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My first attempt at Uranus. It has been corrected for instrument response, but I ran out of time (due to mist) to image a G type star, so divided the image by the G2v reference image in rspec instead to correct for sunlight. Think it looks okay. Have posted both the corrected and the normalised images.

Kate

post-1883-0-55387600-1352981114_thumb.jp

post-1883-0-29749300-1352981113_thumb.jp

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Hi Kate,

The easiest way to correct Uranus is by dividing the uncorrected Uranus profile with an uncorrected G2v (taken with same setup) so the two uncorrected profiles cancel out the instrument response. There may be some other correction techniques applicable using subtraction. Be useful to know.

Be interested to see the raw Uranus profile. It's not the easiest to calibrate (but H beta should be easily visible). I'm guessing that dividing the low res SA100 profile by the higher resolution reference spectrum might have introduced some extra sharp lines in the result? The methane bands are normally quite smooth.

I picked the wrong star to divide by when I tried Uranus. I think I have another G2 star I can try again with.

Looks pretty good though.

cheers

John

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Hi Kate,

The easiest way to correct Uranus is by dividing the uncorrected Uranus profile with an uncorrected G2v (taken with same setup) so the two uncorrected profiles cancel out the instrument response. There may be some other correction techniques applicable using subtraction. Be useful to know.

Yep division by the solar spectrum (not subtraction) is correct. The sun is the light source in this case so we need to divide it out to remove its effect. Wavelength calibration as usual should be done using a separate a type calibration star and the resulting calibration applied to the Uranus spectrum. See also these current posts on the staranalyser Yahoo group for an alternative technique using a library G2V spectrum rather than a measured G2V star

http://tech.groups.yahoo.com/group/staranalyser/message/2639

http://tech.groups.yahoo.com/group/staranalyser/message/2640

Cheers

Robin

www.threehillsobservatory.co.uk

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Hi Robin,

I tried the method you suggested on the yahoo forum as well as using the G2 star I imaged last month. Both results looked very similar and much better than the original which had an aweful lot of extra artefacts in it.

For the moons of Jupiter do you need to follow the same process as for Uranus and Neptune?

Kate

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For the moons of Jupiter do you need to follow the same process as for Uranus and Neptune?

Kate

Hi Kate,

Yes this will work for any solar system objects even asteroids.

To get it spot on you would need to compensate for the effect of our atmosphere. The effect is small for high elevations but can be become very large near the horizon. This can be quite involved to do properly, taking stars at different elevations and calculating the compensation needed but the easiest way to do it is to take your comparison G2V star at a similar elevation on the same night if possible.

Cheers

Robin

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