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Posts Made By: James McSheehy

September 7, 2011 05:15 AM Forum: Solar System Observing

Jovian moons naked eye this morning!

Posted By James McSheehy

I went out to get the newspaper this morning and Jupiter was directly overhead. It was a beautiful Colorado morning with temperatures in the fifties telling me that Fall is here. Stopping to look at Jupiter, I noticed how steady the air was and thought that the seeing must be very good because none of the bright stars had any twinkle. Then I saw what appeared to be a bright spike coming out of the west limb of Jupiter. Could it be? Back inside I checked on SB's iPad app, Gas Giants, and yes -- Io and Ganymede are extended off the western limb with Ganymede out the farthest.

This is the first time I've ever "seen" the Jovian moons naked eye. grin

October 6, 2011 11:59 AM Forum: ASTRONOMY

Move over Hubble, ALMA is here

Posted By James McSheehy

The ALMA array in the high Atacama desert of Chile is coming on line, and the first images are nothing short of spectacular. Only 1/4 of the planned 64 antennas are installed, and when it's complete the array will generate images at 10x the spatial resolution of HST. ALMA operates at sub millimeter frequencies with the unique ability to see through dusty regions that are opaque at visible wavelengths.

Jim M.

December 5, 2011 07:24 PM Forum: SCI-FI

Iron Sky -- see you on the far side of the moon

Posted By James McSheehy

Iron Sky is a a low budget ($10M) scifi flick from Finland that has an interesting premise:

Should be out sometime next Spring.

January 25, 2012 09:55 AM Forum: Equipment Talk

Nightscape CCD camera

Posted By James McSheehy

This is by no means an extensive review, but here are a few words on my initial experiences with the Celestron Nightscape CCD camera and its associated software. Nightscape is a color, one-shot camera likely intended for folks who are considering a DSLR for astro imaging. The camera is made in Canada, probably by the same company that manufactures similar products for the big astro resellers. Build quality appears good and the unit has a solid feel with no unfinished edges or cheap hardware. It does not include an AC power adapter and instead has a standard 12V "cigarette lighter" plug and cord. I kluged an adapter and used a 12V power supply to run the camera. Cooling for the sensor is set-point regulated, as much as 20C below ambient.

The sensor is a KAI-10100, ~ ten megapixels, and at 4.75 microns, the small pixels are probably best suited for use at shorter focal lengths (color binning is supported 2x2 and 4x4 for longer FLs). This sensor has the same linear measurements as the KAF-8300 (22 mm diagonal), and the same well depth and dynamic range. Even though it uses an interline transfer chip capable of electronic exposures, the Nightscape has a built-in mechanical shutter that sets exposures from one millisecond to 24 hours. The chamber window is AR coated and unlike typical DSLRs, includes an IR block that doesn't attenuate red emission lines. Celestron states the camera has a "full frame buffer", and some discussions I've seen on the web imply that this memory buffer allows imaging to continue during downloads. If this feature exists, it is not supported in the current AFX software, and I noted a roughly seven-second delay between subs while the camera downloaded data. Perhaps the frame buffer is used to facilitate readout/binning of color data, but I saw no evidence that it speeds up acquisition.

A key selling point emphasized by Celestron is ease of use, and in that regard this product stands out from the crowd. Most low-end cameras ship with "lite" versions of MaximDL and have a steep learning curve when it comes to calibration and processing. For the Nightscape, Celestron commissioned a custom app from Diffraction Limited called AstroFX to run the camera and process images. IMO this software will make a big difference to the typical customer because it assumes the user is not a border-line-OCD astro-geek (cough, PI, cough, Maxim). The software emphasizes results over arrays of obscure functions and a litany of open windows and menus. Some bugs are there -- the software is V1.x and it crashed several times during image acquisition over the two nights I used it. Processing the resulting image and calibration files was simple and straightforward, and I encountered no glitches on that end. Compared to high-end programs, the tools and adjustments are rudimentary, and many processing settings have an "auto" option.

Here is my initial image, M45 taken from a suburban site (SQM 20.4) with a TV85 refractor at f/5.6 and a IDAS LPS-2 filter. The exposure was 20 x 3 min, unguided, and only darks were used for calibration. All data were captured and processed in AstroFX, and the "auto" settings were used for everything except the initial stretch. No, it won't cut it as an APOD submission, but the overall experience was far less involved and time consuming than a similar project using a DSLR and third-party software.

January 28, 2012 05:00 PM Forum: Solar System Observing

One small step for a Lego!

Posted By James McSheehy

A couple of Canadian kids have captured an interesting view of our little blue marble, all for $400!,news-14015.html

February 2, 2012 04:53 PM Forum: ASTRONOMY

Norman W. Edmund 1916-2012 R.I.P.

Posted By James McSheehy

Norman Edmund, founder of Edmund Scientific Co., has passed away. Edmund started the company after WWII and began selling surplus optics, mirror making kits, and eventually small telescopes. He wrote and commissioned an engaging series of books on optics and telescope making that probably influenced thousands of kids to try the hobby.

He was a true icon -- may he rest in peace among the stars he loved.

April 9, 2012 07:09 AM Forum: Meade

Field flattener for Meade ACF

Posted By James McSheehy

I was perusing the new book from Willman Bell, Telescopes Eyepieces Astrographs, and see the authors have proposed a fairly simple field flattener that would improve Meade's ACF design for astrophotography. The corrector is a cemented doublet using N-SK5 and N-K5 glasses. It produces a coma and astigmatism free flat field about one degree in diameter, but with ~ 25 micron spot size.

April 13, 2012 02:27 PM Forum: Meade

Details on Meade's LX800 ACF design

Posted By James McSheehy

An appendix in the user manual for Meade's new LX800 ACF scopes offers interesting details on the optical design:

"In the ACF design shown above, light enters from the right, passes through a thin lens with 2-sided aspheric correction (“correcting plate”), proceeds to a spherical primary mirror, and then to a hyperbolic secondary mirror."

This is the first time I've seen any mention of a two-sided figure on the corrector plate, and the first confirmation that the figure used on the secondary mirror is a hyperbola. The two-sided corrector must be made using a different process than the single-side figure used on a traditional Schmidt corrector.

Page 55 in:

April 30, 2012 06:44 PM Forum: Refractors

Re: Oil or Air spaced APO lens

Posted By James McSheehy

At the risk of beating that dead ol' horse 8)

Oil spaced:
Two coated surfaces that can degrade or spot
No critical spacers
Less subject to mechanical shock
Modern "oils" are not oils and are extremely stable

Air spaced:
Six coated surfaces that can degrade or spot
Two critical spacing dimensions
Can be decentered/misaligned by mechanical shocks
Poor thermal stabilization in sizes above 20 cm

Air spaced offers the ultimate in correction (more degrees of freedom) if the designer is up to the task and the lens is executed to close tolerances. I decided on an oil-spaced lens because there is a quality source here in the USA, and the only available air-spaced apos in that size come from a factory in Russia, thousands of miles away.

May 1, 2012 05:14 AM Forum: Mounts

Remember the first time you heard the word Hyundai

Posted By James McSheehy

More pictures (apparently from tests of a prototype):

These mounts appear to have serious engineering horsepower behind them compared to the cat-grease rabble from China. Yes, new and unproven, but worth watching.