10" f/8 Pretty as a picture? [Nearing completion.]

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An image of the secondary cell with the two finders now fitted. The primary cell looks rather distant in this oblique view.

Another view below of the secondary cell with 4-vane spider, Vixen 2" focuser and small finder. With a larger 8x50 finder on the opposite side. The larger finder came with a secondhand 6" F8 Celestron CR150HD refractor OTA but was probably not the original finder. It could be a Skywatcher I suppose.

The bottom of the primary cell still just clears the ground despite the balance being moved up the OTA by the extra weight of the finders. Such a long lever increases the moment of any additions.

The balance around the polar axis has changed slightly. Requiring the addition of an extra [5lb] counterweight. [Not shown here]

The MkIV mounting is holding up rather well cosmetically despite its years living outside under a cheap tarpaulin. The Hammerite paint, stainless steel replacement shafts and all stainless steel fasteners help.

I have yet to paint the cell "innards" matt black to kill reflections. Or I could use thin black foam glued on instead. Both will require warmer weather for best results. The foam might affect thermal radiation to the cold night sky.

The low plinth is just a temporary construction from scrap, slotted angle iron. Without knowing the balance point in advance it seemed a waste of materials to make anything smarter. Rocking the OTA when pointing at the Pole Star shows that the base is not stiff enough. The angle iron pyramid is actually flexing. I could clad it in plywood or perhaps build a plywood box to replace the angle iron completely.

The Moon was high in a cloudless sky at 7pm so I set up the telescope. It seems the collimation does not survive a tour across the garden with the OTA on the trolley wheels.

First I used the Cheshire to align the primary and then I messed about with the finders for a while using the moon as an easy target for alignment. Some more mechanical work to do there in daylight.

Fullerscopes MkIV mounting and the trolley wheels for moving the OTA around the garden.

The Moon and Jupiter were clear enough at 100x, at first, but Jupiter soon disappeared completely behind the clouds. The Moon was much higher still visible through the clouds but considerably darkened and slightly softened. It was 5C/41F and probably gusting to 20mph which was enough to make the image shudder occasionally. Gave up and packed everything away again.

Added a new rubber band to the alignment ring of the 50mm finder. Then I found an old pill bottle to make an absent dewshield. The finder would regularly dew over when mounted on the large, Vixen focuser of the 6" refractor. Penny pinching or just ignorance by the makers? The make the same mistake with many Asian refractors.

The Moon was high again before it got dark. I set up the telescope and re-collimated. Misty high cloud rather spoilt the view. Taking the edge off the sharpness. For a while it looked quite promising and worth bringing out the VFO, the drive paddle and connecting up to the mains.

Later, after dark, there were better moments and I pushed the power up to 300x just for a bit of fun. Best view though was at 133x to 200x when the sky cleared briefly. I was then able to glimpse the central crater in Plato. The clarity did not last. Cloud rapidly covered the sky just before 7pm. I had a quick look at Venus and Jupiter. Both were still visible but rather low on opposite horizons.

I need a second clamping bolt for the primary cell. There is some slight sag when the OTA is reversed from east to west of the polar axis. I had fitted the clamping bolt too far up the cell to avoid the primary mirror. I need not have worried. There was plenty of room in front of the mirror surface.

Another clear, late afternoon but with annoying stripes of thin, high cloud. It cleared completely by 6.30pm CET so I set the telescope up again. Slight collimation was necessary to the primary to bring the secondary absolutely central in the focuser.

I started with Jupiter. Which is rising higher with each day that passes. Not spectacular, but with two clear belts and the four Galilean moons were easily visible. Being small and bright, including one very close to the planet. I moved well up and to the right to the gibbous Moon. The difference in clarity from last night was very obvious. I homed in on Plato but struggled to see the central crater due to wind shake.

It felt bitterly cold at 37F with a 20mph, gusty wind which was visibly shaking the telescope. Not helped by the base rocking on a bump on the lawn! I worked my way up to 200x and the image stayed sharp and very bright but wobbly. Yet again the cloud crossed the sky like a lid just after 7pm. Packed everything away.

One other potential problem has proved to be groundless. More by luck than intent, the fixed eyepiece position has not proved to be significant so far. Observing to the East, South or West is not remotely difficult nor uncomfortable. It is only a matter of reaching the eyepiece on such a long OTA. A plastic beer crate has provided all the necessary extra height so far. Note the turnbuckle to maintain and effortlessly adjust polar altitude.

Reaching the finders is proving slightly more of a challenge at higher pointing altitudes. It might be better to have an elbow finder instead of the present "straight through" 8x50. And sights instead of [or in addition to] the small Vixen finder. Which I find lacks enough eye relief. It is also much too small to offer any useful sighting potential along the top of its tiny tube.

Click on any image for an enlargement.

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