7" f/12 R35 iStar refractor: Jupiter. 3/5/2016

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I made no effort to bring out the telescope as I had no idea how the forecast would turn out. It had been a pleasant and sunny afternoon as I worked on the folded OTA. At 10pm the sky was completely clear and it was calm at 42F. The long tube refractor was still assembled in the shed so I heaved it up onto the mounting. I had already fixed a slim Orion[UK] ring to the OTA to mark the balance point. This proved very handy as it gave me something solid to hook over the open, lower ring on the MkIV mounting. Then all I had to do was close both the hinged rings and screw them up tight.

There is an absolute magic about swinging a big, long refractor onto a target. The moment arm of the heavy tube and its ponderous length give a great sense of purpose in the classical sense. I have made no effort to smarten up the galvanized steel tube and bare alloy components. They have a ring of truth about them from an earlier age. No glossy white paintwork or vividly coloured anodizing are desired nor required. They would require I worried about cosmetic issues instead of getting on with the job of observing. Dragging a long and heavy instrument out of "busy" storage and onto a high mounting is not a delicate task at my age. The rings aren't even lined with the traditional felt but are bare laminated birch plywood. This instrument deserves and ought to be in an observatory but must be used out of doors with all its limitations of weight and lifting and carrying.
 
Centering Jupiter at 42 degrees high in the 32mm showed a small but sharp image with three moons. It looked quite promising so I brought out the heavy power supply and connected the drive cables to the box. The extension cable on its drum was unwound and brought out to the mounting. A 50-year old indicator lamp lit up and began to slowly pulse in time with the frequency of the VFO. 

Tightening the clutch on the polar axis wormwheel set it to follow Jupiter for the next hour and a half. The eyepiece in the 2" start diagonal was quite low as I had previously removed the trailer jockey wheels to better suit the [much shorter] folded OTA. So I brought out a folding wooden chair, settled down and rested an elbow on the trailer in perfect comfort.

I started working my way up through my mixed collection of secondhand Meade 4000s. Each shorter lens produced a larger but softer image with obvious thermal agitation on the planet's limb. I stopped at 10mm [actually 9.7mm] for a nominal 216x but an actual 222x. [If it matters] The image was now too soft and I stepped back to the 15mm and 12.4mm. Alternating between the two as my eye sought detail showed yet another tiny moon emerging from the right limb. As usual, I swapped to the 2x Barlow to obtain different powers with longer eps but this brought no obvious improvement.

Star diagonals make images the right way up but left to right reversed. My fuzzy memory can never remember which belt the GRS should appear in depending on various optical conveniences on its way to my eye. Just rotating the focuser with a star diagonal fitted will cheerfully rotate the planet to suit personal taste. I prefer my Jovian belts horizontal. A reflector will show a different view to a refractor. In this case the GRS was in the upper belt according to my rotated view.

I could not tell whether the tiny, emerging moon had been in front of behind Jupiter's stripey jumper. Then a small, black dot appeared projected in front of the planet but on the opposite limb. Both were directly in line with the lower, dark belt. The tan coloured GRS popped in and out of view with occasional glimpses of a whiteness nearby. The belts looked 'rough' at times but such views were only briefly seen.

Despite the relatively poor seeing it was better luck than I had been having. So I persevered as Jupiter slowly began to sag towards the chimney and then the ridge of our roof. Had I the wheels fitted I could have dragged the entire instrument on its massive pier to a better spot, but it wasn't to be tonight. 

Jupiter surprised me by its rapid movements. The GRS moved quite a way from the planet's meridian towards the limb in only one hour. The tiny, bright moon quickly broke free of the limb and was soon putting considerable distance between itself and the planet. The shadow followed suit and was heading toward the center line of the planet.

Every view of the planets should be treated as practice in seeing the impossible against impossible odds. The seeing can clear in brief moments but cannot be predicted. So the eye has to learn to cope with these difficulties and train itself to capture the sharp moments. As it builds up an image distinct from the 'noise' of thermal agitation and variable softness.

I added a 6" and then the 4" stop to the dewshield and found some benefit with the 6". The four inch was just too small. Again the violet haze was more noticeable coming back up from the smaller apertures. It was a difficult choice but I actually preferred the 6" in tonight's seeing. This choice would probably change if the seeing was better or worse.

I removed the 2" dielectric star diagonal and fitted the little, no-name 1.25". No discernible difference that I could see. Just before I gave up for the night I brought out the straight focus extensions. The odd thing was that these seemed to make things worse rather than better. I had already given the interiors a good coat of matt black paint since they were delivered black anodized but all shiny inside!

I rather liked the long tubed refractor for aesthetic reasons. It is far more impressive in scale compared with the rather "techy" folded form. At over 2.2 meters tall when standing on its shorter dewshield it is impossible to reach the focuser to plug it without something to stand on. Once mounted it soars high into the air like a "proper" telescope. It's just a shame it is such a struggle to get it up there! Then having to move it around the garden to find some sky clear of trees, hot roofs and tall hedges! If I built a raised platform 8' high I'd have most of the sky to look at but then I worry about vibration and shelter. It's not easy being an amateur astronomer in the real world! ;-)

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