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Equipment Discussions >> Refractors

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James Ling
sage
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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 (77 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
Carpal Tunnel
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Reged: 12/30/06

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
sage
*****

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 (43 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
Carpal Tunnel
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Reged: 12/30/06

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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Reged: 01/06/04

Loc: Toronto, ON, Canada
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
Vendor (Aries)
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Reged: 11/26/05

Loc: Kherson, Ukraine.
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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Jeff B
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Reged: 12/30/06

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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James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
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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James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5973540 - 07/16/13 03:43 AM Attachment (30 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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James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5973545 - 07/16/13 03:49 AM Attachment (29 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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James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5973546 - 07/16/13 03:54 AM Attachment (20 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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James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II new [Re: James Ling]
      #5973550 - 07/16/13 04:03 AM Attachment (30 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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Reged: 12/30/06

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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johnnyha
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Reged: 11/12/06

Loc: Sherman Oaks, CA
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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James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
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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James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
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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Mark Harry
Vendor
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Reged: 09/05/05

Loc: Northeast USA
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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James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
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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Gord
Carpal Tunnel
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Reged: 01/06/04

Loc: Toronto, ON, Canada
Re: ISTAR 8" F8.8 With Chromacorr II [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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James Ling
sage
*****

Reged: 09/18/10

Loc: Singapore
Re: ISTAR 8" F8.8 With Chromacorr II [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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