Dobsonian

[meddyliol]

I am thinking of selling my 6" Helios Sky Scan and getting a Dobsonian (or is a refractor a better choice). I want to see deep sky objects and of course planets etc. I am looking at an 8" one (I have been reading the post about the comparative virtues of the 8" and 10" scopes so don't want to open another can of worms on 'is size important'). I have been looking at the Skyliner-200P Flextube one for about £748. Are the Flextube ones any good? Another question is relating to how easy are they (Dosonians in general I mean) to set up? What do they actually sit on, a table or what? So many questions. Yet another question, are the refractor sizes like for like with the tube jobbies? e.g. Would I have to get a 6" refractor to equate with my 6" reflector. I know I am mixing a lot of different questions but I know what I mean (most of the time anyway).

Sorry if I am boring you all with yet more inane questions  

Brian

[meddyliol]

Just been looking at the same website (Tring Astronomy Centre) and the 'normal' Dobsonians are a hell of a lot cheaper, an 8" one is only £282, 10" at £442.

[Paul73]

It looks like you have already done a fair bit of research.

I have a 10" Flextube and can vouch that the system works very well. From the price quoted, I'm guessing that you are looking at the GoTo system. This would add to the weight which may make the 10" too much to carry in one go. The GoTo system gets a good writeup for visual observing but won't be up to imaging.

If you have to carry the scope any distance - go for the 8". If you can see the Milky Way from your observing spot, go for the 10" as it will show more of the faint DSOs. Once you get a bit more light polution, the difference between 8" and 10" will be less and there is a school of thought that says a Refractor might be a better bet (a 6" refractor will easily outperform a 6" reflector in everything except cost!!!). If you are predominantly looking at bright objects, the refractor is the way to go. If you want galaxies, nebula etc, then you need a reflector. The reflector will still give good views of the bands on jupiter, the rings of Saturn etc but they won't be quite as crisp as the refractor.

The Dobs generally sit on the ground. You either bend over or sit on a chair. I have had mine on a table to see over a hedge (thought that the table was going to collapse....)

Don't worry about the questions. Ask away.

Paul

[MattJenko]

I have the 10'' solid tube Skyliner without any goto and it just stands wherever you put it. It is a big old thing, so on the floor. Setting up is as simple as taking the thing outside, the only option is whether to carry the whole thing out in one go, or unscrew the tube from the base (15 seconds) and carry out in 2 pieces and reassemble outside.

There is cool-down time for the mirror etc, but that won't stop you looking at objects straight away. For me it takes longer to put my boots on and make a cup of tea than setting up. I don't collimate each time, as mine holds collimation pretty well and I tend to do collimation during the day, or when it is raining.

[Paul73]

Just been looking at the same website (Tring Astronomy Centre) and the 'normal' Dobsonians are a hell of a lot cheaper, an 8" one is only £282, 10" at £442.

They are a bit lighter too. But they take up a bit more space.

These are not small scopes..... They have to be carried and stored. Many, many people have fallen into the trap of buying a scope that is too big and heavy. Then don't use it and the next thing you know, someone is picking up a bargain on ebay (this is exactly how I got my scope - a bit of a risk but turned out well).

Paul

[Tinker1947]

FLO sell Dob's  http://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-200p-dobsonian.html

[meddyliol]

Thanks a lot you guys. This is THE best forum. Had a look at FLO and they are cheaper that Tring. I would like a 6" refractor but the ones I have seen are around the £800 mark. I don't think 'er indoors would be very impressed with that.

Thanks again

Brian   

[Tinker1947]

Thanks a lot you guys. This is THE best forum. Had a look at FLO and they are cheaper that Tring. I would like a 6" refractor but the ones I have seen are around the £800 mark. I don't think 'er indoors would be very impressed with that.

Thanks again

Brian   

You need to do a wife training course, then as stuff arrives be it  big or little boxes nowt is said, just a puzzled frown.....My 300P GoTo Dob plus extra's came in 3 boxes, Her in Door's signed for them then sat in a corner sobbing...

[AndyWB]

From what I've read, Flextubes are pretty good, but perhaps more prone to dewing (due to the open tube), and a heavier (!) than the solid tubes. Personally, I won't bother with GOTO, but I'm a bit of a luddite. A good map 'll see ya proud, lad.

Setup is the best bit about dobs. The setup process is set down, take off endcap (important), and look. Seriously, so much easier than EQ aligning or configuring a GOTO system.

They sit on the floor, but the really dinky ones (not an 8" or larger!) can go on a table or box. I prefer to sit next to mine - I use a drummers stool, 'cos it has an adjustable height and is portable.

They can be big beasts. I have a solid-tube 10" dob and the tube takes up the entire of the back seat of my car with exactly 2cm to spare. I believe the 8" is the same length (and a more forgiving focal ratio, so less demanding on the optics of your eyepieces). They're also fairly heavy (mostly the wooden base) - I'm not small, but I do tend to move mine in two pieces if it's going more than a few feet. I was glad I went and had a look at one first.

Yes, the dimension usually given is the aperture - so an 8" reflector is 200mm. Refractors of a given aperture are normally regarded as outperforming reflectors of the same aperture, but they cost a lot more, and you don't often see them bigger than about 6". Reflectors offer more bang per buck, but with compromises.

