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Equipment Discussions >> Refractors

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James Ling
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Reged: 09/18/10

Loc: Singapore
ISTAR 8" F8.8 With Chromacorr II
      #5921753 - 06/15/13 06:30 AM Attachment (223 downloads)

Hi ALL....

As I have acquired the ISTAR 8" F8.8 for more than 2.5 years, only this year I made the decision to enhance its performance by getting the Chromacorr II...

As I do not want to purchase just the Chromacorr II, and then spend time to make the spacers and getting it properly aligned, I go directly to Valery, and he configured the Chromacorr II for my ISTAR 8" F8.8, so that it is just plug and use straight away....

The Chromacorr II is shipped two weeks ago, and arrived last week, but I only went to my local post office to collect it, since I am working oversea, and back during the weekend....

REgards

James Ling

Edited by James Ling (06/15/13 06:30 AM)


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James Ling
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Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5921758 - 06/15/13 06:37 AM Attachment (160 downloads)

Last weekend supposed to do the chromacorr II field test at my friend's roof top observatory, whereby my ISTAR has been left at his place since the last shootout....

But my friend only discover that his motorized canopy is stuck, and damaged , during the very last minute, we have no choice but to get it repaired , and do the Chromacorr II field test in another week...

REgards

James Ling


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James Ling
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Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5921759 - 06/15/13 06:44 AM

Although the replacement part for the motorized canopy has not being replaced , but the contractor already did a temporary fix..., as such tonight we are going ahead with the Chromacorr II field test, even though we are now hit with heavy haze, from Indonesian fire.....

I hope this field test will be a positive one, transforming the ISTAR 8" F8.8 from classic achro to ED APO (visual)....
after tonight 1st field test at my friend's roof top observatory...

Our prime target will be the 7 days old moon and Saturn....

Will update all of you, after I am back from the field test tonight....

REgards

James Ling


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Gord
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5921879 - 06/15/13 09:31 AM

Congratulations James!

I think you are going to be _very_ impressed!

I had mine out last night and the views are very apochromatic. It will allow you to unleash all the potential of your lens!

Look forward to hearing your report!

Clear skies,


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Jeff B
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Gord]
      #5922025 - 06/15/13 10:54 AM

Me too Gord. Last night here in SW Ohio was one of those rare special nights with stable air and a dry clear atmosphere. The Moon and Saturn were spectacular then later came M13 (wow).

I used the following with my 11" F12 D&G achromat, Intes Deluxe diagonal and Denk IIs (most eyepieces were pairs of my good old Celestron Silver Top Plossls):

7" aperture stop, 4" spacer infront of the diagonal, Chromacor I U-1. Complete APO performance, even at the 300X max. Even the lateral color was reasonnably well controlled at low-ish powers (110-150X). I soon progressed to the 8.5" stop as the lens and atmosphere calmed.

8.5" aperture stop, 4" spacer, Chromacor I U-1. This is a definate sweet spot for this lens and typical seeing around here. Complete APO performance similar to using the 7" stop but the resolving power of the larger aperture was immediately obvious. The transitions from lunar crater ridges to the shadows over the floors was striking. The crater floors were jet black at any magnification up to my max of 300X. There was that distinct, sharply etched rubble effect that good optices immediately display, as a friend of mine said, "Like somebody took a handfull of sharp pebbles and threw them out onto the surface around the craters." Saturn was amazing with the planets ball looking like a hard boiled egg yolk. Many, many white streaks were visible (as well as moons), Cassinni's completely obvious all the way around, Enke's and Crepe visible with care. So I put in the 9.5" stop.

9.5" aperture stop, 2" spacer and Chromacor I N. Similar to the 8.5" stop with the extra inch aperture noticable but a little purple starts to be seen on lunar crater walls. No purple on Saturn, which is yellowish anyway. Quickly moved to the full 11" aperture.

Full 11" aperture with no spacer and Chromacor I O-1. WOW take everything I said about the 8.5" stop and add 40% better resolution and almost 2X brightness. The planet looked 3D and the rings were taking on that subtle, rough phonograph record look. Satrun looked commpletely etched and "fake", "that can't possibley be real!" Boy it was though. The increased resolution at full aperture was well worth the penalty of slightly more secondary spectrum. I did not look at the Moon this way as it was now low in the sky, but I rarely use full aperture on the Moon anyway so I turned the big guy loose on M13 (WOW), Izar & the double double(both beautiful but I typically use the 7" & 8.5" stops for doubles)and Vega (FANTASTICALLY, intensly, bright blue embedded in a beautiful, subtle, dim purple).

Conventional wisdom would say that the Chromacor O-1 would not be suitable for this lens at full aperture and lead to decided over correction. However, that's not the case as this combination is killer. I suspect this works as the lens at full aperture is mildly undercorrected and perhaps the O-1 is not really an O-1 (some, like my U-1, were missed marked). But for what ever the reasons, the combination WORKS and works WELL, giving color performance almost identical to a 4" F12 achromat using the AP Max Bright diagonal and a 4" F15 using the Intes diagonal (The Intes diagonal is excellent but does have a very subtle, but noticable yellow tint to it, like a very weak minus violet filter which works most effectively with the D&G using the 9.5" aperture stop and full aperture.). Yeah there was a bit of purple on Vega but the contrast between it and the intense pure blue of the star was strikingly beautiful.

