Astromart

October 5, 2005 06:09 AM Forum: CCD Imaging and Processing/Solar System

Gomer Sinus

Now that is Mars the way I like to see it processed! No ringing at the edges or overprocessing. Very nice indeed. (I need your seeing here!!)

Rolandio

October 7, 2005 10:44 PM Forum: CCD Imaging and Processing/Deep Sky

IC405 Flaming Star in Auriga -- Revisited

Posted By Roland Christen

That's one of the finest renditions of this object that I have seen. Congrats.

Rolando

October 11, 2005 04:59 PM Forum: CCD Imaging and Processing/Deep Sky

M31 in hazy skies

Posted By Roland Christen

This one is half size. Same data as above.

Roland Christen

October 12, 2005 02:43 PM Forum: Equipment Talk

Pointing accuracy: Titan vs AP1200 or Paramount

Posted By Roland Christen

Most of your pointing in-accuracy is due to the SCT tube assembly, not the mount. C14 tubes have large mechanical flexure which greatly affects the pointing and also the tracking accuracy. In order for you to use any of the mentioned mounts, including your original Titan, you will need a compensating software package like T-Point or MaxPoint. That is really the only way to achieve high pointing accuracy with any mount when you use a large SCT tube assembly.

Roland Christen

October 12, 2005 03:38 PM Forum: Refractors

Are Orion ED lenses machine made?

Posted By Roland Christen

For small doublet lenses up to 100mm, no human contact is needed to achive fairly high corrections. In larger sizes, no human contact is needed if the specs allow a wide range of spherical corrections. Color correction is only a function of the glass materials used, and would not need any human interference either.

To achieve true zero color for wide wavelength applications (eg. imaging), then some matching of glass will be required by a master optician. However, this will be virtually impossible in a doublet design.

Roland Christen

October 17, 2005 07:44 PM Forum: Equipment Talk

Refractor Optics Question

Posted By Roland Christen

>>However, 1/4 to 1/3 turn on either side of the focus shows different diffraction rings- the outside focus image appears to be bigger and brighter compared to the diffraction rings from the inside of focus.>>

Yes, this is correct. They should be different. They will never be the same in a refractor unless it is extremely long focal length, greater then F15.

>I recalled reading somewhere that they should be identical in good optics- or was I wrong?>

Yes, you will read this all the time in optics texts, but it is based on old information about refractors (>F15 focal lengths) and is really only valid for pure reflectors. Most optics texts have never been revised to reflect the reality of the new fast doublet and triplet apos.

You can get similar inside/outside patterns if you use a green filter because that is the place where modern lenses are nulled. Slight differences in focal position of the other colors and sphero-chromatism at short and long wavelengths will make the ring pattern look different on either side of focus (the bullseye ring pattern is known as Fresnel rings). I realize that this looks odd for something very expensive like a fast apo, but it is quite normal and in reality has no effect on what you really want - sharp images at focus.

Roland Christen

October 18, 2005 09:03 PM Forum: CCD Imaging and Processing/Solar System