Need advice on buying telescope

[Amit]

I am considering buying either of the two scopes mentioned below:

Skywatcher 1309EQ2:

Diameter 130 mm

Focal length 900 mm

Secondary Mirror Diameter 34.5mm

Focal ratio F/ 7

Highest Practical Power 260x

Faintest Stellar Magnitude 13.3

Resolving power 0.9

Finder scope 6x24

Focuser Diameter 1.25"

Eyepiece Super 10 mm and Super 25 mm

Magnification with eyepiece 90x and 36x

Variable Barlow (1.5 - 2X - 2.5x - 3x) 10mm: 135x, 180x, 225x, 270x

25mm: 54x, 72x, 90x, 108x.

Mount Type EQUATORIAL

Slow-motion Control RA & DEC

Skywatcher 13065EQ3:

Diameter 130 mm

Focal length 650 mm

Secondary Mirror Diameter 34.5mm

Focal ratio F/ 5

Highest Practical Power 260x

Faintest Stellar Magnitude 13.3

Resolving power 0.9

Finder scope Red Dot Finder

Focuser Diameter 1.25"

Eyepiece Super 10 mm and Super 25 mm

Magnification with eyepiece 65x and 26x

Variable Barlow (1.5 - 2X - 2.5x - 3x) 10mm: 97.5x, 130x, 162.5x, 195x

25mm: 39x, 52x, 65x, 78x.

Mount Type EQUATORIAL

Slow-motion Control RA & DEC

Counterweight's 3.5Kgs

The 1309 model has spherical mirror while the latter 13065 is EQ3 mount and parabolic mirror shorter one. Please I need a sincere advice from those who have an experience or those who have previously owned or are possessing any of these scopes right now.

Also for the same price of 13065 I am getting 6" dobsonian, however I dont want to go with dobs, just a question will one inch difference matter much?

[Amit]

I need to know whats the difference between short focal length and long one.Which one is more better???

[kostur]

Depends. Long ones give bigger magnification, while small ones have small f- number so they are god for astrophotography. If you are talking about refractors: always take the longer ones, but if you are talking about reflectors: if it's a dob, take longer ones, if it's an eq take shorter ones(might use later for astrophoto).

[kostur]

get a 6" dob, or the second one.

[rwilkey]

The second scope comes on a much stronger mount, so that would be my choice, although I would prefer the f/7 ratio to the f/5, but f/5 is OK, just have to choose ep's carefully, must use better quality.

[bish]

Agree with above. The sturdier mount is better. A 150 dob is worth considering but you can add a motor to the equatorial to track objects and there's not a lot of difference between a 130 and 150.

[barkis]

First, an explanation of the two mirrors.

A spherical mirror, by necessity has to have a longer focal length than the Parabola, otherwise you experience poorly focused images at higher magnifications. That's why you won't find an f5 mrror that is spherical. The longer focal lengths cope better with spherical mirrors. That's the simple explanation.

You get higher magnification for a given eyepiece with an f7, than you you would get with an f5.

An f5 is regarded as a fast f/ratio, which is beneficial for astrophotography, because the exposure times can be much shorter than for an f7.

If you are contemplating taking pictures at some future time, then go for the f5 Paraboloid mirror.

All reflecting telescopes performances are governed by Good seeing conditions, and good collimation of the optics.

Long exposure photography will require a driven equatorial mount on which the scope will track the stars during exposures.

Photography can be quite an expensive route , unless you stick to Lunar and Planetary imaging. Deep sky imaging is much more demanding on equipment, and software and camera.

Ron.

[hemihaggis]

hi there the smaller the F number ie F4 will give a wide field of view ,but less mag

the larger the F number ie F10 will give more mag but a narrower field of view

simple

[hemihaggis]

Depends. Long ones give bigger magnification, while small ones have small f- number so they are god for astrophotography. If you are talking about refractors: always take the longer ones, but if you are talking about reflectors: if it's a dob, take longer ones, if it's an eq take shorter ones(might use later for astrophoto).

?????

[themos]

As you've noticed, telescopes come in a fairly wide range of focal lengths. Assuming the market is fairly efficient, people must be buying all kinds so there must be a reason for each choice. It follows that none is absolutely "better"!

The question is what do you want to do with the telescope. Some people enjoy fairly low magnification so that they can look at fairly large objects in their entirety. "Large" here means large compared to the full moon's disk, so star clusters and extended nebulae. These people prefer short focal length instruments. Others enjoy watching the planets or moon craters and these objects are small so they need more magnification so they pick a long focal length instrument.

[kostur]

?????

what?

[hemihaggis]

Depends. Long ones give bigger magnification, if it's an eq take shorter ones(might use later for astrophoto).

answers on a beer mat please, if the above makes sense ??

lol what ??

as far as i know mounts dont have focal lenghts ??

[kostur]

-.- Dobsonians can't move to equatorial mount. Only eq mount can be used for imaging. Therefore, u use shorter ones (with smaller f ratio) on a EQ, so u could use bigger eq later(if u don't have money now). Anything else?

[hemihaggis]

-.- Dobsonians can't move to equatorial mount. Only eq mount can be used for imaging. Therefore, u use shorter ones (with smaller f ratio) on a EQ, so u could use bigger eq later(if u don't have money now). Anything else?

sorry kostur , you are wrong mate

okay your first statment "dobsonians cant move to equatorial mount " ,is wrong , yes they can , a dobsonian is a reflector ,so a 10" dobsonian will fit in set of 10 " rings and fit on any eq mount, it does not matter what the F number is ..in fact many people have just this set up .

your second statement "only eq mounts can be used for imaging " is also completely wrong , have you never heard of a "wedge" these allow alt az mounts to be polar aligned , for instance meade lx 200 and lx 90`s are popular scopes and are alt/az mounted , many people buy a wedge for them to use for astrophotography with awsome results ..there are many members on here with this setup.

anything else ?

[barkis]

Let's try and keep cool heads here Guys.

No need for arguments, I'm sure it's probably language difference in this case.

Kostur is Serbian, and may just be having difficulty explaining what he means, but his intention is to help.

Barkis.

[kostur]

ok, i may have expressed myself wrong. Ofcourse, u can use dob for imaging too. u can use a stick from a backyard for imaging (pro imagings are the best with eq6)

about moving from dob to eq i didn't know. I know my friend tried something like that, and rings he made were not good, so dob droped and lost secondary mirror.

[hemihaggis]

of course .. my sincere apologys kostur ,

i did not mean to sound as if i was having a go at you , but i can see how badly it would have came across with hindsight .

once again my apologys

[Amit]

Ok then suppose I go with 13065. That is good for astrophotography, so I need to play with eyepieces and barlows to get the same magnification I get in 1309, but will the quality be affected in any way?

And I might switch to astrophotography at a later stage. But I may not be upgrading further. So is 5" enough?

[Amit]

I forgot to mention, I live in a heavily crowded city ,not only with light pollution but lots of air pollution, so the scope should be portable like i can take it anywhere by plane , car or so.

[barkis]

Ideally, you need something like this.

I know it's a bit more ambitious than your first choices, but this would fulfill most of your needs for a long time.

The system will be transportable by car.

Not what you would call cheap, but worth saving for to realise your ambition for observational, and imaging astronomy.

Ron.

http://tinyurl.com/7lx4acu