From: "Tim" <tjp314@pacbell.net>

Date: March 20, 2007 11:06:35 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: Saturn March 18th


Jim:


Sorry, I didn't read the caption all the way through.  I note that you

state that you're using a C9.25, but that it needs collimation.  I

highly recommend collimating the scope while you're running Astro

IIDC.  I point the laptop screen toward me at the corrector end of the

scope, and hold the screwdriver (or allen wrench, I can't remember

which it is on the 9.25) in one hand and the control paddle in the

other.  When I tweak the screws, I keep the planet centered with the

paddle.  Until collimation is right on the money.  It goes VERY fast

this way, and the results you'll get will knock your socks flat off. 

The 9.25 is one of the best SCTs alive.


Drift polar alignment works very well using the same technique with

Astro IIDC, only you tweak different screws.


-Tim.


--- In Astro_IIDC@yahoogroups.com, "Tim" <tjp314@...> wrote:


Jim:


I can't remember if you specified anywhere what brand/type color

filters you are using.  If you don't already have a set, you might

want to get dichroic filters, rather than died glass filters.  The

died filters absorb too much of the wavelengths you're interested in,

and have a lot of "leakage" from other wavelengths in the wings.  


I agree with Alan also about the value of trying monochrome for the

luminance, but I would recommend you use green, as there are twice as

many green pixels as red or blue pixels.  Also, depending on the

optics you're shooting with, the best focus might also be in the green

(our eyes are most sensitive to green).  My 6" f/10 Jaegers refractor

does very well at green monochrome with a green filter.  I've tried

monochrome with red and blue separately, but the focus is still too

soft at those wavelengths even if I adjust the focus knob.  So, while

the Jaegers does very well visually on the planets, it doesn't do well

as a planetary color imager.  It does fine on DSOs, though, as the

color abberations aren't objectionable at f/10.


-Tim.


--- In Astro_IIDC@yahoogroups.com, Alan Friedman <alan@> wrote:


Hi jim -


Great to see your two images a year apart sitting next to each other

in  

the files area - the learning curve is paying off.


Saturn is a really tough nut to crack - it demands good seeing

perhaps  

more than any other planetary subject. You can get some help in  

moderate seeing by using the red filtered streams (maybe combined

with  

green) for luminance - the steadiness is always better in red. But

the  

light tradeoff with the red filter means using a much slower

shutter,  

which negates much of the advantage (and of course you don't want to  

bin your luminance data). With my 10" at about f30 even 66ms at full  

gain is very dim and noisy - at 133ms the brightness is acceptable

but  

the noise becomes evident quite quickly processing  a stack of 200  

frames. Really the only way to go is to use unfiltered streams for  

luminance (or a much smaller image scale) - and this requires 6-7/10  

seeing for a good result, I think.


Now the happy news is the Clear Sky Clock forecast for our region  

tonight!!


best -

Alan




On Mar 19, 2007, at 8:31 PM, jimchung2338 wrote:


Hey everyone,


I've given up on trying to get color data from my Unibrain webcam

for  

imaging Saturn and

turned to a filter wheel with my mono Flea. Much better results

in my  

opinion but still

ascending the imaging learning curve.


http://tech.groups.yahoo.com/group/Astro_IIDC/files/Planetary/ 

saturnmar18b copy.jpg


Jim