Askar has introduced a brand-new refractive astrograph, the second long-focal-ratio astrograph from the PHQ- family.
What is an Astrograph?
An astrograph is a specialized telescope designed specifically for astrophotography and is not well suited for visual observing or making general astronomical observations.
Taking images of the night sky is a specialized use-case for telescopes. As we often say in this hobby, ‘There is no such thing as the perfect telescope.’ We say that because there are so many different objects to look at in space and each one has different requirements to see it.
Dim, large things like galaxies and nebulae require big apertures, a wide field with lower magnifications which means short focal lengths.
Bright small things like planets don’t need aperture because they are brighter, instead we want more detail, higher magnifications and longer focal lengths.
What’s more, telescopes with cameras attached work differently than one designed for use by a human eyeball. This is why you see so many accessories like field-flatteners, telecompressors, filters, etc for an imaging telescope you don’t see for visual observers.
Cameras can also do things an human eye cannot, most notably collect photons over a long time to compensate for aperture size, light pollution, etc.
These differences mean we can’t just buy one telescope to do all things and astrographs are a special telescope designed to do one thing and do it well: take pictures of the night sky.
The Askar Astrographs are Among the Best and the 80PHQ is the Newest
The 80PHQ inherits the optical design of the PHQ- family, it has a so-called 3+1 quadruplet lens structure which contains two pieces of ED glass that can effectively reduce chromatic aberration and enhance clarity and sharpness.
A quadruplet refers to the number of pieces of optical glass. In this case, there are four elements: three make up the color-corrected triplet objective lens followed by a curved corrector plate placed further down the tube, closer to the focuser.
This corrector plate is important because it ‘flattens the field’ meaning all rays coming through the lens are not distorted or curved. This effect is especially noticeable in stars at the edge of a field of view viewed through a short focal length refractor: without a flattener, stars appear deformed and stretched towards the edges of an image. A field flattener takes the bending rays of light at the edge of the lens and straightens them out, leaving nice pinpoints of stars at the edge.
A color-corrected triplet means that all curves in the pieces of glass (three of them in this case), are such that all colors of light come to a focus at the same distance. A non-color corrected telescope would show little rainbows in the stars as all colors focus at different points. You could focus on blue light, for example, but yellow, green and red would be out of focus. This is called chromatic aberration and is common is incorrected refractors.
What all this means is that all astrographs from PHQ- family come with an integrated lens combination that flattens the field and corrects for color aberrations. Rather than simply placing three major lenses and a corrector together in a line. This system is set, you can’t remove the corrector plate for example and have the telescope work. It’s all one integrated optical tube and the optical system cannot perform without any of these lenses in place.
For astrophotography, this design leads to a more rational lens arrangement with better vignette control and superior image quality. The focal ratio of 80PHQ is f/7.5. It’s a “long” focal-ratio astrograph compared with other counterparts from Askar. It’s a little bit longer even compared with 107PHQ which is f/7 in focal ratio.
One very big advantage to this design is that you do not need to correct for back focus, a daunting task to beginners and experienced astrophotographers alike. Because the corrector is integrated into the design of the telescope, one focus is all you need to know.
There is a 3" rack-and-pinion focuser on the rear end of the telescope. It’s a smooth focusing unit with dual-speed adjustment. 80PHQ’s rotator is marked with precise graduation which makes your previous subjective adjustment more accurate. The astrograph also comes with four adapter rings for a variety of cameras, and even an eyepiece holder adapter.
A pair of clamshell-style CNC-manufactured black tube rings tightly hold the OTA. So you can just turn two locking screws to loosen or tighten the tube rings simplifying the setup by avoiding the frequent use of small tools like Allen wrenches or socket head screws.
The bright green dust cap, handle, locking screws, focusing knob and decorative rings add more energy and vitality to the otherwise deep and profound astrograph. White and green is the classic combination for PHQ series.
The 80PHQ or the 107PHQ?
Why an 80mm telescope if there is a 107? How different can they be?
Indeed, 170PHQ and 80PHQ are similar in many aspects partially because they are both the newly-developed refractive astrographs from the same family. However even if they all have excellent mechanical design and a sophisticated optical system, there are noticeable differences between these two.
At the first glance, Askar 80PHQ is much more compact. 107PHQ is 603mm in length and weighs 5.7kg whereas 80PHQ is 448mm in length and weighs 3.9kg. So for smaller equatorial mounts, the lighter weight will be welcome. This also means more portability for remote observing. Aperture is not as important in astrophotography as in visual use. Many times the portability advantage far outweighs any light collecting loss because of the smaller diameter, one can adjust exposure times to compensate.
Maximum accessory connection (with the focuser fully retreated)：
115mm（from the base of M48×0.75 male thread)
135mm（from the base of M54×0.75 male thread）
155mm（from the base of M68×1male thread）
168.5mm（from the base of M76×1 male thread）
148mm（from the end of 2" eyepiece holder）
Total length：450mm（including 1.25" eyepiece holder as dew shield contracted）
540mm（including 1.25" eyepiece holder as dew shield fully stretched）
480mm（including the 4-piece adapter as dew shield contracted）
570mm（including the 4-piece adapter as dew shield fully stretched）
Rear-end thread type：M76×1-M68×1
M54×0.75-M48×0.75（M48×0.75 filter thread inside）
Corrected Image Circle
Pair of tube rings
Askar 300mm Vixen dovetail plate
4-piece photographic adapters
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