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  • ●  First Light Report of ATM OTA Equipped with 100mm F12 iStar Optical Achromatic

        December 2013, by Stanislas Maximovich, France

    The last events about your 100mm lens F12. I did the tube construction during last saturday with a simple chimney smoke steel pipe mat black painted both side, 130mm diameter. No internal baffles. I recuperate the 2 ends of the previous tube for the lens cell installing and for the crayford ring installing. Tube rings and 50mm finder too. Alignment was simple with a collimated laser beam. Remains the collimation of the lens on sky. The first light was impressive. I pointed Algenib of m2.0 magnitude and observed the diffraction patterns of the star, intra, extra focus, at focus. Intra-extra pattern looked like a semi apo figure of same image. At focus until 300x magnification, the blue halo, rather a violet halo was very discreet and confidential with a clear first diffraction ring slightly of miscollimation (to be retouched with a 1/10th turn screw at the cell). Surprisingly the figure at 300x was clear without blurring (the vixen 102 didn't go beyond 270x). This could mean high acurate optical surfaces level. Sky conditions were height of Algenib around 55°, seeing 3-4/5 Danjon scale, transparency 6/6, windy.

    I had a look on Uranus with 240x, the disk was knife-edge limb, The south pole of the planet seemed clearer, but difficult to say firmly. I had views of Jupiter, being only 15° above the horizon. In spite of the elevation I noted seeing "holes" where seeing level reached on few seconds period 3-4/5. Without filtering with 133x magnification the disk color was whitish (as with apo like ED design), the limb was surrounded by a thin violet halo of narrow width, almost absent when at focus.

    GRS was near the limb, it appears alone with a narrow gap from the tropical band. Color was without doubt deep orange color. Banding was very clear with so many festoons and nodes in EZ when seeing was at its best. Comparing these results with the TAL 100 and the Vixen 100, I would say the present 100mm is more performing, more acurate, more neutral for the overall coloring of the planet Jupiter. It reminds me the Unitron quality with less chromatic aberration.

    About the quality levels, the TAL 100 is a L/4-5 (coloring yellowish), the Vixen L/5-6 (coloring yellowish) and the iStar probably >L/6 (coloring whitish). These are only numbers coming from comparisons (the TAL and the Vixen being measured).

    I would like to complete the tests with more time on Jupiter, on stars (for a complete star test), on Venus to see what can be performed on clouding features in blue, green and red channels (The TAL performed), on Mars too same channels.

    As a first conclusion in spite of the short period of this first light, this is promising, it seems, the lens doublet seems to be an accurate one with extra low CA amount. I asked a F10 doublet, I got a F12 one. I think we can leave the order as it is with regards to these results. I will do a report with the use of the OTA nextl with a certain period of observation on planets.

     

    My best regards.

     

    Stanislas

     

    2013/12/19 stanislas maksymowicz   < stsma78@gmail.com >

     

  • ●  228mm F/9 Custom Made H-Alpha R30 Doublet as Appeared in Astrosurf French Magazine

         November 2013, Astroturf Magazine

  • ●  Testing of a new 150mm F15 Achromat in homemade OTA

        by Rutilus (CN  member)

    At long last my observatory is now clear of items that I have been storing for someone, and for the past few weeks I have been able to test my 6inch f/15. The lens is a 150mm f/15 Classic Achromatic from iStar Optical. I went for the lens only as the scope needed to be made to some special requirements. Basically the front tube and lens retracts into the rear tube section which reduces the length to a little over 4 feet when the scope is not in use.

    Due to an accident in the workshop, (i.e. yours truly knock a plank of wood over and smashed the baffle system) I have been using the scope with no baffles in place. I also constructed this scope for Lunar, planetary and double star observing. For DSO I use my C9.25.

     

    Star Test: Testing shows the lens to be a very well corrected visual objective. Nothing unusual or out of place detected in the star test. Bright stars such as Vega and Altair show a small but noticeable amount of C.A. around the star. The C.A. is certainly a lot less than that seen with my 6" f/8 Achromat. All-in-all, the lens behaves much as I expected an f/15 to behave. i.e. there is C.A. but it is a small amount and not a problem for me.

     

    Lunar: The lens has given me some of the best lunar views I have ever had. Detail is exceedingly crisp and sharp. At powers above 100x, you can see a very tiny sliver of blue fringing running along the limb.

    What has struck me the most with the lens is the contrast it produces, it is excellent. The moon appears on a jet black background, different coloration hues are easily visible on the Lunar surface. Last night I was observing Plato, with six of the craterlets/spotmarkings easily visible, the crater floor was filled with albedo markings.

     

    Double-Stars: Well, where do you start. The lens is a first class double star splitter. At powers from 200 to 500x it is well on top of its game, producing an excellent spurious diskand faint first diffraction ring. It is very good at detecting close binary stars with different magnitude differences. Each time I have observed 99 Her, the fainter companion instantly shows itself , even in poor seeing conditions I have had no problems seeing it.