So James, not to steal your thread but what did you come up with? One of my ATM projects is an 8" F9 achromat and I just happen to have a Chromacor II N.

Jeff


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James Ling
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Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Jeff B]
      #5922191 - 06/15/13 12:23 PM Attachment (149 downloads)

Hi Gord and Jef....

Thanks for the sharing on your experience on using the chromacorr....

Hi ALL...

As I just returned back form my friend's place , after 2 short hours of testing...the chromacorr II with my ISTAR....

Although tonight the weather is very hazy, but yet I can see something different between using the chromacorr II ....

1. The 7 days old moon is still bright enough, to see the improvement on the CA level....

2. Without using the chromacorr II , we can see the thin stripe of greenish-yellow CA, on the curve edges of the 7 days old moon...
With the chromacorr II, the the thin stripe of greenish-yellow CA, is still there, although it seems to be lesser...

3. Without using the chromacorr II , we can see the the purple CA, on the curve edges of the 7 days old moon..., which is many times thicker then the green colour...
With the chromacorr II, the purple CA is completely gone....

I took both photos with my camera phone, but the result did not show exactly what is seen..., between actual visual, and downloaded onto computer...
(Photo shown is with chromacorr II)

REgards

James Ling


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James Ling
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Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5922219 - 06/15/13 12:43 PM Attachment (129 downloads)

Hi ALL...

I did point the ISTAR to Saturn, but due to the hazy sky condition, I could only able to use my 9mm Nalger to power up Saturn till 200X...

I tried to use my 4.8mm Nalger , but the image breakdown...

At 200X, both the views from with and without the chromacorr II could not show the big difference, as the ISTAR itself already a killer at moderate power....

In fact tonight there are 5 moons spotted, with four very bright one , like a trapezium on top of Saturn, and one very faint one, very close and below Saturn...

Is the view from the chromacorr II seems easier to pick up the faint one, although I also manage to see it without the chromacorr II...

The ISTAR during my last shootout at my friend's place when the condition is right, you can power it up to above 300X, but surrounding the image is not clean, but tonight I cannot verify how the chromacorr II will show at higher power on the planet saturn...

I will need to do more testing, in order to see the full benefit of the chromacorr II....

Regards

James Ling


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John Huntley
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5922272 - 06/15/13 01:18 PM

Interesting results James

It will be interesting to see if Valery has any comments to make but from my experience of using Chromacor I's and II's with chinese 6" F/8 achromats I think you might be able to get even better colour correction than that.

Even with the CC 1 I was seeing virtually no CA rim around the lunar limb at focus. The CC 2 made the scopes colour free to my eyes except on the brightest of stars and then there was just a very slight splash of purple.

Perhaps some experimentation with the spacing of the Chromacor / diagonal would be worthwhile ?

Baader Fine Tuning Rings are good for this as well as the traditional 2" filter rings.

Edited by John Huntley (06/15/13 01:19 PM)


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KerryR
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Jeff B]
      #5922487 - 06/15/13 04:08 PM

Hey Jeff,

I'm curious about what process you use to determine the length of the spacers, the one(s) between the C-cor and diag, you use with the various aperture stops. Mind discussing? I don't want to hijack the thread, so if another should be started, let me know...

I'm always looking for ways to further understand/optimize my C-cor-N and Synta 6" f8...


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Jeff B
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: KerryR]
      #5922503 - 06/15/13 04:27 PM

Quote:

Hey Jeff,

I'm curious about what process you use to determine the length of the spacers, the one(s) between the C-cor and diag, you use with the various aperture stops. Mind discussing? I don't want to hijack the thread, so if another should be started, let me know...

I'm always looking for ways to further understand/optimize my C-cor-N and Synta 6" f8...




For basics you need to first determine if your scope is a bit undercorrected (which the majority of the Synta scopes seems to be in my experience) neutral, or overcorrected ( a relatively small number) in green light using a deep green or deep yellow filter(or both)using a star test.

We can then try to get the best performance out of your Chromacor N. Is yours a Chromacor I or II?

Also, I've written extensively about my Chromacors. So has Valery. You can try a search here and dredge up some postings.

Yes a new thread would probably be best.

Jeff


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James Ling
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Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Jeff B]
      #5922812 - 06/15/13 08:30 PM Attachment (115 downloads)

Hi ALL...

Thanks for your comments and suggestions...

Below is the photos shot comparison I made showing with and without chromacorr II.....

Regards

James Ling


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timps
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Reged: 02/24/13

Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5922926 - 06/15/13 10:02 PM

Quote:

Hi ALL...

Thanks for your comments and suggestions...

Below is the photos shot comparison I made showing with and without chromacorr II.....

Regards

James Ling




I prefer the without chromacorr II image.


