Skywatcher kit lens any good or replace?

[Ravenit]

Hi Guys
First time poster long time viewer...
Have got my lad who is 9years old a 6inch skywatcher dob and it comes with a 10mm and 25mm kit lens which for most part does a good job.
Very impressed with the images
He can find and view saturn, jupiter, mars etc and most stars using the google sky map to find general direction and is really getting into it.
Question is i have never looked through a quality lens to see the difference so i would like to get 1 quality lense what would it be? Budget around $100

I would like a bigger image of planets so maybe a 6mm.
I have a gso barlow 2x on order, I see the gso lenses are only like $30 are they any good? should I be replacing my kit skywatcher lenses with them?
Thanks guys:thanx:
Rav

[barx1963]

Hi Rav and welcome!!:welcome:

Couple of points. Firstly (and I am not being picky here, it is for future reference and to prevent confusion!) the correct term is eyepiece. An eyepiece can consist of a number of elements, and those elements can be called a lense. Sometimes if you are referring to an eyepiece and call it a lense, people think you are talking about a camera lense.
Secondly, increasing magnification has a couple of effects. Mainly it also magnifies and atmospheric disturbances.You will probably see this if you switch from the 25mm to the 10mm and is really obvious with planets. If you go to a 6mm, the effect is even more marked. with a smller scope you really need good conditions to get the best out of a high power eyepiece Also a higher power also reduces the Field of View (FOV) so you have to move the scope more to keep the object in view.
My usual recommendation for beginners is to use the eyepieces that came with the scope for a while before spending money. They are usually not too bad and do a good job, especially the 25mm.
The GSO eyepiece you mention would be essentially the same at the SW ones you have, a basic Plossl design, so if wanting to try a higher power one it will give an idea of what they do without forking out to much $$$, but I wouldn't be replacing at this stage.
A Barlow can be a good idea, just be aware that the optical effects of a shorter focal length eyepiece will still be there with a barlow. The only difference is if you barlow a 10mm eyepiece you get efectively the same view as a 5mm one, but with the eye relief of a 10mm. You are probably already noticing that the 10mm has a smaller eye lense ( there's that word again!) and you have to get your eye much closer to it. The effects is even more so with a 5 or 6mm one.

Malcolm

[Renato1]

Assuming your son's telescope has focal length of 1200mm and focal ratio of f/8 and you have a 1.25" focuser, I'd suggest you add to your eyepieces rather than replace.

Your 10mm eyepiece gives 1200/10= 120X (Exit Pupil 10/8= 1.25mm)
10mm with Barlow= 240X

Your 25mm eyepiece gives 1200/25 =48X (Exit Pupil 25/8= 3.125)
25mm with Barlow= 96X

If you want the widest field of view consider getting a 32mm eyepiece which gives 37.5X . If you get a 40mm eyepiece in 1.25" barrel size, it has a narrower field, and you see as much as with a 32mm eyepiece. But if you had a 2" focuser, you'd really want to think about a 2" 40mm eyepiece.

A 32mm eyepiece has a 4mm exit pupil, which makes the image look brighter (including background skyglow), and a 40mm eyepiece has a 5mm exit pupil.


Highest power for an average 6" reflector - which is well collimated, and on a perfect night (which don't come around that often) is around 50X per inch, or 300X. In your telescope, that's a 4mm eyepiece or 8mm eyepiece with Barlow. Unless you buy a more expensive 4mm, like a TMB one, the Plossl ones work - but their eye relief is very tiny. I had to take the rubber eye shade off mine to be able to use it. Not that pleasant to use.

The 6mm eyepiece you were thinking of getting gives 200X, which should be useable on very many nights (providing your son doesn't aim over houses with lots of heat coming off them).

If your son one day really gets into it, goes to dark sites, hunts galaxies and other faint objects, he'd want a 2mm exit pupil eyepiece, which equates to a 16mm eyepiece. But I think that will be a long time off.

To sum up, my thoughts are that after getting the Barlow, you should be pretty well right for high power, but that you may want to consider getting a lower power 32mm eyepiece.
Regards,
Renato

[julianh72]

Well, I AM going to be picky - the correct spelling is "lens", not "lense". ;)

[astro744]

May I suggest a Tele Vue 8mm Plossl. It is a very high quality eyepiece and will give nice bright views of planets at 150x in your telescope. Current price is $115.00 at BINTEL. This will be a far superior eyepiece than your 10mm Skywatcher.

I also recommend a 32mm Plossl at some stage for low power use and once again Tele Vue make a very fine eyepiece in this size.

How much money do you want to spend in the long term? You could get a Tele Vue 2x Barlow and a 15mm and 11mm Tele Vue Plossl in lieu of the 8mm Plossl but this is a lot more expense but could be a long term solution. To start with I would first buy the 15mm. It will give you some amazing images of star clusters and nebulae. If your interest is planets, go the 8mm and even with a 2x Barlow later you will be able to achieve 300x magnification althought there are not many nights when this power is useful, but when the air is steady, 300x is spectacular on planets.

