Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Refractors

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | (show all)
stevew
Now I've done it


Reged: 03/03/06

Loc: British Columbia Canada
Re: Istar refractors Pros and Cons? new [Re: Scott in NC]
      #5805547 - 04/17/13 09:29 PM

Quote:

I mean, c'mon, they're just refractors!



Blasphemy !!


Post Extras: Print Post   Remind Me!   Notify Moderator  
jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Istar refractors Pros and Cons? new [Re: mikey cee]
      #5805653 - 04/17/13 10:08 PM

Mike:

In my view, there's no credible data at this point sufficient to make me want to buy an Istar telescope. Perhaps with some reliable data concerning optical quality, that will change. I don't think I'm alone in this either. The scopes are not expensive ("charging up Paypal is kind of funny, actually - link your account to your checking account or a credit card and there's no "charging up" needed), but a large one is an armload to transport and mount. I'd rather have a credible basis for expecting that the hassle factor will be worth it. Neutral interferometric test data comparable to similar data for a wide range of competitive scopes taken from scopes already in owners hands rather than cherry-picked vendor samples will go a very long way to providing would-be thoughtful buyers with a basis for keeping Istar on their lists of potentials, or removing it.

But I have no objection to you being happy with your scope, no matter how it would measure up were it tested by Herr Rohr.

- Jim


Post Extras: Print Post   Remind Me!   Notify Moderator  
jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Istar refractors Pros and Cons? new [Re: tomcody]
      #5805711 - 04/17/13 10:26 PM

The FS-128 is a very nice scope. Lightweight too. As I was telling Mike, the problem for me with the big Istars is that I'd hesitate to invest in one (due to mounting demands and oversized parcel shipping needs, coupled with a lack of rigorous reviews and test reports) out of concern that it wouldn't meet my needs and I'd be stuck with an inconvenient beast. While some hands-on time with a 4-incher will be interesting, and I appreciate the loan of the scope, optics are exponentially harder to make well the larger they are. It won't address my questions about the larger instruments.

An affordable 6" to 8" achromat with a genuine 1/6 wave or better figure would be wonderful. One with a 1/3 wave or worse figure would be disappointing and a headache that I would need to unload for pennies on the dollar.

I'm hoping someone with a large Istar optic is willing to be the Rohr guinea pig. Here's his home page for his testing business:

http://rohr.aiax.de/hp_new/

OMI here in the US, also, will do refractor optics interferometer testing. However, they don't have the reference data base of past test data that Rohr has on astro-foren.de. It would be better than nothing, but not not as good as being able to do apples and apples comparisons with other currently available scopes.

Regards,

Jim


Post Extras: Print Post   Remind Me!   Notify Moderator  
The Ardent
Pooh-Bah
*****

Reged: 10/24/08

Loc: Virginia
Re: Istar refractors Pros and Cons? new [Re: stevew]
      #5805720 - 04/17/13 10:29 PM

I dont own an Istar, but I believe I have the credentials to offer an opinion.

Pros:
1. Its good to have a choice. We need more long focus refractors.
2. ISTAR appears to be motivated by passion for astronomy, not pure profit. I believe that if they were in it for the money only, they would only sell imaging scopes.

Cons:
1. They are not D&G
2. Color scheme and general appearance. Long focus refractors should be white, cream, ivory or some variant thereof. Hey Skylight UK, this means you too.

Whoop


Post Extras: Print Post   Remind Me!   Notify Moderator  
James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
Re: Istar refractors Pros and Cons? new [Re: Scott in NC]
      #5805734 - 04/17/13 10:34 PM Attachment (55 downloads)

Hi All....

Let me give some of my personal opinions, with regards to the 8" F8.8 Istar that I have owned for the past 2 and a half years....

I have to admit that I will not be able to find any similar 8" size refractor in my small little country city......to make a direct comparison.....

But with 3 other refractors that I have owned, WO88ED, C6R F8, and my latest APM 152ED APO....., I think is also good to give my personal opinions of the Istar against the rest....of my collection....

1. The WO88ED has the least amount of CA, almost not noticeable, but aperture is aperture....you don't ever think of getting magnification of 250X and above for a razor sharp view of the 2 giant gas planets....

2. The C6R F8 has roughly the same amount of CA like the Istar, but again its performance also cannot go beyond 250X for a razor sharp view of the 2 giant gas planets

3. The APM ED APO, still has small trace of CA, but performs well above 300X for the giant gas planets....I have not able to push it above 400X yet.....

