lunar eyepiece ?

[robbie65]

Hi members

Can sombody tell me what is the best size eyepiece to use for lunar obs,i have read here that high mag is better but when i use my 6.5mm af 50 i can see only a blur that will not focus but when i use 25mm af 40 can see ok no great shakes,have only 2 eyepieces,useing a reflector 150/1400 f9.

:iamwithstupid:Robbie.

[kniclander]

hmm - the moon is usually a guaranteed WOW! I suspect it is either that you are not focusing carefully enough- the "sweet spot" is pretty small especially at high powers. Or the e/ps that came with your scope might be a bit ****. Or it might be that your scope is poorly collimated. I would not rush into getting new e/ps until you have considered the other possibilities. when you do there are lots you can buy secondhand which should be quite cheap but may well be a big step up from what you currently have.

[johninderby]

What brand of scope is it?

A 6mm eyepiece should be OK on the Moon but the 6.5mm eyepiece that came with your scope may be a fairly poor one. I agree with the previous post, first eliminate other problems such as collimation before buying more eyepieces.

John

[robbie65]

The e/ps are plossl are the not considered good and what is collimation?sorry new to all this.

scope is a bigboss from a copany called seben in germany 300 euro probably ****?

[pvaz]

Collimation is the alignment of the mirrors in a newtonian reflector scope.

Read this tutorial, it's very good: Astro Babys Guide to Collimation

From the focal lenght I suspect you have a Seben or similar scope. This are actually a 700mm focal lenght scope with a built in barlow that doubles the FL. If that's the case then a lot of people complain the built in barlow is of poor quality and it produces poor images at high magnifications.

[Moon Lander]

I havn't had to do the collimation on my first scope yet as I am still waiting for the mount to arrive, but by all accounts it is one of the Dark Arts. I am assured it is quite straightforward once mastered.

[kniclander]

collimation is the (dark) art of getting the mirrors lined up. There are lots of instructions out there - on this forum is Astro_baby's guide (you can search for it). "Andy's shot glass" is also pretty good.

as a design, plossl's are fine.

[pvaz]

I havn't had to do the collimation on my first scope yet as I am still waiting for the mount to arrive, but by all accounts it is one of the Dark Arts. I am assured it is quite straightforward once mastered.

Well you need to do it when you have a couple of hours to spend and make sure you're in the mood to read and re-read the guide/scope manual.

Once you done it a couple of times 10 to 15 min is usually enough.

When I have to align my secondary it's actually a bit of a nightmare, as when I tight the screws it always shifts a bit, so it takes me several attempts to get it perfect. The primary needs collimation more often but thats really easy.

[robbie65]

So ths is a poor scope even for a novice Seben???

[Bryndalf]

Im new to all this too but If Pvaz is correct about the built in x2 barlow then a cheap 6.5mm would be very high magnification (equiv of a 3mm??) and prob has very bad optics. Im not aware of Sieben but a search should bring up something

[LukeSkywatcher]

I use a 6mm Plossl for observing the moon. On really good nights i can use a 2x barlow in conjunction but those nights are far and few between. I also have a 4mm Omni but have not had much time on it yet.

[Cornelius Varley]

Im new to all this too but If Pvaz is correct about the built in x2 barlow then a cheap 6.5mm would be very high magnification (equiv of a 3mm??) and prob has very bad optics. Im not aware of Sieben but a search should bring up something

The eyepiece is still a 6.5mm eyepiece. The Seben and the other 150/1400 telescopes sold on ebay have a built in barlow type achromatic lens (Bird Jones) to correct the spherical aberrations of the primary mirror. Barlow lenses do not affect the focal length of the eyepiece but increase the focal length of the telescope.

Peter

[robbie65]

ok so it starting to look like the scope is the primery problem,and thats not a great start for me as a beginner.if i was too buy again what would you pro's advise,for planets and DSO?[£2000]

[pvaz]

Since you want to see both planets and DSOs I would recommend a newtonian reflector. They come in both equatorial mounts or dobsonian mounts.

If you want a very simple to use and very fast to setup gear then go for the dobsonian, if on the other hand you don't mind setting the thing up you can get the equatorial version. The equatorial, after properly setup, will be easier to track objects at high mag, or it can even do it automatically when fitted with motors and a power supply.

I myself prefer it quick and easy so I use a dobsonian. Here are the links for some scopes by skywatcher (largely regarded as the cheapest brand with great quality):

Dobsonians - Skywatcher Skyliner 150P Dobsonian

Dobsonians - Skywatcher Skyliner 200P Dobsonian (same as my 1st scope)

Equatorial:

Skywatcher Explorer 150P EQ3-2

[bombassa]

Astroshop.de who sell this 'BigBoss' write that the quality of the scope is not so good.

[great_bear]

Barlow lenses do not affect the focal length of the eyepiece but increase the focal length of the telescope.

Indeed - and it's worth noting that Seben's quoted focal length of 1400mm already includes the effect of the built-in Barlow - so as Peter says, you should still calculate a 6.5mm eyepiece as 6.5mm