*
Thursday: The weight, size and reach required for my rather large telescopes demanded a much safer way to fit and remove them from the mounting. I had been using a stepladder with my feet about 4' above the floor. Not ideal as my balance was all wrong as I hung over the top of the ladder. 
The folded refractor bayonet system was not proving ideal. Fortunately and I had a piece of scrap 10mm aluminium which could replace two thin plates with a single stiff plate. That meant the OTA had to come down off the mounting again so I could work on it more easily.Chain drilling the scrap plate took much longer than expected. I did three circles using larger drills each time. Then broke through the remaining bridges with the oscillating cutter and a bi-metal blade. Next step is to use a [wood] router to smooth the 20cm diameter circle using a simple plate jig with central pivot point. It was a clear night with moon and Mars but I had no instruments mounted.
____________________________________________
I have had a dirt cheap block and tackle system for years. This would do as a hoist and I had previously upgraded the original cord to something stronger. It just needed somewhere safe to hang it.
This required I lift my two-stretch ladder into the observatory to reach the top of the dome. The folding stepladders having already been taken down. Then I drilled through a reinforcing plate at the top corner of the observing slit and fitted two eye bolts right through the doubled 3/4" cross board.
In the interests of a belt and braces approach these two eyes were joined by a sturdy bolt secured with lock nuts. If one eye bolt should fail then the other provides a bit of extra insurance. Two eye bolts would not be loaded as much as a single one anyway.
In the interests of a belt and braces approach these two eyes were joined by a sturdy bolt secured with lock nuts. If one eye bolt should fail then the other provides a bit of extra insurance. Two eye bolts would not be loaded as much as a single one anyway.
A stainless steel caribener was used to hold the hanging plates of the top block of the pulley system. The 3x3 pulley system requires very little effort on the cord to lift or hold the folded OTA. I would not trust the system with the heavy mounting but it is perfectly adequate for any of the 30-50lb OTAs I'd ever need to mount.
I suppose I could hang a loop of stronger rope from the top to see if the eye-bolts would take my own weight. The dome's top cross board would easily take my weight when I hung from it while I was still working down on the ground.
Update: I have ordered two new triple [yachting] mini pulleys and 30 meters of 5mm rope to make a completely new pulley system. With a much higher claimed breaking strength this should offer a much safer means of lifting OTAs on and off the mounting. The present pulleys are very stiff on their axles. Which increases friction both when lifting and paying out rope. The cost is around £50 equivalent so is relatively small beer, long term insurance compared with the cost of dropping an OTA!
It is a mild 50F, sunny day with a light breeze so I am airing the dome to see if it helps with the sooty mold.
Update: Oxalic acid has been suggested for removing the mold. [See comments.] Unfortunately its toxicity, even in small quantities, makes it an unlikely choice for this job. My wife [The Head Gardener] wouldn't even let me use household ammonia in the dome. This is another widely recommended treatment for mold on wood. The problem is having to work mostly overhead with poor access from ladders. I could bring back my folding stepladders but the wear and tear of working on the building on a daily basis has made my hands and arms increasingly painful. [AKA: Tennis elbow.]
We will soon be descending rapidly into far more typical, cold, Danish winter weather. So natural evaporation becomes much weaker with time. I have been keeping the dome and observatory doors wide open all day to aid drying. With no obvious effect so far despite the mild weather and sunshine.
The next plan is to use more brown soap but using hard sponges [instead of soft] and rinsing with water with a little washing up liquid. Another suggestion from the internet. A heat gun has also been suggested but I have never owned one. The dome is so [deliberately] draughty that I seriously doubt a 2kw fan heater would raise the temperature much. Localized warmth [from a heat gun] sounds far more sensible. I might even get a sense of revenge on the mold for the uninvited invasion.
Just think, I could have had an all aluminium, barrel dome a full year ago. If only a local engineering company had taken my order for rolling four aluminium half circles in angle profile seriously.
Update: I have ordered two new triple [yachting] mini pulleys and 30 meters of 5mm rope to make a completely new pulley system. With a much higher claimed breaking strength this should offer a much safer means of lifting OTAs on and off the mounting. The present pulleys are very stiff on their axles. Which increases friction both when lifting and paying out rope. The cost is around £50 equivalent so is relatively small beer, long term insurance compared with the cost of dropping an OTA!
It is a mild 50F, sunny day with a light breeze so I am airing the dome to see if it helps with the sooty mold.
Update: Oxalic acid has been suggested for removing the mold. [See comments.] Unfortunately its toxicity, even in small quantities, makes it an unlikely choice for this job. My wife [The Head Gardener] wouldn't even let me use household ammonia in the dome. This is another widely recommended treatment for mold on wood. The problem is having to work mostly overhead with poor access from ladders. I could bring back my folding stepladders but the wear and tear of working on the building on a daily basis has made my hands and arms increasingly painful. [AKA: Tennis elbow.]
We will soon be descending rapidly into far more typical, cold, Danish winter weather. So natural evaporation becomes much weaker with time. I have been keeping the dome and observatory doors wide open all day to aid drying. With no obvious effect so far despite the mild weather and sunshine.
The next plan is to use more brown soap but using hard sponges [instead of soft] and rinsing with water with a little washing up liquid. Another suggestion from the internet. A heat gun has also been suggested but I have never owned one. The dome is so [deliberately] draughty that I seriously doubt a 2kw fan heater would raise the temperature much. Localized warmth [from a heat gun] sounds far more sensible. I might even get a sense of revenge on the mold for the uninvited invasion.
Just think, I could have had an all aluminium, barrel dome a full year ago. If only a local engineering company had taken my order for rolling four aluminium half circles in angle profile seriously.
Click on any image for an enlargement.
*
No comments:
Post a Comment