help, don't know what that is, anybody?

[soundworthy]

I was intending to get some imaging of the horsehead as it was a very dark night and relatively good seeing (for the time), but on the test shots there was a, a, thing with a rainbow effect.

First thought was to clean everything.
so i did, cleaned all glass on scope Pflat and dslr.
put it back together and ended up with exactly the same thing.
So I took these high iso and over exposed shots to reveal the anomaly and I rotated the camera only to find it disappeared.
Next i repositioned it a bit to move it to the center and it disappeared, so i moved it away from the rainbow and found it to move with the image.

I found it moves with the sky, not the camera, so what the hell is it.
the shots attached are hi exposures to show it up, the good looking one is a stacked version of it.

i tried shooting other objects like the orion nebula as well and nothing, all fine,
but every time i came back to the HH nebula so did the anomaly
:screwy:

There is also some rings that appear off the the side as well

any advice would be appreciated

[tlgerdes]

I would say looking from the direction of convergence of light, a star reflection from Alnilam.

[soundworthy]

definitely from that direction, but its a little extreme isn't it?
I've never experienced it with any other star.

I went out the night after and did the same thing with the same results.
:shrug:

[Barrykgerdes]

It's quite obviously a fleet of Vogon destructor ships on there way to destroy a system.:lol:

But seriously it certainly looks like reflection from a very bright object just out of the FOV. Alnilam is a good bet.



Barry

[LightningNZ]

What scope are you using? Is it baffled at all? Given the rainbow effect it looks like stray light from Alnilam striking a refractive component (lens) at an extreme angle. Perhaps try making baffles, flocking the tube or putting lens hood on the scope.

[MrB]

My Stellarvue 70ED suffers from this, and I have also only noticed it while shooting the HH and/or M42.
I believe this is a reflection from the internal [edge] of a lens element, which are never very smooth and often have tiny chips and grind marks, hence the striations in the reflection.
I'm not sure what the top APO manufacturers do to reduce this, maybe they etch and then blacken the edges somehow to scatter and absorb the light.
The scatter would obviously affect contrast but it's much preferable to the rainbow ;)
Maybe they sacrifice some aperture by stopping the lens down enough that the edge reflections never make it thru? :shrug:

Not a great drawing, borrowed from a quick google image search, but I think it conveys the idea:

[MrB]

Found a better drawing of the edge scatter and some interesting info about edge blackening from Edmund Optics.
Replace the "Reflective Object" in the drawing with a very bright off-axis star. (or moon/streetlight/torch... whatever)

http://www.edmundoptics.com/learning-and-support/technical/learning-center/application-notes/optics/edge-blackening/

[leon]

Very odd indeed, I have seem plenty of light reflections in lenses and scopes before, but nothing that extreme.

Leon

[MrB]

If memory serves Leon, you have/had very high-end APO's? Your signature says it all ;)
I'm sure the likes of AP, Takahashi, TeleVue, TMB, LZOS etc etc do their best to minimise the chances of this happening.

[soundworthy]

Thanks for the explanations, and I'm sort of glad some of you have had a similar experience. I still think its a bit extreme.
The gear is not far from new, all purchased 2012.
FLT110
P-Flat 68
5D Mkii

I was previously using a similar setup without any optical issues.

Does anyone have any ideas as to what i might do to prevent this?

[Poita]

Does it go away if you remove the pflat?

[soundworthy]

I did think of removing the pflat, but unfortunately the first night i didn't get the time to,but even more unfortunately the next night i just forgot to.:screwy: