Eyepieces for 8 Inch Dob?

[lostpleiad]

Completely new to this, other than spending the last month slowly trying to learn the night sky with binoculars and stellarium, and lurking on this forum.

I have just ordered an 8 inch Orion XT8G dobsonian and I am trying to decide what eyepieces to buy for when I take what will be my first look through a telescope at the night sky.

Some numbers

- Scope is 1200mm focal length.

- Supplied with  28mm 2" DeepView eyepiece

..and 12.5mm 1.25" illuminated crosshair Plossl eyepiece

- My budget is around £100-150 and I am hoping I might be able to get a couple of reasonable eyepieces and a barlow for that amount to get me started  - but if it's a false economy, maybe I would be better to get one other EP and a barlow?

- I would like to be able to look at the moon, the planets, and DSOs if I can (doesn't leave much else!)

My problem is that I understand that a focal length of scope /  focal length of EP will give me xx maginifcation, and I understand the idea of bigger or smaller fields of view - but I just don't know what values I actually need for different targets. And of course, being impatient, I want to have all the EPs I could need the first time I use the scope!

May be too simplistic of me, but I was hoping someone could just tell me

Moon - get a ?mm EP with a ?FOV

Planets - get a ?mm with a ?FOV

DSO - ?mm with a ?FOV

Even better if you can suggest a good brand too. I have read good things about BST.. but I haven't noticed a clear winner on a good barlow in my price range..

I've spent several weeks of evenings just reading and reading about scopes and EPs. I managed to make a decision on the scope, but wit

h the EP's there is so much information that it all just seems to blur into a point where I just don't know where to start. I am really hoping for some friendly and simplified advice if anyone would be prepared to help a newbie.... many thanks.

[NGC 1502]

Hi and welcome to SGL 

I think I'd have a few sessions with what you have, to get the feel for observing with an 8" Dob, see how you get on.

If you want to upgrade later on, there are so many options, and you can get lots of differing advice according to what suits each individual.

For what it's worth, my Dob has the same focal length as yours, and three eyepieces get the job done most of the time, a 27mm 44x for low power finding objects and viewing large ones, a 14mm 86x for medium power, good for many deep sky objects and the moon, and an 8mm 150x for smaller DSOs and planets, closer double stars, lunar close up views etc etc.  

Maybe a 6mm would be good for tight double stars and planets on a good steady night. As already said, opinions can vary a lot.

As for makes, tough call, see what others say about that, but I'd avoid the cheapest, can be more expensive in the long run if you need to upgrade yet again.

Regards, Ed.

[Qualia]

My problem is....I just don't know what values I actually need for different targets. And....being impatient, I want to have all the EPs I could need the first time I use the scope!

Lostpleiad, if possible take your time. Try to appraise your gear first and then you'll have a better idea of where you want to go and how exactly you want to get there. Unless you are loaded, or you just don't care, you ought not to upgrade or buy anything until you know you are missing out on something that is essential to your observing sessions and just as importantly when you know how it can be improved upon and bettered. If you haven't even used your scope, I can't see how you're going to make a sensible and informed decision.

However, if your scope is only supplied with a crosshair eyepiece and the 28mm, it might be an idea to ignore this advice. It's my own personal prejudice, but I've found my most used EPs in the 10" f/5 for general DSO viewing (not open clusters) have always been around that 120x mark and then backing off from that with something around 90x.

With your 28mm, you'll have a nice finder EP and one useful for open clusters and if you got yourself a decent barlow with just these 3 EPs you'd have a spread like this:

28mm = 42x, 84x.

14mm = 85x, 170x.

10mm = 120x / 240x.

You might think - and correctly - that the 85x has been doubled (in both the 28mm and 14mm) and you're right, but I'm figuring that the 14mm barlowed might be very useful for Saturn, Jupiter and Lunar work. Or again, you could think alone these lines:

28mm = 42x, 84x

13mm = 92x, 184x

8mm = 150x

In both cases, the lower mags would be nice for general hunting and framing largish objects, the middle ground for globs, galaxies, nebulae, the higher powers for Saturn, Jupiter and Lunar work and the 240x for those exceptional nights with Saturn or the Moon. If you got yourself some Baader solar filter, your 48x would be also be fine for white light sun observations. The only snag in this plan is not knowing whether planets are your thing. If they were, you might want a bit of a spread of eyepieces around 130x to 200x.

