From: Milton Aupperle <milton@outcastsoft.com>

Date: February 5, 2010 7:08:20 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Damian Peach

Hi Tim;

On 5-Feb-10, at 6:24 PM, doobisary wrote:

Antonio Cidadao of Portugal used to use an AO2 for keeping planets on chip with his ST5 camera.  That device has been out of production for many years, though, unfortunately.

I have an AO-7 with my SBIG ST2000XM.  It's great for "guiding" DSO images, but it (and devices by Orion and Starlight Xpress) can't be used for planetary for a couple reasons.  First, they work at very slow rates (the AO2 did corrections many times/second).  Second, they get their pointing information from an off-axis chip in the camera (SBIG) or a guide camera (Starlight Xpress, via an OAG).

According to the specs, the Orion one runs at up to 40 fps (40 hz), assuming the guide star is bright enough to support that.

I suspect with something like Jupiter, you could lock onto a moon at Mag 4 to 6 pretty easy and run it at 15 to 30 fps. But is that enough to compensate for turbulence?

The main issue is that the guide star and the target may be 10's or arc minutes apart.

I've been curious whether anyone has tried planetary imaging (of faint planets like Uranus and Neptune, in particular) using an image intensifier and really short exposures/high frame rates, to freeze the seeing that would otherwise be crippling with the long exposures required (shortest exposure I was able to use on Uranus with my 12.5" Cass was half a second).

The problem is image intensifiers are really really noisy. So any faint subtle features likely will likely get lost in the noise. You might need to stack thousands of frames before you built up a decent average.

TTYL..

Milton Aupperle