Eyepieces for a Celestron Newtonian 114AZ

[keora]

A month ago I bought a basic telescope - Celestron 114AZ Newtonian, focal length 1000mm, reflector 114 mm.

I’d like some advice on the three Celestron eyepieces supplied with it. There’s a 20mm erecting eyepiece which is useful, although compared to the 10x32 IS binoculars I use, stars seem to be fainter, and Mars shows as a white object in the telescope – the pink colouration of the planet isn’t visible. There’s a 3X Barlow eyepiece which enlarges the image but as far as I can judge it doesn’t show it in any greater detail. Finally there’s a 4mm eyepiece which is quite poor. The planets seen with it are very blurred and I doubt if I’ll use it much. I’ve not got round to looking at distant galaxies.

I’m not complaining about the quality of the eyepieces – I deliberately bought a cheap telescope because I’m not certain how much I’ll use it.

I’m considering buying a couple of replacement eyepieces, but I don’t know anything about them. I wear glasses so perhaps this restrict the types of eyepieces I should use. Could members advise me please on suitable makes of eyepieces, and the sizes I should buy?

I’ve another question. When I look through the 20mm eyepiece, often the image is slightly distorted. There seems to be ripples and eddies in the background which move around the image seen in the eyepiece. I think it’s some kind of optical illusion. Has anyone experienced this?

Edited October 29, 2020 by keora

[jonathan]

The erecting prism 20mm is probably really intended for daytime use, for astronomy you need to get the maximum light transmission possible, and that means the minimum of surfaces for the light to bounce off en-route to your eye.  I'd reserve that 20mm for daytime use as pretty much any decent eyepiece you buy will not be an erecting one, swapping from one to the other will just confuse matters (the view will be back to front and/or upside down).

The barlow can only do so much, and if it's a cheap kit one then it'll probably give quite poor results for astronomy purposes compared to one you might buy separately.  I'd forget the barlow for now, put it away in the box.  Try it with the new eyepieces you buy but don't be too disappointed if it doesn't give great results.

You could spend around £100 on two or three decent eyepieces and they might just transform your viewing through that telescope, assuming the telescope is in good collimation (mirrors are aligned correctly, it's not hard to do).  I'd advise getting your eyepieces first and try them out, if it's obvious there's something not quite right then look up how to collimate, decide whether it's necessary in the first place before you start adjusting anything.  The basic collimation tool can be as simple as a film cannister with a tiny hole drilled in the centre, or pre-made tools do the same job.

You'll probably want an eyepiece around 20 or 25mm as a starter when finding objects or looking at wide field objects such as the Pleiades, the Orion nebula, or Andromeda galaxy.  The BST StarGuider eyepieces are popular and very reasonably priced, the 25mm would probably be a good eyepiece to have from this range, they should be good for using while wearing glasses (according to the description) however I've taken to removing my glasses when looking through the eyepiece as I find I get a much better look; if you have good close-up vision then I'd recommend giving this method a go.

You could stick with the BST StarGuider range and get maybe a 12mm or 8mm, I'm not sure how far one could potentially push that telescope but it should be able to use the 12mm at least and give good views.  Other forum members may be able to give advice on what should be possible, it may even work well with a 5mm eyepiece but I wouldn't like to advise that as I don't know enough about the StarGuiders when combined with a 114mm reflector.

Plus there's a 10% off promotion on 2 or more BST StarGuider eyepieces.

Note that Mars is particularly bright at the moment due to it's recent close approach, it should dim and return to it's usual reddish colour over the next few weeks.  You may find that a simple moon filter will help to reduce the bright glare.  As the name suggests, this filter is very useful when observing the moon, but can also be used when observing other bright objects such as Venus and Jupiter.

If you wanted to increase your recently purchased eyepiece collection's potential then a decent barlow lens could be the answer, you'll notice there's quite a range but you should probably stick to the StarGuider if you buy those eyepieces as it will be optimised with those in mind. 

Others may be able to provide more detailed opinions (or tell me I'm talking rubbish!), but in general a couple of good eyepieces to have will be around the 25mm and 12mm marks.

