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Monday afternoon 72F bright sunshine form a clear blue sky. The poor seeing meant I was wasting my time trying to capture in the heat of the day. As expected, the sun disappeared behind the trees at 18.50pm.
I just need to process them identically to turn them into an animation. Some online research will be required.
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08.17 Captured the disturbed regions in early, steady seeing. Though not particularly transparent.
Some strange triangular filaments in the deep south.
The two ARs are continuing across the disk.
Transparency improving but thermal agitation increasing.
10.16
Seeing briefly clears for half a second before it smudges over again.
Capturing lots of videos and only processing the best where I can see
detail in the opening screen of Autostakkert.
11.00 64F outside in deep shade. 73F inside the dome at desk level in deep shade. The seeing has gone impossibly soft now. It reminds me of looking through glass smeared with Vaseline. I measured the Baader 35nm H-a first filter at 85F. Not much above ambient. Pointing the laser thermometer up the unfiltered focuser briefly produced a reading of 160F. That was with the D-ERF in place. The front of the D-ERF measured only 80F after several hours directly facing the sun. Probably thanks to to its highly reflective nature.
I had a quick look through the Vixen 90mm with Lunt 1.25" Solar wedge for white light viewing. Only AR12827 is clearly visible. I nearly burnt myself on the heat sink! No point in thermally stressing anything. I've put the lens cap on now.
16.30. I have tried at intervals but the seeing conditions remained awful since my last images.
I shall try again later.
Google Blogger is messing about with the editing again.
Impossible to drag and drop images.
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The cloud is back and the seeing soft and thermally wobbly.
So I used my laser guided thermometer to measure the temperature of the 6" refractor's main tube. It and the sun, are inclined at about 44° at the moment. I measured 90F, 85F, 75F respectively: Behind the objective, in the middle and at the back plate.
The cloth cladding inside the dome shows much the same stratification despite being completely in the shade.
The main tube has been shielded from sun's direct rays by the objective cell. Which has been pointing directly at the sun all day. The air temperature on my desk is 79F. The outside temperature, in the deep shade behind the building, is 69F.
Would adding a small fan help to circulate air within the 20cm/8" Ø main tube? Or would it merely draw dust inside it? To coat the optics with pollen and rural grime!
My 7" f/12 refractor is standing on its dewshield nearby but fully in the shade of the dome. It measures 77F from top to bottom despite reaching well above the dome's base ring. So about the level of the middle of the 6" main tube. Why the difference?
Is a stratified temperature regime within a solar refractor tube beneficial or negative regards internal [instrument] seeing? The full aperture D-ERF should be blocking the heat before it enters the main tube. Though it still passes some heat. Because I can burn myself at focus. With only the Baader D-ERF as a heat blocker.
I have now turned the dome to shade the 6". I will give it some time to cool and then measure its temperature again. Thin steel does/should not hold its heat. It didn't. The temperature has dropped to 77F from top to bottom. So, does this mean the sun is heating the OTA from within? There is no direct connection between the objective cell and the main tube. There is a turned, birch plywood counter cell.
Another ten minutes and the main tube now measures 77, 74 and 73F respectively from top to bottom. Does this represent the stratification of the air inside the dome in the absence of wind? I measured the surface temperature of various bits of bare timber in the construction at 74-70F descending from high up and down towards the floor.
I have been promised my Titebond III wood glue for delivery by the post office tomorrow. So I can start building ribs from all the arcs. The air temperature has shot up this weekend after months of very cool and wet weather. I could have used the Gorilla Glue but have been avoiding it because of the low temperatures. The advice being to avoid temperatures below 55F. The Titebond claims a much better performance when occasionally damp. [Not submerged!]
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10.21 First image. NE AR.
10.52 Cropped and enlarged. More contrast.
11.12 Cropped an enlarged.
11.19 Better seeing allowed extra processing.
14.58 Back after a cloudy and sunny periods lunch.
New AR in the south east. There are several disturbed regions nearby
14.57 69/79F. [In/out]
The now familiar AR in the NE continues to change. Solid umbra showing in the west.
at right and left. East and west of the main feature.
17.26 Much less cloud.
18.49 No cloud. Last image of the day as the sun sank behind the trees. Cropped for more scale. There was hardly a hint of the expected clarity on the monitor with later seeing conditions.
There is a bridge across the spot on the west [right] of the disturbed region. Artificial colour added.
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Saturday 29th 61F, grey, cool start then sunshine.
