15 replies to this topic

[stak12]

I use an Orion Dobsonian XT8 for my casual star-gazing. While I've enjoyed using the lens it came with and enjoyed viewing the planets in our solar system, I wanted more. A few years ago I had a "few" bucks and heard of a telescope store closing in Dallas so I went by there wanting to add another lens although I wasn't sure what i wanted because I'm still a total newbie. The guy sold me on a Celestron Ultra LX 70mm FOV lens which I guess means it has a wider field of view than the original lens. I honestly don't remember what the guy said when he sold it to me, but i really haven't gotten anything out of this lens probably because I don't know or understand what it's supposed to do. Last night I decided to use it again and look at Jupiter and Saturn because maybe i would get better definition, enlargement, or something that would justify the 150.00 I paid for it. But when i look through the lense, I just see a big round light from the planet and the reflection of the bottom of the scope and no matter how much I focus, I don't see anything but a light. By contrast, during the day I found a tall tree a couple streets over and was able to look at a leaf at the top of the tree and see bugs walking on the branch. I just figured that when I pointed the lens at a planet like Jupiter for the same effect, that being an enlarged more detailed look at the planet. Please forgive my post, because if it sounds like someone who has no clue about this stuff, you are right. Thanks for your patience.

[SeattleScott]

You need to focus the eyepiece. Focusing at infinity (stars) is different than a nearby tree. It is possible that you might not be able to reach focus without an extension tube. These eyepieces typically have 1.25” and 2” barrels unless you got a 2” model. 2” eyepieces generally require an extension tube in a Dob. Your Dob probably came with one. If it has both barrel sizes you can try both and most likely you will reach focus with one of them without an extension tube.

A quick test is take it out at night, rack the focuser all the way up. If you still haven’t reached focus, pull the eyepiece out until you do. If your eyepiece is sticking halfway out that means you need an extension tube.

Scott

Edited by SeattleScott, 21 July 2020 - 11:48 AM.

[JohnBear]

I can't find anything online about a "Celestron Ultra LX 70mm".   Please double check.

 

Is that the actual description (there is the "Ultima LX"); also do you mean "70 degrees" rather than 70mm?

Poor description = poor advice, etc. 

 

Best way to get really good value and upgrade your telescope EPs is to look at (thru) what other members of you astronomy club are using before you decide what to buy.   You have joined a local astronomy club, right?

 

I also recommend spending a few bucks ($10-15 each) on the Svbony 23mm & 10mm Aspheric 62 degree eyepieces on Amazon or Ebay, to complement the factory supplied Plossls supplied with most telescopes. They are both useful and educational when learning what you need to know and  to look for in EP specifications. 

Edited by JohnBear, 21 July 2020 - 12:19 PM.

[SteveG]

I use an Orion Dobsonian XT8 for my casual star-gazing. While I've enjoyed using the lens it came with and enjoyed viewing the planets in our solar system, I wanted more. A few years ago I had a "few" bucks and heard of a telescope store closing in Dallas so I went by there wanting to add another lens although I wasn't sure what i wanted because I'm still a total newbie. The guy sold me on a Celestron Ultra LX 70mm FOV lens which I guess means it has a wider field of view than the original lens. I honestly don't remember what the guy said when he sold it to me, but i really haven't gotten anything out of this lens probably because I don't know or understand what it's supposed to do. Last night I decided to use it again and look at Jupiter and Saturn because maybe i would get better definition, enlargement, or something that would justify the 150.00 I paid for it. But when i look through the lense, I just see a big round light from the planet and the reflection of the bottom of the scope and no matter how much I focus, I don't see anything but a light. By contrast, during the day I found a tall tree a couple streets over and was able to look at a leaf at the top of the tree and see bugs walking on the branch. I just figured that when I pointed the lens at a planet like Jupiter for the same effect, that being an enlarged more detailed look at the planet. Please forgive my post, because if it sounds like someone who has no clue about this stuff, you are right. Thanks for your patience.

I think you are saying you have a Celestron Ultima LX eyepiece, but you don't mention the focal length. If it's a 2" only model, then it is either 32 or 22 mm, both designed for wide-field viewing of clusters & nebula, but not so much for planetary viewing because the magnification is too low. They also have focal lengths in this line going all the way down to 5 mm, certainly suitable for planet viewing.

 

Can you tell us which focal length you have?