If you wanted to keep the price right down then have a look at the Skywatcher Plossl range, you could get the 25mm and maybe 10mm from this range for a mere £42, probably wouldn't be as nice as the StarGuiders (the field of view is less, might not be quite as bright an image), but cheap and cheerful and should definitely be a noticeable upgrade from the kit eyepieces.

As for the weirdness viewed through the 20mm eyepiece, that could be light refractions bouncing off the internal surfaces, especially if you're viewing a bright object such as Mars.  Bright objects do tend to introduce unwanted artifacts and this is where expensive eyepieces and telescopes come in, they will have all sort of tricks up their sleeves to reduce or eliminate that kind of thing.  I'm sure the erecting prism in that 20mm eyepiece won't be helping matters.

 

Edited October 29, 2020 by jonathan

[Pixies]

Hi,

The 114 AZ is a Bird-Jones design, with a focal length (1000mm) longer than the actual tube itself. This is achieved by using a spherical (not parabolic) mirror and an associated correcting lens placed in the focuser.

This means that the collimation process is much harder - but correspondingly, precise collimation is not as essential with a spherical mirror.

However, as it effectively already has a barlow lens installed, I'd avoid investing in a new one (or using the one supplied).

I agree with @jonathan's suggestion of BST Starguiders or Celestron/SW plossls. If you ever upgrade your scope, you can take these with you.

[jonathan]

3 hours ago, Pixies said:

The 114 AZ is a Bird-Jones design, with a focal length (1000mm) longer than the actual tube itself. This is achieved by using a spherical (not parabolic) mirror and an associated correcting lens placed in the focuser.

The one I found on the Celestron website didn't seem to match the OP's focal length of 1000 and kit eyepieces, it was called Cometron and stated that it had a parabolic mirror.  So I wasn't exactly sure of the telescope specs.  Do you have a link to the correct telescope, just out of interest?

[Tiny Clanger]

Is this it ?

https://www.argos.co.uk/product/5067718

The ExploraScope branding is not obvious on the page, but the eyepieces sound as if they match the OPs post.

[Starwatcher2001]

Hi Keora,

Excellent advice above, but a quick thought about observing and glasses. Depending on your prescription you might be able to use your telescope without glasses. Short or long sightedness can be corrected by just focusing differently. You might get away with mild astigmatism as well, but more severe astigmatism generally needs the correction of glasses or a special additional lens.

Taking glasses off to view, then on to look at charts etc., is a bit of a faff, but if you can get away with it, it does open up the range of eyepieces you can use.

If you're not sure about astigmatism but have a copy of your prescription handy, somewhere like this ( https://www.allaboutvision.com/en-gb/eyeglasses/glasses-prescription/ ) explains how to check it. Or you can tell at the telescope by seeing if the image of stars are point-like dots, or look like lines or seagulls as you try to focus.

I use glasses for longer focal lengths 40mm-18mm, then no glasses for shorter lengths. Shorter eyepieces have a smaller "exit pupil", meaning the beam of light isn't as wide. As narrower beams mean the image is spread across a smaller arc of my eye, my astigmatism doesn't show up as much.

Hope you get on well with your scope and astronomy. This is a fascinating hobby.

Edited October 29, 2020 by Starwatcher2001
improved the wording

[keora]

Thank you for all the useful comments. It's all new to me.

Here's a video of the telescope:

https://www.youtube.com/watch?v=0XkB3xNHuas

The reviewer says the eyepieces are trash but overall it's a good beginner's telescope.

This is a specification for the telescope:

https://www.argos.co.uk/product/5067718

I normally would have bought a scope after visiting a specialist retailer. There's not many where I live and the nearest one in South Yorks was shut because of the virus. Which is the reason I decided to buy something cheap 'n' basic from Argos.

The ripple effects I've seen looking through the eyepiece are odd. Is it because the collimation is out? I suspect not. I bought the scope four weeks ago, the box was undamaged. It's only been used outside twice because the skies have been so cloudy. The rest of the time it's been sulking in the back bedroom. Occasionally there's been fleeting minutes when the clouds have cleared and I've used it looking through the window at the planets and the moon. Aiming the beast at something is a bit tricky, I think I've now got the hang of it.

