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It all started with an EAF.

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Hello all, 

I bought an EAF for my SW150 PDS, while trying to install it I found out I needed additional M3 bolts, as the kit didn't have any to replace the ones on the focuser. I ordered some stainless M3 capped Allen heads on ebay for a few quid. 

While I had my focuser apart and awaiting the bolts I tried out a few other things, before I knew it I had flattened the flat edge of the draw tube, flocked the OTA, made my own apature mask for the primary mirror, moved the primary mirror up by 5mm and finally flocked the inside of the front end ring. If you were thinking king of doing any of these but like me were put off by the fear of flocking things up ( parden the pun), don't be. It was far easier than I expected. 

The draw tube, I had seen posts where people flattened the flat spot as out of the factory its concave. Mine had a thin wear line about 1mm wide on each edge. Showing the contact to the rod was only at the outermost edges. Below is mine flattened with a sharpening stone and some 3 in 1 oil. However I think I need to master the technique of getting then tension right, a slight tweak moves it from too loose to too tight. 



My OTA before flocking, I never thought the inside would reflect as much as this. 


First sheet installed, I measured the width by wrapping it round the outside with a 20mm overlap. Rolled it backwards and peeled and folded back about 20mm of the backing. Placing it against the OTA seam and smoothi g it out, i then took it slow only pulling down about 15mm of the backing at a time and slowly smoothing the flocking out. It pays to go slow as I had zero bubbles. 


The final sheet installed in the same way with about 20mm overlapping the front piece. A remarkable difference I think. 



this is my apature mask for the primary mirror, i did look at ones to buy costing £50-60 posted. In the end i got a custon cut matt black perspex ring on ebay for £7. OD was 170mm ID was 142mm. Although it was matt i covered the front facing edge in flocking as the inside cut was shiney. I left about 15mm inside the ID of the ring and slit it into segments to fold underneath covering the shiny inner edge. 



The mask was attached with silicone sealant, a small blob on each screw of the mirror clips. I had thought of trying to drill a hole for each screw in the perspex but it would leave a shiney screw head visible and require a lot of accuracy. Silicone can be cleaned off the screws and reapplied if needed to remove the mask. Excuse the dust, I puffed most of it away after. 


After refitting the mirror, I also flocked the plate on the inside that supports the finder shoe, the plastic front ring of the OTA (don't know its name) as the inside where the end cap goes is shiney. And I made a front apature mask ( rough attempt with cardboard and spare flocking) as I saw a post where the difraction around Bright stars was cleaner with both the mirror and spider clips masked. 


Ohh, and eventually I fitted the EAF. The m3x 25mm bolts came and I had shorten them slightly. I did however find out the slots in the mounting EAF bracket are not wide enough to fit all 4 bolts so I slowly ran a 6mm drill bit though each slot where my bolts lined up to slightly widen them. All done and fitted. 


I did notice when colimating mtmy scope I fitted the focuser upside down, not sure if it will make a difference other than standing the other side. When I have clear skies I will know I guess. My last bit of DIY was a prototype EAF hand controller. I had switches so just needed a 4.7k resistor £2 for 30 on amazon and a TRRS cable from ebay. Happy its working and fits in my corrugated plastic packing box I made. I can buy the project box for £5 knowing it will fit inside. 


Sods law it was clear while I had the scope apart, and now done the last few nights have been cloudy. Hoping tonight will clear so I can post some stars here to show if it all made a difference to the diffraction round the stars. 


Clear skies


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  • 2 weeks later...

Great sales technique, because they left out a few M3 screws they sold you all sorts of other stuff 😉 looking good and hopefully a clear night will be along soon

Edited by M40
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