Needless to say, there's really no hurry. You might find you don't like using a Barlow, you might find you need dedicated eyepieces etc, but at least you've got some kind of working map to guide you.

BSTs and X-Cel LXs (at FLO) come highly recommended and as you can see, with just the purchase of one or two more eyepieces and the Barlow, you'll have yourself a nice set up for this Spring and Summer

Hope this helps a little

[wookie1965]

The BST starguiders get very good reviews on here at £49 each you could get three an 18mm  12mm and 5mm giving magnifications of 66,100 and 240 the Celestron X-Cel`s get good reviews as well they are around £65 each.

[ronin]

I tend to have a simple rule if 3 eyepieces:

1 at the same f number as the scope,

1 a bit longer,

1 for wide views and finding things.

For yours that would be a 6mm, and 8mm or 9mm and say a 25mm.

Would also suggest ones of the same set, they tend to be reasonably parfocal.

The choice is therefore slightly difficult:

BST's come in 5mm, 8mm, 12mm,,, 25mm.

X-Cels come in 5mm, 7mm, 9mm, 12mm,,,,, 25mm

There is BST in 6mm, the Wide Angle.

So doing a mix and match how about the 6mm BST Wide Angle, the 8mm BST Starguider and the 25mm BST Starguider.

For extra magnification you could later get the 5mm Starguider, and medium the 18mm.

Will say that I find 4 is a better number to get as I think you need 2 for high(ish) magnification, q for medium and 1 for low mag.

[Charic]

lostpleiad........Hi, If it hepls any, my skywatcher 2x Deluxe Barlow arrived today (£20). I'm just using "the lens" from the Barlow assembly (unscrewed)  as a 1.5 factor directly attached to my 8mm BST. My old eyes are not that great, my right eye is getting worse. 

Ive not seen the GRS (Great Red Spot) but I will tonight at this rate. What whats exciting me at present is that I've just come in to text something to anyone,  to the fact that I'm watching the SHADOW of Lo passing over Jupiter. Frikin amazing or what! At about midnight thirty  I hope to see the GRS.

As for Eyepieces, check my signature. Get them from Alan at Skies_Unlimited, ebay. Speak with the Man. Ask him if you can try before you buy ( slight catch* You will pay for three lenses,  if you want to test three ~ their all within your budget)  test them, if you like them, job done. If you dont like a particular lens, you send it back for a full refund.

More importantly though. get used to your telescope first. Its all oh so easy for us to spend your money. Nothing I have in my signature (except the 7x50's) was tried and tested. All bought on merit from SGL. I`m so pleased with what I have. And tonight, I've just found the right Barlow size(1.5x and EP) to get the result I've wanted since October, given the poor weather ect, ect, ect.

Enjoy your new scope, I gotta go back out side. I want to see if I can get M81 & M82 tonight?

[lostpleiad]

Wow. I am bowled over by all these answers. I've asked questions in many forums on many topics in my time - never experienced so many clear and perfectly framed replies. 'Thank you' seems like a weak response.

I am sitting here reading all your answers and googling away like mad at the BSTs and suggested barlows. This has given me the perfect place to

start thinking about the right 'package'.

Unfortunately, one question tends to lead to several more....

1. I like the idea of sticking with all BSTs - does anyone know if they would be parfocal? It doesn't say so on their ebay detailed descriptions.

2. ronin - would the 6mm be useable with a barlow in my 1200mm scope? It seems like it would be pushing to the limit of practical mag.

3. qualia - does your post imply that the supplied crosshair is not useable as a normal 12.5mm eyepiece? i'm not sure if these things have permanent markings which obscure the view, or whether they are done with light only and can be used switched off like a normal EP?

Thank again for all the answers. I've got great information to narrow down my decision.

[wookie1965]

They are parfocal i have 4 of them only have to slightly adjust focus but that's more to do with seeing conditions than the eyepieces.

Heres a review of them just a different name http://www.cloudynights.com/item.php?item_id=1914

[DRT]

One thing I have learned from my limited time in this hobby (or is it obsession?) is that jumping in too quickly and buying lots of bits is a costly business. I bought an X-Cel LX a few months ago and before I knew it I had the full set. I have since sold them all (at a significant loss) as I decided to trade up to 2" EPs.

