beginner telescope but what focal lenght ?

[Tomek]

Hello everyone! So here is my first post.

I am a total begginer and got interested in astronomy just recently. I want to buy my first telescope and I understand bigger mirror is better so I will go for biggest I can afford. But what is the difference between choosing focal lenght. I

see same size mirror scopes with different focal lenght and don't know if I should look at loger or shorter tubes ? What's the difference besides size ?

I am interested in deep space objects mostly but will look at the planets as well.

Is 130mm mirror suffucient for deep space objects or should I go for bigger mirror.

thanks in advance for help.

[Capricorn]

If DSO's are what you intend to look at AND you are thinking of visual only then within reason the bigger the mirror the better.

So far that means a big objective and a reflector.

Next is the mount: Equitorial or Dobsonian are the 2 main ones for a scope.

The equitorial is a lump of engineering, so costs money.

The dobsonian mount is much simpler and at a push you could make one with a jig saw.

I say this to point out the difference.

So as the dobsonian mount is simple it costs less so a bigger lump of your money can go towards an even bigger mirror.

If you want to track things, makes looking at them a bit more pleasant if they stay more or less in view then motors are required. These cost money so the mirror size goes down.

The 130mm is I suspect a bit small but I have nothing over 105mm and get along well enough.

What budget have you?

Also be serious aabout the use, if lurking in the back of you mind is the idea to do astrophotography then consider that as a seperate area completely. It is also a damn expensive aspect.

Rather like getting a 4x4 to carry the family and assorted bits round then wondering hy it doesn't do well at a track day around Brands Hatch, even if it might have the same or more power then the caterham 7 that has just passed you for the third time.

[Jessun]

Hello and welcome!

I'd go for something like a 80mm refractor - no mirrors, just lenses. Great 'entry' type of scope with the advantage, that no matter how many times you upgrade and buy bigger in the future should you get the bug, it will always be useful. Useful for travelling, as a 'grab-and-go', or as a guide scope for something bigger. It will also serve as a great wide field imaging scope on its own.

I have a Skywatcher ED80, and of all scopes, cameras, etc that is the one I know I'll always keep.

Have fun shopping!

[Moonshane]

several things to conider in this area:

• 130mm will provide a good introduction to astronomy and provides good views of many objects
  
• More aperture will provide better views and weigh more, cost more and take up more room - it's worth it though
  
• Newtonians cost less money per inch of aperture than other kinds of scope so are good value for money
  
• Longer focal length allows use of cheaper eyepieces with good results but the tubes can become cumbersome
  
• Shorter focal lengths are the opposite of long as described above re eyepieces etc
  
• With more focal length you get more magnification and less field with the same eyepiece than with less focal length
  
• The smaller secondary of longer focal length (for the same aperture) means you often get more contrast
  

I have only commented on visual observing as this is all I really do but there rae implications for astro-photography if you want to go down that route but I agree with the comment that you generally need two set-ups for visual and imaging.

[swamp thing]

Hi

Firstly, welcome to the SGL.

I am predominately a deep sky observer. I spend nearly all my observing time on deep sky, only giving planets and the moon a tertiary glance.

However there are many different types of DSO,s (deep sky objects) and their viewing requirements vary considerably. I would therefore recommend a good all round scope until you've finalised your area of interest.

If I was starting out in astronomy today. This s the scope I would buy.

http://www.firstligh...-dobsonian.html

It has so many plus points.

1/ price

2/ ease of use

3/ aperture

4/ portability

5/ toughness

6/ resale value

[Capricorn]

Didn't really answer the title.

Longer focal lengths in a reflector means thay need a bit less collimation, it doesn't go out as quick, also the more budget eyepieces can be used, plossl's will generally be fine.

In a refractor it means that a longer focal length gives less chromatic aberration. An f/5 80mm will have a fair amount of CA, an f/10 90mm will have less.

Think there is a 150P dobsonian be Skywatcher that is something like f/7 or f/8, as a first rflector - fully manual - that is a decent start.

In the refractor line consider the Evostar 90.

For any reflector add £30 to the total for a collimator, they are necessary.

[Stu]

Very good advice from Shane.

Briefly, a 130mm will be a good start and will show you plenty. A 200mm will keep you happy for a long time. The SW Skyliner 200p is a very popular choice on this forum for good reason. Great aperture for a good price as you are not paying for an expensive mount or electronics.

Long focal lengths tend to be used for planetary or lunar observing as you get a higher magnification/smaller field of view with the same eyepiece relative to shorter focal lengths. Conversely, shorter focal lengths tend to be better for dso's as they generally need lower magnifications/wider fields to observe. They are more demanding on ep's but there are good options out there and plenty of advise on here.