4. The Istar although has either the same amount of CA like my C6R F8...., it is a scope that is still able to get a good a razor sharp image of the 2 giant gas planets, around 300X...
And it is also the only refractor scope that I am able to pushed it beyond 400X, but of course the image starts breaking down....

5. If you are talking about DSO, then I think the Istar can take on SCT of similar aperture that I have viewed through.....like my Ultima C8, and my friend's C8 edge HD....

6. The 8" F8.8 Istar achro, with its CA level, will not be able to complete with bigger aperture scope like my C14, that during last Monday side walk, whereby I collimated against Spica, and it is able to deliver Saturn with a 450X with razor sharp view....(coz I remove the corrector to clean it after never use it for about a year....)

7. Although some CN members may have asked me , why I still want to keep the 8" istar , after I have acquired the APM ED APO...., my answer is that there are still potential for the use of this istar....such as following:-

7.1 It is one of the cheapest I can find with such a big aperture, although I am not sure whether others may be able to get one much cheaper than istar...with the similar aperture...

7.2 During my side walk, which I do it at least once a month, many peole who has seen the Istar earlier, is asking me why I didn't bring the big one instead....It seems that people think the APM ED APO, 10" Mewlon and my C14, is not big enough....
Even last year , during the venus transit, when I asked the university professor which one he prefer me to bring, C14 or Istar, and the answer is very clear....with below ...

Picture of myself with the famous Prof Roy Patrick Kerr. He is the Distinguished Professor specially invited to grace the NUS Venus Transit 2012.

7.3 The Istar still has the potential to improve its performance with a CA corrector.....to ED APO doublet level.....
And now is in progress... So perhaps you will hear more of this in a month or two to come......

Regards

james Ling


Post Extras: Print Post   Remind Me!   Notify Moderator  
jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Istar refractors Pros and Cons? new [Re: James Ling]
      #5805776 - 04/17/13 10:51 PM

Thanks James.

Would you say that the Istar performs about the same as the C6R at the same magnification-per-inch? With two additional inches of aperture, it makes sense that it can handle higher magnification, so I think your opinion of the image quality in the two scopes operating at the same magnification per inch would be useful.

Regards,

Jim


Post Extras: Print Post   Remind Me!   Notify Moderator  
buddyjesus
Carpal Tunnel
*****

Reged: 07/07/10

Loc: Davison, Michigan
Re: Istar refractors Pros and Cons? new [Re: jrbarnett]
      #5805880 - 04/17/13 11:35 PM

for the price they offer, a 1/4 wave would be good enough for me, but I am not in the market FWIW.

Post Extras: Print Post   Remind Me!   Notify Moderator  
chboss
professor emeritus


Reged: 03/24/08

Loc: Zurich Switzerland
Re: Istar refractors Pros and Cons? new [Re: Scott in NC]
      #5805931 - 04/18/13 12:05 AM

After going through 7 pages of posts.... back on topic.

I would love to see some interferometry done on the ISTAR lenses.
But I would also be hesitant to ship the lens cell half way around the world with the quality of todays commercial carriers.
There are in fact only a limited number of user reports, but given the short time in the market place this is to be expected.

I found the following user reports:
http://neilenglish.net/adentures-with-the-istar-6-f10-achromat/
http://staff.polito.it/bartolomeo.montrucchio/Istar150f15/Istar150mmf15review...
http://neilenglish.net/the-phantom-menace-my-thoughts-on-a-6-inch-fluorite-tr...
http://stargazerslounge.com/topic/130343-istar-5-f8-achromat/

For your reading pleasure.

best regards
Chris


Post Extras: Print Post   Remind Me!   Notify Moderator  
James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
Re: Istar refractors Pros and Cons? new [Re: jrbarnett]
      #5805987 - 04/18/13 01:15 AM

Quote:

Thanks James.

Would you say that the Istar performs about the same as the C6R at the same magnification-per-inch? With two additional inches of aperture, it makes sense that it can handle higher magnification, so I think your opinion of the image quality in the two scopes operating at the same magnification per inch would be useful.

Regards,

Jim




Hi Jim...

I do agree that as the aperture increases, the scope should be able to handle higher magnification....

Although I have not seen through an 6" Istar achro, and able to compare with my C6R F8, but I am sure it should be much more superior than mine, simply my C6R is non collimable cell....and I know it does take a bit of adjustment here and there to get the best view, once I removed it for cleaning...
My disappointment with my C6R F8 is the lens coating flaking.....

