White Crescent in Helios Apollo 15 x 70?

[daveintheshire]

Hello All,

I hope I'm not missing a thread where I introduce myself.  I'm Dave.  I am an electrical engineer and I live just outside a small village near the city of Wolverhampton, England.  I have been a casual binocular observer for about 7 years now, using whatever I could lay my hands on.

I had the great pleasure of meeting Steve Tonkin at the recent Solar Sphere in Mid Wales.  Thanks Steve if you are reading this - your talks were the highlight of the weekend for me.  I hope you'll forgive my slight incoherence when I introduced myself - the previous night's observing was taking it's toll by that point!  Steve's talk on binocular astronomy (and the subsequent acquisition of the second edition of his excellent book) was the push I needed to upgrade from my Opticron Oregon 11x70.  I have managed to purchase second hand a Helios Apollo 15 x 70, pretty much the binocular of my dreams.  The seller was local to me so I collected it from him - a very nice chap who had looked after the binocular with loving care. 

Of course, the curse has befallen me and a week of cloud has rolled in.  From terrestrial views the unit seems to be well in collimation.  The lenses are spotless etc - there is nothing that makes me think the unit has ever suffered the merest hint of trauma.  When I look through it I can perceive a sort of hazy white crescent in the bottom of the view.  If I draw my head away from the eyepiece I can clearly see it as a milky band in the bottom of both exit pupils.  It is worse with my spectacles on, and largely mitigated when I take them off and really "bury" my eyes in the eyepiece.  It is better when I set the IPD correctly (worse when too narrow).  I can make it go away by moving my face so that the exit pupils move to the bottom of the eyepieces, but then I cant see the top of the field of view.  It seems to have a clear band separating it from the bottom of the field of view.  If in invert the binocular I still see it in the bottom of the field of view, if I hold the binocular vertically and peer through one barrel, I still see it in the bottom of the field of view.  That is to say, the crescent is always ground-ward no matter the orientation of the binocular.  This leads me to think that its not aberration of any kind, but I am stumped as to an explanation of what I'm seeing.

Is it a problem?  Should I be worried?  Or is it perfectly normal and I just need to get on with it?  I've yet to turn it skyward so I have no idea how it will perform when observing the night sky, other than the crescent seems move visible with I tilt the binocular to view nearby treetops.

Thanks all and clear skies,

Dave.

[Charic]

27 minutes ago, daveintheshire said:

That is to say, the crescent is always ground-ward no matter the orientation of the binocular

Which suggests could be something else?
Is this phenomenon similar when looking through other binoculars, or just when using the Apollo's.
Could you image the effect your seeing. 

[Stormbringer]

How old are they ?

Just wondering if your looking straight through the binoculars and not looking at an angle through them (ie looking through them top to bottom or vice versa ) and seeing part of a reflection in the binocular ?

[Mark at Beaufort]

Hello Dave and welcome to SGL. I have some Apollo 15x70 and I have no  hazy white crescent. I would assume there is something wrong with the binoculars and maybe rain has entered at some stage and caused the problem. I am also assuming that you had no problems with your Opticron Oregon 11x70 so your eye sight is not causing the problem.

Its highly likely that Steve Tonkin @BinocularSky will see this post and give you a more positive analysis of the defect.

[Stormbringer]

3 minutes ago, Mark at Beaufort said:

Hello Dave and welcome to SGL. I have some Apollo 15x70 and I have no  hazy white crescent. I would assume there is something wrong with the binoculars and maybe rain has entered at some stage and caused the problem. I am also assuming that you had no problems with your Opticron Oregon 11x70 so your eye sight is not causing the problem.

Its highly likely that Steve Tonkin @BinocularSky will see this post and give you a more positive analysis of the defect.

wouldnt that then mean it would be in same part of view ie its at bottom of view using bins but he turned them on their side and its still at bottom as he is looking through them ?

[Charic]

1 hour ago, Mark at Beaufort said:

maybe rain has entered at some stage and caused the problem.

The Apollo's are waterproof and nitrogen filled, so if water has entered, that would be a serious issue.
The fact the aberration is always lowermost in the views, suggests there's something else going on here?
Internal reflections could be suspect, but I would have thought that any internal reflection would  come from a fixed point and  therefore rotate on axis, but reportedly, thats not the case.

