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Post by criverside on Nov 14, 2012 21:11:44 GMT -5
Ales or Mike,
As you know my interest has been in the coming 8" f/9 R30. But Joe's new 6" f/5 R30 has bitten me really hard, to the point I have re-evaluated my needs. I have re-run all the numbers and as much as I would like to stay above f/8, a 8" f/7 works out ideal using a medium wide field 2" eye piece with a field stop close to the maximum, for the lowest power views with the greatest illumination. Or f/9 and back to low power Konigs and Plossls which would be a great view with blinders on! "My Problem", Craig
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Post by Ales - iStar Optical on Nov 15, 2012 12:11:18 GMT -5
Did you ever consider our brand new, not yet even photographed Asteria AT 150-8 R30? This scope will offer beautiful wide field, but much better CA control over the F5 as well as better controlled SA and possible astigmatism. The F5 is extreme super fast doublet but personally I choose F8 due to a better image quality with considerably less CA. Also all F8 will be offered with Raycorr (we still hope to introduce Raycorr for F8 sometimes early 2013).. so think about it. Also, another buyer is interested in 180 F8 R30. If we get two people interested in same scope, we can produce sooner. Always the single lens production is scheduled for last.. for obvious reasons.. let me know, thank you Ales
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Post by criverside on Nov 15, 2012 22:00:53 GMT -5
Thanks Ales,
I am still holding out for a 8", it will give me the tighter field of view with the same illumination. I want a "Rich Field as opposed to a "Wide Field".
Being limited to the available eye pieces, if 2.7" or 3" were obtainable in the types and comparable prices of 2" I would have no problem. That is where a 8" f/7-8 would stand-out using 2" eye pieces.
I agree, 8" f/9 R30 will give me the image quality I desire. With time I may return to my senses, and forget the math, "though the numbers did look good"--------Thanks, Craig
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Post by hebbardr on Mar 6, 2013 11:28:41 GMT -5
Hello, I'm new to these pages. I have been following Istar and am impressed. I would like to see if it is possible to special order an 5" F10 R30? What would the weight & specs be? I would most likely get Istar rings and Losmandy type dovetail with a moonlite focuser adapter (I'ff get the focuser direct from Moonlite). Price wise? Also is there an F10 Raycorr (visual) in the future?
THX Rich Hebbard
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Post by jamesling1000 on Mar 7, 2013 1:23:15 GMT -5
Hi Rich Hebbard....
Welcome to ISTARSCOPECLUB.....
And great to hear that you are looking for an Istar 5" F10 R30......
And now everyone of us, including you will be eagerly waiting for the 1st series of raycorr to be introduced into the market......
Hope you can get one soon and give us your comment on the R30/35 version.....
REgards
James Ling
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Post by Ales - iStar Optical on Mar 7, 2013 2:24:47 GMT -5
Hello dear Rich, yes, it is possible to custom design and custom produce one single lens but I can tell you one thing. You wont be happy with the price offer. I expect the sale price to be in 1800 dollar range. Another news is that we are not planning on introducing 127 F10 R35 version to the market. Not at any time soon. Simply because we offer TWO lenses which are very close to this one, one is F12 and another one if F8- So to produce F10 in special R35 SLIM makes little sense to us adn most users I would say. So in your case, go for F12 R30. This lens cost only 665 dollars including push-pull lens cell (adjustable cell for precise collimation). The MoonLite reduction ring is no problem but you must have MoonLite focuser made specifically for Istar. If you have onother type of the flange (3 bolt, different tread pitch) you must have your reduction ring custom made locally in USA. Cost of the reductioni ring for MoonLite is 66 dollars as per our web site. We are producing several new 127 F12 R30 right now, due to be finished in about 2-3 weeks, most are already reserved but if you act fast we can ship the lens to you right after we receive the payment in full including 45 dollar estimated shipping, handling and insiurance. Contact me direct at ales@istar-optical.com, copy to petr@istar-optical.com so we can talk in more detail or to finalize your order. The F12 R30 shows a very little chromatic aberration and can be used without Raycorr. best regards, Ales
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Post by hebbardr on Mar 7, 2013 20:32:18 GMT -5
Ales, THX for the quick response. My concern is two fold. One is the amount of CA in an F8 (even the R30), and also the ability to get high resolution and magnifications on the planets without using a barlow. The F12 is simply too large of a scope. I have never viewed through an achromat, only just 80mm ED refractors. Rich
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Post by Ales - iStar Optical on Mar 8, 2013 5:25:38 GMT -5
Hello Rich, the maximum suggested magnificaiton for this 150 F8 R35 SLIM would be around 150x. but I know of people having 127mm doublets and going for 300x with still usable image quality. So it will be OK for planetary works, you will see same amount of details as APO triplet would offer, the only drawback is the CA. But CA in these doublets is shifted towards red, so your eye gets used to it quickly and your brain will learn to ignore it all together on many objects. This is something most users of these R35 and R30 doublets are reporting, search the web for their comments and test reports. Also, we work hard on introducing the Raycorr Pro6-V for F8 models, so you can implement this special 6 element corrector and get near APO performance out of your F8 system. All this for a cost of course, but you can strat with the lens or scope now and buy the Raycorr when ever they becomem available this year. Have a great day, talk to you soon, cheers, Ales
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gord
Full Member
Posts: 82
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Post by gord on Mar 15, 2013 21:21:17 GMT -5
Ales,
I think you are being a bit to enthusiastic with your comments here. And/or liberal with your use of the work "details". CA is out of focus light and out of focus light is a loss of detail in and of itself alone, and on top of which it negatively affects other in-focus light so there is a double negative effect.
