Archives

All posts by Star Hunter

I decided to write my impressions of the 685 nm IR-pass filter from Svbony. I bought it in January 2021. The main task is to shoot the Moon with a monochrome camera, since moving to the near infrared range allows you to slightly reduce turbulence when shooting. With a very stable atmosphere, you can set a green filter, while the resolution will be higher than in the red and IR ranges, however, such an atmosphere in combination with the visibility of the Moon is rare, and I get 99% of the shooting of the Moon in monochrome just with red or IR-pass filter. Yes, I also have an 850 nm IR-pass filter from ZWO, but with it the resolution drops noticeably, and the Sony imx178m sensor in my monochrome astronomical camera (QHY5III178m) is not very sensitive in the IR range.

The 685nm filter can be used quite successfully with high infrared sensitivity color sensors, especially Sony imx462 or imx464 sensors. Another possible application of IR-pass filters is flare suppression when shooting galaxies, since LEDs in IR shine much much weaker than in the visible range.

The 685 nm filter may be of interest for shooting Uranus and Neptune at large apertures (from 250-300 mm) due to the higher contrast of atmospheric details.

Of course, it makes no sense to use IR-pass filters for visual observations, since the eye sees very poorly in this range. Moreover, such filters are forbidden to be used when observing the Sun in order to avoid deterioration or loss of vision.

Note that mirror or mirror-lens telescopes are best suited for NIR imaging as they have little or no chromatism. The Barlow lens in the IR range can also add chromatism, which will negatively affect the sharpness of the image. In any case, my tests on mirror-lens telescopes, ED refractors and apochromats, as well as with a 2x Barlow lens, did not reveal a noticeable drop in sharpness due to uncorrected chromatism. For shooting with an achromatic refractor and a monochrome camera, you can try a red or green CCD filter – they do not pass the infrared range, as well as the blue region with chromatism.

The Svbony SV183 IR Pass 685 nm filter is made in 1.25 inch format, but there is also a 2 inch version on sale. From the outside, the surface of the filter seems to be a mirror-like feature of interference filters, but a bright light bulb looks dark red in the light. At the same time, absorbing IR-pass filters look black from the outside. However, interference filters have higher light transmission than absorption filters, and can also have a sharper cutoff of the spectral range.

The filter Svbony SV183 IR Pass 685 nm 1.25″ is supplied in a cardboard box with a plastic box inside. I have no complaints about the quality of making – the surfaces are clean, without cracks, scratches and scuffs.
Читать далее (Read more) > > >

The Sun, November 4, 2022, 10:07

The Sun, November 4, 2022, 10:07

Equipment:
-Coronado PST H-alpha 40 mm telescope
-Sky-Watcher AZ-GTi mount
-Deepsky IR-cut filter
-QHY5III178m camera.
Stacking of 250 frames.

The Sun, November 4, 2022, 10:14

The Sun, November 4, 2022, 10:14

Equipment:
-Levenhuk Ra R66 ED Doublet Black telescope
-Sky-Watcher AZ-GTi mount
-Lacerta Herschel prism
-Baader Solar Continuum filter
-ND3 filter
-QHY5III178m camera.
Stacking of 250 frames.

The Sun, November 4, 2022, 10:18

The Sun, November 4, 2022, 10:18

Equipment:
-Levenhuk Ra R66 ED Doublet Black telescope
-Sky-Watcher AZ-GTi mount
-Lacerta Herschel prism
-Antlia CaK 3nm 393.3nm filter
-GSO polarizing filter
-QHY5III178m camera.
Stacking of 250 frames.

Ко мне на тест попал телескоп Meade Polaris 127 ММ. В этом телескопе для формирования изображения используется светосильное сферическое зеркало диаметром 127 мм, а также линзовый корректор, установленный в передней части трубки фокусера и компенсирующий сферическую аберрацию главного зеркала. При это фокусное расстояние телескопа увеличивается до 1000 мм. Так что технически это катадиоптрический телескоп, выполненный по системе Ньютона (в простонародье “ньютон с корректором”). Судя по всему, это обновленная версия телескопа – ранее с этой маркировкой в продаже был телескоп с четырьмя литыми растяжками диагонального зеркала. В новой версии три растяжки в виде металлических шпилек и другая монтировка.

Meade Polaris 127 MM

Meade Polaris 127 MM

Телескоп поставляется в большой картонной коробке размерами 78 х 38 х 26 см и массой 12 кг. Маркировка на коробке – Meade Polaris 127EQ.
Читать далее (Read more) > > >