Flocking a SkyWatcher Flextube 300P

[Tinker1947]

I put a Baader Click-Lock on my 300P, it works with a Pentax 300 XW no extention needed, i have just changed the Focuser to a Moonlite CR2 not had any clear skys to test it yet, but there are 2 thickness shims come with the moonlite so it shouldn't be a problem, If you haven't got a comfortable chair i can recommend this one from FLO...

http://www.firstlightoptics.com/misc/mey-observing-chair.html

Moonlite CR2...

[DRT]

I wasn't happy with the light shroud I made from a camping mat as it was too flexible and wouldn't hold a cylindrical shape so I have built a new one from a 1372x660x1.5mm ABS Pinseal Plastic Sheet.

This is the same material used by AstroZap and Celestron for their dew shields but I built this light shroud and a dew shield (from a second sheet) for around £20 each. The natural spring in the material means that these hold their shape very well and don't obstruct the primary mirror. They also look quite good

Here are some pictures...

[DRT]

If you haven't got a comfortable chair i can recommend this one from FLO...

I have the same chair - they are excellent.

[Daniel-K]

that looks sweet! ive just ordered my new dobbo

[palatine]

so did you get the 2 shields from one sheet? what size sheet would i need for the dew shield on a 250 flextube? is there an optimum length?.. sorry to mither

[DRT]

so did you get the 2 shields from one sheet? what size sheet would i need for the dew shield on a 250 flextube? is there an optimum length?.. sorry to mither

Sorry for the delay in replying, just returned from holiday.

I had to buy two sheets. You need to measure the outer circumference of the top tube of your 250p and then add about 5cm for an overlap. That gives you the minimum length of sheet you need.

[palatine]

Thanks for the reply DRT.

Sent from my iPhone using Tapatalk

[Guest]

Hi Derek and Daniel,

I was interested to see what you said about changing the red bearings on the side of the scope with the PTFE. I have a 14inch skywatcher dobsonian. The rotation of the base (vertical axis) is very smooth but the tilting of the scope( horizontal axis) is not so good. The tube rests on 4 small bearings, two on each side screwed into the side panels of the base. Are these supposed to rotate? There doesn't seem to be a way of mounting them which would allow them to rotate. I'm beginning to wonder if I've assembled them incorrectly.  So I was wondering how changing the red plastic discs on the scope itself would help make that movement any smoother.

Steve

[DRT]

Hi Steve,

I must confess that I never got around to replacing the red bearings on my 12" before I sold it. I still have the PTFE sheets and plan to do it on my 16" if it ever stops raining!

The four black plastic bearings that support the weight of the tube are not designed to move so you don't need to worry about those. You will see that one of the screw-in handles that fixes your scope to the mount has a spring-loaded washer on it. This should be on the same side as your focuser and is used to adjust the tension between the main OTA bearings and the side walls of the base. Once you achieve the correct tension the scope should move freely and stay at whatever angle you point it at without drifting up or down when you let go. You can adjust the tension when switching from lightweight to heavy eyepieces to compensate for the change in balance.

The idea of replacing the red bearings (which are the friction point between the scope and the base) is that PTFE apparently gives a smoother action than the red stuff that comes as standard. As I say I haven't tried it yet but that is the theory.

Hope that helps?

Derek

[Guest]

Thanks yet again Derek,  On my scope those 4 bearings are white not black but I doubt that makes any difference. But I get the impression that the friction characteristics on that axis are dominated by those four bearings rather than the plastic pads on either side of the scope. As you know the weight of the tube is carried on those four points and I think that's where most of the friction occurs. I thought it would be better if those four things were proper rollers then you'd have complete control over the friction by means of the screw on the side. (I did manage to get that one on the correct side).

Thanks again

Steve

[DRT]

I think you are right, Steve. The main point of friction must be where the weight is being carried but I suspect the design of the fixed nylon bearings and the main plastic rocker unit already accounts for that. Replacing those with something with less friction might give you problems getting the scope to stay still when you want it to.

I still think having something nice and smooth on the flat surface between the main rocker and the base wall must help achieve a smoother action as it would be less prone to sticking. Also, the friction between two large flat surfaces is always likely to be proportionally greater compared to two circular surfaces with very small areas of contact?