     

    Jupiter: I have been getting quite a few early morning observations before going to work. First off, there is C.A visible around the disk, not a large amount but it is there. With the planet I have tried using a yellow filter, blue 80A, Semi-Apo and contrast booster filter, but I prefer the un-filtered view. Visible details on the planet have been excellent, with much detail visible within the belts, the GRS showed darker detail within the spot. Festoons are nicely seen, as well as small white ovals in the southern region of the planet. The North and South polar regions have shown clear mottling patterns. When the seeing conditions are good the whole planet erupts into a wealth of detail, I don't think I would be able draw to it all as there is just so much to see.

     

    I have used aperture masks of 127mm and 100mm on the scope and had very good results. With the 4 inch mask, the views of Jupiter easily match the best views I had of the planet with my Tak TSA-102. Really looking forward to observing Mars with this scope.

    The scope cost me £580 GBP to build and I have been really pleased by the views it has delivered. Now I really must get those baffles fitted to the tube. Here it is in the observatory.

     

     

     

     

    Read the whole thread here.

  • ●  Two sets of iStar Optical 127mm F8 Achromatic Doublets in All Metal Cell

        May 2013 (email reply by L-3 Communications, Warrior Systems Group, EOTech)

    Ales,

     

    Mike did a great job already.  I received 2 lenses yesterday.  We started using them in our holography production today.  The performance looks very good.  We may order another 2 lenses very soon.

     

    Thanks, Brian

  • ●  Test of iStar Optical 150mm F15 achromatic refractor

        by Bartolomeo Montrucchio, Italy

     

     

     

     

    Source >

  • ●  iStar Optical 150 F 5 Binocular ATM project

        by Bill Faatz, Sky and Telescope, April 2013 issue

  • ●  iStar Optical 150mm F/8 R30 versus Meade

        January 2013, by Victor, Canada

    I can just say: Oh boy, oh boy it is amazing view that I saw couple of nights ago through my iStar 6" R30! Finally theYukon had a warmer weather, just about -4 Celsius. I took the scope outside well before dusk. A little ice-dew shattered on the tube and the 2" diagonal. but when it became dark, I was ready for observing my favorite Jupiter. I can tell that the planet's stripes were amazing in my 16mm Zeiss eyepiece (75x)! I was so excited about the view that I started to push the magnification quickly and gradually to 120x, then to 200x, then even to 300x!

    Well, far better images than in my Meade. In other words, they are not even comparable on planets. I have actually never seen the Jupiter so crisp and detail in my Meade refractor compared to my new r30 anastigmatic lens! In addition, the sky was partially cloudy, so that the Jupiter got faint frequently because of the high atmosphere cirrus clouds passing by! Can you imagine what this scope can do in an actually excellent night? The same night I tried to put in my 5x powermate in the focuser then I slid my 25 mm orthoscopic eyepiece in it. The image of the planet did not fell apart, however the sky conditions limited my useful magnification to 250x.

    I am very satisfied with this lens. In addition, using the scope in warmer temperature yielded way less colouring than in minus 40 degrees temperature. I did not see ANY false colour using the 16 mm eyepiece. When I pushed the magnification higher, I started to notice some faint violet colour around Jupiter but it was so insignificant and faint that it did not even bother me at all.

     

    Victor

     

    Read more here

  • ●  Making of ATM-style scope with iStar 150mm F/15 achromatic doublet

        by Eden Orion, Israel

    I've got the lens after a Skype conversation and payment. The lens was sent immediately and after less than two weeks it was at my post office.

     Making the telescope was a great job, some obstacles, but not too much. Finally it was tome to set the exact place of the lens. I've checked it with a first quarter Moon. The first view was fantastic. Very sharp, nice shadows. Than after the lens was set in place and a collimation process was made, I've checked it again.

    It was a Full Moon night and i did not hope to see a lot. but as I've pointed the scope to the moon my jaws dropped! NEVER in my life I was able to see so much details in a full Moon! I was so in shock than a month later I've took the picture enclosed. I was with one of my friends Mr. Adi Cohen which is one of the most professional photographers in the country and also a deep sky photographer. He was also amazed by the contrast and lack of false color that we got.

    You might see some slight color on the edge of the Moon, we both not sure that this is chromatic aberration, since it is more yellow that all other colors.

     

    Eden Orion, Israel

     

    (Note from iStar Optical: yes, the slight yellowish halo is indeed the false color / chromatic aberration. It is indeed very low and practically insignificant especially when compared to other brands of scopes. We are proud to offer a very inexpensive Classic doublets with truly excellent resolution and extremely low level of chromatic aberration).

     

    See the entire build here.

