Glare/reflected light? when using low power eyepieces on Jupiter

dreamstation (James) · #1 05-05-2016, 04:59 PM

Afternoon all,

Lastnight was the first clear night in over a week so naturally I decided to drag the scope out for a look and with the moon all but gone I thought it'd be a good time to do some casual observing. I never intended on doing any planetary work, mostly just wanting to pan the sky and see what was around and maybe catch a glimpse of a meteor or two while we were at it, hence the 31 Nagler.

Later on in the night just before pack up I decided to center the scope on Jupiter for a quick look before bed. I'm not really sure how to describe my issue, so bear with me here. The view was quite pleasant, there's no doubt about that. But while looking through the eyepiece at Jupiter if I put my eye in a certain spot, there was some sort of strange distracting light which seemed to be 'floating' across the view inside the eyepiece. It almost looked like a big mosquito, or strangely enough like a seeded dandelion flower (you know the ones that go white, and when you blow it they fly to pieces). Moving my eye around a bit and it seemed to disappear.

I've never noticed this before as I've never used the 31 Nagler on such a bright object so it's got me buggered as to what I was seeing. Is this a problem with the eyepiece, a problem with my eyes, light getting in somewhere where it shouldn't? It's probably something simple, but as you can see I'm quite the novice. I should note that my partner could also see the light I am describing. We tried the 13 Ethos afterwards to see if the same light was there but we couldn't see it with that one.

Thanks all.

Atmos (Colin) · #2 05-05-2016, 05:14 PM

Did it look like a floater? I've got some pretty strange shaped ones in my eyes

dreamstation (James) · #3 05-05-2016, 08:28 PM

I do have a couple of floaters, but no it didn't look like that. It looked more like light from Jupiter was reflecting somewhere off of the eyepiece as you can only see it at a particular angle. It may not be that at all but that's kinda what it looked like. My description wasn't great but it's hard to really explain in correct terms as I have no idea what's causing it. We tried google searches last night afterwards with no luck so I thought I would ask here.

I haven't noticed this at all with any other eyepiece that we have. Last night was the first time we've experienced it, and as I said my partner could also see it. Putting the 13 Ethos in afterwards, there was no sign of what we had experienced with the 31 Nagler. I realise we won't be using this particular eyepiece on planets all that often but it has negatively impacted on my opinion of this eyepiece and cast some doubt on the quality of this particular eyepiece in our possession.

Anyone else have any ideas? Thanks guys.

Atmos (Colin) · #4 05-05-2016, 08:57 PM

Could it be a reflection of the inside of the focuser? Jupiter is pretty bright and the Nagler 31 does have a considerably wider field stop than the 13 Ethos.

dreamstation (James) · #5 06-05-2016, 03:14 PM

It could very well be mate. Will drag the scope out over the weekend and see if I can get to the bottom of this. Hopefully the clouds stay away but the forecast doesn't look good.

To a lot of the more experienced folk around here, my question probably sounds ridiculously stupid but we've got to learn somewhere/somehow. Was hoping there'd be more of a response with member's experiences with this particular eyepiece and their thoughts on why I'm experiencing what I've described above. It doesn't matter what it is, someone has always been there and done that before you.

dreamstation (James) · #6 08-05-2016, 09:03 AM

Dragged the scope out again last night as it was a nice clear night. This time I used the 26 Nagler to try and replicate what I was seeing with the 31 and it was the same. It was slightly harder to see but it was definitely there. If you get your eye in the right spot it looks like glare, or light reflecting off of somewhere. Not really sure where it's coming from but it's bloody annoying.

Not sure what I can do about it other than not using low power eyepieces on or near bright objects.

barx1963 (Malcolm) · #7 08-05-2016, 10:44 AM

James
What scope are you using? Are there any nearby sources of light? One thought is that the ep's you mention have a fair bit of eye relief, so stray light may sneak in between the eye and the eyelense.

The fact you only see it with a bright object suggests it is a reflection of some sort. When the moon makes it's reappearance, try on that and see if you get a similar effect.

Malcolm

grimsay (Iain) · #8 08-05-2016, 01:26 PM

Hey James,

I think I'm experiencing a similar issue with my Vixen LV. The first time I noticed it I thought it was a mosquito but I've noticed the same behaviour ever since.

