From: Milton Aupperle <milton@outcastsoft.com>

Date: April 22, 2011 11:06:21 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Spectroscopy

Hi Terence;

On 22-Apr-11, at 6:30 AM, Terrence Redding wrote:

Good morning all,

I have been one of the silent followers of this conversation.  In trying to understand the issues involved I have reviewed Buchheim's comments in "The Sky is your Laboratory" and scanned through Tonkin's "Practical Amateur Spectroscopy."  I am surprised my the apparent opportunity for amateur astronomers to do "science" in this area.

It surprising what can be done. Check out

http://www.richweb.f9.co.uk/astro/spectroscopy.htm

and

http://www.rspec-astro.com/sample-projects/

For example, they show how one can measure the atmosphere composition for Neptune. I suspect one would need to subtract or level it using the Suns spectra first to isolate the atmospheric absorption lines.

Using say an 8" scope, what magnitude object will be within reach of the system/design being discussed?  It appears we are talking both hardware and software.  I would have thought our conversation would focus on software use coupled with existing hardware?

The primary thing users have to deal with is the Flats. Rotating the grating so that star Spectra don't overlap means shooting new Flat Frames. To shoot new Flats when it's dark outside means you have have the hardware (i.e FlatMan, home made Flat Frame Light Box etc.), like this:

http://www.themcdonalds.net/~themcdo/richard/index.php?title=Building_a_Flat_Frame_Light_Box_for_SV80S

For other links search with the phrase :

astronomy "flat frame"

Flats level the image out and compensate for vignetting, especially if your using a Focal Reducer with a larger size (> 0.5")  CDD. That affects your spectral profile a lot, as well as photometry.

Darks will be less an issue because your subtracting the sky spectra from them, which includes any dark noise too.

Much of this work appears to be doable from within the light dome of a city and that is of interest to me.   I am keenly interested in the use of amateur spectroscopy in education and wonder if that is being done now with some standard solution as part of a course is physics or advanced astronomy.

As long as your going after fairly bright objects (say < 60 second exposures), you should be able to do it from city lights. However you definitely need to subtract off the sky spectra to remove natural and man made "Telluric" atmospheric influence.

TTYL..

Milton J. Aupperle