  • ●  iStar Optical 150mm clear aperture F/8 Achromatic Doublet - First light report

        February 2012, by Jon Scheuler

    Just had 1st light of crescent moon and Jupiter with 4 moons strung vertically in near center alignment using a 150MM F8 iStar Achromat i installed as a replacement lens on an existing tube assembly - original manuf. unknown. This was impressive. I need to cut off an inch or so of the tube to get the focal range I want, but this was the best I’ve seen yet. Thanks for the care in the creation of the lens, it shows. I'll include some picks. I made the adapter ring (counter-cell) out of a 9" diameter-3" thick section of 6061 aluminum bar stock - plunge cut a plug from the center and bored to the sizes required from there, only a couple of hours on the lathe after the center plug was cut out, the adapter ring almost does the cell justice - it will look as good as the functionality is when it's completed. The best use I've had yet of my shop, this project is turning out Awesome.

    I'm sort of excited, still shivering from the cold, but extremely pleased of the image quality - I was able to step down to about 10 mm on a 9 to 18mm Zoom lens, an also had 1st light on the 2" lens I've started to collect for this scope. I live in the middle of Kansas City Kansas, with street light and an incoming front tonight, and was viewing through the trees that surround my house, If I ever slow down enough from the excitement of the clarity of the images, I'll sleep with the pleasurable feeling of extreme contentment. Thanks again, this is going to be a very nice telescope.

  • ●  iStar Optical 5" F8 Achromat

        January 2012, by  Dave Gibbons

    PART I (8th January 2012)

     

    iStar 5” refractor, an honest review.

       Some of you may remember I purchased an iStar5” f8 Achomat objective last winter and spent a little while constructing a scope machining various bits and modifying a meade ar5 tube adding a moonlite focusser and the promise of a review to follow. Well here it is!

    Firstly I am not an optical expert or a great one for technical analysis with strehl ratios and p-v wavefront figures, I have, however, owned several dozen scopes and been an avid visual observer for 40 years and I know where the iStar sits optically within the Jumble of extensive data catalogued in my head- I just have a bit of trouble finding which bit goes with which scope these days!

    I won’t go into construction as I have posted on this already.This post is all about what the scope can give under the night sky. Suffice to say It is a really substantial bit of kit fully collimatable with a genuine 127mm of clear aperture.

    I had hoped the scope would prove to be a versatile, quick cooling good all rounder. In particular I had built it with binoviewing in mind and had cut down the donor tube to allow enough in travel to accommodate the extended light path binoviewers require. As It turns out I have had to reduce the tube length by a further 50mm and now do not require an ocr or barlow when binoviewing. It also sits nicely on my cg5 mount.

    I was fortunate to own a truly excellent Tal 125r achromat refractor and I have always said if the iStar objective could match that I would be very happy. I’ve also owned several Meade Ar5 refractors- indeed one these supplied the tube used in the build, it had a poor objective.Also owned half a dozen Synta 6” f8’s as well as Tal 100r and 100rs, so have a good idea what Chinese and Russian optics are all about.

    First thing I will state is that on highest power lunar, planetary and double star observation it comes a close second to the Tal 125r. The Tal could be taken to over 100x per inch on doubles on the very best of nights the iStar is good for 75x but then gets a little soft round the edges. Star tests are good but it definitely loses the stellar tightness before the Tal did. It is on par with the best ar5 I owned which is pretty good as this had a longer focal length of f9.4. I must add that last observing session I thought I detected the objective is not in absolute perfect collimation ,something I will address , but I still believe it would come just behind the Tal.

    At f8 false colour is of course present on brighter planets and the moons limb. It is in my mind a tad less than is evident on the synta 6” f8’s and one thing I have noticed is when you do crank the magnification up it does not become overwhelming and is not an issue , I must add I have always found it easy to ignore false colour in an achromat but appreciate that some people can’t stand it and will never see past it. Although I would not wish to look through an achromat shorter than f8 !

    It is very similar to the Tal125r on CA but is a magnitude worse than the f10 Tal 100’s as you would expect. Most definitely colour correction is slightly better than the Synta f8’s. It’s a trade off though with the iStar giving wider fields than the f10 scopes.

    Where I have been blown away by the iStar is in it’s use as a wide field sweeper. I recently purchased a 2” skywatcher 38mm panaview eyepiece and it is a match made in heaven. I know it’s not in the league of super high end eyepieces but with the unchallenging f8 focal length it gives very sharp widefield images across 90% fov.

    The fov just covers Orions belt with Alnitak and Mintaka being on the absolute edges of the view this is really impressive, a little under 3 degrees. The views of open clusters and starfields the double cluster etc, are absolutely stunning .Ah the colours of the stars are almost too beautiful for words, this is something people often miss about achromats but once you are looking at less than 1st mag stars the colours on show are jewel like and very vivid. I thought I had seen it all but many hours are going to be spent using this scope looking at galactic clusters and star fields and picking out brighter deep sky targets.

    It’s wide field performance has surprised me, in as much as it has taken me in a direction I didn’t expect having always thought of myself as more interested in targets such as double stars, lunar and planetary observation, I just didn’t realise just how magnificent discovering the bits in between can be!.

    I am so impressed I’ve decided to buy a sky tee alt-az and stick with pure star hopping and visual observation. I realise now that although I thought I knew my way round the sky and I do , there is so much I just have not seen.

