10" Dob - The Perfect Visual All Rounder?

[Paul73]

Hi Guys

Something struck me as odd last night whilst piloting my 16" mega(ish) Dob around the heavens, with my trusty little ED80 in attendance for the wide fields. That thought?

That the 10" f5 ish Dob is the perfect "all rounder"!!!! Or, Should that be, "Jack of all trades, master of none"??

I used to think the latter. Now, I know it to be the former.

Firstly. I am a firm believer that, a carefully thought out eyepiece collection is essential to making any scope fly. It doesn't have to be a case full of green & black at every focal length! But, it isn't a cheap excercise.

The evidence (errrrrr more of my ill informed opinions and inexperienced observsions):

1/ Portable - Can be carried easily by a reasonably healthy chap. No need for sack barrows and avoiding steps. Can be moved around during an observing session (once set up. the big-un stays put for the duration).

2/ Bright stars - you may be able to see the back of your own head with the little Frac. But the stars are really dim. The 10" has enough punch to make those clusters sing.

3/ FOV - The Pliades are rubbish in the big scope. You can only see a handful in one FOV (the Nebulosity is nice though). With the 10" and a decent 20mm 100° eyepiece you can see the whole lot blazing out at you! Same for the double cluster etc.

4/ Planets - image scale is pretty good and the scope can handle plenty of magnification given UK sky.

5/ Plently of rewarding targets - All of the Messier's and a goodly cinch of the NGC's fall to this scope.

6/ UK Limitations - my 16" doesn't actually show many more galaxies than my 10". Sure, the image scale is substantially better and you can tease out a bit more detail in some. But, if you don't have the sky.....

7/ Siplicity - can you get any simpler than a Dob??? Easy columation, no power to make it work,etc etc

8/ Upgrades - There are generally a load of upgrades that will keep a dedicated tinkerer happy for months

I rest my case!

Paul

 

 

 

[John]

We had a poll on this a couple of years back and I seem to recall that the 10" dob was the winner in terms of best all round scope for visual observing.

I tend to agree with your conclusions but I do wish that the standard Skywatcher 10" focal ratio was something around F/5.3 rather than F/4.7 which is rather tough on eyepieces and demands a little more collimation accuracy.

Small points overall and nothing to detract from your conclusions

[kev100]

I completely agree. Having thought long and hard about bigger scopes, I keep coming back to the idea that the 10 inch dob is just ideal. It's convenient (easily fits in the car), gives great views, etc, etc. Whilst I'd like to have a bigger scope, I don't think I could ever part with my 250PX ...

[bomberbaz]

I concur with your findings paul. I love my 10" dob for the portability. Its 12" bigger brother is another 30lbs in weight. Aside of the issue I have currently with the inteligent side of it I cannot fault the all round experience.

I also agree with John, even my top glass struggles with the F4.7 and for the hieght of the OTA when on the mount, cannot see why Orion and SW don't make them at a higher F ratio. Afterall both of the afore mentioned providers do the 12" at F4.9!

[Paul73]

Re. The focal ratio.

Maybe they thought that the extra 5" of tube would put people off??? I'm a sitting down observer and can get away with a standard garden chair and a couple of comfy cushions to get the correct hight. 5" longer would really annoy me. Although, the savings in eyepieces would pay for a gourmet adjustable observing chair many times over.

Tough on Eyepieces? Provided I don't look through a Frac first, I find the coma ok with either the 21 Ethos or the 24mm ES82°. Much longer and the coma starts to get intrusive. Errrrr. I think that your point has been proved??.

Paul

[kev100]

19 minutes ago, Paul73 said:

Re. The focal ratio.

Maybe they thought that the extra 5" of tube would put people off??? I'm a sitting down observer and can get away with a standard garden chair and a couple of comfy cushions to get the correct hight. 5" longer would really annoy me. Although, the savings in eyepieces would pay for a gourmet adjustable observing chair many times over.

Tough on Eyepieces? Provided I don't look through a Frac first, I find the coma ok with either the 21 Ethos or the 24mm ES82°. Much longer and the coma starts to get intrusive. Errrrr. I think that your point has been proved??.

Paul

Hi Paul,

I've been thinking about getting a 24mm 82 degree ES eyepiece to replace the 24mm 68 degree MaxVision I currently own (which I thought was great when I first got it, but it's increasingly annoying now). I've read good things about the 82 degree version, and am a bit surprised to hear you still experience coma with it. I've heard they're pretty good right to the edge.

