Askar 71F Flat Field Quadruplet APO Refractor - Full Review

[Music] thanks to its obstruction free Optical design a refractor telescope is in theory capable of delivering exceptional image quality but in order to do so it needs to First overcome two major hurdles chromatic and spherical aberations in today's video we are going to see if the new 71f quadruplet refractor from ascar is capable of overcoming these hurdles to become one of the best options in the sub 1,000 bucks price category hi I'm bdan Daman and welcome to another video review Oscar is a brand of Jing sharpstar Optical instrument a well respected Chinese OEM for Mid and high and astronomical telescopes and accessories some of their more popular lineups of telescopes include the two Ed element quadruplet phq series and the triplet Appo series with one Ed element in order to bridge the gap between these sharpstar recently announced the ascar 71f a quadruplet reflector telescope with a single Ed element promising excellent color correction and thanks to a builtin flattener element a very flat field of view as well so when they got in touch with me and asked if I wanted to put it to the test I gratefully said yes here I also want to mention that while they did provide the telescope for the purpose of this review it won't color my opinion about it with this out of the way let's see what's inside the Box the telescope arrived in this unassuming cardboard box inside we find the OTA surrounded by a thick layer of foam and a metal photographic or camera adapter composed of multiple detachable extension rings with this adapter you can attach the camera directly to the draw tube of the focuser this adapter might be required if you want to use a camera with a large sensor and need to take advantage of the full width of the draw tube besides this there is also an 8 mm and a 20 mm plle eyepiece and a 45° erecting prism diagonal as well as some paperwork including a quality control certificate and the telescope's physical specifications looking at the otaa first we see an all metal build painted white with some blue accents for the optical tube and an anodized black focuser assembly at the back the tube rings and the do tail bar are black as well the objective at the front is protected by a retractable duw shield and a metal dust cap both of which are also padded on the inside to avoid scratches the D Shield also has a thumb screw for fixing it in place which is a nice touch the optical tube is held in place by two padded tube rings connected at the bottom and at the top at the top there is a mounting bracket with threaded holes on the sides that also functions as a convenient handlebar on the other side of the tube Rings we find a 23 cm long Dove tail bar with a couple of threaded holes for attaching it to a regular camera tripod this Dove tail bar can slide forward and backward by 7.5 cm to allow for a high flexibility when trying to balance out the otaa on the mount moving at the back of the otaa we find a very nice focuser assembly this is a 2.5 in dual speed rck and pinion focuser with slanted teeth which allows for very smooth and precise adjustments the draw tube features markings both for length and for degrees of rotation which is very nice since this helps a lot to keep constant values during setups even though the end of the draw tube can be rotated by 360° the focuser assembly with the draw tube itself and the focusing gears can like on the sv503 from spon for example this I find to be a bit of a missed opportunity it would have been nice to have this flexibility as well another odd thing is that with the dove tail pushed all the way to the front there is barely room for the screw that secures the draw tube in place this totally contradicts the added flexibility of the long and adjustable duvail bar but other than this the focuser assembly is excellent it's very well built and easy to use also a nice touch are the two finder scope shoes included with the OTA this way you can attach an optical finder a guiding camera and an ASI airbox for example to the otaa the whole otaa is 37 cm long with the DU Shield collapsed and including the 1 and a/4 in adapter making it a very compact refractor telescope because of its weight of 3 Kg including the tube rings and do tailb bar the 71f is on the heavier side for such a small telescope but this is thanks to all the nice glass inside nevertheless you should keep in mind this aspect if you intend on pairing it with a lightweight Mount or a camera tripod overall the build quality of the OTA and the materials used are excellent there is no doubt that this is a well thought out premium telescope by contrast the included accessories are nothing worth writing home about the two plal ipcs are okay they are capable of delivering decently bright and contrast Rich views with good on Center sharpness if you plan on doing more than casual visual observations with this telescope I would recommend upgrading the ipcs to better ones in the long run the included 45° prism is actually pretty decent and doesn't represent a bottleneck for the optical system which is very nice all right so the 71f is shaping up to be an excellent little refractor telescope but how is the optical performance let's start with visual observations first I've tested this telescope over