    Finally Binoviewing with the iStar , what it was made for. Lunar viewing is a joy the amount of detail 2 eyes give is just stupendous. Looking at Plato 4 craterlets are evident and a hint of another. The contrast and texture of the lunar surface looks almost powder like I can see the dust! A wealth of detail is visible in Jupiter’s cloud system and the 4 inner moons show different colour and tiny perfect discs. It was worth putting the scope together for this alone.

    Building the scope has been a really fantastic project, I even got to do most of the machining myself on tube and counter cell, a real labour of love that was. You will never see this in the for sales section as it is the only one in the world and it’s mine, make your own!

     

    Here's a few more pics.

     

    cheers

     

    Dave

     

     

    PART II (16th January 2012)

     

       Collimation is now bang on! scope absolutely on par with my TAL 125R.

       Showed 6 Trapezium stars with ease last night and shadow transit on Jupiter stunning in binoviewers. Error was with Moonlite focusser not sitting square on the tube. Happy camper!

     

    Dave

  • ●  iStar Optical 150 F/5 Classic Achromatic Doublet in ATM style tube assembly

        by John Jarosz

    I'll resurrect this thread to further report on the objective performance.

     

    I was out at my in-laws in Iowa over Christmas. It's a rural area with a good dark sky. Christmas night was spectacular, clear, no moon, 40 degrees. Keep in mind that I'm using the Baader semi-apo filter in front of the 2" diagonal. My view of M42 had the most nebulosity I have ever personally seen visually. I now see how Stephen O'Meara actually can see the stuff he sketches. I'll never be able to see like him but I get the idea after my session on Christmas. Pleiades and Hyades were excellent as well.

     

    The istar objective has more contrast than my 6" F4 reflector. I'm a believer, but I couldn't tell under city skies, I had to get out to the country with a good clear transparent night.

     

    So thumbs up all around for the iStar glass.

     

    John

  • ●  Huge observatory class 250 mm clear aperture F/11 R30 Anastigmatic Doublet objective lens mounted in an ATM-Style OTA

        First light report by Mike Carman

    PART I

     

    Well last night my istar 10" F/11 R30 stunned the sox off me. Bear in mind it has not been collimated as one person cannot do it alone properly. First light candidate....Altair. A bright pretty blue white star. At 110x with my 25mm plossls and binoviewers CA was not apparent. Only at about 180x did CA start to show. Unlike my 8" F/13.3 Brandt the istar exhibited a warmer hue closer to my lavender hued Jaegers. The Brandt has a deeper blue violet hue. I was afraid even with the R30 glass that this 10" was still going to show more color than the 8".

    To my astonishment it actually shows very slightly less color if you can believe it!! I get no more color with a scope that normally would be physically over 30" longer in focal length. That's the real bonus for me. A normal 10" F/11 would be more colorfull than my old 8" that's for darn sure. Jupiter's moons all had tiny flares at the bottom because of the collimation issue. But man could I see detail much easier than with the Brandt. Much better contrast with more saturated colors in the belts. The seeing was soft to boot. The really big surprize that in urban skygow I could easily see the the star next to M57...I could only detect it with averted vision with the Brandt. Globular clusters M15 and M2 were text book perfect and easily resolved across their entirety.

    Tonight Jupiter is a fuzz ball so not much is going to happen there. I should have the scope collimated in a few days. The diffraction pattern inside and outside focus has the same exact perfect rings that the 8" has. Only difference is there is a slight elongation in the pattern that is easier to see closer to focus. But collimation will take care of that. All in all I'm extremely pleased. Ales Krivanek has come thru with high marks on a large lens this time. All other lens reports up to this have been highly positive also. I can tell everyone that as an experienced refractor user if anyone can best Ales more power to 'em but I don't see where istar could be outdone in this category for the money. Again Ales and US rep Mike Harden...

     

    Thanks, Mike

    (link)

     

     

    PART II

     

    My oh my is all I can say! Hot damn man! The minute I viewed Altair I knew full well what this lens was capable of so no further use of the lens was needed. ;D Just a little wry humor to get your goats. Anyway this larger aperture shorter FL lens is outdoing the Brandt 8" F/13.3 on CA. There are flares and spikes at the bottom of all stars and Jovian moons. This because it hasn't been collimated yet. With a laser we also still have to adjust the 10"x32" tube so that it is perfectly on the optical axis. But even so the lens is showing as much detail and more between seeing turbulances. What really took me by surprise was the ease at which I could look straight at the star close to M57.