On this link, there is an image, maybe similar to what the OP is referring too, a  crescent shaped aberration across the image, caused from an internal reflection. https://www.birdforum.net/showthread.php?t=278666

[Mark at Beaufort]

9 hours ago, Charic said:

On this link, there is an image, maybe similar to what the OP is referring too, a  crescent shaped aberration across the image, caused from an internal reflection. https://www.birdforum.net/showthread.php?t=278666

Great link - your answer seems far better and more logical than mine.

[Ricochet]

Charic's link sounds like a reasonable explanation. If so the reason it always appears at the bottom edge is probably because it is a reflection of the relatively bright sky. At night this probably won't be an issue unless observing near the moon. The next time there is a clear night give them a go and see if the issue still persists.

[BinocularSky]

Hi Dave, and thanks for your kind words - a pleasure to meet you as well. ?

14 hours ago, Mark at Beaufort said:

Its highly likely that Steve Tonkin @BinocularSky will see this post and give you a more positive analysis of the defect.

Only just seen this thread. Nothing of substance to add - I agree that it sounds very much like internal reflections. Is this what you see?

That's a daylight view through my old HA 15x70 (taken to demonstrate the off-axis CA with off-axis "eye" (camera lens) positioning), and you can clearly see other artefacts that indicate that it's poor control of stray light at the prisms. However, this is mostly, I think, light getting in through the eyepiece. This could explain your:

16 hours ago, daveintheshire said:

  It is worse with my spectacles on, and largely mitigated when I take them off and really "bury" my eyes in the eyepiece. 

I don't recall seeing it at night, but I recall that there was some ghosting if a bright light/object was just outside the field of view. I don't recall noticing this on first magnitude stars, but it would reduce contrast, but probably imperceptibly unless you were observing something right next to the Moon (where you'd have greater contrast-reducing concerns from the sky!)

 

 

[daveintheshire]

Internal reflection was my gut instinct, and everyone's help in pinning it down is very much appreciated - thank you all.

Charic:  I think you are spot on.  The birding link was very helpful (as well as just plain interesting).   

Ricochet:  Yes this was my reasoning after reading Charic's link. Without the world's most luminous clouds hanging round and confusing the issue I have high hopes!

Steve: The view is very much like your photo , even down to the off-axis CA, but minus the other artefacts.  I'm looking forward to first light so I can see how they perform. 

I'll come back after their first outing and let you all know how they get on - thanks again.

[daveintheshire]

Hooray!  I finally managed first light last night.

In a nutshell the HA weas excellent.  It behaved pretty much as Steve described.  The clouds were persistent but I saw the Moon break through in the SW about 2200z.  I dashed out with the HAs on a trigger-grip ballhead and monopod and decided to cauterise my retinas for a bit in case they clouds did not clear further.  The moon looked better than I've seen through binoculars so far, with very minimal CA on the bright limb and excellent detail in the craters on the dark limb.  Looking at nearby stars I did notice the white crescents, but in practical terms it was only when I was trying to make it happen that it happened.  Thankfully the clouds receded at a terrific pace, but the moon was at 80% last night and combined with the glow from Wolverhampton the sky was looking pretty barren - still beggars can't be choosers!  Turning to Mizar and Alcor I was immediately impressed with the contrast.  The view of the Engagement Ring is the best I've had from this site so far.  The Perseus double cluster yielded more detail than I had hoped considering its position in the edge of the Wolves glow.  I managed to get a positive split of Albireo despite being a bit shaky with the monopod due to being close to the zenith with no chair available (something I couldn't really do in my Opticrons and a big part of the push for an upgrade).  I can't wait to see them again with a tripod.  Delta Lyrae and the fainter stars in the vicinity showed excellent contrast despite Vega's proximity, and framing Epsilon Lyrae so that Vega was just out of the FOV I didn't notice problems due to stray light.  This bears out Steve's idea of the issue being ingress at the eyepieces - further credence is added by the fact that looking out at bright daytime views through a window in a relatively dark room also caused the crescents to not appear.  I can cause the crescent to take on a flesh-coloured hue by attempting to shield the eyepieces with my hands! While taking a break from the HA pointed up at Lyra I was treated to a meteor travelling across the Northern sky.

