Celestron 114LCM with Celestron Ultima LX 5mm

[Judah]

Hello everyone.

I just started a hobby with my dad. 

We are in Durban, South Africa.

We got the Celestron 114LCM and it has been so amazing, so I decided to buy my dad the Celestron Ultima LX 5mm EP thinking that this would be fantastic compared to the 25mm and 9mm which we currently have.

So I did a bit of reading and found that the 114LCM has a 1000mm focal length.  The specs say that the highest useful magnification is 269x, so a 5mm would render a 200x magnification.

We got home, the sky was dark as it is winter, but there is a lot of other light around.

We focused with the 25mm eye piece and then pulled out the 5mm EP. What a disappointment.  Venus was blurry, we could not get it into focus properly at all.  As we focused in it became less blurry and then it started focusing out.  So it was not possible to get a sharp image.

The blurriness has brown/orange at the top and blueish tinge at the bottom.

May I ask, is the EP rubbish, or is it too good for the telescope?  or is it that viewing conditions were not optimal?

We then looked at some stars.  In the 25mm you can see a few stars, in the 9mm you can see more stars, so one would think then the 5mm would be great.  honestly it couldn't focus on anything, it was just black from the top of the "zoom" to the bottom.

Was I expecting too much from a 5mm? 

I figure the problem is either:

1. EP is rubbish;

2. EP is too good for telescope;

3. viewing conditions were not great with quite a bit of ambient light for a 5mm;

Is there a 4th option?

Please help?  I bought what I thought would be a really good EP for my dad's 60th birthday, and it has been such a major disappointment.  Unfortunately the moon isn't out tonight so we cannot view that to see if the EP is a complete dud.  Should this EP be able to see the moon on a night with a lot of ambient light? 

If you think it is the viewing conditions, would going to the mountains solve the problem?  Would we be able to see nebula (in focus)?  Why isn't it focusing?

Otherwise should I rather try swap the EP for a Celestron Ultima LX 7mm? 

Please help if you can.

[happy-kat]

Hi and welcome

How lovely you had been having a great experience up until this little blip.

Your telescope has a focal length of 1000mm though the tube looks half this length?

If so the focal length is acheived by a form of barlow within the focuser unit my Celestron.

I think this combined with the 5mm is just too much for it to work with and the magnification too high.

Viewing conditions if poor would not have helped things but local light pollution shouldn't spoil looking at the Moon.

Try the Moon.

Chasing magnification does not really give a better image it gets bigger but can get soft/blurry.

A smaller sharper image is much nicer to look at.

[Charic]

Hello Judah......Welcome to SGL.

Your telescope should be capable of 114x  power . A 9mm eyepiece would be more suitable giving you 111x power which is closer to the 114x.

Your also right about your expectations, your just exceeding the ability of the scope.

Your scope has a focal length of 1000, this divided by 114mm  (your aperture)  equals a  focal  ratio of 8.7 ( f8.77 )

An eyepiece with an  8.7mm  focal length would give you a power of 114x, matching the scopes ability?

As they don't make 8.77s? I  Think in this case, rounding the the 8.77 up to 9mm,  and  using this as your  guide to selecting the shortest focal length (highest power) you can use safely, suggests the 9mm as your high powered eyepiece.  

What you will find is that the basic 9 mm eyepiece  supplied is just that, basic. You could buy a better  quality eyepiece, which  perhaps will help with the final image as long as the telescope is set-up correctly, and the seeing conditions are suitable. But even the 9mm is still pushing the scopes limits. Further more, any eyepieces you purchase can be used in your next telescope, when you need better and become hooked on astronomy!

Just my opinion. HTH.

[Judah]

Hi happy-kat and Charic,

Thank you ever so much for your helpful replies, I really do appreciate it!

I looked at the moon and it couldn't focus properly, it was soft and a bit blurry as you say, so I agree with what you are both saying, in that the EP exceeds the scopes limits.

What scares me is that the next size up in the Celestron Ultima LX range is 8mm and from what you are saying, that will also exceed the scope's capabilities.  The 9mm that we have is just fantastic, we have seen Jupiter, venus and Saturn with it.  So a better EP like this would be great because of the bigger surface area on the glass, but if it only comes in an 8mm size, then would it be blurry or would it be acceptable (9mm is always sharp, no matter the conditions).