    With the Brandt I had to use averted vision in this urban sky. Ales you and Zdenek will have a tough time besting this. Maybe you boys just got lucky....but what do I care now. ;D ;D I was able to get a 10" F/14.3 into my existing space.....that's what I was after. I even got the tube length correct so my binoviewers had an inch of in travel left with 25mm plossls and no barlow for star filled low power dark contrast sweeping in urban Omaha skies. That alone is worth the price of admission. Therefore to say that I'm a satisfied customer is the understatement of the day. Thanks to Mike H. for double checking those "other" two. ;D

     

    Mike

    (link)

     

     

    PART III

     

    Well I just finished three hours of test observing tonight with the new istar lens. It was cold and windy but the atmosphere was calm and transparent. I used that Brandt 8" F/13.3 for over 30 years and would have put it up against anyone's scope in that aperture range and would have come in second to noone. Tonight however I confirmed two things and several obvious. First of the obvoius is it's a larger aperture. So right off we know to expect twice as bright of an image and second the airy discs should be smaller or tighter....and they were. Now on to the confirmation that this lens is indeed better corrected for CA. In the normal scheme of things if you were to say that CA would increase dramatically going from an 8" F/13.3 to a 10" F/11 you'd be right on the money....right? Not so fast some of you self proclaimed experts. It is so very obvious to me that the 10" R30 is actually controlling it more.

    Before replacing the Brandt I carefully estimated the extent of the bluish purple halo around Jupiter to be slightly broader than the S. Equatorial belt but not nearly as well defined gradually diffusing outward. The istar lens shows a much tighter purplish lavender almost to the extent of the N. Equatorial belt and sharply defined. The Baader Semi-Apo filter gives me the same "look" thru this 10" F/11 that I see thru my Tasco 4-1/4" F/15. That to me makes me an extremely happy camper with this lens. Lastly I have never seen Epsilon Lyrae like I did tonight. Those airy discs were beyond perfect. Absolutely stunning.

    Pi Aqulae one of my favorites was not only brighter but the darkness between the pairs was easily more pronounced. The seeing conditions were close to 8-9/10. Some slight softening every moment or so like the focus was drifting was evident. I felt like if it had just got to a 9+/10 I could've seen white ovals if any were present in the polar regions of Jupiter. Well that's enough rambling for now. Tomorrow nights forecast doesn't sound promising. We'll just have to wait for my DSO in Pegasus another night. Oh I forgot to mention Vega! There is CA but nowhere near what the Jaegers or the Brandt showed. The Brandt had it's usual bluish purple. The istar not only was it's usual lavender purple but Vega itself was a white. In the Brandt there was a yellowish white look. Delta Gygnae never showed the companion better. The secondary was a pin *BLEEP* lavender star...beautiful to say the least.

     

    Mike

    (gallery)

  • ●  Replacement refractor on Mt. Sromlo Observatory, Australia. / iStar Optical 220mm F/15 Achromatic Doublet

        by Tim Wetherrel

     Finally got chance to test the telescope on some terrestrial targets late in the day and the news is all good! The day was a bit hazy so we used a tree about 200m away as a target to cut out atmospheric effects as much as possible. Was very impressed with the lens, it created sharp contrasty images just as one would expect from a good quality large refractor. Using the 65mm wide angle eyepiece it was quite spectacular. When you get to higher magnifications 250x upwards there's a slight violet halo at the edge of branches just as you'd expect from an achromat but the image remained crisp and true. We wound the magnification up to 550x with a 6mm ethos without any real degradation except a little false color, which I'd imagine a minus violet filter would completely eliminate - just didn't have one handy. So in short, I'm very happy with the lens. We'll do some testing on artificial stars when we get the chance but I can tell just from the quality of the terrestrial images that it's a really nice lens.

     

    Tim Wetherell

     

    Gallery

  • ●  150mm F/5 Classic Achromatic Doublet - Binocular Comet Hunter

        Jurrian Zijl, Holland

    Ever since my early teens, I’ve been looking to the stars and after twenty-five years they still fascinate me. At the age of fifteen, I built my first 6” Newton telescope. A couple of years ago, when aperture fever hit and the budget allowed, I built an 18” F4.4 Dobsonian truss telescope.

     

    Observing with this big scope is really exiting especially when I travel to dark sites.

    In The Netherlands, where I reside, a very clear night with good seeing conditions is rare. Sometimes the sky will clear up for a few hours and allow for a quick observing session. However, a heavy 18” telescope is not very practical. So, quite often I missed the beautiful deep sky objects embedded in the star clouds of the Milky Way.

     

    I was looking for a transportable, lightweight instrument that gave me the same stunning views my 18” telescope did especially at low magnification. I began an internet search but discovered what I was looking for was too expensive and too heavy. So, I decided to build a large binocular.

     

    I discovered the 150mm F5 achromatic lenses of iStar Optical. After a successful e-mail discussion with Ales Krivanek, owner of iStar, I decided to buy a pair of these achromats and at a very reasonable price.

    The objectives arrived within two weeks of my order and included a test report for each. I also bought a set of quality eyepieces. I started to build the 150mm binocular. The result was a stable, highly transportable and lightweight instrument. Its total mass is 20 kg (44 lbs) including the tripod, mount, eyepieces and finder.

     

    The first observation session knocked me right out of my socks. Very sharp pinpoint stars and great contrast was the result. All this and a total field of view of 2.2 degrees.

