two protected output plugs. The stepper motor leads have trailing earth leads now fitted with crimp on ring ends. Which I have connected to the mounting now I have an earth rod. I've done a lot of 2-pin plug reversing over the years to minimize such problems. It often seems to work.