These and any other achromats are not going to show the same amount of full details a true APO triplet will unless you restrict the selection of said details to be the most basic of things such as the two main belts on Jupiter, or something as such. Fine details in the APO cannot be matched by the achro.
Clear skies, -Gord
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Post by Ales - iStar Optical on Mar 16, 2013 4:25:49 GMT -5
Hello Gord, My reply is based on comments from Istar scope owners who compared them side by side with APOs. I believe that you even find this right here on Istar Scope Club. These are not my own statements. I stay away from such based on my previous experience and reactions from some amateur astronomers. Your way of thinking is absolutely sound and correct. But the only visible difference seen between these two scopes CAN be (to a very, very small degree usually not recognized by a human eye) in level of contrast and not in the actual resolution and what you see or don’t see at the eyepiece. I talked to our master optician just now about this subject and he confirmed my own personal experience with Achro and APO, even mentioned couple of things I did not know before, both supporting my original statement. If you study physics of atmosphere and its’ impact on the image quality, you will find out that what I’ve written is actually true. You must also take in consideration the amount (percentage) of unfocused light in Achromat or R30 / R35 lens. Under absolutely IDEAL conditions (NO atmosphere, ideally made lenses, etc..) there would be a very small difference in contrast. But once the light goes thru the atmosphere, it will effectively zero out any differences and the resolution/contrast level of each scope of similar aperture will be pretty much the same. Some time ago I personally compared views in Istar 150 F12- and 6" top brand APO triplet. Side by side, tested by 4 people, all highly experienced astronomers. And we came out with similar results as some of Istar scope owners here in ISC. Of course that quality of lenses must be perfect in both the achro and apo in order to compare. If you have crappy achro doublet and top of line APO, than without a doubt, there will be visible difference in resolution and overall image quality. But I believe that this is not the subject of this thread. And just realized, this very same scope, that is Perseus AT 150-12 was tested by a very respected leading staff member of OPT (Oceanside Photo and Telescope) in California. It was about one year ago. He sent us a very excited letter that he could not believe how well our achros perform and that he tested this achromatic scope against his top of the line Japanese top brand scope. In his own words, he did not see any difference in the image quality and resolution, except for the tolerable amount of chromatic aberration. I don’t want to spark yet another fiery dialog. Best way is to get a high quality APO, a high quality achro of similar aperture, comparable FL ratio for both systems and test both from behind the eyepiece. Everyone can than come up with their own result and decision. Again, in my reply I merely repeated what was written by others here on ISC and/or on CN, Astro shop members. I don’t disagree with your way of thinking and the physics behind this. But if you take the actual real life situation in consideration, you will see that what is written above is in fact the truth. Just do some of your own testing and share your experience. Have a great day, talk to you soon, Ales
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gord
Full Member
Posts: 82
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Post by gord on Mar 18, 2013 21:39:42 GMT -5
Hi Ales,
I'm going to have to disagree with you (on a few things here).
1. People's experience on the detail difference between achro and APO
The real subjects here are the planets since it should be explicitly spelled out. I will agree that on DSO's, there is a much smaller difference.
