selline lugu: "Top Ten TALScopes Myths"

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selline lugu: "Top Ten TALScopes Myths"

PostitusPostitas janimi » 18 Märts 2010, 19:24

"Top Ten TALScopes Myths"

# TAL mounts are junk.

False. TAL mounts are built the old fashioned way, with massive solid steel shafts and preloaded ball bearings on the worm and RA shafts. The larger GEM also has preloaded ball bearings on the Declination shaft. The TAL mounts do need adjustment, they have no springs or plastic thrust bearing parts to take up the slack. With periodic adjustment and lubrication, they will last a lifetime.

# The K-Scopes (200K and 150K) are collimated just like an SCT.

False. Adjusting a Klevtsov using the criteria of an SCT or MCT or using the procedures for those scopes has caused awful results, possibly because the corrector has been decentered. The Klevtsov is unique in that it is very unlikely to need any adjustment in the field and that the star test images it produces are different then other scopes. Those who have received their scopes directly from the factory and used them without adjustments have reported great results.

# The TAL-2 needs collimation just like the 150P.

False. The 150P has a parabolic mirror that needs true collimation. The TAL-2 has a spherical mirror that requires periodic alignment only. Spherical systems are far less subject to mis-alignment, don't expect a big change in your TAL-2 but a 150P will show drastic improvement.

# Standard 1.25" eyepieces can't be used on TAL Telescopes.

False. I have used eyepieces made by Celestron, Meade, Intes, University Optics, Gary Russell and others in my TAL-M, TAL-2, TAL-100 and TAL-200K.

# TAL scopes have an awful yellow tint.

False. Most TALScopes have no tint at all, or at worse the tint of light reflected from aluminum. Aluminum tint? Yup, all scopes have a tint of one kind or another, reflections from silver or platinum or when light travels through glass all have a tint. Even protective and reflection prevention coatings add a tint. The TALScopes models having a larger amount of glass, the K-Scopes and the 100R do give the image a faint yellowish tint. Is this awful? Or bad even? Chromatic abberations, caused when bending light by refraction in the glass, usually show up as a blue or violet tint. People use a minus violet or yellow filter to reduce the effect of these abberations. Non-TAL scopes tend to have a blue or violet tint, which actually makes chromatic abberation worse! You might think of the TALScope as having the minus violet filter built-in!

# The large TAL GEM mount is a lot better than the smaller GEM.

False. It is only slightly better. It does have ball bearings on the declination shaft where the smaller mount does not, but the RA shaft and worm bearings are the same size with essentially the same bearings. The smaller GEM has a leverage advantage. The distance from the center of the RA shaft to the attachment point of the OTA is about 1 inch less on the smaller mount. Another factor is that the smaller mount is solid where the larger has hollow body parts. Two disadvantages of the smaller mount are the single small set screw through the arm to prevent it turning on the RA shaft (play) where the larger mount has 2 larger screws; The collar at the top of the column is pinned on and can also develop play.

# All TALScopes need to be tested and "certified".

False. Remember a few years back when car dealers told us that we should buy "undercoating" for our new car that would guarantee rust free operations for years? Then we found out that the cars were already rustproof at the factory and the extra cost treatment actually caused rust?

# TAL mounts cannot be used for astrophotography.

False. Folks are doing all kinds of astrophotography with TAL mounts. You do need a motor drive corrector for running at the sidereal, and lunar rates, the worm backlash adjustment made and a good polar alignment for best results. You can also add a declination motor (MotoDec) and a corrector with MotoDec output (MotoTrak) and Autoguider input along with an Autoguider and you can make long time exposures. But folks have made exposures of up to 16 minutes "blind", with no extra equipment.

# The handwheels (Slow Motion Knobs) are too hard to turn.

False. When the scope is balanced and the clutches properly adjusted the knob is only slightly harder to turn then other mounts. This is actually a terrific feature, because the extra drag is caused by an extra clutch and it is this extra clutch that allows you to simply push the OTA in RA wherever you want it and whenever you want to. You never have to lock or unlock the scope in RA!

# TAL eyepieces and Barlows are of poor quality.

False. Most TAL owners would not part with their 25mm TAL, the 15mm Kellner has proven to produce excellent results when viewing tight galactic and globular clusters. The 7.5mm provides great views of M42 in the TAL-2. Plossl eyepieces have an eye relief of 80% of focal length so Orthos, which have an eye relief of 100% of focal length, are suggested below 15mm if you wear glasses. Tests of the 2x TAL Barlow show that it is as good as the Celestron 2x Ultima or better. I compared the 4x TAL Barlow to the 2x Ultima and found that it produced about the same image degradation at the higher power.
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Liitunud: 22 Jaanuar 2010, 14:36

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