Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

Dobsonian doubts...

Sonia

By Sonia
in The Astro Lounge

Recommended Posts

mark RD

mark RD

Posted
Posted

I think we are all forgetting the young Lady's on a budget ......

I,d get the dobs and when you can afford a decent mount say an EQ6 go for that, A 10inch reflector will be the biggest your going to find in a reasonable budget IMHO

Mark

Link to comment
Share on other sites
  • Replies 63
  • Created
  • Last Reply
Kaptain Klevtsov

Kaptain Klevtsov

Posted
Posted

PS Put a link in Equipment Discussion in case the Gurus are stuck in there.

Now I know you meant that tongue-in-cheek CC but, Astroman aside, there are no Gurus here; just people with different experiences offering opinions/help/advice and generally promoting amateur astronomy :lol:

BUT some of you guys own a telescope, I don't yet. (well technically I do as the plastic already got a whack). Is all I meant, I haven't looked down one yet so all my spouting is copied from books and web stuff that I have read.

I hate to opine (yes really!) about something that I have no experience on, but if Sonia is going to be misled, and because of that not buy the Dob. that she decided she wanted, well thats just wrong.

No Gurus indeed, look at the imaging results, "what can't speak can't lie" to coin a phrase.

Captain Cloudy (oops Chaos)

Link to comment
Share on other sites
FLO

FLO

Posted
Posted

I could be wrong but I think the 4" model is no longer imported. Sherwoods appear to still have some and the price is excellent.

http://www.sherwoods-photo.com/celestron_scopes/nx_gt.htm

Mind you, I'm not sure that it will be enough of an improvement over Sonia's ETX90?

Sonia, if you are trying to keep to a budget then your idea of a Dob' is a good one and, it doesn't need to be a 10" model. The Skyliner 200 (8") is more than enough for most observing.

Link to comment
Share on other sites
MartinB

MartinB

Posted
Posted

Theres an excellent article on cloudy nights regarding aperture. The jist is you can read normal newsprint at 120 feet x aperture in inches e.g. 1200 feet with a 10" scope. This is to a large extent independent of the size of the image. Of course I suppose if you were trying to read black print on a grey background the amount of contrast might be important as well but the article explains clearly the significance of resolution. How it all stacks up when viewing the real sky I don't know.

I do know that my ED80 produces a whole lot better views of saturn with 600mm focal length than my previous Bresser skymax 70mm with f/l of 700mm let alone my Prinz 60mm with f/l of 710mm. The Tal 110 with a f/l of 800 and aperture of 110mm blows them all out of the water on Saturn at higher mags in terms of the detail I can see.

Martin

Link to comment
Share on other sites
russ

russ

Posted
Posted

Hi Sonia,

I seemed to have missed your threads on buying a scope.

I have a read through now and the thing that caught my attention was the fact you only mention the planets and high power. Is that how you see the primary use of your scope?

If so, I have some serious doubts about recommending a dobsonian, especially a 10" dob. Actually i have some doubts anyway.

May i ask, have you ever seen a 10" dob in the flesh?

Are you confident with collimating a Newtonian reflector?

Will it be kept inside the house?

I only ask these questions because:

A 10" f5 tube assembly is a large and cumbersome device. And no lightweight either, the tube weighs approx 10-11Kgs. They are not easy to move, especially if being brought out of a house. This isn't a sexiest thing. I used to own the Orion XT10, identical to the model you are looking at. Kept it in our third bedroom, which meant i had to bring downstairs everytime i wanted to observe. Not matter how hard i tried, i couldn't avoid hitting a door frame or the bannister or something. It got real tiresome after a couple of months.

Which leads onto the next problem...collimation. Fast newts, such as the one you are looking at, need collimating to perform well. It will need really good collimation to perform well on the planets. Newts are renowned for losing collimation, so need tinkering quite often. Especially when transported from the house and taking a knock on the way.

Then there's high powers. If you are looking for a scope to do high powered views of the planets, you shouldn't be looking at a dobsonian. 2 reasons:

1 the dobsonian design - the higher the mag the more frustrating it becomes to control a dob because higher the mag the faster the object flies out of the field. With Planetary observing you need to take your hands of the scope to study the planet. With a dob at high power you are constantly making corrections to keep the planet centered. Which leads onto point 2.

2 the fast newtonian design - fast newts only perform well when the object is on axis, ie towards the centre of the field. Their performance falls of rapidly as the object moves into the outer part of the field of view. This makes point 1 even more important because you have to keep the planet reasonably centered for best performance. This will be even more critical with the budget eyepieces it comes supplied with, as they themselves will only perform well 'on-axis'.

Dobs are fantastic low to medium power devices. Their primary role is deepsky hunting. High powered observing, especially the powers you are hoping for, would be a lesson in frustration.

