From: Milton Aupperle <milton@outcastsoft.com>

Date: November 8, 2010 9:28:55 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Full Light Curves for pulsating variable star CY AQR

Hi Jim;

On 8-Nov-10, at 6:42 AM, Jim Chung wrote:

Milton,

This is really impressive stuff and makes me want to try my hand at it

before participating in the exoplanet search community.

Thanks for the kind words.

I spent more time researching the target star than imaging it and processing the data with Astro IIDC :)

I finally found a decent web site that lists variable (RR Lyrae type) stars so that I can rather easily decide if it's do able or not:

http://dbrr.ast.obs-mip.fr/

Than you have to check the star in your planetarium software and see if you have good comparison stars and a decent guide star (Mag 9 or brighter in my case).

As most nights the sky background is too bright to image the fainter fuzzies (Mag 10 for galaxies appears to be my limit), I'll be likely doing more Photometry (variable stars, asteroids etc.) over the next month or two.

I'll have to put together my notes and conclusions on doing the exceedingly demanding "art" of exoplanet imaging. The biggest issues are consistent turbulence, mount tracking / guiding and  cooling the CCD down to reduce thermal variability.

Basically your need to keep the star exactly on the same clump of pixels and have < 1 pixel of motion off of it for the duration of the event. That means perfect polar alignment to prevent field rotation, accurate guiding / tracking and no mirror flop with an external source.

Form my skies, it's pretty much impossible for me to detect a 1% change reliably as the turbulence and the HEQ5 mount add too much random variability to the stars position. An Adaptive Optics unit to remove some the erratic rapid motion likely would help, assuming one has a bright enough guide star to run at say 7.5 fps or faster. But I'd need a bigger scope for that (at least a  C11 size) and that means a bigger mount too.

HTH..

Milton Aupperle