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Collimation, cleaning and servicing my old Helios Apollo 150.


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This has been on my to-do list for months.

A year or so ago I bought an old Helios Apollo 150 on a home-made Dobsonian mount compete with a 15mm eyepiece and a laser pointer, all for £50. I've used it a few times and it's been pretty good, giving clear views and providing a 'wow' factor at a couple of star parties where it's been used. But, looking critically through it, the views have had slightly odd-shaped stars with some coma around them, so I wondered if I could improve things.

Recently, having sorted out the junk and built a second bench in my workshop, I was able to spent an afternoon collimating, cleaning and servicing the reflector. Sorry if this is a little picture heavy.:



Having noticed that there was no central spot or mark on the main mirror, the first step was to gently remove the main mirror, inspect and clean it and then add a small central mark for collimation.



The mirror looked in good shape.  Most of this was successfully blown off by the hurricane blower I used.



Measuring where the centre spot should go and then placing the mask at the centre



All done and starting to re-build the scope.  Note below the suspension for the mirror - 3x o-rings on each of the three mounting bolts.  However, it all went back on with a bit of coaxing



With no eyepiece inserted the centre spot is visible where it should be!



Now we set up and collimate - starting with the secondary mirror




then we adjust the primary mirror to put the laser light back to the eyepiece



Next step was to strip and clean the sticky residue from the focuser.  Remove, strip and clean first:





Then some Geoptik Type 1 on the ratchet and worm and then re-assemble.PA160148.thumb.jpg.060f568d4c8b4ab9891060f52ce78902.jpg


And finally it's all back together:

But was it worth it?  I think so.  This is M27 - the Dumbbell Nebula - taken on what rapidly became a foggy night, so less than 30 minutes exposure using an Altair Hypertec 533C.  Some purple fringing was removed, but overall not a bad result for a £50 scope and about 90 minutes work.



Edited by savcom
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