I've decided to buy a couple of better quality eyepieces once I've read all your advice again..

 

[Tiny Clanger]

2 hours ago, keora said:

Thank you for all the useful comments. It's all new to me.

Here's a video of the telescope:

https://www.youtube.com/watch?v=0XkB3xNHuas

The reviewer says the eyepieces are trash but overall it's a good beginner's telescope.

This is a specification for the telescope:

https://www.argos.co.uk/product/5067718

I normally would have bought a scope after visiting a specialist retailer. There's not many where I live and the nearest one in South Yorks was shut because of the virus. Which is the reason I decided to buy something cheap 'n' basic from Argos.

The ripple effects I've seen looking through the eyepiece are odd. Is it because the collimation is out? I suspect not. I bought the scope four weeks ago, the box was undamaged. It's only been used outside twice because the skies have been so cloudy. The rest of the time it's been sulking in the back bedroom. Occasionally there's been fleeting minutes when the clouds have cleared and I've used it looking through the window at the planets and the moon. Aiming the beast at something is a bit tricky, I think I've now got the hang of it.

I've decided to buy a couple of better quality eyepieces once I've read all your advice again..

 

Was the strange ripple effect seen only when you looked through the 'scope and the window ?  If so,  perhaps it was down to the window glass .

If not, does it happen with both eyepieces? Does the effect rotate if you rotate the eyepiece ? If so, at least you know it's something easily replaced.

 

That youtuber you linked to has some, er, interesting vids:  https://www.youtube.com/watch?v=6d48ZfrVSiQ

and https://www.youtube.com/watch?v=cpRRM_teNys for instance.

He will even show you where to buy a

" portable, light-based energy device that uses complex wave-forms of light, accurate down to a 10-millionth of a second, to generate an energy field that enhances your own "chi" or life-force energy. Most people can feel it working within seconds! Watch is the Perkl-Light is put in "machine clearing" mode in which the Perkl-Light covers a full spectrum of harmonic frequencies to clear the energy from and charge a quartz crystal! " here

https://www.youtube.com/watch?v=N_CAjz5x6PU

 I think you will get far more reliable telescope advice from the folks on here , but do mention your budget to get the most appropriate suggestions.

[keora]

Thank you for your questions.

The effect I see when looking through the eyepieces of my new telescope is intermittent. It can be seen on both a 20m and a 4m eyepiece. In the background there seems to be ripples and eddies which slowly move across the image that I see. The distortion seems mainly associated with looking at a big, bright object - the moon. Perhaps I rarely see the effect when I look at planets or stars because the image is black with just a few stars or a planet.

I don't think it's caused by looking through a window pane - I often look through the window pane with binoculars and I've never seen the effect. I wondered if it was rainwater on the outside of the window, so I've just splashed some water on the window pane, and aimed the telescope at a TV aerial 50 yds away. I saw that the water on the pane makes the image of the aerial look blurred. I couldn't refocus on it. There were no ripples or eddies visible.

I replaced the eyepiece with a 4mm one, and looked at the aerial again, through part of the window which wasn't wet. I could see ripples on the image, although they were around the edge, not in the centre.

My guess is that somehow I'm seeing reflections of the liquid that lubricates the eye. It's an intriguing effect, but it doesn't matter much, as I'll buy some better eyepieces.

My budget is about £25 per eyepiece.

I saw the other Youtube clips of the person that did a review of the Telescope I bought. I agree they are odd, a strange mix of semi science and mysticism.

I'm impressed by the advice I've received from members. This is obviously a popular and well used forum.