If I were you I would do as some of the posters above have recommended and spend a bit more time with what you have to find out what your scope is capable of in your location before splashing out. In the meantime, save up an extra £50 on top of your current budget and then buy a Baader Hyperion MkIII 8mm-24mm Zoom. It is a fabulous piece of kit and will give you the full range of EPs you are currently considering in one unit. If you need a bit more magnification you can add the accompanying Barlow later.

Search around the forum for reviews on the Baader - it is very well thought of and is seriously worth considering.

Good luck with whatever you choose to do.

[DRT]

PS: There is nothing wrong with the X-Cels - I loved them - they just didn't fit with what I decided to upgrade to.

[Qualia]

qualia - does your post imply that the supplied crosshair is not useable as a normal 12.5mm eyepiece?

Ay, I suspect the eyepiece will have the reticle actually built into it. Of course, I cannot be certain but the suspicion is there. This doesn't mean you can't observe with such an eyepiece but you may find it irritating to do so, and will probably block detail of the observed object - with the crosshairs - if you do. 

Oh, and be careful with the high powers. It's a typical error I see when folk start out to buy big powers, so it's good to understand that 200x will probably be your maximum mean power during a given year and in general such magnifications and higher, although fabulous for a night of good seeing with planets or lunar work or splitting doubles, are not particularly suited for things like galaxies or nebulae.

Like I say, the most used magnifications in my kit during the year in the 10" f/5 are: 180x, 125x, 90x and 50x.

[Charic]

You can go on merit. word-of-mouth, testimonials, web sites, magazines ect, but you wont have a clue until you've actually tested something yourself. Its all personal as to what fits, and what's best.

I bought a Laser. Only use it to finalise the primary mirror with a Barlow. But I'm certain I get a better result just using a collimation cap?

Bought a Telrad, couldn't focus on the reticule without wearing glasses.  I wanted one, but its no use for me!. I've just sold that on and the recipient has done a nice custom chop to suit their purpose. It looks better now.

I bought a Revelation 2.5x Barlow. Too powerful. Sold that on, need another one, less power ( the SW 2x Deluxe has hit the mark now)

(By the way, I'm back in due to the rain? so the Skyliner and D5000 have had a wash. I only came in for a cup of Tea????) I was set up to view the GRS!

So rushing out and buying everything isn't always so good for the wallet, you'll  sell at a loss(normally ~ as already mentioned) although my 2.5x to 2.0X cost the same, so happy there.

Qualia mentions the mean power.  Take the value of your aperture in millimetres  and double it. That's the theoretical maximum, half that to a working/mean/practical limit for general observation. I say general, because I've been viewing the Moon with an 8mm and 2.5 Barlow giving me 375x power. So it can be done, but look at the target your viewing, The Moon, biggest, brightest thing to look at, so high magnifications are easily achievable, but don't expect the same for everything else.

 You want to achieve the highest magnification that will allow, that frames the target correctly ~ Al Nagler )

Seeing was good for me tonight and I managed my 5mm at 360x power (1.5x Barlow lens without barrel).

There will be so many decisions and soon the hurt, as you run round in circles covering the same things you looked at a week ago, and still cannot decide on what your wanting?

A club is the best way to see what's available. you don't even have to join if your not that way inclined. Just show a little interest. I bet they'll sell you the hobby by the nights out.

Enjoy your choosing!

[jetstream]

The Baader Classic Ortho 18mm (49 pounds) and the Baader Classic Q barlow(45 pounds) may be a good choice for you.My 18mm BCO works extremely well in my 1200mm F.L. dob and this barlow gives a 2.25/1.3 mag factor.Should give you 67x,87x and 150x.This eyepiece provides a fantastic view of most anything (rivals much more expensive EP's) although with a narrow field of view.I would seriously consider this option-you most likely will keep this EP for a long time...have fun with your purchase

[lestergibson]

+1 on taking your time to get to know the kit you have before starting to upgrade.  I had the upgrade fever when I first got my scope but I forced myself to take my time and I'm glad I did because when I did start to uograde my eps, waiting helped me appreciated why they were better than the stock eps. I'd also recommend that you have a look at the Maxvision eps from Explore Scientific, at least for medium and low power.  They are rebranded Meade 5000 and are a heck of an ep for the money; sharp and with a nice wide fov.  I'm happy with my Xcel 9mm but I use my 16mm and 24mm the most.