Kev

[MattJenko]

In addition, a 10" newt is doable on an AzEQ6 for AltAz viewing and it also makes for a huge light bucket with nice focal length if you ever want to stick a camera in it. It makes for an incredibly versatile scope.

[Ben the Ignorant]

Having tried many scopes at various magnifications in all kinds of conditions, planetary detail seems to blossom at 240x for my eye. To keep a good density of detail, and a strong brightness, the exit pupil needs to be around 1mm (to my eye), thus the scope should be at least 240mm in diameter.

Faint fuzzies depend heavily on darkness and transparency, so I won't venture saying which diameter is ideal, but the 10-inch mark seems to be confirmed for subjects with strong surface brightness: planets, small planetary nebulas, globs, multiple stars, etc.

[Linda]

Easier than a Dob is a scope that doesn't need to be collimated. I also think a scope should be carried easily by an average length, healthy person (M/F). It is a small advantage if the scope and mount can be carried outside together. The perfect all round scope should fit into your can when you go on a camping trip, besides all the other camping stuff. That is where the 10" Dobson suffers. So for me, the 10" Dob was not the perfect scope.

[bomberbaz]

Just now, Linda said:

Easier than a Dob is a scope that doesn't need to be collimated. I also think a scope should be carried easily by an average length, healthy person (M/F). It is a small advantage if the scope and mount can be carried outside together. The perfect all round scope should fit into your can when you go on a camping trip, besides all the other camping stuff. That is where the 10" Dobson suffers. So for me, the 10" Dob was not the perfect scope.

If I tried putting this in car when off camping the mrs would hit the roof, haha 

[Paz]

It's hard to say there's a perfect scope, but if you could only have 1 scope for visual then i would vote that the biggest dobsonian you can manage would be it, but that size would vary for each person.

Putting an emphasis on packing down small for travel etc would be different but if it's just one scope (and no cheating!) for me the other scopes would have to go and the dob would stay.

[Linda]

A 10" suitcase model Dobson is ideal for packing and can even be brought along on an airplane. But it requires setup time and hassle and is not as stable as a normal Dobson. So every advantage has a disadvantage.

[Piero]

Assuming space is not an issue as pointed out by Linda, I think an 8"-10" dob offers an excellent compromise between power, cost and portability. The trade off between the two seems to be "a bit more portable" vs "a bit more powerful". 

I think it would be nice if the 10" comes in two focal lengths: 1200 (F4.7) and 1500 (F6). This would give an option for those who want to put their dob on the car back seats and those who prefer a more all-around telescope.

The only reason why I opted for the 8" is because a 10" is too expensive considering my limited use (approx 3 times per year when I go back to Italy). On the other hand, my dream scope is something like a 12"-12.5" F5.5. This would also allow me to observe standing most of the time. From 8" to 12", there is a full magnitude gain. An Orion Optics 12" F5.3 weights like a commercial 10" F4.7, so weight is not an issue for portability, although the tube length of the former can be.

[Paul73]

1 hour ago, kev100 said:

Hi Paul,

I've been thinking about getting a 24mm 82 degree ES eyepiece to replace the 24mm 68 degree MaxVision I currently own (which I thought was great when I first got it, but it's increasingly annoying now). I've read good things about the 82 degree version, and am a bit surprised to hear you still experience coma with it. I've heard they're pretty good right to the edge.

Kev

Hi Kev

Don't worry. The 24mm 82° is a cracking eyepiece. You will notice the difference. The field is flatter than the MaxVision and the wider Fov is a real treat.

The Coma comes primarily from the mirror although some eyepieces seem to cope with it better than others. But, the wider you go the more of an issue it becomes. The Ethos shows loads more coma than the a Delos, as 100° plays 72°.

Paul

[Paul73]

1 hour ago, Linda said:

Easier than a Dob is a scope that doesn't need to be collimated. I also think a scope should be carried easily by an average length, healthy person (M/F). It is a small advantage if the scope and mount can be carried outside together. The perfect all round scope should fit into your can when you go on a camping trip, besides all the other camping stuff. That is where the 10" Dobson suffers. So for me, the 10" Dob was not the perfect scope.

Yep. I have problems fitting the children in the car once the "essential" camping gear is on board!!! 

Although, I seem to manage it for starparties when I can pack light.

Paul

[kev100]

23 minutes ago, Paul73 said:

Hi Kev

Don't worry. The 24mm 82° is a cracking eyepiece. You will notice the difference. The field is flatter than the MaxVision and the wider Fov is a real treat.

The Coma comes primarily from the mirror although some eyepieces seem to cope with it better than others. But, the wider you go the more of an issue it becomes. The Ethos shows loads more coma than the a Delos, as 100° plays 72°.

Paul

Cheers Paul. That's good to know.

[John]

The F/4.7 primary mirror will be generating the coma. The classic eyepiece aberration in fast scopes is astigmatism. From what I read, the ES 68, 82 and 100 degree eyepieces are pretty well corrected even in fast scopes so the main aberration visable will be coma. A coma corrector should tidy that up, if it bothers you.

 

[YKSE]

42 minutes ago, John said:

The F/4.7 primary mirror will be generating the coma. The classic eyepiece aberration in fast scopes is astigmatism. From what I read, the ES 68, 82 and 100 degree eyepieces are pretty well corrected even in fast scopes so the main aberration visable will be coma. A coma corrector should tidy that up, if it bothers you.

Exactly, I confused coma with astigmatism when I started, just because coma felt like the right word. The same is happening with aberration and distortion, or field curvature (FC), distortion is mostly miss-used when people actually mean aberration, so the good old link is worth to repost from time the time:

http://umich.edu/~lowbrows/reflections/2007/dscobel.27.html

Back to OP, I totally agree that a 10" dob is an excellent scope for life time, and just like many 4" to 12" scopes, if the owners know what they want the scopes for. I'm not sure if there exists a perfect scope though, it's the word "perfect" make one to hunt for the tiny little improvement, instead of knowing what copromises (costs? portability?optically quality?, ease of use? etc, etc) have to be made to get a "good enough for me" stuffs. For me, it's easier to settle down to use the scopes I have for observing, when the goal for stuffs are "good enough" than perfect. 

[Dude_with_the_tube]

agree on statement that 10" would be the perfect scope for UK skies,but i will agree with John on focal length, F4.7 is too short for my liking and i would rather have 10" dob but in F6 or even better F7

But as there is none of that sort of available unless you do a custom order,then i will stick to my old ole refractors

[cotterless45]

I'm a fra fan , but for deep dark skies 10" f5 is absolutely lovely.

We don't have much room in the car, but having a Lightbridge for five years has meant easy transport. Collimation stays tight, just label the struts so they assemble the same. In addition a 24mm Panoptic gives the loveliest of views.

At f5 it's just the right height for a comfy 18" bench to absorb the views. In addition you need 

clear skies !

Nick.

[spike95609]

I've nothing to compare my 10" dob to as it's the only scope I've owned, but I did a lot of research before buying and ended up with this one as it seemed the perfect balance of price, weight, simplicity and performance. Two years and I'm still surprised at the number of obscure DSOs it manages to find, and in skies which aren't the best - a couple of miles from Wolverhampton. I've no plans to upgrade.

[Dude_with_the_tube]

2 hours ago, spike95609 said:

I've no plans to upgrade.

ugh,never say never  but i have to say that 250PX was lovely instrument.Held collimation very well,provided with great images on planetary and DSO`s.

i started off with a 10" dob and a 3.75" refractor and then it spiraled off...(14" dob,few others on loan,on test) and actually currently i have no telescopes at all hahaha,well sort of none.there is one in building stages so i am sitting on boxes with spare parts and waiting on CNC machining.Hopefully another week and we might see something coming together.

[niallk]

Love my 250px - it has shown me so much: a great all rounder imho.

I do almost exclusively use my 15" now though tbh, but I won't sell the 10"

 

 

[spaceboy]

I'm also a fan of the 250PX. I tried a 12" flexi tube dob last year and couldn't get on with it as it was just too heavy and cumbersome in comparison. The 10" just seems to fit in that goldilocks zone of portability and punch. Although saying that I'm not sure how the heavier 10" flexi dob are to handle compared to the solid tube ?? I have no idea why SW gave up on the solid 250PX ? I could understand going down the route of a 10" flexi dob if you were to increase the focal length to f/5 - f/6 but to remain at the relatively short f/4.7, a solid OTA fit easily across the back seat of even the smallest cars I've owned ??

[swamp thing]

On 3 October 2016 at 11:13, Paul73 said:

 

6/ UK Limitations - my 16" doesn't actually show many more galaxies than my 10".

 

 

 

 

Err yes it does. Try going to a dark sky.  

My 10" gathers dust these days for exactly that reason. My 20" blows it into the weeds.