[stak12]

I think you are saying you have a Celestron Ultima LX eyepiece, but you don't mention the focal length. If it's a 2" only model, then it is either 32 or 22 mm, both designed for wide-field viewing of clusters & nebula, but not so much for planetary viewing because the magnification is too low. They also have focal lengths in this line going all the way down to 5 mm, certainly suitable for planet viewing.

Can you tell us which focal length you have?

[stak12]

On the box it reads 8mm 1 1/4" - 2"

[SeattleScott]

Ok so you can use it with the 1.25” adapter or without. Most likely it will focus one of those ways. If you are putting in your extension already to use with a low power 2” eyepiece, you might need to remove the extension to use the 8mm.

Scott

[JohnBear]

Sounds like you may want to learn a bit more of the basics about telescopes and astronomy. For that a local astronomy club is highly recommended.  Since you have not listed a location in your CN profile, you could be from anywhere in this quadrant of the galaxy - so here is a list of sites to find most clubs on Earth.

 

https://www.go-astro....b-search.htm  

https://skyandtelesc....ganizations/  

https://www.astrolea....bs-usa-state  

https://nightsky.jpl...ov/club-map.cfm   

 

To learn more about specific aspect of amateur astronomy and telescopes try these links:

Ed Tings "Advice for Beginners" page. and 

"Telescopic Watch", a nice semi-commercial website developed by several CN members.

 

There are also numerous YouTube videos on varioous aspects of astronomy worth watching.

 

Last but not least, get a good book on astronomy like "Turn Left at Orion" or "NightWatch". You should find these very helpful.

 

I hope you will find these links helpful. 

Edited by JohnBear, 21 July 2020 - 03:02 PM.

[stak12]

Ok so you can use it with the 1.25” adapter or without. Most likely it will focus one of those ways. If you are putting in your extension already to use with a low power 2” eyepiece, you might need to remove the extension to use the 8mm.

Scott

So when I try to use this lens for planetary viewing it is closer to focusing in and pulling back only makes it more unfocused so I don't think the extension tube is going to make a difference. (Regardless if I use the 1.25 adapter it came with it the 2". I'm starting to wonder if this lens is more effective with deep space objects or if it's a poor companion to my Dob.

[SteveG]

So when I try to use this lens for planetary viewing it is closer to focusing in and pulling back only makes it more unfocused so I don't think the extension tube is going to make a difference. (Regardless if I use the 1.25 adapter it came with it the 2". I'm starting to wonder if this lens is more effective with deep space objects or if it's a poor companion to my Dob.

No, it’s a quality lens that should show the planets as good as any. I think your problems are elsewhere, possibly bad seeing due to the planets being very low on the horizon (for northern observers), or possibly a poorly collimated scope. I think post #8 is where you should be looking. Where are you located?

[stak12]

No, it’s a quality lens that should show the planets as good as any. I think your problems are elsewhere, possibly bad seeing due to the planets being very low on the horizon (for northern observers), or possibly a poorly collimated scope. I think post #8 is where you should be looking. Where are you located?

Hello, I'm in DFW (Texas).When I use the .25mm plossl,I have no problem focusing on Jupiter/Saturn with great clarity. I did try back-focusing as far as I could go and then pulling eyepiece out and pulling back further, but the light source of the planet only got larger. Seemed it was getting more focused as I moved it closer, but even all the way in it was too blurry.

Edited by stak12, 23 July 2020 - 04:06 PM.

[SeattleScott]

You can try removing the 1.25” adapter and sticking the eyepiece directly in the focuser using the 2” barrel. This might give you the extra focus travel you need.

Scott

[JohnBear]

4th Corollary to the 43rd rule for No Regrets Astronomy: "Try Before You Buy." 

Or, "Why happy beginners join astronomy clubs".

[SeattleScott]

4th Corollary to the 43rd rule for No Regrets Astronomy: "Try Before You Buy."
Or, "Why happy beginners join astronomy clubs".

Except you can’t right now.

[JohnBear]

Except you can’t right now.

Scott - You never know until you try. It isn't impossible - just take reasonable precautions during the pandemic. It worked out today for another member lost in deep kimchi:    https://www.cloudyni.../#entry10361127   

[39.1N84.5W]

Hey JohnBear... your posts could be more helpful.

To the OP: so with the 2" adapter removed and the focuser racked all the way in... you still can't reach focus?