To Barlow or not to Barlow... That is the question

[Aikidoamigo]

Hi Everyone, this is my very first post so please excuse if questions are covered elsewhere as I am new to the site.

we have a skywatcher 127 goto scope and it has taken me a few sessions to just get the hang of set up and alignment.... It really must be for dedicated folks! ;-)

Anyhow, my question is should I be using my Barlow lens or not? So far EVERYTHING I have looked at has just looked like a white dot pinprick through the lens.... Typically using at 40mm or 25mm both with the Barlow in place.

Even Mars / Jupiter look like nothing much at all (I can see red hue for Mars).... Please tell me I am doing something wrong.

maybe I need different lenses, the lowest I have is 10mm but struggle to spot anything with that so far.

appreciate any advice you could give.

 

thanks

 

[popeye85]

Stars will always just be pinpricks in the EP owing to the vast distance away that they are (they really are quiet a distance!!) As for Mars then it isn't at the best position for viewing and you won't be able to pick up any detail whatsover, and I'm afraid that will be the case for a couple years now. DSO's (deep sky objects) tend just to be faint smudges! 

When it comes to Barlow's the thing to remember is that although they double the magnification they also make things dimmer so are not really ideal for DSO's. When it comes to planets though I like using the Barlow and when viewing the moon they really do come into there own! (By they way when you say'everything' you've viewed, does that include the moon? You might just be out of focus?)

Recommend you read the excellent thread "what to expect to see". A great read and should give you a better idea of what to expect. Good luck!

[Aikidoamigo]

Hi thanks for coming back to me so quickly...

the moon, well I am really enjoying the detail I have with the Barlow + 25mm EP.... Detail within craters etc. and flow lines etc. it's been very bright last few nights (south Spain) so great for observing but stifling star gazing.

i get the feeling then this is a bit like fishing, more to do with finding items than detail once you have found them... Sure we have a smallish scope but maybe if I remove the Barlow things will become more clear.

 

been fun so far but took a lot of time just getting used to alignment and our goto mount.

;-)

[popeye85]

To be honest the key to getting most out of this hobby is patience! The more you look at a object the more detail your eyes will pick up- take Jupiter for example, at first glance it isn't much-you need to spend time at the eyepiece, even up to half a hour to tease out all the detail and you will be amazed! Obviously for this reason comfort must be a priority! Wrap up warm and get a chair...

[Aikidoamigo]

Thanks

 

yes I have felt the discomfort of continual stooping and bending my neck at strange angles for long periods of time! The other issue is also re-focussing as any touch on the scope sends the image into a wild frenzie... Because we are new to this we have been flitting around the sky trying to pick things out, as you say, I think best plans will be to spend one night on a particular subject and stick with it.

we have the 'turn left at Orion' book and that is a great guide, think now I will start to work through it slowly, step by step.

thanks again for your advice

[laudropb]

Why not try M42, the Orion Nebula and the nearby M45, the Pleiades. Both are well placed in the SE just now. Try with and with out your Barlow and you will see the effects it has.

[popeye85]

Plus download stelarium to your laptop- it is now considered a almost essential piece of kit for this hobby! And it's free! 

Another thing to remember when you are selecting targets to view is to try and pick things that are high in the sky-that way you aren't looking through as much of the earth's atmosphere and it will be allot cleaner image.

 

[Floater]

Somebody has to tell you this, so  it might as well be my turn. The 'white dot pinprick' is what you're going to see when it comes to stars.

In fact, that's good; that's what you should see. A nice, tight, dot of light.

Now you can hunt for dots to split into two, or more. You can enjoy dots of different colours. But 'dots' are what they are going to be in every amateur astronomer's telescope. Yours and mine.

Don't feel let down or disappointed. As Popeye writes above, patience and perseverance. Cast your eyepiece over the Milky Way and wonder at the sheer number of stars. Think about what you're seeing; how long it's taken that light (those photons) to get to your eye.

Plenty to be happy about and no, you're not doing anything wrong - unless being in a hurry is wrong? ???

[Nyctimene]

Seems you are on the right path, getting sharp views of moon features. Stay with bright objects for a while, e. g. M42, M 45, M35. Your scope will show you much more, have patience!

Stephan

 

[BXRO]

Hi

 

Try looking at one object but using different magnifications, you will be surprised what you tease out of a target at different magnification, then try and compile your findings into one picture in your mind or on paper

[Aikidoamigo]

Thanks for all the feedback

the first few nights I really struggled withy the alignment, not knowing the stars and then not understanding how our goto mount worked... We now have that figured. So it is really a case if holding out until the moon is not so bright and then going again.

