From: Mark Gaffney <markgaffney@me.com>

Date: December 8, 2009 8:54:57 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] cold weather..


Milton, 

I`ve had a look at those sites & bookmarked the last one (Astropixels). I hope I remember I have it when the time is ripe. The steps involve using Photoshop which I have & seem quite specific. Some of the info on the other ones is very technical but I`ll make a note for myself of what date you sent them for future reference. (Much good this making a note does me sometimes!). I imagine it`ll be 2-3 months into next year before I can afford the Astrodon E-series filters but if I can get a grounding in B/W images in the meantime & master autoguiding to some extent I`ll be going well!


Mark. 

On 09/12/2009, at 1:19 PM, Milton Aupperle wrote:

Mark;

On 8-Dec-09, at 5:53 PM, Mark Gaffney wrote:

> Hi Milton,
> I`ve got a lemonade & some ice-blocks here now! Talk about two
> different extremes of weather at different parts of the globe! Your
> Crab Nebula looks a little better than the previous one with the
> Grasshopper! (although I don`t have them here to compare side to
> side). Thanks for the details of exposures.

That won't help you though.

Those exposure times are what works for the Grasshopper EXHad CCD with
my Astro Done E-Series filter and a Hutech IDAS LPR. Without the LPR
filter, I need to use a different ratio of RGB exposures. With a
different set of filters or a different CCD you would need different
RGB exposure times.

You have to calibrate the camera and filters using a star that
approximates the sun (a G2V star) to get your balances. That's what I
have done and know that without the LPR I need to use ratios of L 1.0
R 1.7 G 1.0 B 0.85 and with my Hutech IDAs filter I need to use L 1.0
R 1.5 G 1.0 B 0.67.

These sites

http://www.astropix.com/HTML/I_ASTROP/CUSTOMWB.HTM

http://www.astrosurf.com/~buil/us/cmy/cmy.htm

http://www.astropixels.co.uk/LRGB_primer.htm

covers the basics.

> They`re beginning to make more sense to me due to a little more
> experience (though not really practical) with these things. I`m
> ordering an Atik FIRA 1 filter wheel on Christmas eve but it`ll be a
> while before I can get the Astrodon`s. With a bit of luck I`ll be
> able to take some B/W shots of one DSO or another this summer. It`d
> be nice to get some results of the moon to compare favourably with
> Howard`s using the Scorpion though. He seems to be the yard-
> stick..i.e. the other person posting moon images on the group with
> this camera. I can`t work out whether I`ve got some setting wrong
> but my fine focus whilst OK with the Flea 2 is lacking with the
> Scorpion...

I doubt it's a camera issue.

More than likely you have turbulence and aren't recognizing it as
such. I have some nights where even with a 25 mm eyepiece, I can't
achieve sharp focus visually with my eyes. With the camera it's a
blurry mess. It took me about 12 months before I finally had a night
of clear skies with very good seeing before I knew the difference
between the two.

Milton J. Aupperle