Rusted

Unused 150mm f/8 achromats are taking up cupboard space all over the world. They sound like fun until you need to limbo dance just to get under the eyepiece. You need a very tall pier and solid mount to make the most of them. They are very nose heavy and most tripods lack the masculinity to cope. I'd second making an appeal for donors.

When I were lad... we had shirts which needed ironing. Now that I am a man I have put away such childish things.

I gave my Poncet platform a cone and [narrow] friction wheel speed adjustment for the threaded drive rod. That was before computers had shrunk from sports hall dimensions and pinhole astrophotography was still all the rage.

I tried to make a plywood/standard Dob bearing equatorial for my DIY 5" f:15 refractor over 30 years ago. Far too much friction! A couple of lazy susans might have been the answer. Or, just replace the PTFE pads with journal bearing rollers, set on edge. There are other platforms. I made a Poncet Platform 50 year ago. Easier to design and make. Though stability with larger instruments might be an issue.

Wooden steps with chicken wire netting applied to the treads?

There's an opening here for a mobile "kiss of life" service. You could have your own App and become White Van Man..

A solar telescope is the "Live Broadcast" of amateur astronomy. Compared to the barely perceptible, prehistoric smudges. Of an ancient cave art depicting anything more distant. I blame Peter Drew for opening my eyes to the wonders of Solar H-alpha. Sunbathing in shorts at the telescope. As you capture visible changes over a mere, few minutes. The only light pollution is decoratively dappling the nearby shade and your chilled glass of orange juice. Brought out to you by your long suffering, "observatory assistant" to admire your latest spots. Instead of huddling into a thick, down jacket, gloves and balaclava. While fending off nocturnal hedgehogs. With a [further] cooled camera struggling to keep the icicle off the end of its nose. Those of an impoverished disposition should acquaint themselves with the secondhand market. As have I, over the last half century. There is a sweet spot between vintage and modern. Or, join an astro association and beg, steal or borrow a glimpse of the H-a sun at another's expense.

I know my place.

I was going to suggest steel cable "guy lines" with tensioning turnbuckles but this is like deliberately setting up hurdles in the dark. While vibration may not be a problem during tracking, one only has to manually adjust the focus for the wobbles to return with a vengeance.

Human sacrifice, eh? One pandemic and we're back to the Olde Ways?

You have built an inverted pendulum with a low resonant frequency and high Q, much like a metronome. The joint at the thin base plate to column is totally inadequate to control these vibrations. As others have said: You need gussets. Tall steel triangles welded to the base plate and up the column. The stiffness needs to be highest at the junction but can be reduced as the column rises. This gives the column a better damped stiffness. With a lower Q across a much wider range of frequencies. The gussets will make up for the thinness of the base plate if you gusset generously. Uses a wide base to the triangles at the base plate. I built a tall refractor pier of 4" thick wall, steel tube. Even empty it weighed "a ton!" Later, I filled it with concrete after sand filling failed abysmally to cure the wobbles. You could still see the vibrations at the top of the pier when the telescope tube was lightly tapped. I had to dig the pipe out of the lawn again. The concrete filling made it so heavy I could not longer lift it! I ended up using a very long steel pipe, a length of tree trunk as a fulcrum and Prusik loops to lever it out of its hole! My present pier is nearly 4m or 13' tall. It is a huge pyramid built from timber 4x4s. With 3/4" plywood cladding above observatory floor level. Over 2.5m square at the base and tapering only slowly. It stands on buried concrete anchors and is bolted to heavy steel brackets at ground level. It works by avoiding flexure and is [of course] isolated from the 2 storey building. The load at the top is probably a couple of hundred kilos but the resonant frequency is satisfyingly high.

Interesting. I wonder if your retina is "wobbly" rather than the lens or cornea at fault? I am not an optician. Just wildly guessing here. Your optician should be able to confirm the cause. After wearing glasses for decades I started cycling high mileages when I retired. My eyes went from needing one diopter correction to becoming completely neutral.

I would have thought you could obtain a lens to fix your cyclopic astigmatism. Even cut/grind down a spectacle lens which provides your personal correction. If you wear specs you may have an old lens handy to sacrifice to science. Tape that over the eyepiece and pray. [If that isn't sacrilege.] Make sure it is the correct eye lens or it won't be useful. The lens will obviously have to be rotated to find the correct orientation to cure your astigmatism. Talk to your optician about this if you make no progress with hacking an old pair of specs. The optician may be able to source a suitable cylindrical lens for you. They should at least know the required cylindrical power you need.

I wouldn't worry about the noise. That was just me playing with the processing. A straight crop is rarely beneficial.

UTTERLY AMAZING! I've been doing it all wrong! 😱 Worrying about image drift over 2 second videos at 300fps? Nah. That is so yesterday! Who's a silly, senior, sausage, solar imager then? Twirly Moi! 👴🏻 I'm definitely using the [PPPUT] Pete Presland Push Up Technique from now on! I just need to get my easterly bias sorted. Then it's all downhill from there. Now I'm off to practice my "5 meter Solar Snatch and Jerk!" BTW Pete: NASA wants their solar telescope back ASAP.

Hi Peter, My PST ITF was DOA. So I never enjoyed Gong quality images with it. I'd reject GONG H-a too if that was all I was seeing. PS. You had a mention on Astrobiscuit [on YouTube] when he bought Big Bertha. A 10" F/6 Astrosystems 'scope. He's taking some nice images through it from his rather wobbly, flat roof in London.

