21.3.15

20 March 2015. Partial solar eclipse

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Heavy grey overcast all morning provided only brief glimpses of the eclipse. It was so cloudy that I did not see the point of setting up a proper mounting. Then it began to brighten occasionally so I fitted the 90mm f/11 Vixen refractor onto my video tripod with a Baader Solarfoil,  full aperture filter in place. 

Even then the cloud was often so thick and the solar disk so dimmed that I often couldn't find it in a low power eyepiece. The first image shows the wrong camera time stamp. So, quite accidentally, it was quite close to maximum obscuration at 10:48 CET. To add to the timing confusion my watch is in for checking after it started eating batteries within months of purchase.


Image taken with Canon Ixus, short zoom, compact camera hand-held to the eyepiece. [Extra-focal imaging.]

Partial Solar eclipse: March 20th 2015 10:48 Near maximum obscuration..

Vixen 90mm F/11 refractor with  25mm Meade 4000 Plossl EP and 1.25" star diagonal for comfortable viewing and photography.


  Another image taken near the end of the partial eclipse. Now using Lumix TZ7 hand held to 35mm eyepiece. Note the large sunspot close to the obscuring lunar limb. The Moon finally disappeared from the sun's disk just before 12.00.

The two, rather poor, images are the best of a number taken during the eclipse.





Click on any image for an enlargement.
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20.3.15

Fullerscopes MkIV on eBay[UK]

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Auction text: Selling a MKIV Fullerscopes mount:

Fullerscopes MKIV telescope mount | eBay

It is at the moment in original powder crackle finish but am repainting grey primer. so revised photos to follow. RA and Dec axis mild steel 1.25" shafts are being cleaned up and re greased. RA wheel in good condition, worm may need re working. Old spec showed 12" newtonians with cast aluminium rings so will take newer 14" scopes, very sturdy mount capable of excellent tracking, easily fitted with AWR goto. Pick up Fareham or can courier at cost. Buy it now includes Courier free of charge to UK mainland otherwise extra at cost. Any questions call Chris 07717037633 also advertised eleswhere.

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These are absolutely dreadful auction images considering these are intended to sell the object! Inexplicably photographed in a very dark place. I have brightened the only two auction images worth copying and have increased brightness, contrast and sharpness considerably.

Unless the seller has all the original nuts and bolts this is more a kit of parts with some potential in the hands of somebody with metalwork experience and/or manual skills. Getting replacement, British threaded bolts is not easy in this time of metric standards. Particularly finding coarse threaded replacement in more desirable stainless steel. Metric threads are much too fine and will not grip safely in the soft, light-alloy castings. Not even if the threads are re-cut with the correct equipment as I did myself. Replacing the original shafts in 1.25" Imperial stainless steel would be very desirable unless the mounting was kept indoors and dry. [Bringing it outdoors for each observation is not recommended on the grounds of weight alone!]

Some sort of secure cover in a permanent outdoor set-up is very desirable. Not necessarily in a formal observatory. A secure, waterproof box on a permanent pier would do. A sack truck could be used to move the mounting on a low pier. One which is stored in a garage or shed with a smooth threshold and hard surface. A tall pier, for a refractor, would require large, sturdy wheels and a smooth, hard surface to run on safely without tipping. I speak from years of experience using the MkIV on various pier heights all of which are endlessly sinking into the lawn or gravelled parking space. Just lifting the bare MkIV onto a pier working alone is hard work in itself. Anything which makes set-up difficult will mean an instrument is hardly ever used. 

Manual slow motion to the Polar axis only. [Assuming the worm is still usable] Beacon Hill could supply new worms and wormwheels, drive motors and controls. While AWR has long experience of offering very sophisticated, stepper motor drives for the MkIV, including smart controls and Goto. There is really no need to replicate the original 6" Fullerscopes ring-type wormwheels. Changing to larger wormwheels of [say] 8" or 11"/25cm would allow smaller drive motors with higher accuracy. All without having to resort to drive belts to get enough torque from large stepper motors. The MkIV would make a good base to practice improved bearing types over the original, plain, bronze collars. Taper roller bearings or ball thrust bearings would reduce the torque requirements on the polar axis drive if properly applied. 

Seller was originally asking £225 Buy it Now price.
Re-listed at £195 'Buy it Now' or bids/offers over £125.
Note that "Buy it Now" price includes free carriage within mainland UK.


Click on any image for an enlargement.
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1.3.15

10" f/8 Hargreaves strut?

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I think I need a Hargreaves strut to stabilise the secondary cell to the end of the Dec shaft. This will help to avoid spar flexure in windy conditions. It is only rarely quite still where I live.  I just need to find suitable clamps for the long length of 10mm stainless steel tube I found amongst my stock.

The answer to the Dec shaft clamp problem was hiding in my cycling junk. A seat tube, quick-release clamp for holding the saddle pin tight in a modern bike frame. BTW: These clamps have a small flange on one edge of the machined bore. This is partially cosmetic but also to stop the clamp sliding down the seat tube when loosened. This can confuse if the clamp is applied to the shaft the wrong way around. I didn't notice the flange while I was fiddling in the dark and had completely forgotten its presence. I shall file the flange away or spin it in the lathe to allow the Declination shaft clamp to be easily fitted in the dark.

A small tube clamp will be fitted under the large clamp's knurled adjustment nut to hold the lower end of the Hargreaves strut firmly. The large Q/R clamp will allow the strut to be fitted and clamped to the end of the Declination shaft in an instant. The other end of the strut will fit in a similar tube clamp and be fixed to the top end of the OTA. A wing nut will speed the clamping of the top end of the strut into the tube clamp. Adding the Hargreaves strut permanently to the OTA would increase the weight to be carried out to the mounting. More images to follow when I find suitably small tube clamps for the strut itself. Bicycle "brake clamps" are very suitable if I can find the correct size amongst my endless boxes of old cycle junk.

 An easier alternative is to use a rear, bike light clamp on the Declination shaft. A couple of packing washers help to trap the small clamp ears and tighten it perfectly just as the large clamp screw is fully tightened. I decided to add the clamp above the counterweights to avoid using a very long strut. A 45/45/90 triangle is all that is desired to triangulate the OTA to the Declination axis.


Click on any image for an enlargement.
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