Eta Carinae in UV

[sjastro]

Given Marc's excellent NIR images including the Keyhole nebula here is a UV image of the same region.

Image details.
4 hrs with a UV pass filter using a BRC-250 and ST-!0XME.

Higher resolution here.
http://members.iinet.net.au/~sjastro/EtaC_uv.html

Regards

Steven

[seeker372011]

4 hours!

That's some serious exposure..and on such a bright object in the visible part of the EM spectrum...

Interesting

[multiweb]

Good stuff Steven. So we're looking at 340nm or there about? Are you using the Baader U filter (http://www.company7.com/baader/options/u-filter_bpu2.html)? (Venus one)? That could be mapped in the blues in a palette arrangement.

[sjastro]

Thanks Narayan.
Most objects are very faint in UV including Eta Carinae.
The other problem is that atmospheric extinction is much worse than in the visual range.



Marc I use a 340nm-400nm Astrodon filter.
To make UV "colour" imaging a bit more interesting and challenging, I have blended L(UV)RGB(UV) and LRGB images where the strength of the UV emission is seem as yellow.

I haven't done this with EtaC, but the UV emission shows up nicely in the attached Tarantula.

Regards

Steven

[seeker372011]

Do post when you get around to doing this.

Narayan

[multiweb]

Just so I've got this right: You use 100% UV as LUM, then blend UV into R, G and B as a %?

[gregbradley]

Nice work Stephen. There is a lot of filter work on this forum, from you, from Marc and from Bert. Its great. You guys are pushing the boundaries.

Richard Crisp did some work a few years back with polarising filters.
You take several with different angles of the filter like 45, 90, 180 and assign them to different colour channels.

It works on some objects, like the Crab Nebula. It may work on Eta C. I have one of these filters but ideally you'd need 3 set to different angles of turn otherwise I'd have to manually spin the filter each time I wanted a different channel.

Greg.

[sjastro]

Marc,

Two separate images were taken of the Tarantula.
One was a conventional RRGB image with the red filter used as luminance.

The second image was taken with a UV filter as luminance. The data was also used for the B channel.
This formed a (UV)RG(UV) image.

The LRGB and (UV)RG(UV) were then combined at 50% opacity to form the final image.



Greg,

I actually tried something very similar on a solar image.
The end result were two destroyed polarizing filters:(

After nearly five moths I'm still waiting on the replacement filters from Lumicon.

Regards

Steven

[Ross G]

Great work Steven.

It's good to see the imaging boundaries being pushed.

Good luck.

Ross.

[Merlin66]

Another excellent UV result!
Well done...
Although the filter bandwidth may go down to 340nm I'd be very surprised if the CCD QE curve when far below around 370nm, so I'd say the UV image would be a 370-400nm data set.
Keep them coming............

[sjastro]

Thanks Ken,

At 340nm the QE of the ST-10XME is around 25-30%.
It's a great camera, the sensitivity is offset however by the ease at which even moderately faint stars can bloom.



Thanks Ross.

Clear skies

Steven

[Merlin66]

Hmmm
25% at 340nm....I think I need one of those for spectroscopy!!!

[sjastro]

The ST-10XME uses the KAF-3200ME chip.
According to the specs a QE of >30% at 340nm is possible.

Regards

Steven

[Merlin66]

Thanks for that.
The ATiK 314L+ (ICX285AL chip) QE curve stops at 400nm where it shows 50% RELATIVE response.....
I've just been taking some solar spectra (for another project) and will push down into the UV - I'll be able to tell you the exact limit of the ATiK 314L in a few minutes....
(I see your curve is also the relative QE...the best absolute is around 60%, so this would give <20% QE in the UV...)

[Merlin66]

Steven,
I set up the ATiK314L on the spectroscope and took a solar spectrum down in the UV....
The limiting wavelength was 3660A....
Not bad.

[sjastro]

You should post your results.

Regards

Steven

[Merlin66]

Will do....

[Merlin66]

The raw spectrum, taken with the Spectra-L200 and the ATiK314L, shows the solar spectrum down to and below 3660A. Below that limit the s/n is very low.
The calibrated profile, normalised for 6100A shows the drop off...
The Liege solar spectrum is for reference.
Hope this helps.

[sjastro]

Very interesting Ken.

When using spectrometers for "terrestrial" applications generally one doesn't have the information overload as seen in the Leige solar spectrum.
In fact if I didn't know what I was looking at I'd swear the graphical representation of the Leige solar spectrum looks more like noise with the exception of the broad absorption band at ~3930A. (Is it due to broadening of the H-Epsilon line?);)

I'm impressed with your resolution.

Regards

Steven

[Merlin66]

Steven,
In the Liege extract you're actually seeing the CaK absorption line at 3933A
This feature is MUCH wider than any of the H Balmer series.
Most of the other features come from Fe /CN....
Check out the complete Liege solar spectrum at:
http://fermi.jhuapl.edu/liege/s00_0000.html
I think more amateurs should get involved in Spectroscopy..."the final frontier" ;-)

[sjastro]

Of course the CaK line.:thumbsup:
Many fine images of the Sun have been taken in CaK.

Steven