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mikey cee
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: timps]
      #5923104 - 06/16/13 12:54 AM

So the Chromacorr makes the Moon look yellow?? I don't believe I'd care for that. Mike

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ValeryD
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: mikey cee]
      #5923200 - 06/16/13 03:54 AM

Hi all,

I can't tell exactly what James need to tweak now, coz he didn't test the Chromacor-II under clear sky and with
different eyepieces.

When the object shows a greenish-yellow rim, this normally mean that a large focal length eyepiece was used and that this eyepiece has it's own later color.

So, the proper test should be as follow:

1. When the laser collimator is installed in the focuser's 2" adapter, the laser beam should strike the objective lens exactly in the center. In this case the focuser is well collimated.

2. Chromacor-II should be installed in the 2" adapter in the focuser with no play. Just very little - enough to install the Chromacor. Chinese 2" adapters in standard 6" refractors have too much play.

3. Point the telescope with CC-II in place on a bright white star. Install 10mm or shorter eyepiece and look at the star. No purple halo should be seen around the star when it is in the center of the FOV.

4. Defocus the star somewhat before and after focus. One will see some residual chromatic CA. The residual CA halo before and after focus must be very symmetrical. If one side of the defocused star has more color and the opposed side has less color, this mean that Chromacor's optical axis is not coincide with objective optical axis.
One must slight tilt the Chromacor-diagonal rig along the direction of the color asymmetry.

Once the symmetry of the defocused star (or planet) will be reached, then the Chromacor is properly collimated.
Now all objects being placed near the center of the FOV will be color-free.

The only problem can be the atmospheric dispersion - so, such a test must be done on a star near zenit.

Hope this help.


Valery.


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James Ling
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Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: ValeryD]
      #5924822 - 06/17/13 03:14 AM

Hi Valery...

Thanks for the instruction for the proper test that I need to conduct , and making the adjustment....

I already notice the big shift of view of both the moon and Saturn when I interchange the chromacorr II against my other diagonal...

I will use a laser collimator to ensure is concentric, before doing the chromacorr II retest again, as I can adjust the 5 ISTAR countercell holding screws.....

Unfortunately heavy haze from Indonesia fire just stuck us last weekend, and looks like it will take a few weeks to a month for the blue sky to appear again.....

I hope I can do another test in two weeks time, as my friend is also tied up with his personal commitments in coming few weeks...since this is our school vacation....

One question I wanted to ask, is that the visual view through the chromacorr II seems to be smaller as compared to the view without chromacorr II...

Regards

James Ling


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BluewaterObserva
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5925774 - 06/17/13 03:28 PM

I used my Chromacor I N with my home made 8" F/9 for nearly a decade. It is a difference that has to be experienced to be fully appreciated indeed. The 8" F/9 lives as a dedicated Solar telescope now so I just listed my Chromacor N in the classifieds.

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ValeryD
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: BluewaterObserva]
      #5925974 - 06/17/13 05:14 PM

Quote:

I used my Chromacor I N with my home made 8" F/9 for nearly a decade. It is a difference that has to be experienced to be fully appreciated indeed. The 8" F/9 lives as a dedicated Solar telescope now so I just listed my Chromacor N in the classifieds.




Can you start the thread about your 8" F/9 telescope's second life? I now too in the solar astronomy with my SW150/750 deeps sky telescope transformed in to a dedicated Solarscope with H-a 0.7A filter and second 0.7A filter as a double stack.


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BluewaterObserva
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: ValeryD]
      #5925983 - 06/17/13 05:21 PM

Not real sure it would be worthwhile for most....

I use a really old 1000 Oaks .8A filter. The proms are nice and bright though. I would like to try something double stacked on it at some point though.


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Jeff B
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: BluewaterObserva]
      #5952691 - 07/03/13 08:33 AM

James, have you had a chance to continue your use of the Chromacor II with the 8"?

Jeff


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James Ling
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Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Jeff B]
      #5953986 - 07/03/13 10:53 PM

Hi Jef....

The timing on receiving this chromacorr II is really not a good time, whereby the Indonesian fires , is causing the whole region, to be blanketed by a thick haze...

The fires already burnt for more than one month, and now maybe 75% are pulled down , and the weather is improving, with blue sky coming back....But this is followed by daily heavy downpour....
But this is not over yet, as it depends on the wind direction...

This weekend, I may arrange to have a short session at my friend's place again to test the chromacorr II.....when I returned back from oversea work assignment....
Just hope the planned session is not affected by the rain or haze....

REgards

James Ling


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James Ling
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Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5958739 - 07/07/13 11:09 AM Attachment (72 downloads)

Hi All...

This weekend , although I have no chance to try out the chromacorr II with my 8" ISTAR, but I managed to test out with my C6R F8, during the day time,as the sun is still shining through the cloudy sky....

I have used a statue at around 500M away, and using a 9mm nagler to view at the object...

Without the chromacorr II, as the light from the Sun hit the statue, the edges of the whole statue shows the greenish yellow tint, which is indicated in the photo attachment...