Fortunately we don't work all year round so have plenty of time to stay up late without consequence. Also my mum lives in a real dark sky area so will spend some time with her next month and should get good results if the weather is kind.

I have had some trouble with heavy condensation (dew if you prefer) caused by setting up early evening after a warm day and then the nights being really cold this has meant very wet equipment by the time I come to pack up.... That concerns me. I'm not talking of a fogged lens / mirror, I'm talking about tube / motor mount etc getting very wet indeed. Any comment on that which could help? I'm trying to set up later now so that the scope is not 'warmed up' by the evening sun.

[Stu]

Try not to think of this about Barlow or not Barlow, but what magnification you are ending up with.

The Skywatcher 127mm has a focal length of 1500mm. You find the magnification by dividing the focal length of the scope by the focal length of the eyepiece. That means the magnifications you have are as follows:

40mm - x37.5

25mm - x60

10mm - x150

with the Barlow this gives:

40mm barlowed - x75

25mm barlowed - x120

10mm barlowed - x300

basically this rules out the 10mm barlowed, but any other combination should work.

Maximum mags for scopes are a much debated topic, but up to x1 per mm of aperture is one measure i.e. x127 should be quite achievable, and up to twice this under excellent conditions.

For good planetary observations you need to be at around x150, up to say x180 or x200. Mars is a tough object at the moment as it is at the farther reaches of its orbit from us.

Jupiter should look good at x150 and above, as will Saturn when it is at opposition.

Your scope's long focal length means that it will have a relatively narrow field of view. Even with the 40mm you will only have around a 1.3 degree field of view, so finding objects will be challenging without accurate goto and/or a well aligned finderscope. Objects like M45 and M31 you will not fit in the field of view but anything else including M42 will be no problem.

Keep at it, I'm sure you will get used to the scope and get finding those targets.

[popeye85]

Oh dear! Fraud you're opening up a can of worms by uttering the 'd' word!

Tbh the the tube dewing up isn't really a issue-it's when it gets the mirrors and eyepieces that it makes a difference-others on here will advice better then me the ways to assist with this problem but I often hear that a12v hair dryer solves allot of problems.

[Putaendo Patrick]

For much of astronomy, high magnifications are not necessary or desirable. A good eyepiece at x120 together with good atmospheric conditions, for example, will split most double stars. Higher magnifications really become interesting with lunar and planetary observation (but again, your telescope and the atmospheric conditions are always limiting factors).

There is (or used to be) a convincing argument that the more glass you have in the optical path, the more problems you will have. At the premium level (also known as expensive ) Barlows such as Televue will have little adverse effect on the eyepiece. At the very cheap level, an optically poor quality Barlow used with a poor eyepiece will be a disaster!

If your 10mm eyepiece came supplied with the telescope, be aware that these are often quite poor quality. In the future you might want to upgrade, perhaps adding a 12mm and an 8mm to your arsenal to give magnifications of x125 and a realistic top of x187.

Barlows work by increasing the effective focal length of your scope. When you already have quite a a long focal length (as in the case of your 1500mm), personally I feel that Barlows are less useful.

[Aikidoamigo]

Could you advise on 'good quality' eyepiece; is there an opinion on best quality / price range. 

 

Of course the spectrum is wide but for the likes of the average man in the street what are the best brand names to look at?

as always, thanks in advance

[Putaendo Patrick]

Your telescope has a focal ratio of about 11.8 which is the focal length (1500mm) divided by the aperture (127mm). This is considered as slow, which means that almost every eyepiece will perform well with it. Obviously there are really cheap EPs which are just bad, full-stop!

But there are eyepieces from about 20 to 25 pounds which will work well. At the premium level, there are eyepieces which cost 500 pounds or more! But really won't work much better in your telescope . The difference in price is partly due to optical quality and in large part due to the design. Design will determine two factors: field of view and eye relief. Field of view means how much you see, 82° will allow you to see a much wider view at the same magnification than 50°. Eye relief means how close your eyeball needs to be to the glass - very close can be uncomfortable, and if you need to wear glasses to observe will be impossible.

The minimum design I would recommend is the Plossl. Celestron Omni, Skywatcher and Revelation are all good in the 20-30 pound range. Vixen NPLs at about 40 pounds are better quality. Then come the BST Explorers (also branded as Starguiders) with a wider field of view and longer eye relief, at about 50 pounds. And finally the Explorer Scientific 82° series at about 100 pounds.