My 6" f/10 H-a refractor's, main tube length is 2cm longer than the maximum permitted. It is 121cm long instead of 119 absolute maximum. Which means I cannot reach the PST etalon's 200mm magic number inside focus for best performance.
I have removed the OTA from the mounting and have it resting [minus
optics] in the jaws of a B&D workbench. It is ready for sawing a
ring off the tail end after lunch. Think of a number. Make the new tube
length to match the middle of the focuser range? Not that the focuser
should be used. Except for making very small adjustments to fine focus.
17.20 63F Still making adjustments to tuning, spacing and focus. The weird AR is plodding westwards. The seeing conditions are very slowly improving. Though with irregular de-focusing.
18.50. 62F. Last image today. The trees were already blocking the sun. The light level drops like a stone and flashes dark and light if there is any wind in the trees.
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10.25 Ready to start imaging. Waiting for cloud to clear. Imaging through thin cloud.
10.34 Very soft Sun wobbling on the monitor. Difficult to find focus! The dreadful first image tells it all. The two complex ARs are approaching the limb.
11.48 55F. The spots are an easy target in white light on the NW limb. 90mm f/11 Vixen + Lunt 1.25 solar wedge + Baader Solar Continuum contrast filter.
It was interesting how hot the camera became with the sun shining directly on it in the Lunt solar wedge. 48C. The camera is usually in the deep shadow of the 8" tube of the 6" H-alpha refractor.
Afternoon 14.40 58F Lunch over. Back again and waiting for the [solid] cloud to clear...
18.06 Still here. Waiting for better seeing conditions. AR12814 is right on the limb.
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Afternoon: 15.50 I was teased by the blue patches and brief intervals of sunshine. Centered on the sun and focused but still waiting for a clearing. Fortunately the wind is from the north west. So not blowing into the dome. Downside is not being able to easily monitor the northern sky for clearances. It looks completely overcast again. The two layers of quickly moving cloud appear to be veering more westerly.
16.39 Pushed it much harder in ImPPG. Completely artificial but better detail.
16.57 A little long break of sunshine. Slightly less sharpening.
I am getting 98fps. 500 frames in about 4 seconds. SharpCap Pro
Using 75 frames of 500 for stacking in Autostakkert AS!3.
17.12 Still experimenting with ImPPG and frame size. The seeing is very soft on the monitor. Making focus and etalon tuning very difficult.
Lower frequency thermal undulation now. I prefer 800x600 frame size where the etalon sweet spot is more even.
I should be moving towards the better seeing conditions if it remains clear. [Now and then!]
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Wednesday 26th 46F, heavy overcast and windy. With all day rain promised.
I have been doing some homework on GRP. It seems that epoxy resin would be a better choice than polyester. Much better adhesion, higher strength, longer lived, low odour and much more waterproof. I might even use epoxy plus glass as a sandwich for the plywood ribs. I need to do much more research into this.
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Tuesday 25th 55F, breezy, heavy rain, sunshine and heavy showers. Denmark is enjoying its second wettest May in 100 years.
I managed to cut out six more arcs before the sky became menacing again. I raced round and put everything away. Then it poured down. I need a roof on my outdoor workshop!
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I spent the morning trimming plywood arcs with the router and trammel.[radius bar]
Agritech, the manufacturers of the GRP dome, were prompt and helpful in responding to my email.
Afternoon: After marking out an other 6 arcs the sun came out. Set up for imaging only for lots of cloud to appear.
16.04. 63F Lots of fine detail but an unusual, central sweet spot. I've tried re-tuning the etalon but it isn't helping so far.
16.59 A few more breaks in the clouds. Gusty wind.
17.00 Solid cloud.
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23rd 50-56F, grey morning, sunny afternoon. Westerly gales all day.
I was going to try imaging this afternoon. With gales blowing from the west I realised it would be a waste of time. It would be blowing straight through the slit and into the dome. I missed the massive flare around the sunspot because of the bad weather yesterday. There were some excellent animations of the flare on Solar Chat! The specialist, solar discussion, imaging and observation forum.
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Saturday 22nd. Overcast with rain forecast. Just another blog post where I share my thoughts [usually with myself] on the dome project. I find it beneficial to think aloud [in text] as a rehearsal for the real thing. As a one man, solo, project builder I don't have anybody sensible to laugh at my sillier ideas. Though my wife tries to keep me on my toes.
