From: Milton Aupperle <milton@outcastsoft.com>

Date: December 10, 2011 11:25:56 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] ISS Lunar Transit over Toronto ..... SUCCESS!

Without knowing more, that would be my guess too.

You could use Dumpster to look at the actual time stamps of each frame, but that's sort of involved to describe as your looking at different internal atom lists to determine it.

Frame drops have has gotten a lot worse with Spotlight and some of Apples other processes like Time Machine or Cloud services at the same time.

What I do to minimize it is makes sure that the folder I record to is added to the "Privacy" tab of spotlight so that it never indexes that folder (well lat least in theory it doesn't'). I also turn off any software updates and usually turn off networking too.

On older Macs, your also running at near the limits of what IDE or EIDE can reliably sustain writing to disk when recording at 30+ megabytes per second.

Lastly you were not running at 24 fps.

Running at 24 fps 1600x1200 in 8 bit is 43.95 megabytes of data streamed to disk.  FireWire 400 can not push more than 31.25 megabytes across the wire (8000 packets per second and each packet is a maximum of 4 kilobytes for Iso transfers). The best you would get is 17.07 fps and that is under ideal conditions where each packet is completely filled with 4096 bytes of data. That generally does not happen.

FireWire 800 doubles this number  and also is a bit more efficient in how data is moved, so were closer to the 75+ megabytes per second range . FireWire 3200 would be amazing and would be in the ESATA range for data transfers (i.e. 300+ megabytes per second)  but that's dead.

Too bad Apple won't support USB 3, as the PGR USB 3 cameras are now out and we should be able to support them.

HTH..

Milton Aupperle

On 10-Dec-11, at 10:48 AM, Stephen W. Ramsden wrote:

dropped frames.  happens on all my solar transits.

Stephen W. Ramsden

www.solarastronomy.org

On Dec 10, 2011, at 12:44 PM, Jim Chung <jim_chung@sunshine.net> wrote:

Thanks Milton! Cal Sky predicted a transit time of 0.85 seconds but

it seems more like 0.5 s. Here's a question. The ISS images seem to

be generally evenly spaced as one would expect but there are 2

sizeable gaps. Any idea why?

regards,

Jim