200PDS Spider & Secondary upgrade

[Rob]

I've just completed a upgrade /change to my 200PDS secondary. I always felt that the stock secondary spider was always flimsy and collimation was made worse because of that. The second part was to move from the secondary collimation grubs biting into the aluminium of the secondary support. This then prompted me to re-think how the secondary is held to the spider. 

The first step was to move to a CNC spider. I located a CYCK machined aluminium one. It was a lot cheaper than the alternative. I have to say it’s very good quality.

The second step was to incorporate a steel A2 stainless wash to fix to the back of the secondary. I had to lightly sand the secondary support to smooth out the previous bits from the collimation grub screws. Next to fix the washer to the secondary with a thin layer of silicone. 

The third step was to re think how the secondary connects to the spider. I decided that a M5 long grub screw and lock nut with a washer was the way to go here. So I purchased a 55mm long A2 stainless grub and screwed directly into the secondary. Also purchased the M5 lock nut & M5 Wash, again A2 stainless. Pushed through the spider with the original spring in place and pushed on the wash then fixed up with the locking nut. The happened to sit nicely in a small recess already on the spider (see pics below). and started the secondary positioning to the focuser draw tube. I could already appreciate this felt like a major step up from the original factory setup.

The fourth step was to add Bob's knobs for easy collimation. This proved to be a dream to collimate the secondary. All done in 5 mins. I have to say the washer, grub bolt and locking nut system just seems so much better for fine tuning everything.

Project complete!.. I just wanted to share this as it’s made a huge difference. The CNC spider is of course optional.

Clear skies. Rob

 

[russ]

That looks great Rob

[faulksy]

very nice, see you put ptfe on your colimation bolts 👍

[bosun21]

I also fit a washer and Bob's Knobs to every Newtonian I've owned. I also spray the washer matt black to prevent any possible reflections.