My own experience is that the achro shows distinctly less detail on the planets with Jupiter being the harshest test. The physics behind this backs it up as well since the polychromatic strehl of an achro is quite low (like 0.6 or something) as compared to ED's, good APO's, and reflectors. The only achro's that do well are the ones where the f-ratio is long and they don't scale. 6" F15 is a large scope and is already starting to be quite affected by the secondary color.
Honestly, I don't see many sharing experience that their achro is showing the same details as the APO on here or anywhere. There are some that enjoy the "experience" of the achro (especially long ones) more, but not in terms of details.
I have a quality achro (one of yours!) and it provides enjoyable views. It doesn't show as much details on the planets as either of my C8's or reflectors. Most other peoples experience with ED's and APO's is that they will show more than a C8, so this too is more than what the achro will show.
2. The atmosphere's effect
The seeing will have an effect and is the biggest limitation for the full amount of detail that can be seen. However, my experience is that it is never constant (either bad or good). You statements suggest that it is so overwhelming that it will negate any benefits that can be seen over an achro. Definitely not true, we have all experienced otherwise.
3. Some of your use of terminology
Resolution - your statements around resolution are true but add nothing to the argument of achro vs. APO. Why? Assuming you are talking about the same size of scope, and comparing like quality, the resolution is the same. You comment about the atmosphere effect on it (see above) is true and false. It will have the same effect on each design but since there is nothing to "zero out", nothing will be zero'd out!
Contrast - Contrast is effected by the out of focus secondary spectrum. And it's very much dependent on how out of focus the color is which is highly dependent on the design (f-ratio, glass types, color balance, etc.) and the color(s) of the object. It's also effected by the size of the objective. The atmospheric conditions have to be extremely poor for them to reduce all details to the point where there is no difference in details seen in each design, and I don't think that is the normal case we are focusing on.
It's important to keep in mind from all of my comments, I'm not saying that an achromat is a bad thing or not enjoyable to use. I enjoy mine all the time! It just is what it is though, and what I'm pointing out is what it's not: the equal of an APO in terms of rendering planetary details. I think it's important to keep expectations in line with reality to avoid disappointment.
Clear skies! -Gord
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Post by Ales - iStar Optical on Mar 19, 2013 4:10:00 GMT -5
Dear Gord, we both have somewhat different experiences behind the eyepiece. Yes, achro will exhibit less contrast. And larger you go for example between 8" achro and 6" APO the image in 8" scope (but not only limited to achro) will be sort of "lighter" but this is due to a light gathering power. You will see same amount of detail only dark will be darker in APO/smaller scope and white or yellow will be brighter in smaller/APO. But Im leaving this fact aside since I merely repeated what was said by others and what was said by our optician. A person who is giving lectures in optics at universities, works as a problem solver for NATO, etc.. I do take his words and opinions seriously. Unfortunately, he is way too busy to reply directly to any internet posts. There is one onother thing. What you have written would suggest that refractors, namely achromatic doublets are poorest choice of all systems out there. It makes me wonder why anyone with plenty of experience is going for a good quality achromatic refractor as his planetary scope of choice. Or why such experienced person as sales manager at OPT would bother to compare his APO with our Achro and than put his finding in writing. He saw same amout of detail in ISTAR 2000 Achro as his 8 000 APO... I will leave it at that, averyone can come up with their own results based on physical evidence behind the eyepiece. I strongly suggest that you read a few year old article on internet where APOs and Achoros are compared in this technically in depth analysis, taking in consideration all aspects and how they affect the visual performance. I had this article saved in my system, it may even be somewhere on our web site, not sure. I will look for it, too bad I dont remember the autor's name. It was all hard evidence and facts and written for regular people, not graduated opticians. But thank you for your replies, it keep this place alive. If I only had more time to write and to reply. But it is hard with my 24/7 job, even though I enjoy most of it. Have a wonderful day dear Gord, respectfully, Ales
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gord
Full Member
Posts: 82
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Post by gord on Mar 19, 2013 12:07:27 GMT -5
Hi Ales,
Yes it seems our experiences are different. You'll have to forgive me if I don't believe the experience the person from OPT had as you describe it, that they saw the same amount of planetary details in a 6" achro vs. an $8000 APO. I have seen the varying performance levels of many different scopes in terms of size, quality, and design. A top-shelf APO in these 6"+ sizes isn't going to give up so much to a comparable achro (or even a large one to a point) in that use scenario. You can look no farther than our own James Ling's experience with his 8" IStar and 6" APM ED.
