New EP question [should I keep it?]

[pevsfreedom]

I ordered a Celestron Luminos 10mm and tried it out tonight. I have a f/4.92 10" dob.

Had some questions as this is first new EP I've used in this scope. 

When I look at Saturn, there is a definitive ghost Saturn that appears. When I look at a bright star, there are definitive 'ghost stars' in the field of view. When I look at M13 or M4, everything looks fantastic, no weirdness or ghosts. This is NOT apparent when I barlow it. 

I'm primarily a DSO observer, with some planets/stars on occasion. Should I be worried about the 'issues' with this EP? Is this normal? My stock 9mm cheap-o EP doesn't have this ghosting on bright objects, but looks worse on DSO's (the Luminos looked great).

Should I return it and try an X-Cel, or just keep it? 

[michael.h.f.wilkinson]

Bright objects can cause ghost images in some EPs. This is more-or-less inherent in the design of these EPs, and has a lot to do with the level of coatings and whether certain reflections lead to a more-or-less sharp image. Faint one also cause ghosts in the same EPs, but these are generally too faint to see. I have heard of the Luminos design causing ghosting

[pevsfreedom]

Thanks for response. Would you say try something different? Or keep it? It's my first EP purchase. 

[ronin]

Does not sound correct, so I would start considering returning it.

Sounds like internal reflections from some source, possibly poor coatings.

Cannot think of anything in the scope to cause the problem - you haven't polished the inside of the focuser ? :grin:

You may just be the unlucky person to have a poor one, these things happen.

Could you request another in exchange thne chek the performance of the replacement? They are 82 degree eyepieces and you will lose some of that field if you went for X-Cels. Equally X-Cels are good eyepieces and you could get I guess about 3 X-Cels for a Luminos.

Just dug up a page about the Luminos from ther Astronomics site, https://www.astronomics.com/celestron-luminos-eyepieces_c59.aspx

it says:

"They are designed to be particularly effective with high quality flat field telescopes, such as the Celestron EdgeHD flat field high definition catadioptrics, and refractors with field flatteners, such as the SkyWatcher Quantum refractors. "

Your 10" f/4.9 is not going to be flat field.

Maybe they need a scope that is say f/6 or slower to work in, I say f/6 as some time back f/6 and slower was what WO recommended for a few (not all) of their eyepieces.

Have a read of the CN review: CN-Luminos

Starting to think that you may just have the wrong eyepiece in the wrong scope. :D

Irrelevant to the performance but over here a search turns up prices that seem to range from £97 to £229. That doesn't make sense. :confused:

[pevsfreedom]

It's about 2 x-cels for 1.5 Luminos last I checked  x-cels over here are about $55-70 avg and Luminos was $85. 

Thanks for the links. I have heard that 'fast' scopes are a little more sensitive with these types of things. It was definitely annoying, and my viewing of the planets/stars was pretty bad compared to the stock EP, though DSO's definitely looked nice. I also had a lot of 'blackening' I guess with the eyepiece cup lowered, which removed all of the field of view, so maybe I just got a dud. 

[ronin]

If you do not wear glasses then the eye cup should be up/out.

I liked the CN comment that on one Luminos the eyecup had to be rotated clockwise and on another it had to be rotated anti-clockwise. :eek:

The Luminos was a good price.

I am leaning towards it being the wrong eyepiece for the scope, not specifically a dud, just incompatible.

DSO's likely came out OK as they are dimmer so less of the ghost images, and some of the ghost image will be within the field of the DSO and lost.

Bit like CA on DSO's there generally is none or very very little, they just do not put out enough light to make it apparent, whereas planets and stars do.

[pevsfreedom]

Yeah I had it rotated out, which removed the field of view benefit at least I thought it did. Am now looking at Meade 5000 UWA, as I liked the wide angle for DSO's. Also have a 15mm Luminos coming in tomorrow, wonder if that will perform any better. 

[webtubbs]

I had similar ghosting with my Celestron Omni 9mm. I searched everywhere and it appears it could be caused by the image being reflected back off your eyeball. I put in a cheap lunar filter and the ghost disappeared, and I could actually see more detail in Jupiter as it wasn't so washed out.