Parallel to these there are also some very good alternatives including orthoscopic designs such as those offered by Baader Planitariun at about 50 pounds. Limited field of view and tight on the eye relief, but superb for planetary observation.

 

 

 

[Aikidoamigo]

Slow meaning? .... 

 

Does it mean 'not very serious'?

 

;-)

[Astro Imp]

1 minute ago, Aikidoamigo said:

Slow meaning? .... 

 

Does it mean 'not very serious'?

 

;-)

A great discussion can be found here:- https://stargazerslounge.com/topic/284668-why-is-it-called-fast/

[Putaendo Patrick]

20 minutes ago, Aikidoamigo said:

Does it mean 'not very serious'?

Not at all

Focal ratio is really a measure of sensitivity to light which can be used to compare different telescopes. Below 5 is fast, above 7 is slow. It's largely useful for astrophotography, but it does also effect the performance of eyepieces. Eyepieces should be sharp in the centre of their view - but as you look out towards the edges, they will begin to display some optical distortion. Fast telescopes are more demanding on eyepieces, and make this distortion more apparent. Expensive eyepieces are generally very well corrected (part of what you're paying for!) but many less expensive EPs don't work so well in fast telescopes.

[Aikidoamigo]

We needed super portability so settled in the one we have; least I know how to use my Barlow now as will buy a decent 8mm EP to use stand alone.

[kilix]

On 9. 1. 2017 at 14:19, Aikidoamigo said:

We needed super portability so settled in the one we have; least I know how to use my Barlow now as will buy a decent 8mm EP to use stand alone.

I have the Skymax 127/1500 too, I found that I like the Explore Scientific eyepieces. Plossl design is like looking through a keyhole, which I don't like. ES 70° 15mm is my favourite with this scope. The moon fits just exactly in the eyepiece, the image has a nice, sharp contrast.

I also have the ES70° 10mm, which is vastly superior to the 10mm which was supplied to this scope.
70° Explore scientific tend to be around 50€ a piece, 82° are 100€, they may be a good value, but I don't feel like shelling out 300€ for 3 eyepieces. Maybe I will try the ES 8.8mm 82° in the future, it may be a good planetary EP with this scope.

I really, really dislike the supplied 2x Barlow, don't know exactly why. I only rarely use it for Jupiter. And if I buy an eyepiece with power around 180-240x (6-8mm) I will probably not use the barlow anymore.

I also bought Meade 32mm super plossl to view bigger objects like M31, M42. It also helps when searching for some object, or when I am aligning the GoTo on this scope. With it's lower power, it gives field of view of about 1.3°, which makes orientation on the sky easier. Also, the M42 looks nice in it.

Our scope is like looking through a straw, so practice with the finder, if you struggle with GoTo alignment. Good practice is to use the finder with both eyes opened, one eye on the crosshair and one eye looking naturally on the sky, when the views align, you have your target. Then switch to lowest power eyepiece and align the target in the center of the eyepiece, switch to higher power and align again. Also, one nice trick is to defocus the scope, so you dont see the star as a dot, but as a huge circle. It's easier to judge if the circle is in the middle of the EP.

[barkis]

The Barlow, as already explained above, Artificially Doubles the Native Focal Length of your telescope.
So, If your scope is f11 using a x2 Barlow Increase it to  f22.
A nice number for Lunar Imaging, without the need to include an eyepiece into the Optical Train. 
I've never been an avid fan of the Barlow lens, perhaps because I never owned a good quality one.
Like eyepieces, there are good ones, and there are bad ones, Many a good telescope can suffer badly from using inferior quality Eyepieces, and 
additional lenses, whether  a Negative one (Barlow), or Positive ones,  (Focal Reducers).

[N3ptune]

My Barlow is good I use it often, I don't feel oppressed by it. It's providing me a wide range of low and medium powers with a 25mm and a 18mm (1 1/4"), some could say the 2 EP are too close but I think they are giving me an interesting low/medium power range (usable all the time) 25mm 40x/80x and 18mm 55x/111x (plus another 2" eyepiece which gives me 31x. )

My low/medium range is well covered, 31x, 40x, 55x, 80x, 111x. These magnifications are almost always usable on less then perfect atmospheric condition except for 111x. With the barlow I saved the purchase of 1 eyepiece, the optical quality is decent.

For planetary works I have a separate eyepiece 4.7mm which gives me 212x power, that’s the maximum usable magnification for my instrument. But again, occasionally it can be used with the barlow on the moon to get 425x, just for fun.

--> IMHO I don't think it's required to have a wide range of magnifications over 100x because these magnifications can't be used often. (Unless you have a high interest in planetary observation)