When the chromacorr II is plugged directly into the focuser of the C6R F8, the differnce is very obvious....
Only a smaller greenish yellow tint is visible, and is only at the head of the statue...

And the surface detail of the statue which have many porous marking are easily visible, which without the chromacorr II, is very faint....

And is very obvious, the chromacorr II is working fine with my C6R F8....And I may bring this combination for my coming side walk, which is also the 1st qtr moon.

The testing on my ISTAR is re-scheduled to next weekend, which again is subjected to the weather.

Regards

James Ling


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Jeff B
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5958786 - 07/07/13 11:38 AM

The thing really does work! I almost hate to suggest this but a comparison between the CR6 w/Chromacor II and the APM 152 F8 would be most interesting.

BTW, I should have an 8" F8.8 achromat ATM project completed within the next couple of months and I've N, O1 and U-1 in Chromacor I's and a Chromacor II N. It should be fun to compare notes.

Jeff


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James Ling
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Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Jeff B]
      #5960023 - 07/08/13 04:46 AM Attachment (40 downloads)

Quote:

The thing really does work! I almost hate to suggest this but a comparison between the CR6 w/Chromacor II and the APM 152 F8 would be most interesting.

BTW, I should have an 8" F8.8 achromat ATM project completed within the next couple of months and I've N, O1 and U-1 in Chromacor I's and a Chromacor II N. It should be fun to compare notes.

Jeff




Hi Jeff....

Great to hear that your 8" F8.8 achromat ATM project completed within the next couple of months..
And definitely you are going to have good comparison on the result on using the different types of chromacorr that you have possessed..

Hi Jeff and ALL....

As for the visual view on C6R F8 with chromacorr 2 against the 152 APM ED APO,
Yes, I did a comparison last weekend, and I just want to say the APM ED APO is really performing as per my expectation...as it even didn't show a tiny bit of greenish yellow when viewed through the same statue object with the same 9mm nalger...
The statue's surface through the APM ED APO is able to show much higher clarity of the porous marking as compared to the C6R F8 with chromacorr 2....

The following are the details of what I have seen from both the C6R F8 with chromacorr 2 and the APM ED APO..( refer to photo attachment)

1. C6R F8 with chromacorr 2 only the top of the statue's head shows a small amount of greenish yellow tint...

2. APM ED APO shows not a single trace of CA...on the statue....

3. The C6R F8, with chromacorr 2, when moving the visual view of the statue towards the edge of the eye piece, the greenish yellow tint disappear......and when it at the edge, a small amount of purple violet appears...
For the APM ED APO, there is no appearance of the greenish yellow tint, when moving in the same direction, but a smaller amount of purple violet appears when the statue's head is near the edge.

4. The C6R F8, with chromacorr 2, when moving in the opposite direction, towards the other edge, the greenish yellow tint, still remains, but just at the statue's head....
For the APM ED APO, a very very smaller amount greenish yellow tint appears when the statue's head is near the other edge....

I am not sure whether my C6R F8 lens cell is centered , as I do not have the laser collimator with me now....
Otherwise I may be able to further improve the C6R F8 with chromacorr 2 to match or get close to its contrast detail........

REgards

James Ling


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Jeff B
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5960303 - 07/08/13 10:32 AM

James, the major limitation for the Chromacor is off-axis lateral color where the red, blue, and green colors start to separate out from each other laterally,just like in a prism. This starts to occur a few arc minutes off axis. For me, this is easily seen on the Moon, for example, starting about half of the way out in the field of view of your typical Plossl eyepiece. I personally don't find it objectionable because I'm always focused (HAH!, just had to say that) on the color free image in the center. Also, a little trick is that for objects lower in the sky, the chomacor's lateral color can actually reduce atmospheric dispersion effects.

So this also shows the attraction of double ED scopes for me in that even though the ED scopes may not be as well corrected directly on-axis as a really good achromat with a well chosen Chromacor, the ED scope, however, has much better correction over a much larger field of view. I too much prefer my good old 4" F9 ED scope over a similar F10 achromat with a Chromacor for daytime use. Saturn, however, is a different story, though, I have to admit that the Chromacor II cost me as much as the two scope combined...ouch.

Jeff


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Gord
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Jeff B]
      #5961357 - 07/08/13 10:36 PM

Hi James,

Glad to see you are finding something to do with your scopes if you can't look at the sky! I may have to try that myself... perhaps try looking at that thing outside that looks like a tornado!

Anyway, I was just going to make the same comment that Jeff did. You will only see the benefit from the Chromacor at/near the center of the field. Works great on planets and doubles and specific features on the moon that you want to look right at.

I myself don't like the look of things as they get farther off axis so wouldn't leave the Chromacor in for example during DSO observing (other than maybe a small globular). This is where the true ED/apo's shine, having things look great everywhere.

The big advantage of course comes in when you start going up in size. At 4-5", there is not really much place for chromatic correction so much since real ED/apo's are so affordable. But the price of them goes up quickly beyond that and the Chromacor comes into it's own!

