Which Scope & Other Questions

[GazOC]

(I dunno - in my tiny brain I just assumed lens + mirror would be better than just mirror) - *sigh*...

Optics is one area where "simple" is generally better. A Newt is a very simple design.

[Kaptain Klevtsov]

(I dunno - in my tiny brain I just assumed lens + mirror would be better than just mirror) - *sigh*...

Optics is one area where "simple" is generally better. A Newt is a very simple design.

I prefer the word "elegant" WRT Newt. design. No lenses so no chromatic abberation - sorted.

Captain Chaos

[GazOC]

You miss the point CC, "simple" is a compliment not a put-down for an optical system.

The Mak/Cass is a more "simple" design than a SCT, they are easier to mass manufacture to a decent standard.

Everytime you put something in the optical train than "corrects", bends or flattens an image, its basically a bodge. The image maybe better for it, but its it's still a bodge. You'd be better off, optically speaking, with a system that didn't need the additional elements.

Simple is good!!

[GordonCopestake]

Can't get much simpler than a refractor. 2 lenses and one of those is the eyepiece Although then you get into doublets, triplets, petzvals, flourite crystals and dont talk about naglers on the other end of the OTA. Amazing all that glass is transparent!

[Kaptain Klevtsov]

Can't get much simpler than a refractor. 2 lenses and one of those is the eyepiece Although then you get into doublets, triplets, petzvals, flourite crystals and dont talk about naglers on the other end of the OTA. Amazing all that glass is transparent!

But the glass isn't 100% transparent, and it bounces light back at every transition from air to glass, glass to air and glass to glass. The ray trace diagram turns very messy very quickly if you include the reflected light to calculate baffle positions. Why baffles? Because some of the light bounces back off the back of the lens, then back again off the front of the lens and ends up goodness knows where.

The APO type Fracs have several layers of glass, air, oil and more glass, all with surfaces to lose the light with. Simple? NOT!

That Newton guy had it sussed.

Captain Chaos

[TomS]

Pretty much everything. Both have 2" focusers. The 10" dob is f/5 if remember right and the 102SLT is also f/5 i think so all eyepieces would work equally well in either scope. The magnification would obviously be different given the 2 focal lengths

Now I'm confused again (this is getting to be a habit  ).... aren't the eyepieces supplied with the 102SLT 1.25", whereas the 10" dob comes with a 2"x 26mm wide-field eyepiece? Is it the case that any 2" focuser will also accept 1.25" eyepieces.

While we're on the subject, if I was to buy one additional eyepiece to get me going with my new scope(s), and didn't want to spend more than £40, what should I get? A barlow?

Cheers,

Tom

BTW - how do you include the name & date of a post when you quote it?

[GordonCopestake]

Pretty much everything. Both have 2" focuser's. The 10" dob is f/5 if remember right and the 102SLT is also f/5 i think so all eyepieces would work equally well in either scope. The magnification would obviously be different given the 2 focal lengths

Now I'm confused again (this is getting to be a habit ).... aren't the eyepieces supplied with the 102SLT 1.25", whereas the 10" dob comes with a 2"x 26mm wide-field eyepiece? Is it the case that any 2" focuser will also accept 1.25" eyepieces.

While we're on the subject, if I was to buy one additional eyepiece to get me going with my new scope(s), and didn't want to spend more than £40, what should I get? A barlow?

Cheers,

Tom

BTW - how do you include the name & date of a post when you quote it?

A 2" focuser will accept both 1.25" eyepieces and 2" eyepieces, obviously a 1.25" focuser wont accept 2" eyepieces. A barlow would effectively double your eyepiece collection as you can use each eyepiece at half it's focal length (assuming a 2x barlow)

If you just hit the "quote" button the name and date are filled in for you.

[TomS]

Is there any particular sort of Barlow I should be looking at? Am I better off getting one £40 Barlow rather than, say, two £20 high magnification eyepieces?

[The Warthog]

Given those price points, I would say yes.

[MartinB]

Tom, you are going to be using your scope for high power views of planets, low power views of M31 and lots of stuff in between. An ideal range of EPs would be something like a 40mm, 32mm and 10mm plus a good barlow. This will give you 6 different focal lengths to work with. Your barlow should come in for lots of use so it pays to get something of good quality - the celestron ultima x2 barlow springs to mind.

[TomS]

Well, the Celestron 102 NexStar arrived today... it's all set up and ready to go, so just praying we get clear skies tonight. Hoorah!

I will let you know how I get on.

Now I just need to decide whether to go and buy that second hand 10" dob I had my eye on. Do you think two scopes in two days would be greedy?

Thanks again to everyone for helping with through my chronic indecision!

Cheers,

Tom

[FLO]

No, no, no ..... not the Celestron 102 .................................................. Just kidding :mrgreen:

[Kain]

Ive got the 10" Dob, and I think it's brilliant!

I also live in a flat, so I have to lug it up and down a flight of stairs. It's not heavy, it's just abit awkward, however if you got someone to give you a hand, it's simpe to move.

I don't know how much difference in viewing between the 8 and 10, but you will not be disapointed with the 10.

From base to the top of the scope its 4ft 6" and the diamiter of the tube is 38inch.

Theres my Scope at work lol

Hope that helps

Kain