 

Edited October 30, 2020 by keora

[DaveL59]

sounds like you are seeing an eddy current, heated air in the scope moving around or perhaps even in front of the tube from warm air in the room moving past. Ideally the tube needs to be open and the internals allowed time to cool and stabilise to get the best viewing. Likewise heat rising off roof and road etc can cause a turbulent image given the magnification a scope brings to the view. Remember too that air trapped between glass in double glazing also moves since the outer glass is colder than the inner, this may cause some effects that above the range of mag a bino will give become noticeable thru a scope. Looking at targets outside can have the same effects with wind and moisture in the air, it can feel like looking up through flowing water on some nights, a disadvantage of being ground based that we can't do much about 🙂 

Given your budget for eyepieces you might consider buying one zoom eyepiece, say 7-21mm that would essentially give you a range of magnifications in a single piece, cost approx £40-70 and then if you stay with the hobby you could look to purchase individual wider angle eyepieces to improve your experience. The Hyperflex gets good reviews as do the Svbony ones, the latter sv135 costs around USD 50 from their store on Ali and generally shipping takes a week.

[Tiny Clanger]

26 minutes ago, keora said:

The effect I see when looking through the eyepieces of my new telescope is intermittent. It can be seen on both a 20m and a 4m eyepiece. In the background there seems to be ripples and eddies which slowly move across the image that I see. The distortion seems mainly associated with looking at a big, bright object - the moon. Perhaps I rarely see the effect when I look at planets or stars because the image is black with just a few stars or a planet.

I don't think it's caused by looking through a window pane - I often look through the window pane with binoculars and I've never seen the effect.

I'd agree with DaveL59 , it sounds like air currents ( I previously wondered if it might be some diffraction ) . Is there a radiator under the window ? If so, the thermostat willl turn the heat up when it's a cold clear night, increasing the distortion. The reason you've not noticed it in the binoculars is likely down to the far lower magnification you have with them, probably no more that 10x.( It's the first number in the e.g.  8x30 you find marked on them . The second is the diameter of the front 'objective' lens in mm.)

Your telescopes magnification depends on the eyepiece you use in it, and the focal length of the 'scope, which in your case is  1000mm . Divide the focal length of the telescope by the focal length of the eyepiece.

So with your 20mm that's 1000 divided by  20 = 50 , or with the 4mm 1000/4 = 250.  So you are magnifying everything ( both what you are hoping to see, and the atmospheric or other problems in the way !) a lot more with the 'scope than the binoculars.

The general way to avoid annoying air currents is to set the 'scope up outside (with the caps on the front and the eyepiece holder) , leaving it to adjust to the outside temperature for a while before you begin to observe, and to avoid standing it on materials that soak up heat in daytime and radiate it up and out at night (like concrete and stone) , but rather set up on a grassy area if possible. It's inconvenient, and a faff, but at least it costs nothing !

When I got my scope a few months ago (one of these https://www.firstlightoptics.com/dobsonians/sky-watcher-heritage-150p-flextube-dobsonian-telescope.html ) it came with a couple of 'get you started' type cheap eyepieces, a 10mm and a 25mm. With nothing to compare them with (except some even worse ones that came with a 'scope I inherited) I was unsure if I'd appreciate the difference with more expensive ones, so cautiously bought a skywatcher 17mm plossl for around £20. I chose 17mm because the magnification fell between the two I owned, so if it turned out they were comparable, I'd not have duplicated what I already owned. The 17mm is far sharper and better than the  bundled eyepieces, and I've added a 32mm of a similar type, which is also fine for someone on a tight budget. 'Plossl' is a specific arrangement of lenses inside the eyepiece, and plenty of brands offer them. The plossls are harder to use in low mm /high magnification eyepieces, so I spent double that on one of the well recommended  BST Starguider EPs for my 8mm , this is generally regarded as a 'budget'  range !

Hope that helps

Heather

 

[RT65CB-SWL]

Hi @keora and welcome to SGL. 

1 hour ago, keora said:

The effect I see when looking through the eyepieces of my new telescope is intermittent. It can be seen on both a 20m and a 4m eyepiece. In the background there seems to be ripples and eddies which slowly move across the image that I see. The distortion seems mainly associated with looking at a big, bright object - the moon. Perhaps I rarely see the effect when I look at planets or stars because the image is black with just a few stars or a planet.

Ripples and eddies are normally trapped air currents in the tube. Best to leave the OTA for about 30 minutes to acclimatise to the surrounding air.

 

1 hour ago, keora said:

I don't think it's caused by looking through a window pane - I often look through the window pane with binoculars and I've never seen the effect. I wondered if it was rainwater on the outside of the window, so I've just splashed some water on the window pane, and aimed the telescope at a TV aerial 50 yds away. I saw that the water on the pane makes the image of the aerial look blurred. I couldn't refocus on it. There were no ripples or eddies visible.

Do not observe through a window. Window glass is not perfect... and believe it or not glass is classified as a 'liquid' even in its 'solid' state... (a little bit of useless info via i'net).

 

1 hour ago, keora said:

I replaced the eyepiece with a 4mm one, and looked at the aerial again, through part of the window which wasn't wet. I could see ripples on the image, although they were around the edge, not in the centre.

My guess is that somehow I'm seeing reflections of the liquid that lubricates the eye. It's an intriguing effect, but it doesn't matter much, as I'll buy some better eyepieces.

With higher magnifications you maybe seeing floaters. This is 'normal' and is cells floating in the eye. 4mm is way to much for your OTA - sorry!

 

1 hour ago, keora said:

My budget is about £25 per eyepiece.

You could try these... https://www.firstlightoptics.com/bst-starguider-eyepieces.html
or these... https://www.firstlightoptics.com/vixen-eyepieces/vixen-npl-eyepieces.html

[AstroMuni]

Hi @keora

You can remove the erecting prism on the 20mm eyepiece. That should slightly improve the image quality.

[keora]

Thank you to those who suggested the optical illusions I've seen are due to eddy currents. If I use the telescope inside, it's only 3 or 4 feet from a heated radiator. So there will be eddy currents in the air. I would never have guessed it.

The advantage of viewing from a first floor room is that I can see stars/planets which are low on the horizon. If I use the telescope in the garden, I've restricted vision because of nearby houses, street lights, trees...

Edited October 31, 2020 by keora

[Tiny Clanger]

5 hours ago, keora said:

Thank you to those who suggested the optical illusions I've seen are due to eddy currents. If I use the telescope inside, it's only 3 or 4 feet from a heated radiator. So there will be eddy currents in the air. I would never have guessed it.

The advantage of viewing from a first floor room is that I can see stars/planets which are low on the horizon. If I use the telescope in the garden, I've restricted vision because of nearby houses, street lights, trees...

Distortions due to warm air currents are sometimes visible on hot sunny days ( remember them ?) above heat radiating surfaces like tarmac roads . You can even see a mirage of a pool of water on a perfectly dry  road ahead caused by convection currents , I've seen a few over the years. Come the festive season (or a birthday cake !) look carefully above a candle flame in a draught free room and you may be able to see a small ripple effect.

As for location, I have a similar problem, tiny garden, many houses nearby, but fortunately a gap to the east with just fences and one tree, and some sight to the south with one blasted big tree right in the middle of it. North and south-west to west are hopeless directions for anything low. The first evening I got my 'scope home I happened to notice  Saturn was visible from the back bedroom window , but not the garden : 'scope precariously balanced on it's own delivery cardboard box got me my first ever sight of the rings, through a double glazed window ! Trust me, you can see far better without window glass and air currents in the way ...

If you can find a relatively open patch of ground to take your 'scope to you'll see stuff far more clearly , as well as being able to point the 'scope overhead .  At the very least, could you switch the radiator off and open the window for a couple of hours before observing ? Keep the room door shut to isolate it from the warm air in the rest of the house ? The other thing that may be helpful is a program like the  free open source Stellarium, where you can set your location and run the time forward to see what is where in the sky, and plan your observing accordingly. I've added a panorama of my back garden as a background in Stellarium, so I can see when Saturn vanishes behind that blasted tree ... it's a faff to set up, but it has helped me enormously.

Edited October 31, 2020 by Tiny Clanger
spelling stupidity

[keora]

After reading all the advice from forum members I’ve decided to buy extra eyepieces to use with my new telescope. It’s a Celestron Explorascope 114AZ Newtonian, f/9, focal length 1000mm, reflector 114 mm. The  best eyepiece supplied is a 20mm Erecting Eyepiece, the other two, a 3X Barlow and a 4mm, seem to be of low quality.

