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Old 23-01-2009, 12:35 PM
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Help with imaging IC 2118

Hi All,

Had my 2nd attempt at imaging IC 2118 last night.
Have the IC 2118 region between Rigel, Cursa and HIP 23364 centrally located in the frame.

Imaged with my 450D, used a 17-85mm EFS lens at 85mm, F5.6 and ISO 800. Took 16 x 300 second subs, 6 x 300 second darks and 16 x 1/30 th second flats. Took the flats at ISO 100 as per Humayun's advice.

Processed in Images Plus
Guided with my DMK using IC Capture and Alls Reticle.

Not much of a hint even of IC 2118.
What am I doing wrong here? I would have thought that 80 minutes would have been long enough to capture it.



Any advice greatly appreciated.

Regards
Trevor
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Old 23-01-2009, 03:23 PM
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Screwdriverone (Chris)
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Hi Trevor,

I'm no expert, but is the 450D modded or standard?

Could be the issue with the nebulosity not showing on a standard camera that blocks most Ha perhaps?

Of course, if I am wrong, then so be it, someone will tell me I am sure. Seems you got the Witchhead Nebula near Rigel showing up, although it looks a little B&W like M42 looks, and obviously small at that widefield scale.

Just my noob 2 cents, hope it helps?

Cheers

Chris
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Old 23-01-2009, 03:53 PM
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Hi Trevor.

I'm not sure if it is the Witch Head Nebula but if you have a look to the bottom left of Rigel you will see a patch of what I believe to be IC 2118. It is extremely dim but refering to my planetarium software, it is in the exact spot of the nebula.

I strecthed the image in PS and circled it in red. The only other thing it could/might be is a reflection off the lens.

What do the others think?

It might be worth having a look at the high res version as well.

But like your last image focus and tracking is spot on.

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Old 23-01-2009, 04:24 PM
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Hi Trevor,

Hope you don't mind,
I did a comparison with CDC of your field.

Approximately the same size and orientation here.
Cut one and paste it over the other with 50% opacity and
it matches.

I think you're being too hard on yourself here Trev, the
Witches Head is a very dim object and you're only using
a DSLR lens....

I'm curious, like Matt, exactly what it is you got to the left of
Rigel though...(Sorry Matt, I don't think it's IC2118, you're a little
off).

Was your aperture wide open?...silly question I know.

Steve B.
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Old 23-01-2009, 04:52 PM
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Quote:
Originally Posted by Screwdriverone View Post
Hi Trevor,

I'm no expert, but is the 450D modded or standard?

Could be the issue with the nebulosity not showing on a standard camera that blocks most Ha perhaps?

Of course, if I am wrong, then so be it, someone will tell me I am sure. Seems you got the Witch head Nebula near Rigel showing up, although it looks a little B&W like M42 looks, and obviously small at that wide field scale.

Just my noob 2 cents, hope it helps?

Cheers

Chris
Thanks Chris,

My 450D is unmodified.
IC 2118 is not an emission Neb it is a reflection neb, therefore it doesn't emit at Ha wavelengths it is reflecting mainly blue light. This is why I chose this subject to image, it should suit my camera.

Regards
Trevor
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  #6  
Old 23-01-2009, 05:03 PM
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Ahh yes, see Trevor, I said I was no expert.

That blob that Matty P circled is what I was referring to. That's the Witchhead I believe.

Chris
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Old 23-01-2009, 05:08 PM
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Hi Steve,

Just had a look in the Herald Bobroff and they go down to their "D" series of charts for this region. The small blue area in my image is within the area they have marked for IC 2118. They have nothing else marked in this area.

Comparing the star field with wide field images taken at similar apertures on IIS this blue feature is not part of those images.


This is pretty strange, early in the night while I was waiting for it to get dark enough, I took three 300 sec JPEG's, just to confirm that my alignment was right. The small blue feature shows up in each of them.

In the stack of 16 x 300 sec raw files this small blue feature really is not that much better defined.

Regards
Trevor
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Old 23-01-2009, 05:16 PM
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Quote:
Originally Posted by Screwdriverone View Post
Ahh yes, see Trevor, I said I was no expert.

That blob that Matty P circled is what I was referring to. That's the Witchhead I believe.

Chris
Hi Chris,
It doesn't matter if you are not an expert, I appreciated your reply regardless.

The Witches Head is a massive object and even on my image scale should cover about 25mm. Comparing the same star field with similar images posted on IIS that small blue area in my image is not part of the object, however, as I was saying to Steve, I checked it out with the Herald Bobroff Astro Atlas. This Atlas is very good and has very high res charts for this area, the region they mark out for IC 2118 does include my small blue area.

Regards
Trevor
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Old 23-01-2009, 05:18 PM
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Quote:
Originally Posted by Quark View Post
Hi Steve,

Just had a look in the Herald Bobroff and they go down to their "D" series of charts for this region. The small blue area in my image is within the area they have marked for IC 2118. They have nothing else marked in this area.

Comparing the star field with wide field images taken at similar apertures on IIS this blue feature is not part of those images.


This is pretty strange, early in the night while I was waiting for it to get dark enough, I took three 300 sec JPEG's, just to confirm that my alignment was right. The small blue feature shows up in each of them.

In the stack of 16 x 300 sec raw files this small blue feature really is not that much better defined.

Regards
Trevor
If you're in any doubt about where the nebula is, take a cut and paste
of this guy's image...resize it about 55% and overlay it on your image.
With some opacity. Again about 50%.

http://www.photographytips.com/page.cfm/5552

Puzzling....

