Charlotte Daniels writing for BBC Sky @ Night Magazine
"Heading inside, we were curious to see how the field of view looked in post-processing. Stretching the data confirmed a flat field with pin-sharp stars edge to edge. We could not detect any fringing around the stars either, which further helped our processing as it made balancing and controlling our colours more straightforward. Despite the relatively short exposure times, we were left with images from which we were able to get optimal results as we weren't inhibited by bloated stars or uneven background gradients.
Price-wise, the Sharpstar Z4 is positioned towards established astrophotographers rather than beginners, though it is certainly user-friendly enough to be suitable for any and all imagers, as long as they use APS-C DSLR cameras. Ultimately, the Z4 proved a superbly-made and smart astrograph that contributed to beautifully clean images. It's a sophisticated optical system we would certainly wish to use again and again.
As a sextuplet astrograph, the Sharpstar Z4 comprises three lenses at the front and three at the back of the optical tube assembly. Two of these are extra low dispersion (ED) glass, one positioned at either end of the tube. These are designed to dramatically reduce the effects of chromatic aberration, including star halos. The Z4's optical layout promises and delivers a flat field across a 36mm image circle - equivalent to the APS-C (crop sensor) DSLR or astro cameras used by many astrophotographers. This means that vignette is minimised when coupled with APS-C cameras. Moreover, the sextuplet's built-in flattener removes the expense and complexity of purchasing and correctly spacing a separate flattener.
With an aperture of 100mm, f-ratio of 5.5 and corresponding 550mm focal length, the Z4 also has an excellent profile for deep-sky widefield imaging. This astrograph provides the perfect field of view for many popular nebulae and star clusters, and notable improvements on edge-to-edge image quality for photographers upgrading from budget or intermediate telescopes."
About this product
Model: askar_z4
Part Number: Z4
Optical Bench Test
At FLO we check all SharpStar refractor telescopes on our optical bench before dispatch.
This ensures you can be confident your telescope will, from the outset, have well-figured optics, negligible false colour and spherical aberration, and no astigmatism (the bane of any optical system!). Star shapes will be round, not triangular, oval or egg-shaped!
The SharpStar Z4 Astrograph with 100mm f/5.5 Sextuplet optics will cover up to APS-size sensors without needing an additional reducer or flattener.
A flat-field astrograph telescope perfectly suited to today's dedicated CMOS Imaging Cameras and modern DSLR and Mirrorless cameras.
With an aperture of 100mm and a focal ratio of f/5.5, the six-element design (3-element front lens group + 3-element rear integrated corrector) provides a wide and flat field of view.
The tube ring has a handle on the top, making it easy to carry and assemble. The handle also has an integrated slot for mounting accessories.
The large, sturdy, 3.4” dual-speed focuser has a 1:10 fine adjustment and 360° rotation for precise focusing and angle adjustment.
Includes M82, M68, M54, and M48 adapters. The M48 adapter has an internal thread for 2” astronomy filters.
The long 300mm Vixen-style dovetail plate makes it an easy telescope to balance.
Specifications
Focal ratio: f/5.5
Objective lens: sextuplet fully air-spaced APO (including two ED glasses)
Image circle: 36mm
Back focus: 55mm（from the M48 thread）
Total length: 482mm
Net weight: 4.3kg
Gross weight: 5.6kg（without the aluminum box）
Rear-end thread: M48×0.75 male thread
Tapered adapter:
M86×1-M68×1
M68×1-M54×0.75
M54×0.75-M54×0.75
M54×0.75-M48×0.75（with M48×0.75 filter thread）
What's in the box
- 100mm tube rings
- 300mm Vixen dovetail plate
- Carry handle
- 4-piece photographical adapter
- Instruction manual
Customer reviews
| Average Rating (3 Reviews): | |
13 January 2024 | Frank
The scope was delivered in good time and seems as good as described. It is certainly an excellent looking scope, well made and very versatile when it comes to connection of cameras, etc.
First light has indicated that this is a high performance imaging scope
14 November 2023 | Martin
I wanted a refactor with a focal length of around 500mm for imaging with a ASI533MC pro and an Atik 314L+ pro but didn't want the hassle of field flatteners so this OTA was ideal for my needs.
As the previous reviewer states the sextuplet optics are superb. Round pin-sharp stars right to the edge with no chromatic aberration which makes for easier processing.
The build quality is also excellent. Focusing is smooth and doesn't move when locked in place and can be adjusted for heavier cameras. A simple addition of a locking screw for the dew shield is a nice touch as well.
Overall I'm extremely happy with this OTA and would highly recommend it to anyone looking for high quality optics without the hassle of a field-flattener.
I like the grey livery too. A nice change from white.
29 May 2023 | Niel
What a great telescope!
Attached your camera, filter wheel, OAG, or whatever you have and don't worry about back focus!
This works straight out of the box with awesome field flatness to the edges of the frame, with my ASI 2600MC Pro camera.
My backlash compensation setting on my ASI Air+ with an EAF is set at 30 steps (I have seen videos on other telescopes where the backlash was up to 90 steps). This, to me means that there is minimal backlash on the focusing knob you get on this telescope.
I highly recommend any buyer to consider this product, because you don’t need a reducer or field flattener. This also includes almost all the sizes that you will ever need to attach your dedicated camera gear. (M86-M68-M54-M48). If you don’t want to spend money on an extra filter drawer, this will happily take your 2” filter in the train without extra expense.
I could not be happier with this purchase!
Clear skies!
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