What is your setup of the Chromacor on the C6R BTW? Are you using any spacers? Jeff would be a good one to comment on this since he has a 6" F8 and a C-II N (Jeff?).

My experience with two different Chromacor's now is that the color correction improvement is really only part of the story (and this echo's comments that Jeff has made before). When I had the incorrectly matched Chromacor O1 in my 6" F10, I saw a dramatic improvement in color correction, but upon closer study, not so much improvement in actual fine details. When I switched to the better matched one (Chromacor-II U1), the difference was _huge_ on all fronts! Basically no color, but more importantly was the detail change (again, in the center area).

Clear skies!


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ValeryD
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Gord]
      #5961837 - 07/09/13 08:51 AM

Hi James,

Gord and Jeff both have correctly mentioned, that Chromacor must be matched to a given objective in spherical correction, properly spaced in the telescope and very precisely collimated.
If only your Chromacor-2 rig has even slightest inclination to the optical axis, then you will see color correction imperfections even in the center of the FOV.

Spherical aberration aside, the Chromacor must be exactly (at least very close to) at the optical axis.
Then you will see no colors at all in the center of the FOV.

Also, this is random unmatched test. This given Chr-2 was re-designed, disassembled and re-worked specifically for 8" F/8.8 achromat and appropriately spaced for the best work at this cone F/8.8

I would not advice you to change something in the plug&play Chromacor-2 in the goal to improve something in it's performance with random 6" achromat. Better to use your Chr-2 with the scope it was redesigned for.

As soon as you will have good sky and can work with 8" refractor, your 6" will not be used especially because you do own a 6" ED by APM.


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: ValeryD]
      #5963136 - 07/09/13 10:36 PM

Ah, very important Valery and explains a lot.

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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Jeff B]
      #5963579 - 07/10/13 06:54 AM

Hi Jeff, Gord and Valery..

Thanks for all the explaining and clarifying.....

I hope this weekend I can try out the chromacorr 2 , at my friend's roof top...

I may pull back my ISTAR for coming Monday , our monthly side walk, which I think the 1st quarter moon , will be nice to view through with the chromacorr 2.

Will report again on any new finding on the use of the chromacorr 2....

Regards

James Ling


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5973540 - 07/16/13 03:43 AM Attachment (27 downloads)

Hi All...

Following is an update on the chromacorr II as I still have no chance to do any planetary or star test....due to the bad weather...

I did pull back my Istar back from my friend's roof top observatory, and planning for yesterday night monthly side walk...activities....

But again yesterday bad weather has prevented me from having it tested again, as such over this weekend I did some laser collimator test, which I loan it from my friend....

Following is the photo of the Istar scope that I laid it on the floor for the laser collimator testing...

Regards

James Ling


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5973545 - 07/16/13 03:49 AM Attachment (24 downloads)

1. The 1st test is placing the laser collimator directly through the focuser , and observing the laser position at the lens cell end.....

This is the 2nd time I am doing, as I did this the very last time when I cut the tube and machined a connecting sleeve, then joined back the 2 tubes as one, to ensure the tube is straight...

The laser at lens cell end is at centre and not shifted since my last check...

continue...


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5973546 - 07/16/13 03:54 AM Attachment (18 downloads)

2. The 2nd test is by placing the laser collimator through the 2" diagonal ( The new diagonal that shipped together with my APM ED APO ), and laser observed from the lens cell end is also at centre....

This is the diagonal that I used to do all the comparison against the chromacorr 2 and its NPZ diagonal...

continue....


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5973550 - 07/16/13 04:03 AM Attachment (26 downloads)

3. The 3rd and final test is to place the laser collimator through the NPZ diagonal and the chromacorr 2 assembly, and the laser observed at the lens cell end...
Surprisingly, the laser position is offset by around 2 inches....
And maybe this is the reason why when i did the preliminary tests, it seems that I still observe the greenish yellow tint of colour ....
looks like I will need to wait until another night of good weather to retest this chromacorr 2 and check on the result on the planets, moon and the star pattern, before deciding what to do next....perhaps is adjusting the NPZ diagonal....to bring the laser back to the centre of the lens cell.....

Regards

James Ling

Edited by James Ling (07/16/13 04:04 AM)


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Jeff B
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5974012 - 07/16/13 12:09 PM

...and that would be a problem.

For my big D&G achromat I also had the Chromacor in the light path for both the laser and cheshire testing and everything was fine. Can you put the Chromacor on the APM diagonal?

Jeff


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Jeff B]
      #5974138 - 07/16/13 01:23 PM

Wait. At first blush, this seems to be a problem of the Chromacorr II not the diagonal. Why would you even consider adjusting the diagonal, when everything is otherwise collimated? This would not get the best results.

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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: johnnyha]
      #5975409 - 07/17/13 02:33 AM

Hi Jef..../ Johnny...

I think I can test the chromacorr 2 by unscrewing it form the spacer, and thread it onto my APM 2" diagonal and check on the laser path, this coming weekend when I am back home....