[damnut]

I have the 10mm Axiom, and this does not exhibit any ghosting. These are supposed to be the same internally as the Luminos.

[spaceboy]

On brighter objects I have experienced ghosting in ES82°, Televue Radian, BCO, BST explorer and TMB clone eyepieces in the past so it's not like it's an uncommon occurrence. Some may say they have never experienced ghosting but I'm sure that's either because they  have top of the line eyepiece or they have never really noticed it. I have never experienced SA in my achromatic refractors but I know it must be there. 1) I don't want to know the effects of SA so I'm less likely to go looking for it 2) My kit is for looking at the night sky and not for me to spend the night scrutinising every little short coming.

Then again there is the possibility the eyepiece doesn't suit your scope or something is slightly out of alignment. Maybe try it in another scope and see if they experience the same effects. Stray light can also cause ghosting which is basically the reflection of your eyeball in the lens so try cupping the eyepiece.

It is also worth considering that we all have a budget and our expectations should match. If we expect a £100 eyepiece to perform like a £200 eyepiece then it we will never be happy. This is often the reason why a lot of astronomers end up with Televue.

[pevsfreedom]

I had similar ghosting with my Celestron Omni 9mm. I searched everywhere and it appears it could be caused by the image being reflected back off your eyeball. I put in a cheap lunar filter and the ghost disappeared, and I could actually see more detail in Jupiter as it wasn't so washed out.

That's interesting. I've heard of that as well, but it moved opposite of whatever was causing it, and I even tried moving my eyeball around to test it! 

[pevsfreedom]

On brighter objects I have experienced ghosting in ES82°, Televue Radian, BCO, BST explorer and TMB clone eyepieces in the past so it's not like it's an uncommon occurrence. Some may say they have never experienced ghosting but I'm sure that's either because they  have top of the line eyepiece or they have never really noticed it. I have never experienced SA in my achromatic refractors but I know it must be there. 1) I don't want to know the effects of SA so I'm less likely to go looking for it 2) My kit is for looking at the night sky and not for me to spend the night scrutinising every little short coming.

Then again there is the possibility the eyepiece doesn't suit your scope or something is slightly out of alignment. Maybe try it in another scope and see if they experience the same effects. Stray light can also cause ghosting which is basically the reflection of your eyeball in the lens so try cupping the eyepiece.

It is also worth considering that we all have a budget and our expectations should match. If we expect a £100 eyepiece to perform like a £200 eyepiece then it we will never be happy. This is often the reason why a lot of astronomers end up with Televue.

Yeah I hear you, I got annoyed by my 'scrutinization' as well, but with something costing $100 I'd expect no 'false images' that the stock eye piece definitely doesn't produce so I wanted to double check on here. I think I'll order 1-2 more types and compare them all and make up my mind and move on, I have bad enough OCD as it is do try and discern minute details in eyepieces! Takes the fun out of it, but then again I don't wanna 'waste' my semi-hard-earned-money either. 

[rwilkey]

Hi Pevs, I have heard about internal reflection on these (aka. ghosting) and have the early incarnation of this ep, the Axiom LX 10mm, I guess this is more prominent in fast scopes as I have not experienced this myself.  Like anything else, its all down to whether you can live with it.  Mine is also great on DSO's, you cannot really call it a planetary ep, that is not what this focal length was designed for.  Me, I could live with that.

[damnut]

@RWilkey.

Robin, I have the Axiom 10mm (&23mm)  and have not noticed any ghosting. I wonder if it could be dependent on the eye relief generated from twisting up the eyecup??

[rwilkey]

@RWilkey.

Robin, I have the Axiom 10mm (&23mm)  and have not noticed any ghosting. I wonder if it could be dependent on the eye relief generated from twisting up the eyecup??

Hi Damian, I have the 7mm and the 23mm as well, and have not noticed it on these, if anything, twisting up the centre eyecup I feel is a great attraction to this ep and most useful.  Having said that I have now bought many ES82's and love them, albeit, tighter eye relief.