Steve

Last edited by kinetic; 23-01-2009 at 05:46 PM. Reason: please respect the copyright disclamier of the suggested author's picture
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Old 23-01-2009, 05:23 PM
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Quote:
Originally Posted by kinetic View Post

I'm curious, like Matt, exactly what it is you got to the left of
Rigel though...(Sorry Matt, I don't think it's IC2118, you're a little
off).
Thanks for the correction Steve. I thought given the exposure time, something should've shown up after processing. I'm guessing that the blue patch is a reflection.

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Old 23-01-2009, 05:48 PM
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Quote:
Originally Posted by kinetic View Post
If you're in any doubt about where the nebula is, take a cut and paste
of this guy's image...resize it about 55% and overlay it on your image.
With some opacity. Again about 50%.

http://www.photographytips.com/page.cfm/5552

Puzzling....

Steve
Thanks Steve,

I have been using an image at 98mm by Doug and Humayuns 50mm and 300mm images to very accurately define the region. Doug and Humayun posted links to their images for me in an early query on how to go about this.

Regards
Trevor
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Old 23-01-2009, 05:53 PM
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Originally Posted by Matty P View Post
Thanks for the correction Steve. I thought given the exposure time, something should've shown up after processing. I'm guessing that the blue patch is a reflection.

Hi Matty,

Just had another thought, I was going to take the 450D to Hawaii and put a polarizing filter on my lens but changed my mind because I wasn't familiar with the camera and I would never get the opportunity to redo the images if something went wrong.

The polarizing filter is still on the lens. What effect might that have on capturing blue light?

Regards
Trevor
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Old 23-01-2009, 05:55 PM
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Quote:
Originally Posted by Quark View Post
Thanks Steve,

I have been using an image at 98mm by Doug and Humayuns 50mm and 300mm images to very accurately define the region. Doug and Humayun posted links to their images for me in an early query on how to go about this.

Regards
Trevor
Interesting Trev,

I suppose it's not outside the realms of possibility that it's a recently
illuminated part of another clump of dust. AKA McNeils Nebula.

I hope it is, then it will be named after you!!


I'll certainly take a widefield shot tonight of the spot.
Could also be a lens flare from Rigel, did your camera orientation
change at all compared to where Rigel was in the frame?
That usually identifies a lens flare.

regards,
Steve.
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Old 23-01-2009, 06:13 PM
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Originally Posted by kinetic View Post
Interesting Trev,

I suppose it's not outside the realms of possibility that it's a recently
illuminated part of another clump of dust. AKA McNeils Nebula.

I hope it is, then it will be named after you!!


I'll certainly take a widefield shot tonight of the spot.
Could also be a lens flare from Rigel, did your camera orientation
change at all compared to where Rigel was in the frame?
That usually identifies a lens flare.

regards,
Steve.
No Steve, the camera orientation never changed.
As I said before, the blue area even showed up, albeit faintly, in the 300 sec JPEG's that I took early on to check the field alignment.

Regards
Trevor

Last edited by Quark; 23-01-2009 at 06:14 PM. Reason: spelling
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Old 23-01-2009, 08:36 PM
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Hi Trevor

I believe that you have a reflection, that blue/green blob is typical of a bright star being reflected by one of your lens elements or the filter you have attached.

Cheers
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Old 24-01-2009, 05:08 PM
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Hi Trevor

I believe that you have a reflection, that blue/green blob is typical of a bright star being reflected by one of your lens elements or the filter you have attached.

Cheers
Thanks John,

Thinking just how dim Ic 2118 is and the fact that this feature showed up on just a 300 sec sub, I would have to agree with you. It must be a reflection.

Regards
Trevor
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Old 24-01-2009, 05:43 PM
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I'd have to agree with Steve and John....it probably is a reflection in your lens, but you are in the right area. You have to remember you're only shooting through a camera lens and the Witch's Head is pretty dim. You will need to go longer using the camera lens, but you may pick it up if you decide to go through the prime focus of your scope using your 450D..
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Old 25-01-2009, 06:55 PM
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I'd have to agree with Steve and John....it probably is a reflection in your lens, but you are in the right area. You have to remember you're only shooting through a camera lens and the Witch's Head is pretty dim. You will need to go longer using the camera lens, but you may pick it up if you decide to go through the prime focus of your scope using your 450D..
Thanks Renormalised,

Yep, it is the correct field and that has to be a reflection. I suspect the polarizing filter that I forgot to take off.

The 450D on my 16" F4.5 would provide nothing like the field of view for this object. Doug has a nice shot of it in a 98mm lens and Humayun captured it with a 50mm and also a 300mm lens.

If I am ever going to image this object it will have to be with my camera lens and as it operates at F5.6 at 85mm, I think I just need more data. Next time I have a go I will use my current image to align the same field, then I will be able to add the new data to the old and end up with more signal.

Regards
Trevor
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Old 26-01-2009, 07:30 AM
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Hi Trevor,

The reflection is almost certainly an internal lens reflection, not from the polarising filter. Try different lens/camera orientations wrt Rigel to minimise it.

I suspect that you got nothing from the reflection nebula because of the polarising filter. They are good at removing reflections from terrestrial objects, so probably do so for non-terrestrial objects as well.

Cheers
Stuart
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Old 26-01-2009, 08:52 AM
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Hi Stuart,
Thanks for your thoughts on this. I think you may have hit the nail on the head, so to speak, regarding the effect a polarizing filter might have on a reflection neb, or at least one as dim as this one.

Regards
Trevor
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