the past month on nights with good seeing conditions from my backyard under bortle for Skies to eliminate any bottlenecks I paired it with a quality 1 and 1/4 in prism diagonal from B Planetarium and as ipcs go with the 9 mm Delight from t view and the SV 215 Zoom ipce from sioni right from the Geto I was greeted by some really nice crisp views of the Moon contrast and sharpness are excellent allowing for very fine details to be visible like the Shadows just below the rims of the craters on the Terminator line the edge of the moon to the space is a high contrast situation one that can easily overwhelm the optical system of lesser refractors resulting in traumatic aberrations but here the 71f managed to master such situations without hiccups resulting in views with no color Distortion whatsoever if there is any color fringing then it's not visible to the naked eye as Saturn starts to become visible in the early morning hours I wanted to test if the 71f could make a decent planetary telescope as well and it clearly can even if the maximum theoretical magnification is only 140x it's enough to enjoy the beautiful ring planet even if right now it sits very low on the horizon and only becomes visible shortly before the sun comes up so while the 71f is a small telescope it is definitely a capable instrument for low and medium power visual observations but its main intended purpose is astrophotography which is why I also did some extensive testing here as well so let's see how it [Music] performed for these tests I paired it with my onstep powered eq5 Mount and the SV 705c color camera from siboni a flattener wasn't necessary since the 71f already has one built in as a fourth lens element at the back of the optical tube additionally I added an UV I a cut filter as well to improve the final result even more for this test I decided to capture the nc7000 also known as the North America nebula capturing was planned and executed in Nina while postprocessing was done with deep Sky stacker and after a couple of test shots I DED in the following settings for the main test 150 lights and 30 darks with an exposure time of 30 seconds and a gain value of 200 out of the 75 minutes of total exposure I've ended up using only 60 minutes now I'm going to start with the image as it basically came out after stacking before I did too much postprocessing on it as I want to first show you the raw performance of the 71f in terms of sharpness chromatic aberration and the flatness of the field of view here is the IM image and if we zoom in a bit we can see the stars appear as sharp and round Points of Light which is great even looking over at the corners we can see that the stars appear as sharp and round circles if you nail the focus then you can be sure that the 71f can deliver Sharp Images across the entire field of you here it's important to note that the sensor size of the SV 705c I used to take this picture is only 11.2x 6.3 mm Pig a bigger fullframe sensor might reveal areas around the edges that aren't perfectly sharp like the rest of the field of view I will test this in a future video once I get my hands on an appropriate camera another aspect to look at is chromatic aberration the lack of color fringing I saw during my visual tests gets confirmed here when looking at this image if we zoom in on some of the brighter Stars we can see that there is only very little color shift bottom right versus top left but this is really nothing worth mentioning the 71f with its four lens element design manages to correct the incoming light very well allowing for nice accurate colors even in high contrast situations after stretching the image to bring out the colors and more details of the nebula the final result looks like [Music] this for 1 hour worth of exposure I believe the 71f was able to gather a great deal of light information a longer exposure time would definitely yield more details and a less grainy image [Music] what sharpstar managed to do here with the Oscar 71f is very interesting when I first got the telescope I wasn't very impressed with it at first glance I thought that while it's nicely built its aperture is too small for it to be able to deliver great views and images of the night sky and boy I was wrong surely there are some minor aspects that can be improved especially with respect to the focuser assembly but overall the 71f is a great little refractor telescope one that is capable of delivering an excellent Optical performance both for visual and astrophotography applications especially with respect to the latter when paired with a good camera and a stable go-to Mount the 71 FK yield spectacular images of the night sky and as far as I can assess its only real limitation is the skill of the one who's using it anyway that's been it I hope you all enjoy this video let me know what you think about the 71f do you agree with me or do you have a different opinion I'm very interested in reading your comments below and while you're at it also get subscribed if you haven't done so already thanks for watching and catch you guys in the next one [Music]

Channel: Bogdan Damian

Views: 2,793

Keywords: Askar 71F Flat Field, Askar 71F review, Askar 71F refractor telescope, Askar 71F astrophotography

Id: jEZqVsjkoxI

Length: 14min 0sec (840 seconds)

Published: Fri Jun 21 2024