Posts Made By: Carlos E. Hernandez

Bruce,

Thank you for posting your latest image of Mars. I note Sinus Meridiani and Mare Erythraeum in your image. I look forward to your future images.

Carlos

Bruce,

An outstanding image of Mars showing much detail. Sinus Sabaeus and Sinus Meridiani for the "pipe" towards the preceding (left) limb. The dark, rectangular albedo feature past the CM is composed of Margaritifer Sinus, Mare Erythraeum, and Aurorae Sinus. Niliacus Lacus and Mare Acidalium are visible towards the north limb (although partially obscured by the bright North Polar Hood (NPH).

The Celestron 9.25-inch SCT is an excellent planetary instrument, if provided with diffraction-limited optics and properly collimated (a point that can not be stressed enough with SCT owners!).

I look forward to your future images.

Carlos

Bruce and Dan,

Thank you for your kind compliments on my latest observation of Mars. I was impressed with the amount of detail visible over this region of the planet. I expect that we will pick out even more detail in the future as the planet becomes larger in apparent diameter.

I do not mind discussing instruments to be used for lunar and planetary observing as long as the discussion is focused and respectful. The first thing I must state is the "There is no perfect instrument for the Moon and planets." The classical refractor (including Apo's) and long-focus (>f/6-8) Newtonian are considered by many to be "perfect" for use on the Moon and planets, but they too have their disadvantages. The classical refractor is an unobstructed optical system and therefore provides maximum contrast on the Moon and planets. I have had wonderful observing experiences using well made refractors on the Moon and planets in the past. The problem with this design is the expense for apertures greater than 4 inches (10 cm) and the mount required for the long tube. A shorter tube Apo refractor is a solution to the mounting problem but these are very expensive! The long-focus Newtonian (>f/6-8) is another high resolution design for the Moon and planets. This design allows for a smaller diagonal (e.g. central obstruction, <20%) as well as an achromatic image. The problem with this design is similar to the refractor in the stable mount required for it to be used at high magnification. These instruments may be close to perfect but still have their problems as noted. Many amateurs therefore resort to the classical Newtonian (1/4 wave) and on a stable mount this can be a powerful instrument for use on the Moon and planets. The classical Cassegrain reflector (>f/20) is another possibility for use on the Moon and planets. The problem here is the difficulty in producing acceptable primary and secondary for this long-focus design and maintaining collimation. The Schmidt-Cassegrain reflector is also useful for the Moon and planets as evident by the excellent observations posted on this forum using this design. The problem with this design is the size of the secondary (~33-35%) and the variability of surface accuracy by SCT manufacturers. I too own a quality SCT (vintage Celestron 8") which I used for many years. If well figured and collimated they can make good planetary instruments.

This brings me to my current design the Maksutov-Cassegrain which I am fond of. The more I use my instrument for the Moon and planets the more that it impresses me. I am not calling this design perfect as it can become expensive in the larger apertures (as refractors) and the meniscus which holds the secondary can take some time to cool off in temperate climates. Living is South Florida my variation in temperature is not too great and my cooling period is brief (usually < 1 hour). The tube is compact and easy to maneuver. I find the images produced by this design to be the sharpest and of high contrast of many designs that I have used in the past. This may be a personal preference but I am very happy with my instrument.

The best lunar and planetary instrument is the one that the amateur uses regularly on the Moon and planets in order to gain experience in observing these beautiful objects!

Regards,
Carlos

Ron,

A nice image of Mars showing Mare Cimmerium and Mare Tyrrhenum separated by a bright Hesperia. The South Polar Cap (SPC) appears small. I look forward to your future images and observations of Mars.

Carlos

Dave,

An excellent image of the beautiful conjunction of the Moon, Jupiter, and Venus that many of us witnessed. Thank you for sharing it with us all.

Carlos

Doug,

Thank you for sharing your excellent images of AR 10808 with us all. The penumbra of this interesting sunspot group appears very delicate. The group is also very large!

Carlos

Ivan,

Thank you for the compliment on my latest observations of Mars. I look forward to your excellent images of Mars and the rest of the planets as well. The best of luck and may you have clear and steady skies.

Carlos

Jeff,

Thank you for posting your image of Mars. You captured Syrtis Major, Sabaeus Sinus, Meridiani Sinus, and Margaritifer Sinus in your image. Please keep imaging the red planet.

Carlos

Ron,

Thank you for the Spooky Saturn image. The Televue Mars type B filter appears to enhance the South Equatorial Belt (SEB) and South Polar Region. I look forward to your future images.

Carlos

Darlene,

I am glad that you have experienced a good night of Mars observing! When the atmosphere (Earth's) steadies and allows one to see all the delicate albedo features over Mars it is nothing short of a revelation. It becomes difficult to record all the features noted during such a view. I hope that you have many more such observing sessions in the future with Mars. Your 5" APO sounds like a fine planetary instrument.

Carlos