As it flicks around in only a small area periodically my conclusion was a long eyelash catching the guard of the eyepiece and reflecting some light. Moving my eye back slightly seems to solve the issue. No more mozzie.

Cheers, Iain

inertia8 (Australia) · #9 08-05-2016, 04:26 PM

Had something like it the other night but indeed it was a bloody mozzie!
Once the thermacell fired up it put paid to them!

dreamstation (James) · #10 08-05-2016, 07:56 PM

Quote:

Originally Posted by barx1963

What scope are you using? Are there any nearby sources of light? One thought is that the ep's you mention have a fair bit of eye relief, so stray light may sneak in between the eye and the eyelense.

The fact you only see it with a bright object suggests it is a reflection of some sort. When the moon makes it's reappearance, try on that and see if you get a similar effect.

I'm using a 10" F4.7 and no there are no sources of light in the immediate vicinity. We usually turn all the house lights off so it's quite dark. I mean there are other houses around but the closest is approximately 60-80 metres away and even then the sheds block out most of the house.

Will give them a go next time the moon is up, but I've used both on the moon before and I don't remember noticing anything like this. Thanks for the suggestion.

Quote:

Originally Posted by grimsay

As it flicks around in only a small area periodically my conclusion was a long eyelash catching the guard of the eyepiece and reflecting some light. Moving my eye back slightly seems to solve the issue. No more mozzie.

Thanks for the suggestion Iain. Will keep that in mind next time we're out under the stars. Haven't had any issues with eye lashes getting caught up in any of our shorter FL eyepieces with shorter ER though. Not sure why that would affect only those particular eyepieces if that was the case. Crazier things have happened though.

I suppose one positive is that it affects both the 26 and 31 from what we've seen so at least I know it can't be anything wrong with the eyepieces. Unless both have something wrong haha

dreamstation (James) · #11 16-05-2016, 06:37 PM

Quote:

Originally Posted by barx1963

The fact you only see it with a bright object suggests it is a reflection of some sort. When the moon makes it's reappearance, try on that and see if you get a similar effect.

Took the scope out for a quick look last night and I tested the 31 Nagler on the Moon. There was a LOT of stray light/glare/whatever it was, particularly on the left side of the view. It was even more pronounced than when I'd used the eyepiece on Jupiter.

Would a poorly collimated scope cause this issue? Information from another thread on here has me questioning the collimation of my scope and I'm wondering if maybe it's showing up due to that. It may also explain why previously I haven't noticed it.

AEAJR (Ed) · #12 30-05-2016, 06:38 AM

I have an Orion XT8 Intelliscope.

I have lots of light around me. Street lights and house lights. Nothing dark about my site.

I do get stray reflections in the eyepieces.

What I have learned to do is to use my hand to shield around the eyepiece at various angles to see if I can block a light source. Usually I find one that is somehow reflecting off my end of the eyepiece.

In the winter I use a hooded sweatshirt to cover the focuser as I am viewing. In warmer months I use a baseball cap with the wide brim turned in various directions to block that stray light.

Try using your hand to see if you can block a stray light source.

The other thing I have is a flexible dew shield from an 8" SCT that fits perfectly over the end of my Dob.
https://www.astrozap.com/scripts/pro...?idCategory=25

This helps block any stray light or reflections from entering the tube or interfering with the secondary. This has helped too.

Kunama · #13 30-05-2016, 11:59 AM

I have seen something similar with my Dob using the N31t5 on Jupiter, I put it down to the very shiny filter threads on the TV eyepiece and the fact that the Nagler 31 required the focuser racked in much more than others. I tried to replicate the 'aberration' with my Pentaxes and could not. The XW threads are flat black......

Not saying this is the cause..... Just typing out loud .....

gaseous (Patrick) · #14 11-07-2016, 04:38 PM

I occasionally have this issue when looking at Jupiter/Saturn/moon under high magnifications - my theory is that I'm actually seeing the light of the planet or moon reflected off my eyeball and back onto the outside surface of the eyepiece glass, creating a sort of faint glare/ghosting effect. The fact that it's only visible at certain angles of viewing tends to support this theory (I think). Or perhaps my eyepieces are just crap.