But if you will to ask me what disappointment do I have with the istar, my answer is it does not come with any lens shade or cover?????

Regards

james Ling


Post Extras: Print Post   Remind Me!   Notify Moderator  
john@dps
member


Reged: 02/06/13

Loc: Granada Hills, CA
Re: Istar refractors Pros and Cons? new [Re: Scott in NC]
      #5806013 - 04/18/13 01:52 AM

I really like everyone's view on the istar scopes, butt some posters act like we all have 20,000 dollars apo's and that's just not true in almost all cases. I will say again that a good 3000 dollar scope made the best it can be made is not a bad deal. Those who complain of weight just need to stick with 80mm ed's. You want a 6,8 or 10" refractor don't talk to use about weight. Talk to jenny craig.

John


Post Extras: Print Post   Remind Me!   Notify Moderator  
chaoscosmos
sage
*****

Reged: 01/26/13

Loc: Mission Viejo CA
Re: Istar refractors Pros and Cons? new [Re: john@dps]
      #5806022 - 04/18/13 02:14 AM

You should do what suits you. For most people, large refractors up to 8 and 10 inches are not practical. But it's not a macho issue, after all. It's just a scope.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Kunama
professor emeritus


Reged: 10/22/12

Re: Istar refractors Pros and Cons? new [Re: chaoscosmos]
      #5806032 - 04/18/13 02:40 AM

Although I have now sold the Istar, I did get a chance to compare it to my Takahashi TSA120 F7.5 Super Apochromat side by side. The Istar was a 150mm F10 Perseus. Using GSO 2" diagonal in the Istar and a WO 2" diagonal in Tak with Vixen LVW eyepieces of 3.5, 5, 8, 13, 17 and 22mm
The CA of course was even more evident against the colour free Tak but as far a resolving detail on the Moon and Jupiter the Istar performed surprisingly well up to 300X showing good detail on Jupiter and excellent detail on lunar craters. With the addition of a Baader SemiApo filter the Istar was all the scope one would ever need for visual astronomy.

The Tak did outshine in every regard, esp on Sirius, but so it should at near 3 times the price.

I sold the Istar, not because I was unhappy with it, but because my Vixen mount could not cope with the moment arm of such a long scope. I have since bought a T-Rex Alt Az mount and now wish I still had the big Istar.

The Istar is an extremely well built, robust scope but needs a mount to match its mass.

I really don't care if I never see an interferometer test of it, I really did like the scope and would have no hesitation to buy another, especially if the planned Raycorr comes to life.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Kevin Barker
super member


Reged: 04/22/09

Loc: Auckland, NZ
Re: Istar refractors Pros and Cons? new [Re: James Ling]
      #5806107 - 04/18/13 05:46 AM

Hi James
Were you a student at Canterbury University, New Zealand?

Professor Kerr lectured me in Calculus there back in the 1980's. I was studying Physics there. Kerr is famous for the formulating of the "Kerr solutions" which are most probably rotating black holes.(from memory)

It occurs to me that a big fast refractor is not likely to have a very impressive test report across a range of wavelengths (i.e a low polychromatic strehl) when using an interferometer. I was unable to find many reports on Rohr's website of big achromatic refractors.

The vast majority of reports are of very expensive apochromatic refractors.

I wonder how many amateurs would really understand these reports?

Kevin


Post Extras: Print Post   Remind Me!   Notify Moderator  
James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
Re: Istar refractors Pros and Cons? new [Re: Kevin Barker]
      #5806126 - 04/18/13 06:21 AM Attachment (35 downloads)

Hi Kevin....

Great to hear that you are one of Professor Kerr's student....

Sorry.... I have never been to New Zealand....

Last year , our local university, invited Professor Kerr to Singapore as a special VIP guest for this Venus transit....
And I am glad to be invited to this special event with my Istar scope...

And as usual, the Istar is really the main attraction in this special event.....with long queues waiting to see the final moment of the transit....

This is one of the event that I will never forget ....

Regards

James Ling


Post Extras: Print Post   Remind Me!   Notify Moderator  
tomharri
sage
*****

Reged: 09/19/08

Loc: USA
Re: Istar refractors Pros and Cons? new [Re: James Ling]
      #5806991 - 04/18/13 03:52 PM Attachment (24 downloads)

Been building Jaegers refractors out of the Surplus Shed sell offs. Also did The Shed's 5" f/9.4 & it's the best of all the achros. But really my APM 107/700 triple out performed all these 4 & 5" scopes on planetary targets.