I thought I’d buy these two eyepieces:

An eyepiece of about 30mm to give a wider view of the skies. The magnification would be about 33X. 

I’m not sure of the maximum magnification possible with this basic telescope. I’ve read that a normal magnification is the equivalent to the width of the eyepiece in mms. This would be about 115X – equivalent to using an eyepiece of 8 or 9 mms.

I’ve considered  buying a Barlow eyepiece as well. It would give a wider range of magnifications. But is it necessary for a beginner?

I’d be pleased to receive any comments on these ideas. My budget is about £25 per eyepiece.

Edited November 1, 2020 by keora

[DaveL59]

Celestron say a max mag of x269 tho we'd usually say 2x aperture on here. I assume it is a bird-jones being F=1000 but the OTA is only 2ft long (it'll have a lens done in the bottom of the focuser drawtube) so you may find it is soft at the edge of field.

Eyepieces a 30mm will give a wider view yes, and an 8mm should give you a useful magnification. A Barlow I would say 2x would be a useful limit but how well they really work in a BJ configuration I don't know. Probably better to aim for eyepieces in a range and no barlow, say 30, 20, 12, 8 but then budget soon evaporates away. Decent budget eyepieces are likely to cost in the region of 35-50 each. Plossls are good and not too expensive but as you drop down the FL range below say 10mm you start to find less eye relief and smaller occular lens so may not be so easy to use if you wear glasses for example. The Vixen NPL are good (I have the 20 & 10mm) and around £35-45 each

As I mentioned before, a zoom might suit as that will give a range of mags for a single price although the FoV will be narrower than something like a BST/Vixen single FL eyepiece they are quite usable and save swapping eyepieces while viewing. The hyperflex 7-21mm from others recommendations or the Svbony sv135 7-21mm would cover the useful range for approx the cost of 2 single eyepieces or less, allowing you to zoom in gradually to get the best view for the conditions/target. I yesterday received the SV135 and can say it is well made and sharp, currently costs around USD 49 and takes about a week to arrive, a quick test on the LT70AZ in daytime it showed very well and is smooth in operation so I am happy to recommend it. Their 8-24mm SV171 is very good too but is huge and heavy but would also work if you wanted to go that route.

Edited November 1, 2020 by DaveL59

[Alan64]

2 hours ago, keora said:

After reading all the advice from forum members I’ve decided to buy extra eyepieces to use with my new telescope. It’s a Celestron Explorascope 114AZ Newtonian, f/9, focal length 1000mm, reflector 114 mm. The  best eyepiece supplied is a 20mm Erecting Eyepiece, the other two, a 3X Barlow and a 4mm, seem to be of low quality.

I thought I’d buy these two eyepieces:

An eyepiece of about 30mm to give a wider view of the skies. The magnification would be about 33X. 

I’m not sure of the maximum magnification possible with this basic telescope. I’ve read that a normal magnification is the equivalent to the width of the eyepiece in mms. This would be about 115X – equivalent to using an eyepiece of 8 or 9 mms.

I’ve considered  buying a Barlow eyepiece as well. It would give a wider range of magnifications. But is it necessary for a beginner?

I’d be pleased to receive any comments on these ideas. My budget is about £25 per eyepiece.

I have a Celestron "Bird Jones" as well: a 127mm f/8, and with a focal-length of 1000mm...

It, too, came with the same eyepieces and that worthless barlow.  The 20mm is not all that good.  The 4mm, actually, is quite good.  I took snapshots of Jupiter and Saturn through the bundled 4mm inserted into that telescope...

The live view was much sharper.

However, upon arrival, the images were terrible.  I saw two or three of everything.  I then collimated the telescope, and voila.  I sincerely hope that yours is collimated as it arrived, because it's a rather involved process to collimate a "Bird Jones".

