Can autoslew correct for atmospheric refraction?

[Corpze]

Hi, bought a new USB "weather station" from Blue Astro" and it can send temp/pressure/dewpoint data to 10Micron mounts so it can correct for refraction in the atmosphere, can Autoslew do this as well?

 

http://blueastro.se/index.php?id=5

 

/Daniel

[P.Keller]

the influence of temperature dependency for refraction correction is minor and neglegible compared to other errror sources like hysteresis etc.

Also, the temperature gradient in the atmosphere is something that cannot be measured anyway, even if you measure the temperature at the altitude you are observing, you can have a temperature inversion above etc.

So there is no real sense in doing this.

[Corpze]

Ok (is that's why they measure with laser at the big observatories?)

Thank you for the fast response!

 

/Daniel Sundström

Edited June 30, 2015 by Corpze

[Corpze]

the influence of temperature dependency for refraction correction is minor and neglegible compared to other errror sources like hysteresis etc.

Also, the temperature gradient in the atmosphere is something that cannot be measured anyway, even if you measure the temperature at the altitude you are observing, you can have a temperature inversion above etc.

So there is no real sense in doing this.

I have been doing a bit of reading, first of all, I have mixed up atmospheric refraction and distortion, so please discard post no.3 :-)

 

I have been reading this paper regarding atmospheric refraction; http://astro.ukho.gov.uk/data/tn/naotn63.pdf

 

In witch you find this table;

 

If I understand this right, a increase of 10hPa increases the refraction by 23 arcseconds.

Also, a increase of 2.5K in temperature brings the refraction down by 34 arcseconds.

 

One thing i am uncertain of is if these numbers add on top of the "standard refraction" of 5 arc minutes at the horizon and 2 arc minutes at 30 degrees elevation.

 

In my mind, this is huge numbers, please fill in my knowledge gaps of how these numbers are neglegible.

 

Regards, Daniel Sundström

[MarkS]

Hi Daniel,

 

I think the numbers in the table you show refer to elevations of 0 - 30 degrees. Surely these angles are 'out of bounds' for photography?

 

My schooling, such as it is, has taught me not to image below elevations of ~55 degrees.

 

Or am I missing something here?

 

Regards,

Mark

[Corpze]

I was interpretating the table as how much the refraction interfere at a given altitude (60 and 90 degrees in this case) at different changes in temperature and pressure.

And as you point out, no need to photograph pretty pictures to low on the horizon.

 

/Daniel

[MarkS]

Hi again Daniel,

 

The zenith angle referred to in the paper is, I think, the angle FROM the zenith - ie 90 degrees zenith angle is horizontal, not vertical.

 

Regards,

Mark