If the laser at the lens cell end is at centre, then the chromacorr 2 should be alright, and it maybe the NPZ diagonal is out of alignment , during the shipment....

Valery has told me not to adjust the NPZ diagonal first, but to verify on the symmetrical of the stars first, but this may need to wait a while, as the weather in my region is cloudy and raining almost daily, after the haze is gone...

Regards

james Ling


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6017078 - 08/10/13 03:48 AM Attachment (40 downloads)

Hi All....

This is my latest update on the chromacorr II , and today I managed to do a daytime visual test over a distant object.....under bright sunlight.....

The result is very obvious this time, from the photo attachment comparing with and without chromacorr II...

And come to 17th August 2013, will be great to see this 8" ISTAR in action , at our next plan astro talk and side walk event....

Regards

James Ling


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6017088 - 08/10/13 04:25 AM

Now -THAT- is quite a difference!!!

What eyepiece did you use here?
Mark


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Mark Harry]
      #6017100 - 08/10/13 04:47 AM Attachment (26 downloads)

Hi Mark...

The photos are taken with a canon DSLR 550D , set at manual mode, with auto ISO setting, and manually focused the image, before taking the single shot...
(Refer to photo attachment)

As for visual viewing through the ep, I used my favourite Baader Hyperion Mark III zoom , setting it at 8mm, and from the result, I adjust the attachment or spacer distance, for the most optimum distance between chromacorr II and the diagonal.. (the attachment is 15mm threaded for at least 10mm of distance for my trial and error....

REgards

James Ling


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6017121 - 08/10/13 07:47 AM

MUCH better looking James! Can't wait to hear how you find it under the stars. I hope things are improving for you for the local conditions (fires, etc.).

Clear skies!


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Gord]
      #6017247 - 08/10/13 09:45 AM

Hi Gord...

Yes, next weekend our group is organizing an astro talk cum side walk activity , so if the weather is not that bad, I should be able to use my DSLR to shoot some photos, especially the 11 days old moon and Saturn should be good objects for comparison...

Regards

James Ling


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6017365 - 08/10/13 10:49 AM

James it looks to me like either the Chromocorr is dimming the image or the same shutter speed was not used. This can affect the blue intensity. Can it not? Mike

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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: mikey cee]
      #6017576 - 08/10/13 12:58 PM

Hi Mike....

Yes, you are right... it seems that from the photo shot, the one using chromacorr II is dimmer...
But visually , is not easy during the day, to determine a major difference in the brightness.

I checked both photos file on its details, and since I set ISO to auto, the camera itself will select the one that it determines is correct...
The chromacorr II photo ISO is 320, while without chromacorr is 500.
The shuttle speed is 1/100 sec for both photos.

But one thing for sure, I want to emphasize on what I have seen through visually from the 3 scopes which I have, when using the chromacorr II...

1. 152 APM ED APO. without the chromacorr II the view during daytime at the same statue the contrast is very sharp and clear...without CA.
But with the chromacorr II, it become soft and contrast is worst..., and CA is presence (violet), and you can tell the difference very obvious...

2. C6RF8. without the chromacorr II the view during daytime at the same statue the contrast is not sharp and clear...with plenty of CA.
But with the chromacorr II, it become sharper and contrast is improved...,but still cannot match the APM ED APO, and although CA is presence but is reduced drastically (especially the violet), and you can tell the difference very obvious...

3. 8" ISTAR.
The 1st attempt at my friend's roof top observatory with poor and cloudy weather, cannot show any significant difference in term of CA and surface details of the moon...
Today is my 2nd attempt, and although is a daytime comparison, the following are being observed...
without the chromacorr II the view during daytime at the same statue the contrast is very sharp and clear...but with CA and is a bit intrusive. (like the C6R F8)
But with the chromacorr II, the contrast is still sharp and clear..., and CA is presence, but very minimal and not intrusive, and you can tell the difference very obvious...caused the view is more pleasing....
I cannot conclude at this moment , whether the surface details does improved, but for sure the overall visual view is much better , which is mainly due to the drastic reduction of CA...Until this coming weekend when I test it at Saturn, I should be able to tell the difference under a clear sky...

And I now really envy those who has / have received their 8" R30/35 version.... coz I know is definitely much better in terms of performance, especially with a well controlled and reduced CA, over my classic model....

REgards

James Ling


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A. Viegas
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Gord]
      #6018793 - 08/11/13 11:00 AM

James,

If its possible I would be curious to see the difference in visual performance using a Viloet Fringe killer or a semi APO filter versus the Chromacor. I suppose it's all a matter of preference, but there is obviously a very large financial step from achromatic to true APO and along the way I was wondering how effective some of these filters are versus a more expensive Chromacor. For my 6" R30 I detect very little Violet fringing at low power, on lets say Altair or Vega... But at higher power, like anything over 100x it starts to become much more apparent. At very high power like 250x to 300x or more it's not practical to use as the CA is just too overpowering...

Al


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: A. Viegas]
      #6020300 - 08/12/13 07:53 AM

Hi Al Viegas.