The only reason I mention Tele Vue is that you mentioned quality and I can think of no better product and their Plossl range is priced very favourably.

Just to clarify:

If you only want to spend around $100 and buy just one item and nothing else for a while, get the Tele Vue 8mm Plossl. You will not be disappointed.

You can later add other Plossls and Barlows if you want.

If you want to spend more now then the 15mm and 11mm plus 2x Barlow would give you 5.5mm, 7.5mm, 11mm & 15mm which is more than enough for high power viewing.

Note you could also get the Tele Vue 15mm and 2x and 3x Barlows giving you 5mm, 7.5mm, 15mm.

There are many options and of course it can get expensive but purchases can be spread over time and the eyepieces can be used on any telescope.

Note Tele Vue do not make a Plossl under 8mm so if you want a 6mm then either an 11mm with 2x Barlow or 20mm with 3x Barlow will be close and both these options will provide for a more comfortable view due to better eye relief.

If I were you I would buy the 8mm now and see what a difference in image quality you get over the SW 10mm. It will be noticeable.

[barx1963]

:P oops!

Malcolm

[brian nordstrom]

:) , :welcome: Rav .
Good advise on the TV Plossls , yes they are a little more expensive but they are that well made and optically perfect these will stay with you forever , and you only have to splash out once .
I have and love TelVue eyepieces I have Plossls , Panoptics , Radians and Naglers and I love the few TV Plossls I have , 8mm ,15mm ,and 40mm and I wont ever sell them or change .
My advise is grab a TV Plossl 15mm and 32mm and along with a good 2x TV barlow and your existing eyepieces you will get a good range of magnifications with your scope .
My 5c.

Brian.

[Ravenit]

Thanks all for the great replys will look at getting the 32mm and a 15mm eyepiece with a barlow should give me 8 different combinations.
Hopefully my lad keeps at it, he has been watching the cosmos series tv show at the moment and really enjoys it.
I Grabbed a pluck case from supercheap auto for $34 to keep all the eyepieces in one spot and protected, was cheaper than the ones they sold at bunnings here.
Collimation is good using the star method, it is a 1200mm fl and has a 2inch adapter.
I also tried out a inverter tube( erecting tube) from a mate on my dob to use day time and that worked fine so many mixed reviews online people saying dobs cant be used in the daytime upside down image but it was good on the 25mm. Saves the kids looking in the eyepiece backwards
cheers

[Renato1]

As you have a 2" focuser, perhaps think about getting a cheap Guan Sheng (GSO) 32mm, 40mm, or 42mm Plossl or Super View eyepiece which have either 65 or 68 degree fields of view, possibly at Andrews Communication.
http://www.andrewscom.com.au/site-section-10.htm
At $49 each, don't expect great performance at the edges. If you live somewhere with a dark sky, 40mm may be the way to go, but for light polluted skies, 32mm may be the better bet.

The advantage of low power viewing is that it is nice in its own right (because big objects fit in the field rather than overflow outside the field), but beginners also find it easier to use and find things.

Another thing above, is where you mention getting a 32mm and 15mm eyepiece, and having more combinations. That's true, but a Barlowed 32mm eyepiece gives you the same as 16mm eyepiece, which isn't going to be all that different from a 15mm one.
Regards,
Renato

[astro744]

I wouldn't Barlow the 32mm as the eye relief may be a little to long. The 32mm would be a low power eyepiece only. An alternative would be the 24mm Panoptic but it costs a lot more.

Yes you could go a 40mm in a 2" size and given f8 you would still have only a 5mm exit pupil meaning skies would not be too grey. At f8 even a cheap 40mm may perform OK at the edges and perhaps someone with this combination could comment further.

I personally dislike poor edge performance and I'm talking about eyepieces that are out of focus in the outer 30% of field. I would rather have a narrower apparent field or pay extra for a wider apparent field eyepiece that is sharp to the edge. However this was not always the case and when I was just starting out I did buy a 32mm Erfle that had a nice wide field and I enjoyed the views and didn't really notice the poor edge performance or at least it didn't bother me back then.

Note if you stay with a 32mm Plossl in 1 1/4 size you can then use 1 1/4 filters for all your eyepieces. Note if you do want to go to 40mm then the 2" size is better as the apparent field on the 40mm Plossl is only 43 deg. and not 50 deg. as on the 32mm.

I'm sure once you get a couple of Tele Vue Plossls you will eventually add the full range up to 32mm to your collection as they are very good.

[Ravenit]

For those that are interested after some more research I have the modified achromats (MA), in 25mm and 10mm eyepiece's.
Read online that the 25 is OK but the 10 is soft.
Still waiting on the moon to show so can test out the sharpness, clarity etc.

[Renato1]

I have a Meade MA 25mm, and I think it just barely okay. Any 25mm plossl I've tried is better.
Regards,
Renato