My [lovely] wife often refers to me as a "chocolate teapot" but this clever bloke really takes the biscuit.

If the limb or edge of the disk is nicely sharp then the disk itself should have some sort of "granular" look to it. Like a Christmas tree, glass bauble which has been given a coarse "sugar coating" to represent frost or snow. This graininess may not cover the entire disk. You do need some practice to fully enjoy H-alpha views. When I first started visual H-a the surface graininess would drift in and out of focus. As if my eyes were really struggling to focus. I had over 50 years of practice with every other kind of subject. Then after a while of concentration and relaxation I would be finally be able to force my eye to "lock onto" the surface. It would then appear like a finely textured bed of coals with glowing cracks between the grains. This is a rather "flowery" description and the true scale of the overall features was tiny. I am simply trying to suggest my own perception of the appearance at the time. Once focused the surface would remain continuously visible. Quarks have a very poor, online reputation for quality control. Forum members, here and elsewhere, have returned numerous examples for exchange. This is the main reason I have not invested in one myself. I persevere with my endless PST mods. Nor do I need to use such extreme focal ratios. A very good Quark may beat a PST mod. A good PST may match or beat a Quark. I have seen absolutely stunning "live" videos from both. If you have an astro camera, then a few seconds of "live" video [posted on YT or elsewhere] will tell us far more than a fuzzy single [chance or lucky] image. You don't usually have the ability to "mess" with video [with free software] like you can so very easily with stills. Here's a video with a similar level of surface detail you should be seeing routinely: The size of the disk will vary with the instrument and eyepiece.

Thanks. Indeed there is a lot of space down below. A handy place for timber to be stored for the next project. Your choice of spiral staircase has me intrigued. I use a big aluminium, warehouse ladder with flat steps and handrails. This means a large access hole in the floor of the observatory. I fitted counterweights to the trapdoor but it is still a constant danger. An external ladder would be subject to ice and snow, weather conditions and would certainly reduce security. However, we are getting away from the subject matter of this thread. Raised observatories are not at all commonplace. However desirable they may be for many different reasons. Only some of which are mentioned here.

Hi Nicolàs, Your dome and building are a truly remarkable project! My 3m, self-build, plywood dome is raised but I still suffer from dew. Perhaps it needs to be taller?

Good points from all posters. A round building has less room than any other shape. So a storage bay [or three] offers space which you'd otherwise lose to supporting furniture. Though you can hang a monitor or laptop shelf on a really solid pier. You can't type during an exposure though. Even pressing capture can trigger the wobbles. I saw a GRP dome listed on a national online small ads website. It didn't sell! Within easy reach with a car transporter trailer hired from the local garage. A bargain for a 2.7m [dome and base ring] at £700. Up and over shutter on rails. The trouble is it's in Denmark. Postage to the UK might be a bit steep. 😱 I was very tempted, but went another route. Because I need more room, not less.

Location, location, location! You are sheltered but fixed to the spot. Houses or trees spoiling your view? Oh, deary me! Potential eyesore for neighbours? This has seriously undone some observatories. They say Sage green is nice. White domes demand the neighbours wear welder's goggles 24x365. [Allegedly.] The very same neighbours who constantly blast you with kilowatts of their "insecurity" lights. Incoming light trespass? A dome provides more shelter. Constant breeze? A dome provides more shelter. Frosts: As above. Rain: No problem. Instant gratification. Check! Enough space for expansion? Including yourself if you don't have a black belt in limbo? A big enough budget to have your every desire? You can certainly have it all but other people usually expect to be paid. Pulsar offer delivery and erection at a price. Dome drives at a price. A turnkey solution at a price. Only you can decide if it is all worthwhile. It may be your only option. Unless you choose a ready-made roll off roof and hired labour. [Not keen on so much sky exposure.] A lack of DIY skills is not a judgment. Just a statement of fact. People always forget that their unpaid, one-man-band [slave] can be moody and fragile. They need very expensive new tools they never knew they'd need. Nor budgeted for. Table saws, mitre saws, laser levels, routers, bits and drills. Can you afford time off for a bad back? Will missing fingers set back your sell-out, global concert tour? Materials cost another fortune. The glue, sealant, nuts, bolts and brackets even more! Save several fortunes! Forget DIY unless you are a tradesman. With an existing account at several builder's merchants. I speak as a non-tradesman who built a raised 3m or 10' dome on a self-built, two storey building. A year on and I am already designing a bigger building and dome. Repeat after me: Observatories are never, ever big enough! Observatories are never, ever big enough! Observatories are never, ever big enough!

Hej Lars, Congratulations on completing your epic historical piece. Living so far north you should find interest in solar observing and imaging. Something to do on those long summer days and evenings when it forgets to become dark.

I wear down filled clothing. Mostly bought from charity shops years ago. Layered down jackets, for staggered seams, when it is really cold. Roomy salopettes, over fleece, again from the charity shop. A pair of fur lined winter boots. Claimed good for -50C and cheap online. They are superb when I'm sitting day and night in the obs. imaging in winter. Thin, thermal, long johns are essential wear too. Save the planet! I chopped the finger tips off some cheap winter gloves so I can still typo.

I haven't seen any data on the colour correction of their H-a achromats. I also have one of iStar's R35 180" f/12 achromats. This defocuses to magenta rather than the usual violet. It is claimed that the R35 offers colour correction equivalent to f/16. Rather than the colour correction to be expected from a nominal f/12.