Yes, get some good eyepieces: a 32mm Plossl and a 12mm Plossl...

https://www.365astronomy.com/32mm-GSO-Plossl-Eyepiece.html

https://www.365astronomy.com/12mm-GSO-Plossl-Eyepiece.html

If you want a barlow, all you need is a quality 2x... https://www.rothervalleyoptics.co.uk/antares-x2-achromat-fmc-barlow-lens-125.html

I have that one, along with the 3x under that marque.  They're keepers, and for life.  You can barlow both Plossls for differing powers.  

Do give that 4mm that came with the telescope another chance someday.  My own is very good for a basic eyepiece...

...again, much sharper live.  

But the telescope must be collimated spot-on.

Edited November 1, 2020 by Alan64

[beka]

On 29/10/2020 at 16:06, Pixies said:

Hi,

The 114 AZ is a Bird-Jones design, with a focal length (1000mm) longer than the actual tube itself. This is achieved by using a spherical (not parabolic) mirror and an associated correcting lens placed in the focuser.

This means that the collimation process is much harder - but correspondingly, precise collimation is not as essential with a spherical mirror.

However, as it effectively already has a barlow lens installed, I'd avoid investing in a new one (or using the one supplied).

I agree with @jonathan's suggestion of BST Starguiders or Celestron/SW plossls. If you ever upgrade your scope, you can take these with you.

Hi All,

I have used the NexStar 114 which is also a Bird-Jones 1000mm FL 114mm diameter scope and it seems the collimation is critical for getting a good image. Though the primary is spherical it has a short focal length and my guess is that there is a lot of off axis aberration - so the mirror has to be aligned to the lens in the draw tube.

Best

[keora]

Thank you for the information on eyepieces, I'll go ahead and buy some.

A final question - how do I know if the telescope needs collimating? When I've looked at the moon, or distant tv aerials, the image doesn't seem distorted.

[beka]

1 hour ago, keora said:

Thank you for the information on eyepieces, I'll go ahead and buy some.

A final question - how do I know if the telescope needs collimating? When I've looked at the moon, or distant tv aerials, the image doesn't seem distorted.

Use your 4mm eyepiece on a brightish star, center it in the field of view and focus in or out slightly. The star will de-focus into a doughnut shape with a few bright rings which should be perfectly concentric when collimated. If the rings are asymmetric then you have to use the knobs at the back of the scope to align the mirror. You have to re-center the star after adjusting and checking again. There should be instructions on how to use the knobs in the scopes manual. There are screws that lock the mirror in position which should be loosened first. You then use the adjustment knobs and re-tighten the lock screws when you are done. It is not difficult after a little practice. You can also try in the daytime with a high contrast point like object in the distance.

Cheers!

[keora]

Thanks, the telescope I've just bought has some useful instructions, although there's nothing about collimating. I'm sure there'll be something on the Celestron website. I've also seen collimation articles on the net.

[AstroNebulee]

Hi @keora

I used to have the 20mm erecting ep with my astromaster 130eq and I took the prism out of it which made it easier to use, as for the budget for ep I bought some of the astro essentials plossls from flo as they are good quality for the price and I'm happy with them, obviously bst are more pricey but once you've honed in on which ep you use more of then you can purchase a bst or even as I'm planning to do and buy a zoom ep for future use. As for the collimation issues, maybe purchase a Cheshire collimator from flo, I have the long Cheshire as once you've done it a few times it can be done in 5 minutes. Though as yours is a bird Jones telescope not sure how it would collimate so found this video on YouTube for you when using a laser collimator. 

 

 

Clear skies 

Edited November 4, 2020 by LeeHore7

[reezeh]

4 hours ago, keora said:

Thanks, the telescope I've just bought has some useful instructions, although there's nothing about collimating. I'm sure there'll be something on the Celestron website. I've also seen collimation articles on the net.

Hi Keora

I'm not sure if this is your model, but hopefully it has useful or usable info

https://www.manualslib.com/manual/221749/Celestron-114lcm.html?page=31

 

I can't seem to home in on it on celestron's site, so I gave you this link as I'm a little short on time right now. 

I hope it helps

[keora]

Thank you for the video clip and the printed instructions on collimating, I'll use them. I've just bought two good quality Skywatchers eyepieces which should improve the view through the telescope. All I need now is for the clouds to clear.