    At first glance, I saw a number of faint fuzzies, many dark structures in the Milky Way and a magnification of 31 times. For example, NGC 7000 was easily visible with a UHC filter even in my light polluted backyard. I also saw the faint Merope nebula (NGC1435) around the bright stars of the Pleiades (M45). I was quite impressed.

    Later, I tried higher magnification (63 times). The quality of the image starts to reduce a bit but the view is still appreciable. I would not recommend magnifications of more than 100 times.

     

    I think I have found the perfect instrument for accomplishing quick observation sessions. Just set the binocular up in the backyard and start viewing the faint fuzzies. It’s very similar to the performance of a large aperture telescope running at low magnification.

    iStar Optical delivered very nice achromats for this project. I would recommend these lenses to anybody who wants to build his own rich field binocular telescope.

     

     

    Jurrian Zijl

    The Netherlands

    Gallery

  • ●  iStar Optical 204mm F/11.7 Achro

        First light report by Leslie Hess, Arkansas, USA

    Gallery I am proud to say that I now own one of only a handful of 204mm f11.7 achro lenses produced by iStar Optical. After much discussion and considerable deliberation I settled on this lens for my ultimate scope, initially I had decided on the 6 inch f15 objective and even placed the order. However, I changed my mind and contacted iStar the next day to change the order. iStar agreed to produce a single lens. This is not normal stock for iStar, but the single lens was produced at no extra charge. It was delivered on time in about 6 weeks. I cannot stress enough how superb iStar customer service is.

     

    I have been an optics-geek since I was a kid. About 10 years ago I built my first entry level scope. A 10 inch Dob which I used for several years.

     

    As I unpacked the lens it proved to be in perfect condition. The coatings were beautiful and flawless. Initial star tests showed no coma or astigmatism and had good surface quality. The lens was slightly over-corrected which is fine with me as it proved not to be an issue. Quality of the lens overall is quite good.

     

    After months of constructing my OTA, I was finally ready to test in the real world. I double checked the OTA collimation to ensure all was square, mounted the 7 foot assembly to the base and waited for dark. Cloud cover was clearing and I was hopeful for a triple play.

     

    The eyepieces I used are the ones I use in every scope I own. This eyepiece set includes the Russell Optics 11mm swa, 32mm konig, 19mm uwa, and my cheap 2x Barlow.

     

    Before the moon rose I had a break in the low cloud cover to get a clear view of M42. Absolutely the best view I have ever seen, bar none. The young star cluster tightly grouped so perfectly even the 5th faint star in the tight 4 star cluster was easily resolved. I saw more detail in the cloud itself than ever before. Absolutely no coma or astigmatism was present leaving superb contrast. Only the brightest stars in the sky had slight chromatic aberration, which could be due to the cheap eyepieces I was using.

     

     

    The star test proved to be dead on. The lack of chromatic aberration, coma and astigmatism conspired to make this a genuine joy. I have to keep reminding myself that this is an f12 scope!

     

    A cloud bank rolled in and took an hour to clear. By this time the moon was at about 40 degrees high. This scope is so eager to magnify. The 2400mm focal length and the 11mm barlowed by 2X yielded 430X. Boy does it add up fast. The moon was at 98 percent full; I had one cratered edge to enjoy. With the 32mm, the moon was gigantic, super sharp and totally CA free edge to edge. With the 11mm the detail really began to pop out, now we are getting down to business. I added the Barlow and pushed very high power. Sky conditions were far from ideal but the clarity, sharpness, contrast and total lack of CA blew me away. I am positive this instrument would have yielded much higher useful magnification but I ran out of sky and eyepiece possibilities. The clouds rolled in. Unfortunately, it was cloudy by the time Saturn rose.

     

     I made the perfect choice for my purpose and would purchase this lens again. Within the last 12 months I looked through a 24 inch truss reflector, 8 and 10 inch dobs and several large aperture compound scopes. This 204mm objective most closely compares to a 14 inch compound scope. I ended up with a superb telescope and look forward to years of use.

     

    Fast forward a couple of weeks and I have finished the scope and mount. I am taking off work Monday to see Saturn and report to my friends here at Cloudynights. But the clouds rolled in again the same as last time.

     

     

    -- Leslie Hess

    Gallery

  • ●  A custom built telescope using iStar 150/F15 achromatic doublet lens in cell (pictorial)

        by Fred, France

    Cette lunette est construite a partir d'un objectif iStar de 150 mm F/D 15, d'un porte occulaire en 3", d'un tube en alu de 160 mm de diametre 1950 mm de long 2mm d'épaisseur et de baffles interne.

     

    See pictorial.

  • ●  iStar Achromatic lens in cell 150mm (6”) F/15

        June 2010, by Sean Cunneen

    It has taken a while but I have spent the last 3 weeks using the lens I purchased from you in March. I have been thoroughly impressed. I am not one who gushes over equipment and this is the first time I am writing a dealer however the lens I received has surpassed all of my expectations.

