Skyliner 200P Dob (and raiding the spare parts bin)

[johninderby]

Skyliner 200P Dob

I wanted to get new "in-between" aperture scope, something not too expensive but that would still give me some nice views when I didn't want to get a bigger scope out. The Skywatcher 8" dob seemed like a good choice and I already had some bits and pieces in my "spare parts bin" that I could use to upgrade it. So I placed the order on bank holiday Monday with FLO and it arrived on Wednesday. I also ordered a Revelation dual speed crayford from Telescope House as they had their 10% off sale.

As soon as the scope arrived it was stripped down so I could begin the mods. The standard single speed focuser was sold the same evening, and with the proceeds of that sale it meant that the Revelation crayford only cost me £50.00. First job was to mark out and drill the holes for the two handles, Next the finder shoe was moved over closer to the focuser, this only required drilling one new hole.

Then I could get on with the flocking, a straight forward job really, and the most time consuming part was cutting out all the holes in the tube before re-assembling the OTA. I had purchased a new base for the focuser that would bolt straight onto a Skywatcher dob from Scopes'n'Skies for £2.00 when ordering some other bits and pieces from their Astroboot a few weeks ago. With that it was just a two minute job to fit the focuser. The focuser knobs aren't the standard Revelation ones but have been replaced by some I already had.

I already had a 6x30 right angle finder and a Rigel Quikfinder. The 6x30 will be fine for zeroing in on the target after finding it in the Quikfinder. I had the dual wheel locking casters already. While they're not essential for moving the 200P around, as it's light enough to pick up the whole scope easily, they're still very convenient and make the base a few inches higher. I fitted the eyepiece tray on the side of the base as it's a lot more useful there. While the ALT movement was fine the AZ movement was a bit jerky. I used the old trick of cutting a washer out of a polythene milk jug and putting it under the teflon washer between the base and ground board. Now the AZ movement is perfectly smooth.

I've only had one evenings observing with it so far but very,very pleased with it. Saturn was as impressive as ever, nice and sharp showing banding on the surface, the rings shadow was clearly defined and a few moons viable. The whole scope has only been a £315.00 outlay

I couldn't help taking a photo of it beside the "Blue Whale", my OO 14" Dob with StellarCAT. I'll have to come up with a suitable name for the new scope. The "minnow" perhaps?

John

[stafford_stargazer]

oh no weird we both posted our pics same time,that big blue one is a beast.lol.

Very nice job ya done on 200p,veryy nice focuser,ummm feel a mod coming up;)

Well what can i say,we must of both been doing pretty much the same thing this weekend.

Cheers for advice john.

Looks great.

G

[WillEyedOney]

Nice mods indeed.

Did you use a single washer or one on top and one below?

I have been fettling my mount and have replaced the ptfe washer a stack of 7 milk carton washers about 75mm dia, which has improved the movement but I still notice a little stiction.

[johninderby]

Just one single washer underneath the teflon washer was enough. I also tried putting some car wax on the surface the teflon pads run on which helped a bit, but then I tried some spray furniture polish that had some silicone on it which worked a treat. Just polish the surface afterwards so there's no liquid polish left.

John

[WillEyedOney]

Thanks. I have some silicone spray here so I will give that a whirl and I will try your single washer mod. Did you find the flocking made any difference?

I know there is some lateral movement because the central pivot sleeve is not a good fit in the hole but that doesn't affect the stiction.

[johninderby]

The flocking helps improve contast a bit, which helps on planets / lunar.

The central pivot sleve is a snug fit on mine. You could wrap yours with some tape to make it a better fit.

John

[WillEyedOney]

Mk II mount fettle with the single washer below the ptfe washer has improved it again, just a little bit of stiction now. just wondering how I could reduce it further.

Maybe I am being too much of a perfectionist, silk purse sows ear n all that.

The sleeve fits 'ok', but you watch the mount as you nudge it, it moves <----> laterally before it rotates.

Oh btw, I have put a milk carton washer between the two steel washers on the baseboard and rocker box.

[johninderby]

The sleeve fits 'ok', but you watch the mount as you nudge it, it moves <----> laterally before it rotates.

Oh btw, I have put a milk carton washer between the two steel washers on the baseboard and rocker box.

How tight is the bolt? I set mine by tightening it up until I felt the slightest additional resistance when rotating the base, and then backed it off about an 1/8 of turn.

You could add a second washer and see how it works, or perhaps one cut from a slightly thicker milk carton. You only want to just barely relieve the pressure on the teflon pads around the base.

I've tried some silicone spray in the past that didn't seem to work that well. The furniture polish worked better and I buffed it with a cloth so that it was dry to the touch. Any liquid residue caused "stiction".

John

[WillEyedOney]

I tighten the bolt up until I can just rotate the milk carton washer between the steel washer and rocker box, nipped up rather than crammed down until the threads squeal for mercy.

I used Pledge instead of the silicone spray (it's buried in a cupboard somewhere and I can't be bothered to get the shovel out and find it )

I might have a bash at this mod to eliminate the annoying lateral jump.