Dob questions and thoughts..

[emadmoussa]

I received my GSO 10" Dobsonian yesterday. To cut the long story short, base is black not white, focuser is excellent, accessories are of good quality and tube is not really that heavy. Haven't fiddled enough, but I already have some questions.

It's very clear that the set-up is an open domain for mods, and I can see myself doing a thing or two to utilize it for my personal needs.

1. The GSO allows you to amend the position of the altitude knobs for balancing, but not quite a quick thing to do. You need to take the tube off the base and adjust the hex screws. It seems I'll need a quick balancing solution when I don't have the time to do the proper adjustments. Do you guys use magnets?

2. Feeding the tube into the base is easy. However, taking it out requires a bit of fiddling and some strength. I'm not sure whether it's about practice or the gear needs a bit of time to achieve more flexibility. What's your experience with that?

3. When you take the tube out it's almost inevitable knocking it against the base. I'm thinking about adding some sticky padding bits on certain areas around the lower part of the tube in order to absorb any shocks.

4. The OTA also keeps knocking the base front, and for this reason I'm thinking about adding some padding on the inside as well.

5. Here's the tricky part, having assembled almost everything in the base I realized that the central bearing bush (sleeve axle) was missing. Instead there was an extra washer. I'm not sure whether this is meant to be, or simply an error. Image attached. I put things together and placed the extra washer underneath the sliding plate (between the sliding plates and the bottom wooden base. It seems to slide smoothly without a problem.

6. Does your base have a soft ''whooshing'' sound when you spin it? Is it normal?

Thoughts appreciated, many thanks!

Emad

[swamp thing]

Emad

I use a magnetic knife rack on my 10". This allows me to place weights on it and slide to balance. Simples

Edit should have said, "I fixed a magnetic knife rack to my Dob"

[Rustysplit]

Emad, I would be inclined to get onto your supplier and get them to send you out the bushing sleeve. In the long run it will prevent premature enlargement of the holes in the base boards. It is meant to spread the side loading evenly and prevent any slight "slippage" from side to side.

[emadmoussa]

Yep, already sent them an email. Waiting to hear. Can you find these bushing sleeves from a DIY shop or off ebay??

[Rustysplit]

You could certainly buy a length of steel or better, brass tube, but probably easier to wait for them to send you it. You will be fine using it in the meantime.

[JED-E3]

Your GSO dob came with instructions?  you're lucky, mine came with none.

Regarding the bearing noise, i 'think' thats normal, mine does it when moving the scope quickly, I guess it's because those roller bearings are spinning pretty fast. 

[emadmoussa]

To be honest I assembled it without looking at the instructions since I watched the Zhumel video a couple of hours before  the Dob had been delivered. It was straight forward. I think probably they decided in include some instruction following a bunch of complaints.

May I ask, did you receive a sleeve bushing with yours?

[rory]

Congrats on what's sure to be an excellent observing tool. Look forward to reading some reports.

[Avocette]

5. Here's the tricky part, having assembled almost everything in the base I realized that the central bearing bush (sleeve axle) was missing. Instead there was an extra washer. I'm not sure whether this is meant to be, or simply an error. Image attached. I put things together and placed the extra washer underneath the sliding plate (between the sliding plates and the bottom wooden base. It seems to slide smoothly without a problem.

6. Does your base have a soft ''whooshing'' sound when you spin it? Is it normal?

Hi Imad,

The SW 300p flextube uses the same lazy Susan bearing arrangement made from two galvanised circles sandwiching a plastic former with steel needle cylinders which roll between the galvanised steel sheets. It is important that the galvanised circles are flat against the melamine coatings of the two parts of the base. So you should remove the spare washer you mention. In my case I bought the Dob second hand and found evidence of wear due to the dry metal against metal pressure. I cleaned up the whole assembly with methylated spirits, allowed it to dry off, and then lubricated the steel cylinders with just a little cycle gear grease. I bought the clear 'waterproof' kind. With the grease in place there is no longer an obvious metal on metal sound.

The missing tubing sleeve is important in the longer term since the chipboard will wear and the holes could become larger.

I'm still contemplating how to improve the friction feel of the azimuth bearing on the 300p which is a little too loose in comparison to the altitude bearing (and in comparison with otherer Dobs I have used which use three PTFE pads and no lazy Susan bearings).

Clear skies for your first light soon!

[emadmoussa]

Hi,

The washer is not actually sandwitched between the plates, it is just underneath them all on top of the wooden base. It does provide a level of stability.

[JED-E3]

To be honest I assembled it without looking at the instructions since I watched the Zhumel video a couple of hours before  the Dob had been delivered. It was straight forward. I think probably they decided in include some instruction following a bunch of complaints.

May I ask, did you receive a sleeve bushing with yours?

Mine is the 12" version but i think the base is mechanically the same, and it did come with the axle sleeve tube. 

James.

[Avocette]

If I'm following you correctly, you're saying that the washer is between one of the galvanised steel circles and the coated chipboard base circles. The problem with this is that in time one or other will become distorted and/or the Dob OTA will rock a little. If a washer was needed in this position it would be shown on the diagram!

[emadmoussa]

The washer is outside the 3 circles.

[Rustysplit]

In your diagram you show the extra washer underneath the bottom metal disc, therefore  on top of the baseboard. This will cause a hump in the middle of the bottom of the bearing discs. I would take it out. The discs rely on being flat. Only a small thing, but you spent the money on it, so may as well have it working as well as it can.

Good luck and enjoy using it.

[brantuk]

The large washer should be on top of the top baseboard and under the knob - then you can tighten down on the AZ axis till you get the right amount of sticktion. Is there another small circular bearing in the pack at all?

[emadmoussa]

The large washer should be on top of the top baseboard and under the knob - then you can tighten down on the AZ axis till you get the right amount of sticktion. Is there another small circular bearing in the pack at all?

I'm not talking about the large washer. Things are done this way. inside the knob from top to bottom: small washer > bearing > big washer.

The problem is that there should a be an axle sleeve that feeds into the hole on the bottom wooden base and then you slide in the 3 sliding plates and on top of them you place the base then you insert the knob. Like in the manual, instead of axle sleeve I received an extra washer which I doubt  has any use.

I've been in contact with Teleskop Service and asked them to send me the missing part but haven't heard back yet. I'm concerned that lack of axle sleeve might compromise the plates in the long run.