This Ultima EP is also very heavy and creates a bit of a shake in the scope, is there anyway to stabilize this?

Do you think that if I got an 8mm it would be ok?  If not, hopefully they will take the EP back and we can swap it for something else.  After experiencing the 9mm that came with the scope I really do not want to go with a 13 or something like that, as that is the next size up

Thanks again for your advice, I really do appreciate it, it has given my dad and myself some hope as at least we know what is wrong.

[Charic]

An 8mm EP would be fine. There is no definite cut-off as to what you can/can't use? Your finding the 5mm to be extreme, the 9mm good, the 8, then 7,6 and 5mm will push the limits slowly.

Did your scope come with a 2x Barlow ? if so use that with your 25mm  ( this effectively now gives you a 12.5mm EP with 80x power ! )   try the 25mm on the Moon then  Barlow the 25mm ( that's if you have the Barlow ) Not worth trying the 9mm (4.5) as the 5mm has proven its limit?

Technically, if you were in a vacuum, no atmosphere, no weather, no Moon, your telescope could achieve twice the aperture in mm ie 228x power?, but because of the reasons , you will struggle to achieve this.

Your trying to get 200x by using your 5mm, there lies the problem.  166x from a 6mm, 142x from a 7mm,  125x from an 8mm and so on. This is calculated by dividing the focal length F-1000 by the Eyepiece Focal length to get you magnification.

[happy-kat]

Your tripod legs if hollow perhaps filled with sand would make it heavier and more stable.

Or try hanging something dead centre underneath to add weight or perhaps sit something on the accessory tray if it has one.

Also don't fully extend it (less wobbly), if you can sit to view that might help.

Re eyepieces in my telescope I use my 16mm giving x40 the most lovely images and great for clusters and Orion and even Jupiter. Chasing magnification is not always best for everything you want to look at.

My 16mm has a wider fov then the stock eyepiece which is nice too.

[happy-kat]

I would not use a barlow I think your telescope tube is around 500mm long so a barlow is not ideal if your focal length is 1000mm.

[Charic]

happy-kat.........Does not the fitted Barlow create the F-1000  for a short tube OTA?  My Celestron was the same, yet still came with a Barlow, so I see no reason not to use one on the longer focal length!

Were learning all the time. The internal Barlow just permits the short tube to think its a big boy! or so I thought?

[happy-kat]

I thought a barlow on a barlow might degrade the image.

If it doesn't that's great.

[sdkfz181]

Within the Celestron range, you might consider the X-Cel LX 9mm or the Luminos 10mm. The X-Cel, the same magnification, should be a noticeable improvement in quality, with a slightly wider field of view. The Luminos, a slightly lower magnification, should be a noticeable improvement in quality, with a much wider field of view. If the seller of the eyepiece is reputable he/she should understand that you really need to try them out to find out if they suit, and be willing to exchange them if they don't.

[Judah]

_{Hi Charic, happy-kat and sdkfz181,}

_{Wow I must say, I am sooooo happy to have joined SGL, you are all so helpful!  Thank you very much!}

_{With regard to the weighting suggestions to stabilize the tripod, that's great, I will try what you have said because a more solid base would give a much beter experience.}

_{Regarding the barlow, no, the scope only came with the 25mm and the 9mm, however I ordered a 2x Omni barlow which should come next week, so we can double the 25mm as you say.}

_{We are hoping to go the mountains sometime and have a look from there, apparently you can see nebula etc, so it would be great if the 8mm works, then we will have the 25mm (plus barlow as you aay for a 12.5), the 9 and a really nice 8.  I still cannot get over the fact that the 5 was so bad, but thank you for letting me know that the 8mm will be fine because a proper eye piece like that is a lot more comfortable.}

_{Regarding the X-Cel and Luminos EPs, unfortunately the supplier in South Africa does not have them.  So it was the Omni Plossl or the Ultima LX, unfortunately no in between. In my city too people don't keep stock at all, so it has to be ordered from the distributor in another city and this is where I am hoping the place I bought it from wont have a problem.}

_{If they swap the EP out, I will probably only get it next weekend and will let everyone know.  In the meantime I am goingto trawl through this site as it just has so much helpful information.}

_{Thanks again for your advice and help, I really do appreciate it.}