I have a WO minus 1 filter, which I have tried previously onto my Istar, and it doesn't improve at all.....
And I still prefer to use polarized filter to dim down the brightness when i am looking at the moon...
For other objects, I don't use any filter at all.....
Coz i prefer to look at DSO such as star clusters, nebulae,etc....

I know your 6" R30 can perform better than most of the doublets, with the same focal length, except the ED doublets....
And since I am now testing the chromacorr II , in this 8" Istar, I would think is worth the price to pay for.... , But for a 6" R30 doublet, with the chromacorr II added, it is not able to get even near to my APM ED doublet...as i have tested the chromacorr II onto my C6R F8....maybe you should consider it carefully, before getting one to try it out....
Perhaps the Istar Raycorr , may be introduced very soon, and is specially designed for R30 version...., which people like you are and others like Mike, are the one best benefited, and I am definitely going for one as well....

Regards

James Ling


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A. Viegas
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6020307 - 08/12/13 08:02 AM

Thank you James... My conclusion is the same. I will wait on the RayCorr and see how effective it is. Aside from that it's just knowing the Istar is a high quality build achromatic with or without some meaningful amount of CA reduction using the R30/35. I find the visual view in the refractor to be much more pleasing than in my SCT which are exclusively now Mallincams... Hopefully Istar delivers on the RayCorr.

Al


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beanerds
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: A. Viegas]
      #6020315 - 08/12/13 08:15 AM

James , just looking at the shots of the statue the CA is a lot better with the Chromocor that's for sure .
It looks about the same reduction I acheaved on my Synta 150mm f8 I have in NZ , that my nephew is using .
It took me a while to tune mine in by cannabalising old 2 inch colour filters without the filter, just the threaded rings to move the Chromocor out away from the diagonal ,trying thinner ones , etc.. some times more sometimes less , but after about 3 months of this , one night it just snapped into place !! , Gotcha .
They work when set up right .
Brian.


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: A. Viegas]
      #6021788 - 08/12/13 10:10 PM

Hi Al Viegas....

yes, I fully agreed with you that the Istar quality, whether is the build or the details seen through the ep are great...

And I am very sure those who have or going to receive the 8" F12 R30, which is now tested and reported by Mike, the CA level should be very much closer or maybe better than my 8" F8.8 with chromacorr II...(just wtg for Mike to take some photos....and put it up in the forum)
My advantage is of course a shorter tube, and my G11 is able to handle my 6Ft long Istar.....

Regards

James ling


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: beanerds]
      #6021804 - 08/12/13 10:16 PM

Hi Brian....

Thanks for the advice....
And that is also why I am making the new attachment or spacer..., which the screw threads allows me to play with the distance of +/-5mm from the pre-determined distance...
The day time visual adjustment for the photo taken, is just a preliminary, as I may need to further adjust the "right" distance , when come to actual night time testing...

This coming weekend, at our star gazing activity, I should be able to further fine-tune the chromacorr II, provided the weather is fine.....(coz is raining the past few days)

Regards

James Ling


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beanerds
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6021897 - 08/12/13 11:16 PM

James , I think from memory the optimal distance from the Chromocorr's front lense to the focal point is 161mm + or - 2mm in a 150mm f8 , so that spacing is critical and depends on the type of 2 inch diagonal you are using .
I used a standard 2 inch GSO mirror diagonal and about 9mm of spacing was required , from memory ,from 4 years ago .
I would not know the optimal distance for your 8 inch , trial and error I am afraid .
Good luck , because when its right on , you will know .
Brian.

Edited by beanerds (08/12/13 11:18 PM)


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Gord
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6022497 - 08/13/13 09:25 AM

Quote:


And I am very sure those who have or going to receive the 8" F12 R30, which is now tested and reported by Mike, the CA level should be very much closer or maybe better than my 8" F8.8 with chromacorr II...(just wtg for Mike to take some photos....and put it up in the forum)
My advantage is of course a shorter tube, and my G11 is able to handle my 6Ft long Istar.....





Hi James,

I wouldn't be so sure about this. Even a 50% improvement in color correction wouldn't match the improvement you are showing in the image above with the Chromacor. There isn't any technical info available yet on this design and there was a post recently here from someone in Czech who seemed familiar with IStar's designer that said the improvement was from the seelinger effect. This would not be an improvement (overall) per se, but rather an optimization at a specific wavelength.

Also an interesting factoid about the Chromacor you might not have known, is that it can correct the spherical aberration at wavelengths other than just green. Normal refractors (even ED's and apo's) are only corrected at green (usually), but with a Chromacor you can have better correction at the other wavelengths too.

But as Brian has mentioned, it will take some playing and once you hit the sweet spot, you will know. Your adjustable spacer sounds like a really good idea! I have other ideas for mine as well, but I really need a lathe.

BTW, how does your objective look in terms of correction in stock form? Over, under, or neutral corrected? Also I wonder what the color balance of yours is as well? Valery has said that the Chromacor is designed best for a traditional C-F balance. In testing I've found mine to have blue closer focus than red, but even in this case the Chromacor improves things greatly. But I wonder if it could be even better if they were balanced. In the same testing, I've found a prism diagonal improved this balance to be neutral again (specifically measured the de-focus) so I would like to see if that improves the Chromacor image as well.

