Veil Nebula 31 May 08

Some crops from the 02 june picture

zoomed in a bit just to show the area. Its easier to see on the full picture.

It's been a fun rollercoaster, but like the lads say above, it's worth giving your images a quick once over within 24 of capture, you never know what you might find.
The weather is going to be good this week, anyone imaging around the veil region anytime soon.?

johnomahony wrote:

DaveGrennan wrote:

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TBH I'm very inclined to favour the ghost reflection theory. The key is that it is on the opposite side of centre from the bright star. There was a long discussion about this very thing on the minor planet mailing list recently and even some big observatories have been fooled by internal reflections. In fact I've seen something very similar when I was working with a similar setup.
?

As the image was an unguided shot there is some tracking error. If you zoom in you can see the tracking error. If you look at the close up of the "object" it appears that the tracking error is reversed (or mirrored compared to nearby stars) which would suggestion a reflection. You may be right Dave.

Folks - I've been looking at the image again and I'm not convinced that this is a reflection. I'm no expert on reflections but I still don't buy it fully.

1. The object (let's call it that) is not diagonally opposite to the bright star. If you determine the centre point of the image then draw a line between the centre and the bright star, then extend the line to the upper right for the same distance, the object doesn't sit at that diagonally opposite point.

Sure, its close and maybe that still fits in with particular optics in question. But to say that its diagonally opposite and that's a tell-tale sign of a reflection, well I need more convincing

2. I really don't buy the "reversed tracking error" argument. Firstly, I don't see a clear mirroring of any eggy shape at all. Secondly, I'm not buying tracking error. I'll buy rotation because that's what it looks like to me.

3. If its a reflection, why is it not simply a dimmer version of the bright star? I see a central core with a much dimmer and diffuse outer edge. Not a dimmer version of the star...

4. The second image taken in June is tenuous at best. If we look at the original image, we see the object. Very close to the left of it is a bright star. Directly above this star is a second bright star. In between these bright stars and slightly to the left is a third star. That's "our" triangle. So, the object is to the right of the triangle and in line with the lowest of the three point (stars).

Looking at the June image, I can make out a "blob" for want of a better description, that is not in John's image but *could* be an image of the object a couple of days later and having moved in the intervening period.



But, no more than I'm not convinced by the reflection theory, you may equally not buy into this theory - hell, I'm not sure if even *I* buy into my alternative theory

Any comments, other viewpoints?

I've taken the liberty of butchering both images to show what I mean - see them here:
www.astroshack.net/images/object%20JOM.jpg
www.astroshack.net/images/object%20JOM2.jpg

Cheers
Dave

It would be interesting to see a single exposure (unprocessed) of the June image (6 inch scope with a modded canon 300D). I did actually process my image of "that frame" with a dark and flat a day or so after taking it and stretched it out to bring out the nebula. While the "object/ reflection" is still visible it doesn't stand out as anything special. The processing removed its contrast (its in my flickr account). But it is quite obvious in the raw image.
Thoughts?

dmcdona wrote:

1. The object (let's call it that) is not diagonally opposite to the bright star. If you determine the centre point of the image then draw a line between the centre and the bright star, then extend the line to the upper right for the same distance, the object doesn't sit at that diagonally opposite point.

That would be down to the inherent nature of imaging setups which mean the light path is never centred exactly on the chip. Even the teeniest tiniest amount of salck in any of the points in the optical train, and there are lots of these points in any setup makes it hard for the light cone to be perfectly centred. If you look at how the illumation falls of across John's image and point with your finger to the centre of the illumination you will see that the 'object' is diagonally opposite.

dmcdona wrote:

Sure, its close and maybe that still fits in with particular optics in question. But to say that its diagonally opposite and that's a tell-tale sign of a reflection, well I need more convincing

One of the reasons that convinces me is I have seen exactly this with the CLS filter. In fact its possible with any interference filter because unwanted light is reflected instead of absorbed. What happens is some of the light from the bright stars reflects off the CMOS, then back off the underside of the filter to be detected by the sensor. I anyone wants to do the geometry on that good luck to yas:)

dmcdona wrote:

3. If its a reflection, why is it not simply a dimmer version of the bright star? I see a central core with a much dimmer and diffuse outer edge. Not a dimmer version of the star...

Because of diffraction. Microscopic fissures and irregularities in the glass of the filters cause some of the light to be spread out over an area.

dmcdona wrote:

4. The second image taken in June is tenuous at best. If we look at the original image, we see the object. Very close to the left of it is a bright star. Directly above this star is a second bright star. In between these bright stars and slightly to the left is a third star. That's "our" triangle. So, the object is to the right of the triangle and in line with the lowest of the three point (stars).

I agree. There does look to be something on the June image. The only issue I'd have is the colour processing of that image is causing all sorts of artifacts all over the image however that one does look suspect. Thing is the movement suggests that a simple search should be enough to prove disprove etc. I'll some up with some rough positions based on the two images. Thing is the June 2nd image is not timed from what i can tell. Which makes it more difficult.

Dave.