200-250 dob

[JonnyK]

I was just wondering how easy are dobs to use?I have only ever used an eq mount with slowmotion controls and find it relatively easy to track planets (not tried anything more adventurous yet) how difficult/easy are dobs to track with?also can you get decent webcam results with one?

[RikM]

I find a Dob very easy for visual use on planets. I do use 70° EP's and that helps, but even with a 50° Plossl it's not difficult. The higher the magnification you use, the quicker the planet moves across the field of view, but it's no big deal.

I have never got satisfactory results with a webcam and a manual dob. The chip size is just too small to be able to get a decent length avi. A tracking Dob like the SkyWatcher Skyliner Auto / GoTo's would be much better for that sort of thing.

[JonnyK]

Thanks for the reply Rik, I do fancy a bit of webcam photography which is why im leaning towards the Mak's. Just out of intrest I see you have a 250 dob and a 127 Mak, which one do you use most (I know it's horses for courses but they are 2 of the scopes on my list)

[RikM]

250PX wins by a country mile on any type of object. I have more or less given the Mak to my son. Not my favourite scope by a long way.

[spaceboy]

I'm not the biggest fan of dobs I must admit but they do have there advantages. They can be set up in no time, you get a lot of scope for your money and in the focuser is always in a comfortable position. Using a large newt on an EQ mount can be hard work with the focuser ending up in some very odd positions requiring you to use small steps or rotating the OTA in the rings.

[NGC 1502]

how difficult/easy are dobs to track with?

If the movements are smooth with no sticking, a Dob can be a joy to use. When you get used to it, you are hardly aware that you are nudging the scope, a bit like steering your car, it comes naturally. However, it doesn't suit everyone.

But if the movements are sticky, then a Dob can be a pain. The good thing is that basic DIY can sort out a sticky Dob.

Regards, Ed.

[swamp thing]

how difficult/easy are dobs to track with?

Like falling off a log buddy.

Easy peasy. Just push/pull whatever direction you wanna go. A Dob doesn't move on axis like other scopes they move equally easily in any direction. Just pick which way you wanna go and you're off.

[estwing]

please tell me how to stop a jerky dob..help!

[RikM]

Clean the teflon pads, make sure the clips holding them on aren't protruding through and rubbing, and then buff the bearing surfaces with Turtlewax (other brands of car polish are available, but they don't work as well).

[JonnyK]

I like the idea of having a big 250 dob i've looked at the 250px flextube, does anyone own one?Do they require collminating more often?That's another thing putting me off a reflector. I even looked at the more pricey 10" meade light bridge. I think this decision is going to take some time.

[RikM]

Other than they look cool, there is no real advantage to the truss design dobs at 10" size. They are more expensive and heavier than the solid versions and they need a shroud to cover the trusses. Apart from being a bit shorter they take up exactly the same room as well. Especially if you store them upright. A 10" solid tube dob will easily fit in a small hatchback for travel to a dark site.

[SFlowers]

My hubby and I are looking at getting a 12" dob next but are unsure what to go for. We are leaning towards the meade but we don't have a shop nearby I would really like to go in and have a proper look at one.

[JonnyK]

If I knew I could use a webcam on a dob I would definately go with the 250px, I spent les time choosing my car!

[GazK]

I like the idea of having a big 250 dob i've looked at the 250px flextube, does anyone own one?Do they require collminating more often?That's another thing putting me off a reflector. I even looked at the more pricey 10" meade light bridge. I think this decision is going to take some time.

I've got a 250 flex, it keeps collimation well between setups. Collimation is not super important for visual anyway. If you need to collimate its, ooh, at *least* a 20 second job.

Get a dob, you'll not look back!

[GazK]

Apart from being a bit shorter they take up exactly the same room as well.

Or to summarise, they take up less room than a solid tube. LOL!

I politely disagree. Collapsed it is much easier to handle/carry than at full stretch, especially through doorways and in/out of the car.

[RikM]

Or to summarise, they take up less room than a solid tube. LOL!

I politely disagree. Collapsed it is much easier to handle/carry than at full stretch, especially through doorways and in/out of the car.

Okay, I should perhaps have said they take up the same floor space

Fair point about carrying them about though. With a collapsed truss Dob I can imagine you don't have to worry about bumping the end of the tube on the door frame on the way through

[tjr]

Quick question if I may... is the secondary mirror likely to mis-aligning if you're extending and collapsing the truss tube each time you use the scope? Is this a potential advantage of a solid tube or not really a concern?

[RikM]

If you're going to own a big dobsonian you are going to need to collimate it. I check mine every time I observe it's no big deal. I don't think the flextube system makes it any worse.

[Mike73]

Quick question if I may... is the secondary mirror likely to mis-aligning if you're extending and collapsing the truss tube each time you use the scope? Is this a potential advantage of a solid tube or not really a concern?

You can fit thumb screws from Bob's Knobs to adjust the secondary easily but to be honest you don't have to touch the secondary much, unless its had a good knock. Extending and retracting the flex tube doesn't knock it out of alignment.

Maybe a quick tweak of the primary is all thats needed.

[GazK]

Quick question if I may... is the secondary mirror likely to mis-aligning if you're extending and collapsing the truss tube each time you use the scope? Is this a potential advantage of a solid tube or not really a concern?

No. Secondary collimation is a once-a-year job, solid or flex.

[Moonshane]

please tell me how to stop a jerky dob..help!

my advice based on experience of various types is as follows:

1) alt bearing and azimuth bearing should both have approximately the same radius - alt bearings are often too small on commercial scopes.

2) a sheet of bobbly formica (this does not have to be ebony star - I buy mine for £2 a square foot from a local kitchen maker) glued to the underside of the alt bearings and the rocker box along with etched teflon pads glued to the ground board as widely spaced as possible and the radii at the top of the rocker board (i.e. where the alt bearings ride) will work wonders, especially if waxed with turtle wax (and even more so if you pay attention to 1).

to get a dob working well takes a little work but it's rewarded every time you observe. I can push my 16" dob around (literally) with one finger.