    I was able to bring the scope to the Bootlegger's Star party this past weekend and put it through it's paces in very dark skies and I was enthralled with the images. I was able to see detail in the whirlpool galaxy, the ring nebulae looked like it was lit with a fluorescent lamp!

    The director of the Prairie Skies Star Party spent a good deal of time looking through it as well. He was very impressed and said he may be contacting you directly to purchase a 6" f/6!

     

    The most telling was a direct comparison with an Astro-Physics 6" f/9 where except for the color tone of the images, the iStar lens matched the AP for both detail and sharpness. This lens is really very good and I wanted to thank you for selling it to me!

    I will also be showing it at the Prairie Skies Star Party this October in Illinois and I can't wait for the long lines and disbelief I am sure to see!

     

    Thanks again and keep it up!

     

     

     

    Sean Cunneen

  • ●  150mm F/10 Achromatic Lens in Cell

        First light report by Jeff

     So here's an update. About a month ago I managed to get good enough weather and seeing to do some more testing on the 6" F10 lens. At high power I saw the "glow bar" again that I had reported on earlier. This appeared as a subtle, thin, diffuse bar that bisected the entire diameter of the lens. On one side of focus it was slightly brighter than the surrounding diffraction pattern while on the other side of focus, it was darker. It's position or character did not change despite swapping out diagonals and eyepieces so I ended concluding that this was a subtle zone or nonuniformity in the glass. Odd though as it's not a type of zone I had ever seen before. Approaching focus the airy disk swallowed everything and the in focus disk looked good with no spikes or other odd effects

     

      I contacted Ales and he was quite concerned. He got in touch with his chief optician who was also quite concerned. The three of us spent many e-mails going over the scope's design and my observations. We finally decided to try imaging an artificial star and then send the photos back to iStar.

     

      Well, the other night was clear and calm so I set up the 100 micron artificial star over 60 meters away. I looked straight thru and took pictures but they did not come out very well. Besides, there was nothing unusual to see!!

     

      Once the tube and optics had thermally stabilized, the diffraction pattern looked just about perfect. Using 240-300 X, with and without a green filter, and 4-5 rings of defocus, the rings were very sharp, uniform and perfectly circular on both sides of focus. As the pattern of the first two rings was so uniform, sharp and well defined intra and extra focally, I felt there was no obvious spherical. Expanding the pattern showed there were no bars, notches lines, or ANYTHING else that indicated zones. At focus, the airy pattern looked great. These results were repeated when I used the scope on a real star.

     

      The only time I saw the "bar" or anything else was when the scope was pointed vertically on a real star. I thought I saw the bar on occasion then but it would appear weakly then disappear with the seeing. Of course, I was also seeing the other, usual junk and transient zones in the image as the lens continued to cool. For example, I could watch the airy disk wonder from just perfect to slightly astigmatic and back again as heat rose off of the lens and, in particular, the diagonal cooled.

     

      Mars was very sharp with plenty of surface detail and clouds. The polar caps displayed texture and ragged edges.

     

      So this is a very, very good result. I'm concluding right now that the bar I saw twice before was induced somehow by cooling and is NOT a problem with the lens.

     

      As much as I continue to like the lens, I have to say I was really impressed with the way Ales was handling my initial reports. He and his optician took them seriously and displayed real interest in what was going on. Unlike other companies I've dealt with, there was no hand waving or look down their nose dismissive attitude. They spent some time with me on this and were in no way upset when I finally had to admit to a false alarm.

     

    Highly recommended.

     

    Jeff

  • ●  150mm F/15 Achromatic Lens in Cell

        First light report by Sean

    It has been a busy couple of nights in the basement this week. I ordered a 6" f15 objective from iStar last week Wednesday and it arrived Friday. It came very well packed. I have been wanting a 6"f15 for quite sometime but the cost was prohibitive. I had contacted some Chinese manufacturers but I had second thoughts because of the shipping cost, wait and lack of recourse should something go wrong. Enter iStar Optical. They had one listed for $415+$29 shipping. After a couple of weeks of emails I called to place the order. The lens arrived very quickly, very well packed but now what?

     

    The first thing I checked were the coatings, a nice green with no defects. I gave it the flashlight test and though there were light scratches, I saw nothing I hadn't seen on any other lens, in fact I would say the lens faired better. The cell is nice and beefy, quite thick but well put together. I suspect the lens is from Barride Optics Co in China, they look very similar to Barride's objective cell offerings. Barride is a pretty good company who are the originators of the Antares line as well as the Astrozap Petzval scopes.

    So I have spent the past two days jerry-rigging a scope together as I wanted to test this lens asap. If there was a problem I wanted to have ample time to return it. My test OTA consisted of the tube from my old 8"f/8 newt with a section of 5" PVC sewer pipe to act as an extension for the focuser. I glued some wood blocks into the objective end to secure the lens to. A quick trip to Ace netted me a pipe mount. A very BIG pipe mount. My tube is open on both ends so I had to stuff crumpled newspaper around the cell and focuser to block stray light as well as tape over the old focuser hole, but that's more a subject for the ATM forum.