I got my 10" for occasional "big nights out" and star parties - my 5" sees a lot more use, but for shorter stretches, and in town. It's worth thinking about where and how you plan to use it, and to see one in the flesh first, if you can.

[meddyliol]

Excellent bit of info. I am nearly hooked on a Dob now. Still not sure to go for an 8" or 10". What is a Goto anyway?

[John]

GOTO is a facility within the mount of a scope which will find objects for you and then track them when they are being observed. You need to spend a little more time setting the scope up at the beginning of a session for the GOTO system to be accurate and it does add a fair old chunk to the price of a scope.

It's quite possible to use a scope that does not have GOTO or any sort of drive system and many members here do that. Quite a lot like to have the GOTO facility and there is a good sized fan base for that approach as well.

It's down to preferences and budget at the end of the day.

[meddyliol]

OK, Ta. I could, have course, Googled some of the questions but I like to have the personal touch.

[Tinker1947]

My preference for a GoTo Dob was not to use the GoTo to find unseen Messiers ect this can be done just by pushing the scope round and using a Telrad, but to use the GoTo to track stuff once found which it does very well will a wide FOV EP i think it will track for a hour without the object going out of view, as for setting up, GoTo or not type of Dob , place the base on a flat surface drop the tube into place with the GoTo there's a single Bob's Knob's type of screw to do up, then a 2 star align takes a couple of minutes with a Telrad, i gave up with the Finder Scope as cloudless sky's are few and far between....so really its down to price and convenience of tracking with the Skywatcher 300P other brands i can't off a opinion on......

[swamp thing]

Excellent bit of info. I am nearly hooked on a Dob now. Still not sure to go for an 8" or 10". 

For a first scope i would go with the 8" myself not to do with size but the 8" is a more beginner friendly package IMO.

This is because the 8" is 

1/ it'll be more forgiving on budget eyepiece specially if you find yourself being drawn to wide field views.

2/ The lighter 8" mirror will need collimating less than the heavier 10" one.

oops nearly forgot when you come to upgrade from an 8" a 12" is fine......from a 10" it isn't and your looking for something big 

[John]

OK, Ta. I could, have course, Googled some of the questions but I like to have the personal touch.

No problem. Threads like this are helpful to others going though the same thought processes as well   

[bingevader]

If you're not going for the goto 8" model, then I think I'd go for the solid tube rather than the flexi.

Other than the height, there wouldn't be much difference in storage size.

The flexi would need more collimating than the solid tube.

I seem to remember it being heavier than the solid tube too.

[C7tsj]

I have an 8 inch dob and it is a beast. I transport from shed to patio in two pieces as it is too unwieldy to do in one go. Perhaps it is cause I ain't the tallest but I admit I wouldn't manage shifting the 10 inch model on my own.

Dewing is an issue though, need to consider some sort of dew mat, and a red dot finder.

Mark

[meddyliol]

I have just been reading one of my books, 'Philip's Atlas of the Universe' and it says something I wasn't expecting relating to the Dobsonian. Namely, "It cannot be mechanically guided and is unsuitable for lunar and planetary observations". This has throw a little confusion into the melting pot. 

Any comment would be appreciated.

Thanks

Brian   

[John]

I have just been reading one of my books, 'Philip's Atlas of the Universe' and it says something I wasn't expecting relating to the Dobsonian. Namely, "It cannot be mechanically guided and is unsuitable for lunar and planetary observations". This has throw a little confusion into the melting pot. 

Any comment would be appreciated.

Thanks

Brian   

I'd wager that the vast majority of dob owners here use their scopes for observing the moon and planets and have great fun doing it. I've used my 12" dob at up to 500x magnification or more and frequently at 250x-300x on the moon and planets. I'm afraid Philips Atlas of the Universe has got it completely wrong there !

And the current generation of dobs can track and GOTO so they are wrong there as well !.

I expect the text was written back in the 1970's and badly needs an update.

[avtaram]

Totally agree with John.

Avtar

[jetstream]

Me too, my best views so far have been with the 10" dob, which is a perfect stable platform to observe through.

[meddyliol]

The book's edition is 2004 so is quite out of date I suppose. 

Thanks for your inputs

[AstroAdam]

I have just been reading one of my books, 'Philip's Atlas of the Universe' and it says something I wasn't expecting relating to the Dobsonian. Namely, "It cannot be mechanically guided and is unsuitable for lunar and planetary observations". This has throw a little confusion into the melting pot. 

Any comment would be appreciated.

Thanks

Brian   

What a load of old cobblers.

Sometimes, even the famous books get it wrong.  And they couldn't be more wrong.  Had 10 years of successful and satisfying planetary and lunar observation with an 8" Skyliner before I ever even thought of going for another scope, and that was only due to wanting to start imaging...

[AstroAdam]

The book's edition is 2004 so is quite out of date I suppose. 

Thanks for your inputs

2004 is not out particularly of date - Dobs haven't changed that much, apart from maybe introducing more in the way of driven and GoTo options, so you can forgive them for that.  But the lunar and planetary comment?  Nah!

[faulksy]

i used to have a sct, it was a celestron 9.25. it was a great scope and a good all rounder. when i sold it to part fund my scope in my signature i was a bit concerned especially the thought of planets not being very good, that was until i looked through it, it blows the socks of my sct in every respect and its great on planets