So in short, I don't think, regardless of it's value for money, a 10" dob would be a good scope for you.

If you do plan on doing deepsky as well, then buy the 8" version. The 8" is all your need, the 10" is over kill. The difference in physical size between the two is large, the difference in performance is not.

Regards

Russ

Link to comment
Share on other sites
daz

daz

Posted
Posted

A celestron nextstar 4GT will be as good or out perform a 10" dob in so many ways.

Portabilty is a big issue. Try taking the 10" dab on holiday with you.

Which ways?

Portability - no it isn't. That is not the point of Sonia's question. Someone has given her some conflicting information and all she wanted was some clarification. She had already decided on the dob, so portability was not the issue.

Link to comment
Share on other sites
russ

russ

Posted
Posted
Portability - no it isn't. That is not the point of Sonia's question. Someone has given her some conflicting information and all she wanted was some clarification. She had already decided on the dob, so portability was not the issue.

This is what worries me. All Sonia mentions is high powered views of the planets. And there's no real connection between a dob and high powered planetary observing. I feel Sonia has arrived at the wrong choice of scope entirely.

Russ

Link to comment
Share on other sites
Sonia

Sonia

Posted
  • Author
Posted

It is now going to be saved for me by end of the month, and will be putting a deposit down next week for it. I will be using it for planets, nebulas and galaxies.

I am also thinking of putting in the etx 90 for the coronado PST Solar scope.

Link to comment
Share on other sites
Sonia

Sonia

Posted
  • Author
Posted
Portability - no it isn't. That is not the point of Sonia's question. Someone has given her some conflicting information and all she wanted was some clarification. She had already decided on the dob, so portability was not the issue.

This is what worries me. All Sonia mentions is high powered views of the planets. And there's no real connection between a dob and high powered planetary observing. I feel Sonia has arrived at the wrong choice of scope entirely.

Russ

Can i please SCREAM AT YOU! I have a budget and that is only £350 so i thought the 10" dob would be the best choice!!!

Link to comment
Share on other sites
Sonia

Sonia

Posted
  • Author
Posted
I will be using it for planets, nebulas and galaxies.

Phew that's a relief Sonia! Although I still feel the 8" is all you'll need. Use the money saved for a good eyepiece.

Russ

I have a selection of eyepieces.

26mm plossl

25mm

H12

10mm

SR4

and a 3x barlow

Link to comment
Share on other sites
russ

russ

Posted
Posted
All i wanted to know was how big the objects will appear.

What i will see (red spot,cloud bands, swirls, spirals on galaxies, cassini divission etc)

Not to cause so much hassle

Sorry :lol::p:D:(:p

You'll see stacks of planetary detail in the 10". And the deep sky will be real nice. Don't worry about the size of the planet.

Russ

Link to comment
Share on other sites
OXO

OXO

Posted
Posted
OK guys if your were given the choice of a 12" Dob and a 7" Meade Mak. Which would you take?
7" Meade Mak anyday :lol:

Sonia you ask about the size of planets compared to your etx 90, the Size isn't as important as the Light Gathering so when you use your 10" Scope you can really get the Magnification up more than the ETX90 you will love it!

James :(

Link to comment
Share on other sites
GazOC

GazOC

Posted
Posted

Damien,

Have you ever owned a 7" f15 Meade Mak (probably a silly question I know!!). I'm really close to getting one (as in next week), the only thing putting me off is the FOV. I know they are planetary/lunar/doubles scopes but are they of any use on other objects?

Gaz

Link to comment
Share on other sites
Astroman

Astroman

Posted
Posted

Have you owned both Astroman?

Owned, no. Observed with, yes. Side by side? Yes. Keep in mind, I've observed through telescopes from 2" antique refractors up through the 24" Clark at Lowell, up to a 41" F/2.1 reflector. All on a regular basis, at least annually, at the Grand Canyon Star Party. I've personally owned the 2" refractor, 4.5" newt, 6" F/9 newt, which I built, 5" F/14 solar, which I also built, C8, 12.5" F/4.9, yes, I built it. Get the picture?

A 10" Dob can be a teriffic instrument! The best view I've ever seen of Jupiter, including through the Lowell Clark, was through a hand made 10" F/5 Dob. No, I didn't build that one, a buddy of mine did, but the view was nothing short of breathtaking at ~ 450X. It's a fine choice, Sonia.

Link to comment
Share on other sites
Saso

Saso

Posted
Posted

Astroman or anyone else of course,

have you view M1 and M78 trough 3.14" refractor or something similar and 10" dob? What can you tell me about comparing images? Beside my ED80 I plan to buy in a year or so bigger telescope for deep sky and I think that 10" dob can be a good decision.

Saso

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.