Clear skies,


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: Gord]
      #6024408 - 08/14/13 02:36 AM Attachment (23 downloads)

Hi Gord....

I would not want to say or comment on the result of the chromacorr II at this moment....but we know the CA is well controlled at the central of the view....
And I still can see CA starts appearing, but not that much against without the chromacorr II, when you move the target object away in both directions (greenish-yellow in one direction, and violet in the other direction)

And I am still waiting for the opportunity for the next setup of this ISTAR during the night time, which I hope I can do so on this coming weekend...., and make the adjustment for the trial and error on the spacer distance...

The photo shows a cnetral attachment or spacer I have my machinist machined for me to thread between the diagonal forcuser end, and the chromacorr II end...
The thread that goes into the diagonal end, is able to extend out for at least 10mm....for my trial and error....testing...

REgards

James Ling


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6024412 - 08/14/13 02:41 AM Attachment (28 downloads)

Hi Gord...

And the machined attachment is tested with a laser collimator , after assembled onto my other diagonal and the chromacorr II...
The the assembly is again , mounted onto my Istar forcuser, and the laser beam is projected from the lens front to a wall 3M away, and final adjustment is on the Istar countercell 5 holding screws....

This will ensure my tested object is at the centre of the view....and that is easier for my adjustment on the spacer distance....

Regards

James Ling


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James Ling
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6031666 - 08/17/13 08:04 PM Attachment (45 downloads)

Hi All...

This are two photos I shot from the 8" ISTAR with the chromacorr II, using my canon 550D with 2X barlow...., at the 11 days old moon, during the end of the side walk session at our army club house....

Regards

James Ling


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beanerds
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6031917 - 08/17/13 11:04 PM

Woaw! that's very good James , the chromocor looks to be working very well .
Brian.


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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: beanerds]
      #6032445 - 08/18/13 09:04 AM

Hi ALL...

Last night testing done at the 11 days old moon confirmed the following :-

1. Using my TV55mm eye-piece at 33X,there is a thin stripe of greenish yellow CA visible on the edges of the moon.
The amount is very much reduced, more than 50% to 80%,very close to my APM 152 ED APO...

2. When I used my baader zoom eye piece, to power up , and move the edges of the moon closer to the centre of the FOV, the CA completely disappear....IS COLOUR FREE AT CENTRE OF FOV.

3. When I further moved down the edges of the moon away from the centre of the FOV, the slight trace of violet or purple CA appears....

4. When I shoot the moon with my 550D , now the edges are colour free, with the chromacorr II, whereas previously my photo shot, will show the purple or violet at the edges.

Last night beside the moon, having a good visual view, the giant gas planet, is not able to make a good comparison....

It is sighted quite low, less than 30 deg, and with plenty of " atmospheric disturbance ".
I can even power up my Istar to 450X with my 4mm eye-piece..
and still see the view of Saturn and its 2 moons with good contrast, except is not able to show the cassini division very clearly (razor sharp), as well as the cloud bands...

Regards

James Ling


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James Ling
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6042879 - 08/24/13 02:58 AM Attachment (43 downloads)

Hi ALL....

This is a better photo comparison of the moon photos shot through the 8" ISTAR, using the same Canon 550D.
Although they are taken almost 3 years apart by me, but when using the moonlite focuser, the focusing is precise, from the 3" viewer, before the photo shot is taken...

In both occasions, no UV/IR cut or contrast booster are taken...
So the Chromacorr II is able to eliminate the purple or violet CA, when a photo shot is taken.

Regards

James Ling


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Psion
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6043455 - 08/24/13 11:57 AM

Nice report thanks.

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jrbarnett
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #6044253 - 08/24/13 09:18 PM

The Chromacorr really works!

Brilliant design. Sheer genius on the designer's part.

Very nice images, too, James.

Regards,

Jim


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mitsos68
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: jrbarnett]
      #6180653 - 11/07/13 09:55 AM Attachment (20 downloads)

Hi,
I am old user of Chr II. I have a 152mm f/8 scope with a fine objective from RR Holland (original strehl 0.95). My focuser catch the diagonal / chromacor complex with a self centering adapter, and the focuser itself is push pull squared adjusted to the OTA. You can magnify the lower part of the scope to sse. Results as perfect you can imagine.
Regards
Dimitris
Athens-Greece


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mitsos68
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: mitsos68]
      #6180667 - 11/07/13 10:06 AM Attachment (11 downloads)

The focuser complex

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mitsos68
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: mitsos68]
      #6180671 - 11/07/13 10:07 AM Attachment (25 downloads)

test with the Chr II

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mitsos68
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Re: ISTAR 8" F8.8 With Chromacorr II new [Re: mitsos68]
      #6180673 - 11/07/13 10:07 AM Attachment (25 downloads)

Test 1. CHr II on

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