Now an important point to make is the absolute amount of difference. Is the $8000 APO four times better? Absolutely not! At least in terms of amount of detail. Although it could be argued that things are much more black/white than that if it comes down to being able to see something or not, but that's a more philosophical discussion.
When you question what is the value point for the achromat as a planetary instrument, I think it comes down to value and experience/nostalgia. They are not the first choice in terms of performance when doing an apples to apples type comparison. Many others are ahead and it's why you see they are not the dominant choice any longer. But it doesn't mean they don't offer good value and they offer a unique experience in observing, and a link to our astronomy past.
And in some cases, such as at smaller sizes and longer f-ratio's, they do hold their own (or even better) their APO bretheren (packaging issues aside). A 3" F15 CF achro is pretty apochromatic in performance, and has less other errors than a short focus refractors. But the main issue with all refractors, is they don't scale. Once you hit a certain size, packaging and especially diminishing returns in performance and rising costs take over and there just ends up being better ways to get there. That middle ground is where the APO's really shine, although a quite a cost.
Anyway, we will have to agree to disagree, but it is good to have these discussions!
Clear skies, -Gord
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Post by jamesling1000 on Mar 19, 2013 21:37:25 GMT -5
Hi ALL....
Let me give everyone my opinion, based on my finding with the shootout , and is only for you to take reference but not to totally agreed with my views, since my hobby is only 15-17 years ....
I am 51 years old, and not sure whether my 80 deg eye-sight is causing me not able to see the very very intricate details that many people are reporting they see colours that I don't....
1. 1st comparison between 152 APM triplet and the 8" istar....more than 2 years ago , the same day I received the Istar .... 1.1 The view of Jupiter is compared when both pointing at Jupiter around 11pm, when is almost vertical.....
1.2 The 6" triplet and 8" istar power are cranked up to 400X... with the triplet slightly higher, as the ep used by my friend is different from me, after all our FL are different....
1.3 The result are as follow..... on the surface details of Jupiter, there is nothing what one scope can see while the other cannot, except.... the triplet disc is very clean and sharp, while the achro is a bit soft...The shadow of one moon , shown on the triplet is very dark, while the achro is lighter.....
2. 2nd comparison between 152 APM ED APO and ES127 triplet at side walk......APM power is 300X while the ES triplet is around 250X...
2.1 The result are as follow.... on the surface details of Jupiter, there is nothing what one can see while the other cannot....
2.2 The triplet seems to have a much more cleaner disc than the APM...
3. 3rd comparison between APM ED APO and Triplet APO....with both power around 300X.....+
3.1 The result are as follow..... on the surface details of Jupiter, there is nothing what one can see while the other cannot.....
3.2 The triplet seems to have a much more cleaner disc than the APM...
3.3 The 4 moons of Jupiter still show as solid disc in the triplet, while the ED APO, shows CA.....at such a high power.....(low power around 200X no issue)
4. 4th comparison between APM ED APO and 8" Istar, at my friend's roof top observatory....on saturn and the moon.
4.1 The result are as follow..... Both scopes show CA at the moon, while the Istar CA is similar to my C6R F8, the ED APO shows a very thin layer, maybe 1/3 or lesser.....
4.2 Both shows similar views of the moon under visual, and you need to see the photo I posted earlier , to make your own judgement....
4.3 APM ED APO shows Saturn with a very clean and sharp view, with darker bands lines and very dark cassini division....
4.4 8" Istar shows saturn not as clean as ED APO, but the surface detail is similar , except the bands lines are lighter, and a lighter cassini division....
5. M42 Trapezium star E between APM ED APO and 8" Istar, at my friend's roof top observatory.
5.1 8" Istar picks up star E so easily.... while my friend's edge C8, well collimated , also cannot picks up a slight trace of it.....
5.2 APM ED APO struggles to picks up star E........
5.3 FYI, I re-collimated my ultima C8 twice last weekend, and try to spot star E, but fails on both attempts.....
I hope the above finding will be helpful to anyone who wants to know what you are expected to see , when you are viewing through these scopes.....
I have to admit that usd4k for the APM ED APO could not perform up to the same level as the usd8k triplet.......especially on the CA.... But some will say why not go for the ES127 triplet which is almost half the price..... So is up to individual to decide....., simply the bigger aperture definitely has the advantage when going for DSO....
Regards
James Ling
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Post by astrotrailer on Mar 23, 2013 10:58:47 GMT -5
What is the current status of the R35 180 F12 lenses
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