Not so brief but hopefully of help

Stu

[breezy]

hi tomek, welcome to SGL

you have had good advice so far mate, see how easy it is to get it here?

and in easy to understand language too especially capricorns (which is a bonus for me).

i started with an 80mm refractor via fleabay and that gave me great moon views, then got my 127mm maksutov which is even better ,

i also use binoculars as well and am currently working on an excuse for a 300mm dobsonian mounted reflector but im getting concerned by the evil looks from the mrs

[66mikeg]

The best advice I've seen on the forum for total beginners is to join a local astronomy club and try different types of mount and 'scopes to give you some idea of what to expect from each. It is a very friendly hobby in general and no one minds giving first hand help and advice.

[VigdisVZ]

Hello fellow beginner

I am no expert (I hope to become one day) but I'll add my thoughts. Feel free to correct me if im lost in space on this.

Being fairly new myself my research on the internet and advice from my local astronomers club have led me to order a 150mm aperture Skywatcher Explorer 150PDL. It's cheap and not to huge and has a focal length of 750mm. This lets you capture large brigth and rewarding objects like the Orion Nebula, Andromeda and the moon in their full glory. And since the tube is cheap I got more money for a stable GO-TO mount.

Simpler refractors should get the job done but since I want to start taking pictures with my DSLR I went for the newton since f/5 seems nice and bright

Hope you find your scope and start catching photons soon!

Carl

[JamesM]

Hi and welcome to the forum.

Shane has made some excellent points regarding the effects of focal length, especially the point that longer scopes aren't so demanding on eyepieces which allows you to pick up some good performing eyepieces be they used or new like the BST's. You give a budget but I would strongly recommend that you save your pennies and get the Skywatcher 200P dobsonian. It's the U.K best selling scope and with 8" of aperture will perform well on both planets and deeps sky objects (DSO's) like galaxies and nebula. If you then find that astronomy is not for you (...I doubt it but there's always a chance ) then you will find the resale value of this scope will be high due to its popularity when compared to smaller dobsonians. Starting off with this size will provide plenty of good view to sustain your interest in the longer term and will help you avoid wasting money on upgrading should you opt for anything smaller. I cannot agree with '66mikeg' above about going along to a couple of public observation evenings that are orgainsed by your local astro club. All the specifications and data on scopes won't mean a thing unless you have established your datum point from which to hang all other information. There's no rush as, '...the stars aren't going anywhere' so take a deep breath, do some practical research and go with what meets your expectations. Seeing these scopes up close is also useful to judge their portability (should you need to set up away from home at a dark site), set up and cool down times and lastly the eyepieces that are being used, as they can often make a difference to the view you see.

Clear skies and enjoy the forum

James

[66mikeg]

JamesM i hope you mean that you don't DISagree I thought it was good advice

[JamesM]

My typing thumbs were getting ahead of my thoughts (....not that difficult really given the speed my brain works! ) To be clear, going along to public observation evenings is ESSENTIAL in researching what first scope to buy because we all have different expectations of what will maintain our interest.

Thanks for the clarification Mike. :grin:

James

[Tomek]

Thanks you all. It all very helpful.

So I went to local astronomy shop with my wife and end up with very early Christmas present from my wife: 10" sky-watcher colapsable dobsonian. It was from display so with reduced price.

Hope it will not affect performance but it looked like new anyway.

Yesterday was lovely night so I spend good 4 hours with it. I didn't find any deep sky objects actually I seriously need to learn a lot. My best object at the end was jupiter and its 4 moons.

It looked awesome.

Scope is not colimated but I need to learn how to do it first so performance was affected.

It was hard to looked trough finder scope as well. (are you guys using some king of star diagonal because looking straight trough is very hard).

thanks.

[brantuk]

Congrats on your new scope Tomek - the 10" is a bit more than a starter scope and coming from a shop it will be pretty much mint condition and should carry all the usual guarantees. I have the 12" version of your scope and they are very nice to use.

First thing you need to do (in daylight) is get the finder aligned with the main tube. Pop in a 20-25mm eyepiece and find a well defined targe a mile or too away - I use a pylon tip or top of a church spire. Get it dead center of the eyepiece - then adjust the finder so it has exactly the same item in the cross hairs. Then change to a 10mm eyepiece and repeat to refine the accuracy. This will give you enough accuracy to start finding stuff.

Download "Stellarium" (free software) if you haven't allready. Configure it and pick an object - I'd suggest starting with some of the messier objects. Find out which constellation your object is in and pick the nearest bright star from which to hop to your object. It'll take 12 months to learn the sky as the seasons and sky change over that time.

Apart from that - all you need is a good collimation tool and learn how to use it - I'll let others comment on that for you - but it's really very easy once you get the hang of it. Happy star hopping

(oh - if you find the straight through finder a bit awkward to use - you can easily replace it with a right angled finder - I use the Orion one but Skywatcher have similar equivalents)

[nytecam]

Go along to your local astro society viewing evening - there's usually a wide variety of scopes and look through and ask questions