Then I built the Istar 5" f/8 R30 just to see. Finally a neo-ed scope that exceeds the 107 in every way, planetary and deep sky.

Next build will be the APM 6" f/8 ED China built lens, you know the one people are already bashing and there is only one out there.

Will they shut up when a few dozen arrive soon? Or just get louder?


Post Extras: Print Post   Remind Me!   Notify Moderator  
jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Istar refractors Pros and Cons? new [Re: john@dps]
      #5807184 - 04/18/13 05:31 PM

"[A] good 3000 dollar scope made the best it can be made is not a bad deal."

I don't think anyone is disputing this. The questions at hand, though, are (1) are these "good" $3000 scopes?; and (2) are they made "as best they can be made"? The answers to those questions will determine whether they are a so-so, good or fantastic deal, I think.

I also think that weight and length are correlated with optical quality in the following way. A longer heavier scope requires a larger, more costly, more capable mount to hold stably. Making such an additional investment for an affordable, great quality cumbersome scope might make sense. Doing so for one with poor optics, though, would be a monumental waste of time, effort and budget.

Jenny Craig might help you lose weight, but it won't make you pretty if you're ugly.

Regards,

Jim


Post Extras: Print Post   Remind Me!   Notify Moderator  
john@dps
member


Reged: 02/06/13

Loc: Granada Hills, CA
Re: Istar refractors Pros and Cons? new [Re: jrbarnett]
      #5807898 - 04/18/13 11:10 PM

"Jenny Craig might help you lose weight, but it won't make you pretty if you're ugly"

That's why Jenny didn't work for me. I didn't have a chance to start with.

I might have a real case against Jenny because they didn't disclose that in the TV ad.

Edited by john@dps (04/18/13 11:13 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Istar refractors Pros and Cons? new [Re: john@dps]
      #5808035 - 04/19/13 12:59 AM

Yeah, me too. And they even taught me to read the fine print, and I missed it.

But think of it this way. You can get a C6R OTA for $500 or a Kunming 6" f/5.9 OTA for between $700 and $900. Optically the C6Rs vary a bit from decent to just so-so, and the Kunmings tend to be decent to good optically (but loaded with CA, of course). A $1500+ 6-incher has to be better across the board than these scopes to support its considerably higher price. On the other hand, once you go bigger than 6" the competition thins out considerably, and it gets harder to argue with the price being asked.

If Istar doesn't bring the Raycorr out soon, maybe Aries would consider a new run of updated reasonably priced Chromacorr Is to tide the big achro folks over. I think the existence of a new run of Chromacorrs would help everyone selling fastish achromats I suspect.

Regards,

Jim


Post Extras: Print Post   Remind Me!   Notify Moderator  
James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
Re: Istar refractors Pros and Cons? new [Re: jrbarnett]
      #5808088 - 04/19/13 02:51 AM

Quote:


If Istar doesn't bring the Raycorr out soon, maybe Aries would consider a new run of updated reasonably priced Chromacorr Is to tide the big achro folks over. I think the existence of a new run of Chromacorrs would help everyone selling fastish achromats I suspect.

Regards,

Jim




Hi Jim....

Although Istar has plan to introduce their CA corrector, or known as raycorr, in this year...., but according to them is optimized for their R series.....
So perhaps the raycorr may not give the fullest improvement to other brands of achro.....

Many Istar owners like myself are also waiting for the release of this product, but I have decided to go for one that already being introduce into the astronomy world many years ago....., although I ever mentioned I still prefer to wait....

Regards

James Ling


Post Extras: Print Post   Remind Me!   Notify Moderator  
stevew
Now I've done it


Reged: 03/03/06

Loc: British Columbia Canada
Re: Istar refractors Pros and Cons? new [Re: jrbarnett]
      #5828515 - 04/28/13 02:35 PM

Quote:


Thanks to a very kind CNer, I now have a 4" Istar on loan. Once I get it unpacked it will be used for some "same night, same site, same magnification, same targets" comparative testing along side some other 4-inchers (TV-102, AT111EDT and Antares 105/1500). I'm looking forward to it, and after comparing notes with the owner, will start a new thread (with plenty of pictures) discussing the results/impressions of the scope relative to some peers.


Regards,

Jim



Jim, any word on the 4 inch Istar you have on loan??
What do you think of it?
Steve


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | (show all)


Extra information
27 registered and 34 anonymous users are browsing this forum.

Moderator:  Scott in NC, FirstSight, panhard, star drop 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 11931

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics