14" Dob - what to expect?

[Charic]

You can't increase surface brightness it's not possible.

Have a read of this

http://www.rocketmime.com/astronomy/Telescope/SurfaceBrightness.html

 Reading that link, and maybe a play on words here, but if I start out with a medium power EP then change to a lower power EP,  have I just not increased the surface brightness by a factor, upto its maximum, as the maximum surface brightness is always  achieved with the minimum magnification. I only wish there was a definitive guide on the theory. We all want the facts and the knowledge, but I always wish to dig deeper, with the knowledge. like Barlow lenses. So many folk just think it halves the focal length of the EP in use. Not so!

[Charic]

John........I don't doubt your theory, and/or  experience, but  a bigger aperture, takes in more of everything. the Good and the bad, but Its the theory of why, by taking in more of everything, especially light pollution / sky glow, is it able to separate and still give better results. Most folk agree that the bigger aperture works better "for them" but I'm digging for the definitive reasons as to why this occurs?

[Charic]

broadly, if you ignore light pollution, a larger scope will show many objects that are not visible with less aperture. the smaller aperture cannot see them in the same way that our eyes with their even smaller aperture cannot see them. so a larger scope will make 'invisible' objects visible.

if you include light pollution, then the only difference is that the contrast of the object has reduced in comparison with the sky background. this is to a 'standard' level across the sky so relatively speaking the situation is as above but with a different contrast starting point.

moonshane.........as I said earlier, surely thats because The only reason 'invisible' objects become visible with aperture from darker skies is that your eyes have a minimum threshold for detecting incoming light, which is the reason we use the telescope. I agree with your first statement, But bring in the LP or poor seeing, and if that object you wish to view is overwhelmed, isn't it game over?

[beamer3.6m]

Was the OP'S post about the practicality of a 14" scope not the more aperture is better argument.

[John]

Was the OP'S post about the practicality of a 14" scope not the more aperture is better argument.

Thats a good point 

I've stopped at 12" because thats the max aperture that I can move around my garden and in and out of the house relatively easily. If I had more suitable circumstances for one I'd have a larger aperture scope like a shot

My restriction to a 12" aperture scope is nothing to do with the lack of potential performance gain though, just portability practicalities.

[John]

John........I don't doubt your theory, and/or  experience, but  a bigger aperture, takes in more of everything. the Good and the bad, but Its the theory of why, by taking in more of everything, especially light pollution / sky glow, is it able to separate and still give better results. Most folk agree that the bigger aperture works better "for them" but I'm digging for the definitive reasons as to why this occurs?

I don't have a theory - it's just what I observe happening.

In theory my 12" scope should not be able to resolve the <500m wide rille that runs down the Alpine Valley on the Moon. But when the observing conditions are good, I can see that rille

Perhaps it's a good topic for another thread.

[Charic]

beamer3.6b.........Hi, point taken but the first question was "Any thoughts?" those were my thoughts at #2. Then digression ensued. Its all part of the fun and leaning curve and  being part of a forum,  but apologies to emadamoussa if I was hijacking?

[Rustysplit]

Emad, why motorised? The biggest joy of the Dobsonian design is the near instant set up and go and the ability to fling it around the sky dodging clouds or lookimg at whatever you fancy. Having sold my eq6, imaging scope and all the power leads that go with the territory, I know what has made me enjoy astronomy more

[Moonshane]

my concern was the view (which Charic is entitled to hold) that light pollution should be a consideration in the choice of a scope is one that I completely disagree with. the size of a scope and the weight are valid considerations as is the eyepiece height but light pollution is irrelevant. this is my view and I'm entitled to it also.

in answer to the original question, a 14" scope would be a substantial upgrade in every way from a 10" scope and if well adjusted and smooth would work extremely well as described even if a manual option. personally, I'd recommend a manual 16" f4 in this situation but this is based purely on my own experience. that said, I use my 12" f4 a lot more than my 16" at home as it's so much easier to put out and bring back in and cools a lot more quickly. I have o store my scopes indoors. if not then the 16" would get much more use than the 12".

[crashtestdummy]

i had a motorised 300p and hated the motors and would never go back to a motorised dob as they are far less precise than manual ones.

to the original question-it all depends on what scope you have come from as to what you can expect from a new one.i went from a 12" to a 16" and generally I think I cant see much fainter but from my garden in the 12" I couldn't see the crab nebula or m110 but I can quite easily in the 16".in a 14" under good conditions assuming your eyes are good you can potentially see all the messiers and the entire ngc catalogue although I would say that some of the ngc's would be a massive challenge.i struggle to see above mag 13 in my 16" but know people who have seen mag 14+ with a 10-12".im really bad at using averted vision though so pretty much all my objects are viewed with direct vision.

[emadmoussa]

Emad, why motorised? The biggest joy of the Dobsonian design is the near instant set up and go and the ability to fling it around the sky dodging clouds or lookimg at whatever you fancy. Having sold my eq6, imaging scope and all the power leads that go with the territory, I know what has made me enjoy astronomy more

Wouldnt argue with that. For me personally I find planetary observing quite tiresome without auto tracking...if I can get the dob to track, then sorted.

I'm assuming motorized Dobs are also manually flexible and you can use them exactly like non-motorized ones?

[itmo]

You need to be careful , not all dobs are flexible. My skywatcher flextube has dual encoders so I can use it with goto, goto and push manually, or without electricity and just push around. 

[emadmoussa]

You need to be careful , not all dobs are flexible. My skywatcher flextube has dual encoders so I can use it with goto, goto and push manually, or without electricity and just push around. 

Yes. I'm aware of that. But in terms of movement, is it as smooth as a normal non-motorized dob?

[faulksy]

hi emad, as you might no i have just upgraded from my cpc 9.25 to a 00 uk vx14 1/10 and the views are outstanding, i realy cant describe how good it is, i have also fitted a push to system using sky safari pro so i can locate anything i want with no noise and as smooth as any dob, i went for the 14" as it is ideal for transporting