     

    So tonight I took it out for the first time. After an hour of cool-down time I star-tested it. first off I am NOT a star-test expert but I'll tell you what I saw. Identical inside and out, nice and round, no flares or spikes and the defocused donut on both sides was nice and smooth. No SA that I could see nor Coma(though I would've thrown a fit had any coma appeared).

     

    Next I found Saturn and cranked up the power. Focus was very easy and sharp. As I moved through my eyepieces I was getting more excited as everytime the planet would pop into focus. For me, I measure progress through power and I was very pleased when I hit 300x and didn't see any issues. I popped in my Pentax 5XO at 475x and proceeded to do backwards flips. the image was nice and sharp with good detail (seeing permitting) and are you ready for this? No color. Hot darn. I mean it. I had the 6" f15 piggy-backed with my 5" f10 and the difference was night and day. The 5" was a rainbow of violet haze but the 6" showed none that I could tell. I will try it out on the moon next chance I get to see how good it really is, but as for now it is a winner.

     

    Sean

  • ●  210 F/8.8 Achromatic Lens in Cell

        First light report by Keith

    As we all know, you can tell how good a company is not by what they sell but how well they support you after the sale, especially if there is a problem with their product. As with most companies, a lemon can slip through the production process from time to time. I had planned on giving a report on the 203mm F/9 lens that I received from iStar Optical but there was a problem with the lens. Instead of blasting the company with a bad report on the web I decided to wait and see how they would respond to the issue concerning the lens since I had plans on buying more lenses in the future.

    Ales of iStar Optical answered all of my e-mails promptly and apologized for the inconvenience. He spent all the time needed to work with me on resolving the issue. I do admit that I was a bit nervous since the company was fairly new and I had spent all my hobby funds for the lens purchase, but my fears were unfounded.

    Through our e-mail discussions, Ales and the optician had a clear understanding of the lens problem. I was informed of the time required for a new replacement lens. They were true to their word and delivered the new lens in a timely manner (20 working days). Even though Ales was traveling back to Germany, his representative in Arizona made sure e-mail communications remained open and shipped the product on time. Now that’s customer service! I can’t say I have always had this type of service with other companies I have purchased from over the years. I would rate iStar’s customer service as first class. Communications were clear, prompt and they completely resolved the problem. Would I buy another lens from them? Yes, without hesitation. They stand behind their products and care about their customers.

     

    Now, on to the lens test:

     

    My original test involved an optical bench using an artificial star placed at 150 feet. During the “down time” waiting for a new lens I constructed a “rail scope” that allowed me to do my tests using the night sky. Here are my results:

     

    The weather has not been kind with wind, bad seeing, rain and high clouds.

    Ronchi Test (250LPI Glass grating at 2 to 3 bands): Edge clean, bands straight and of high contrast (prison bars).

    Star test: About 1/6th wave. The visual test matches the interferogram. (.168PV .014RMS)

     

    Mars (9arc sec): Details clearly seen on the globe.

    Saturn: Crisp and well detailed when the seeing allows.

    Multiple Stars: I have not had a night good enough to “go the limit” but stars like Eta Gemini are child’s play. Zeta Orion is clean split even in sorry (2-3/10) seeing. All six stars in the trapezium are very easy.

    Chromatic Aberration: I was expecting a lot of color but was surprised how little there was considering the focal ratio.

      The seeing has not allowed me to push the telescope hard but eventually I will. The lens is a very good one. For the refractor purists, yes, I will install the lens in an enclosed tube. Currently I’m having fun with the rail scope.

     

     

    A few test nights later:

     

    Well... Had a couple of fairly decent nights and this lens ranks as one of the better ones I have ever owned (top 3). Last night I split 78 Ursa Major in 5/10 seeing. I could detect .5" Zeta Bootes under the same conditions. I could see the polar cap on Mars and the melt line as well.

     

    Tonight I was able to see Rhea only 1.9" away from Saturn's globe (144x). 5 moons visible. I also beat my personal record of over a decade ago when I could see the Cassini division in Saturn's ring as a well defined arc through a 12.5" F/8 reflector with Saturn's rings only tilted 3 degrees. Tonight I could see the division as a black arc with the rings only tilted 2.5 degrees (360x TMB 5mm Planetary Eyepiece/Williams Optic 2" 99% diagonal). Seeing tonight about 6/10. Division seen multiple times during moments of steadiness (about 1 sec). Seeing gauge: Airy disk visible but faint rings broken up by the seeing (Zeta Orion). Can't wait for a good night.

     

    The limiting visual magnitude here in Lancaster, CA is 4.5 ( I live in the middle of town with many street lights in my area). I was able to see a 13th magnitude star last night. So the light transmission of the lens is quite good.

     

    Keith

  • ●  iStar Optical Achromatic lens in cell 5” F/12

        by Sean Cunneen

    The lens is an iStar lens ordered in early March. I tried it out and saw no aberrations that I could see. I took it up to 575x with a pretty good image, fingers crossed....

     

    Sean Cunneen