I ought to know if it will allow normal adhesion with polyester resin before I commit myself further. Much as I wanted to avoid working with the sticky and smelly resin again. I have decades of different, weird and wonderful, GRP projects behind me.
The shiny green coating may be intended to help the farmer keep the interior clean. In its everyday use as a calf shelter. Or, it may simply be part of their normal polyester and CSM [chopped strand matt] spray-up system. A wipe with acetone, to degrease the surface and I may be ready to go. If warmer weather ever shows up this year! Or, I may have to abrade the surface to get a proper key. Best avoided for itchy dust reasons alone!
After looking at my 3m plywood dome again, my 2x12mm mock-up ribs are looking a bit mean. I used 2x16mm for the ribs of my last dome. 3x12mm makes much more sense and provides the desired odd number of plies. Particularly given the increased weight and bulk of the much larger, GRP dome. My attempts to reduce the shutter projection, above the dome, demands even more bulk in the outer ribs. Or much more serious reinforcement!
"Glassing in' plywood ribs in a GRP construction has a long history. Kit cars and boats are built this way. The stiffness of the plywood bulkhead, or rib, is carried into the structure to avoid more costly glass and resin. Which would have to be considerably thicker and heavier to achieve the same stiffness if used alone. The mass of glass fibre forms a nicely radiused fillet at the junction between plywood and the shell. Thereby spreading the loads safely into a much stiffer monocoque.
Plywood would be a poor choice under these special circumstances. The animals might even injure themselves against the plywood projections. These low profile GRP ribs would go completely unnoticed as the animals rub against them. [Image left. Sorry about the mud!]
The extra weight of another layer of 12mm ply for the ribs and rings will not be lightweight. It will also use more raw materials. Still, better to be safe than sorry. The increased weight will be distributed evenly over 14, heavy duty, industrial, rotation rollers. Each of which is individually rated to carry the entire weight of the dome. Which will, in turn, be distributed over 22 solid concrete, foundation blocks and 22 sturdy 100x100mm upright posts.
I may remove some of the octagon's posts downstairs but will be extremely wary of doing so. Six of the original octagon's post will end at [the unchanged] observatory floor height. Where they will still support the joist system of the old observatory from below. Leaving the new observatory floor clear out to the new, perimeter wall. Which has all been securely tied into the older structure.
The inner, 12mm, plywood cladding of the new observatory, will further increase the stiffness and strength of the expanded building. [4.3m diameter over the old, 3m octagon.] The older plywood dome and building were open on the inside with exposed woodwork. This time, the exterior plywood cladding has provided a mass of useful offcuts due to the narrowness of the many, wall panels. The edges will have to be cut straight on the table saw for neatness.
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10.39 Seeing slightly sharper than yesterday when the cloud clears. My first, presentable image. 912x912 and cropped.
I usually use 800x600. The latter rather limits frame size and resolution when cropped. Usually resulting in a digital enlargement being required to get a decent sized picture for the blog. The larger frame slows capture rate to about 94FPS. I'm hoping to use the 2.6x GPC with the larger frame for the same scale as 800x600.
11.01 52F even more cloud! Seeing improving in the short gaps of clear sun. Pushing ImPPG much harder than usual. It seems to tolerate a lot more sharpening when the seeing is better. Far more than I ever dared to try before.
I tried the 2x Barlow but it was far too much for the seeing conditions.
Swallows keep looking in, doing an orbit and leaving via the observation slit.
12.16. Last image for a while.
Heavy cloud is making it pointless to continue.
14.48 55F, Still trying during brief glimpses of the sun.
Ellerman bombs or micro-flares are visible all around the AR. [Active Region]
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14.45 I have the telescope pointing at the closed shutters. Without having had a chance to confirm a sighting for a Sync. I hope the Baader D-ERF is waterproof! There is rain on the laptop.
15.12 I was finally favoured with long periods of sunshine. I keep capturing and processing. Tried all three GPCs. 2x seems best. The seeing is slightly soft but rescued by ImPPG. Trying hard not to overcook my images.
15.30 56F. The seeing is getting worse. Soft, thermal wobbling and high frequency shaking now
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16.59 56F Trying different set-ups. 2.6x GPC :
17.12 Still using 2.6x GPC but pushing harder in ImPPG. Too much cloud now.
Afternoon.
14.48 55F. I was teased back by a few glimpses of the sun.
Few, but showing some interesting detail. Ellerman bombs or micro-flares.
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