Posts Made By: Roland Christen

Beauuutiful!

Rooolando

Fraunhofer refers to the geometrical configuration that eliminates coma. It does not refer to any sort of color correction.

Rolando

Wow, you have captured a huge amount of detail. Great image!

Rolando

What you're really asking is: Does 100% QA on amateur equipment have a future? If the answer is yes, then you will have a reasonable assurance that what you buy will perform to its top level. If the answer is no (and this depends on all your fellow amateurs voting with their pocketbooks), then you will not be assured that the equipment that you buy will perform to the highest level. In that case expect to send stuff back repeatedly until you get something that works properly, and know that whatever you sent back will go to another person and another until it finally finds a home. Chances are that the low level of performance of that returned product will un-inspire that person and they may drop out of the hobby altogether.

Rolando

I have tested the 10"LX200R version of Meade's new "RC" line of SCTs. I woudl not say that it was fully comparable with an RC. It has sphero-chromatism (over and undercorrection at blue-violet and red wavelengths). This defect is approximately twice what you would see in a standard SCT, so for visual and planetary use it is not as good. Bu then neither is an RC particularly good for planetary work. Visually a well made Mak-Cass will walk all over the both of them, as will a Newt with a good mirror.

The Meade design has outstanding field characteristics. The stars are free of coma and astigmatism, so in that regard it is a step ahead of a true RC. It has field curvature (field is not flat) but then so does any RC without a field flattener.

Can you take good astrophotos with this scope? Yes indeed you can. Take a look at the attached M33 image, which I took with the 10" LX200R at F7.5 and an SBIG ST10XE using the AP .75x telecompressor. The scope was mounted on a Mach1 mount. Exposure was limited to about 30 minutes, taken in severe light polluted conditions here at my observatory in the city.

The advantage of this LX200R is that you can mount it on any good GEM and be imaging without having spent a whole lot of money. You can have a first class astrographic outfit of serious aperture for a fraction of what it costs for other types of scopes. Will you have the highest resolution possible for any given aperture? Probably not. Can you do better imaging with other types of scopes? Yes, but it will cost ya.

Rolando

In a side by side test using an STL11K camera my 160F7.5 EDF had somewhat better resolution than my 10" F10 LX200R. The 160EDF produced 2.11 x 2.11 times larger field for a total of 4.5 times larger sky area, so the final image looks more detailed - like the difference between a print taken by a large format view camera and one taken by a 35mm camera.

Under my local seeing conditions the SCT produced stars sizes of 4.5 pixels FWHM at .73 arc sec per pixel (resolution of 3.3 arc sec). At the same time the refractor produced stars of 1.5 pixels FWHM at 1.54 arc sec per pixel (resolution of 2.3 arc sec).

Reasons for this difference might be local seeing conditions that favor a smaller aperture and the central obstruction on the SCT that spreads light into the diffraction rings, thus lowering the FWHM resolution. The 10" aperture does gather more light, so theoretically the signal to noise ratio favors the SCT. However the faster focal ratio of the refractor at F7.5 produces a higher signal for any given exposure time, and the higher resolution of the refractor more than makes up for the theoretical difference in sig/noise of the smaller aperture. In effect, the 160 refractor acted more like a 12" obstructed telescope.

Rolando

The costs of making a refractor goes approximately by the cube of the diameter. Therefore, for any particular performance level, if an 80mm costs $600, then the same performance level in a 100mm will cost (100/80)^3 x $600 = $1171. A 120mm will cost (120/80)^3 x $600 = $2025 and a 130mm will cost (130/80)^3 x 600 = $2562.

Reason for the power of 3 of the cost is that the costs of glass, metal, machining etc goes up by the volume of material used and volume goes up by the 3rd power of diameter. If any scope lies above or below these numbers, it will probably be because the performance is either higher or lower in some fashion. Whether you need higher or lower performance is something you must judge.

Rolando

>>Here's what you can do with an unlimited budget and lots of free time>>

And the truly dark skies of Arizona.

Rolando

Mewlon 250 and Tec 140 in tandem on a Mach1

NO! (please)

Rolando

I combined more images, 50 total of 20 sec each for a better final result.

Rolando