I had my first honest-to-goodness viewing of Eddie's Coaster last night.  I've been trying for this all month since the August edition of the Binocular Sky Newsletter reached my inbox and I must confess I had begun to attribute it to the "eye of faith" a little bit.  But last night there it was, larger than life, filling the surprisingly contrasty 4.4 degree FoV.  Delightful indeed!

All in all very promising.  Back to the waiting game...

[Stormbringer]

glad everything is ok with your bins and that you got to the bottom of what caused the milky crescents

[Mark at Beaufort]

Dave at some stage you may wish to purchase some filters - UHC or O-III which will give you a good wide FOV of objects like the Veil or North American Nebula to name a few.

[daveintheshire]

1 hour ago, Mark at Beaufort said:

Dave at some stage you may wish to purchase some filters - UHC or O-III which will give you a good wide FOV of objects like the Veil or North American Nebula to name a few.

Yes indeed - this is an avenue I'm interested in.  Any recommendations?

[Stormbringer]

I posted asking about filters for Helios Apollo bins a wee while back and got some good advice

Here

 

[Mark at Beaufort]

Dave I have had my Apollo 15x70 for nearly two years and part of the reason for buying was the ability to screw 1.25" filters into the eye cup. I already had UHC and O-III filters and because I live in a reasonably dark site it was a good opportunity to experiment. I mix and match the filters around and I have had excellent views of the Rosette, Helix, NAN, The Veil plus the delights of Scutum and Sagittarius (M16, M17, M20 and M8). I have also use H.Beta filters and saw the California Neb.

There is a whole debate on the forum about what is the best filter - although I have Lumicon and Astronomic I have had good views using the Castell filter range.

These are truly great binoculars and the ability to add filters just makes them brilliant IMHO.

[daveintheshire]

5 minutes ago, Stormbringer said:

I posted asking about filters for Helios Apollo bins a wee while back and got some good advice

Here

 

Thanks Alan, much appreciated.

[Stormbringer]

1 minute ago, daveintheshire said:

Thanks Alan, much appreciated.

no probs mate happy to help

[daveintheshire]

11 minutes ago, Mark at Beaufort said:

Dave I have had my Apollo 15x70 for nearly two years and part of the reason for buying was the ability to screw 1.25" filters into the eye cup. I already had UHC and O-III filters and because I live in a reasonably dark site it was a good opportunity to experiment. I mix and match the filters around and I have had excellent views of the Rosette, Helix, NAN, The Veil plus the delights of Scutum and Sagittarius (M16, M17, M20 and M8). I have also use H.Beta filters and saw the California Neb.

There is a whole debate on the forum about what is the best filter - although I have Lumicon and Astronomic I have had good views using the Castell filter range.

These are truly great binoculars and the ability to add filters just makes them brilliant IMHO.

Thank you Mark - some real delights to look forward to there.  I'm looking forward to getting out to the Shropshire hills with them when there is not a honking great Moon in the sky for a look at some DSOs.  Sagittarius is stunning from the top of the Long Mynd in my unfiltered Opticrons, so the filtered Apollo should be a real treat.

[Trikeflyer]

I have the same bins and i can mimic the effect you are describing. I think it is inherent in the design. I can make it happen if i tilt the eyepiece relative to my eye. It goes if i get the eye and eyepiece position more square on so to speak. if I tilt the binocular the the effect increases.  Hasn't bothered me until now so i think its 'normal' for this binocular and if i get the tilt right, i can minimise the effect to such a level that it is unnoticeable.

Clear Skies

Steve

[daveintheshire]

5 hours ago, Trikeflyer said:

I have the same bins and i can mimic the effect you are describing.

What you describe matches my observations exactly.  Its been a hugely useful to to get such detailed feedback in this thread - many thanks for yours, Steve.

[BinocularSky]

Glad you like them, Dave. Heavy, but the mass seems to damp vibration a bit, I found. As for filters, IMO if you only get one, get a decent UHC (mine's a Lumicon, but there are others) - I find it more generally useful than an [O-III] (although a decent [O-III] is a cracking filter for what it does).