Stars in a Large Telescope

[Corkeyno2]

I am thinking about investing in a 16 inch dobsonian telescope. Will I be able to see any shape in nearby stars?

[rockystar]

No, stars will be points of light no matter how large your mirror. what you will be able to do though is see fainter stars, resolve more stars in globular clusters and see fainter objects such as galaxies and nebulae. You should see more details in these objects too. You may also be able to split closer doubles

[Corkeyno2]

16 minutes ago, rockystar said:

No, stars will be points of light no matter how large your mirror. what you will be able to do though is see fainter stars, resolve more stars in globular clusters and see fainter objects such as galaxies and nebulae. You should see more details in these objects too. You may also be able to split closer doubles

Thanks

[ronin]

A large scope is really intended to collect more light, so it enables a person to see dim objects better and also then make formerly very dim objects a bit less dim. As such an observer then is able to pick out greater detail. As a generallity it does not, or is not primarily to make things bigger.

The galaxy group at the rear of Leo is an example, in an 8" scope you will see say 80 small disks, in a 16" you will see say 160 small disks. Strill small disks but more of them.

[Pig]

The only star you will see any real definition on is our very own star  the sun, and a Dob is probably not the type of scope to use for this.
You also need very specialised filters for our sun.

[Charic]

Not sure what scope you have at present, but a 16" scope under good skies should provide remarkable results, and with the larger aperture, greater light capture is afforded, which could show  fainter objects, under the right conditions, and if your eyes are up to it.
Unfortunately, the  Stars  themselves are so far away, that obtaining any structural detail is nigh on impossible, from Planet Earth using the scopes available to us.
Its the main reason I choose low powered Binoculars for viewing the Stars, as I don't expect to see any details, but enjoy seeing more, within the wider field of view, of which I have just over 8° field.

[glynnlondon]

Globular clusters should be pretty impressive in a scope of that size. Also planetary details will be very good.

[brantuk]

Yup - globular clusters is what I was gonna suggest for a good aperture comparison on stars. See M13 here half way down the page:

http://www.obsessiontelescopes.com/

Hth

[spaceboy]

People often ask will a bigger scope show any detail in night time stars which always puzzles me when you consider the equipment available to see a huge star right on our doorstep. Even a 40mm Ha scope will show you masses of detail although granted at a price. Even the cheapest of scopes will show surface detail on the sun with the use of £20 baader solar film (never look at the sun without a filter). What a large scope does is collect more light so basically make dull objects that bit easier to see. It will not make something far away appear closer.

[Timebandit]

Hello Corkey. Stars in a telescope whether it is a 6" or 16" or even much larger aperture will appear as points of light through the eyepiece. What a larger aperture will allow is more light into the scope and therefore the opportunity to resolve faint light source in more detail. The larger aperture allows you to push the magnification more on the scope to therefore resolve these faint light points and therefore allowing you to see faint stars or galaxy DSO that you would not see in a smaller aperture scope. A larger aperture also allows you to push up the magnification on planetary detail and therefore you will also see more details of planets on a larger telescope than you will a smaller telescope (as long as other factors such as mirrors ect are the same). As a basic rule aperture allows more light therefore you can use more magnification and therefore can see faint object better in the eyepiece compared to smaller aperture scopes. 

If you see any amateur astronomer into galaxyn hunting, dso they go for aperture to get better views of the DSO , just ask the Dob mob?

[swamp thing]

5 hours ago, Corkeyno2 said:

I am thinking about investing in a 16 inch dobsonian telescope.

That is a big scope. Have you seen one in the flesh?
If not, I strongly advise you to go and see one first. Otherwise a 16" Dob suddenly turning up on your doorstep is likely to be a big surprise. Be aware that huge scopes in showrooms or at star parties look smaller than when standing in your lounge.  

[acey]

53 minutes ago, swamp thing said:

Be aware that huge scopes in showrooms or at star parties look smaller than when standing in your lounge.  

And they look even smaller on a computer screen. I'd suggest 8" as the largest size for a first telescope.

[Corkeyno2]

2 hours ago, swamp thing said:

That is a big scope. Have you seen one in the flesh?
If not, I strongly advise you to go and see one first. Otherwise a 16" Dob suddenly turning up on your doorstep is likely to be a big surprise. Be aware that huge scopes in showrooms or at star parties look smaller than when standing in your lounge.  

I have seen many pictures of them next to a man. They are giant! I'm planning to use a relatively low magnification. All I'm looking for is a sharper image. Thanks for the advice.

[Corkeyno2]

1 hour ago, acey said:

And they look even smaller on a computer screen. I'd suggest 8" as the largest size for a first telescope.

This is actually my fourth telescope. My first was a Tesco 'how cool is this?' then a small Newtonian. After that I got a Nexstar 4SE but need a sharper image so decided to go for a really big scope.

[spaceboy]

Tesco superscope

 

And what do you mean a sharper image ? Was the image not sharp in the 4se

[spaceboy]

Ahhh I think I know what you mean. You'd be wanting plenty of time cooling the scope to ambient temperature and a refractor if you want sharp stars.

[swamp thing]

1 hour ago, Corkeyno2 said:

I have seen many pictures of them next to a man. They are giant! I'm planning to use a relatively low magnification. All I'm looking for is a sharper image. Thanks for the advice.

You're welcome  

When you say relatively low mag, you are aware that as you increase aperture you will be forced to use higher power aren't you? The minimum power for a 16" scope is around 60x (if I remember correctly) that is allowing for someone with young eyes that can fully dilate to around 7mm.

Another point worth noting is 16" Dobs are fast focal ratios by their very nature (no one builds 16" f/8 scopes). The sharper image you are after will be effected by coma. Also unless careful attention to eyepiece quality is observed the very eyepieces you are using may give astigmatic views. Both of these problems can be cured with coma correctors and premium eyepieces.

If you have premium eyepieces and a coma corrector have fun. If not........be ready to spend £££££'s to get those sharp views.  

Regards 

[happy-kat]

The 4SE had a central obstruction, a reflector has a central obstruction from the secondary mirror.

If the OP wants sharp stars mentioned several times (atmosphere etc. permitting) surely they should be considering a ED or better refractor ?

[John]

Your 4SE will probably show sharper images than the average 16" dobsonian, provided that it's cooled down and is being used with reasonable quality eyepieces.

The big aperture will show much, much fainter objects though.

 

[Corkeyno2]

48 minutes ago, swamp thing said:

You're welcome  

When you say relatively low mag, you are aware that as you increase aperture you will be forced to use higher power aren't you? The minimum power for a 16" scope is around 60x (if I remember correctly) that is allowing for someone with young eyes that can fully dilate to around 7mm.

Another point worth noting is 16" Dobs are fast focal ratios by their very nature (no one builds 16" f/8 scopes). The sharper image you are after will be effected by coma. Also unless careful attention to eyepiece quality is observed the very eyepieces you are using may give astigmatic views. Both of these problems can be cured with coma correctors and premium eyepieces.

If you have premium eyepieces and a coma corrector have fun. If not........be ready to spend £££££'s to get those sharp views.  

Regards 

cheers