35 replies to this topic

[fate187]

Ok let's dig this thread up. Just yesterday I drove some hours to pick up this beauty! The seller (a very nice guy) was first reluctant to sell, due to its uniquness. I fully understood him. I tried to find other vendors or scope makers, that would offer such a scope in similar size. There is only one possibility, that I found and I know off. But after some back and forth the person finally offered the scope to me...the Astro Optik Manufaktur 160/1600. Yes, thats right - F10. A doublet lens with a FPL-51 element. Put into a Kruppax tube with a giant 3.5" Feathertouch focuser. I may start a seperate thread or use other "long focus" discussions to describe the view and my findings.

However, I also want to share DPAC analysis. First thing you will notice, is something that looks like astigmatism. But I doubt, that this is due to scope, but my flimsy DPAC setup. I do see this also in my other scopes. The bowing introduced makes it a little difficult to judge just how good the lens is in green. I need to figure out how to improve on this regard.

 

Hover over the images for names. left is inside focus, right outside of focus.

red/green/blue

 

There is a small center zone visible in the focus image:

 

Overall, from judging the DPAC the lens looks excellent in green with undercorrection in red and overcorrection in blue. I cannot wait for the bad weather to subside to have a look at a star test and the planets. The figuring looks excellent as well. No visible defects and splendid condition due to the previous owner taking care

Enjoy

Edited by fate187, 09 July 2021 - 06:20 AM.

[Jeff B]

Pretty cool Michael!

 

Yeah, I see a little "key-stoning" of the lines and that typically means some sort of alignment issue somewhere in the system.  Astigmatism would be seen as a clocking of the lines as you pass from one side of focus to the other.

 

If your images are from a single "white" light LED with the red, green and blue color channels isolated, the longitudinal color correction looks really good with red and green focus on top of each other and the blue ever so slightly different.  You do see the spherochromatism at work in the red and, especially blue images but this should be visually a basically sharp, color free scope, even at high power.

 

Tell us what you see with the star testing!

 

Are there any others out there?

 

Well done!

 

Jeff

[donadani]

 

Thought long about selling and after TOA-150B, LZOS-152, CFF160 and AP-155EDF had long gone it was my last 6" scope... will definitely miss it.

 

Take good care on her...  looking for your firstlight report 

Edited by donadani, 09 July 2021 - 10:37 PM.

[peleuba]

Overall, from judging the DPAC the lens looks excellent in green with undercorrection in red and overcorrection in blue. I cannot wait for the bad weather to subside to have a look at a star test and the planets. The figuring looks excellent as well. No visible defects and splendid condition due to the previous owner taking care   

 

 

I would agree - a nice lens.  My sense is the color correction is quite decent - even with FPL-51 - and very similar to the TAK FS152.

 

I would like to own a telescope like this...   

 

Here is an annotated view of the Autocollimation null (if I can use that term...).   It shows, basically, a smooth surface with two zones that correspond to small kinks in the Ronchi bands.   

 

Again - Very nice telescope.  One I would love to own and keep outside covered ready to use.

 

Attached Thumbnails

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[Jeff B]

It's been my experience that those mild donuts in the middle are rather common in refractors, even with "high end" lens/scope makers.  But the middle is where they have the least affect too. 

 

Here's one where I hyped up the contrast to pull it out in more detail.   The scope is very sharp and I bet yours will be too Michael.

 

Jeff

Attached Thumbnails

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[donadani]

I would agree - a nice lens.  My sense is the color correction is quite decent - even with FPL-51 - and very similar to the TAK FS152.

 

indeed... - more important then FPL-51 is the partner glas N-ZK7 here that results in a very good color correction.

 

 

 

 

Compared it 1:1 vs. the LZOS 152/8 and FS152 - color correction was 1:1 comparable to the FS and the views a bit brighter then the LZOS - but as always with high end scopes differences getting subtle and don´t really matter for visual - loved the views of the AOM.

Edited by donadani, 09 July 2021 - 01:38 PM.

[Tyson M]

AOM's are extremely rare and highly desirable!  Long focus apo's 

 

Congrats!

[fate187]

Good care will be taken, Donadani. Promised!

According to Donadani, there are 5 or 6 of these 160/1600 scopes out there. I know of one german user on Astrobin with very good photographic results using this model. I think he uses a Riccardi reducer.

Jeff and Paul, you are both right there on spherochromatism. There is also not a lot focal shift of the respectives colors, because there is no shifting of the Ronchi bands visible between R-G-B, right?

And Jeff, yes, that is from a white light LED and color separation was done in done software to each of the channels.

 

What I find interesting is the comparison to the LZOS f/9 in this thread. As you know this a long focus apo using a triplet lens. If you look at the respective images for R-G-B you will notice, that there is no bowing of the Ronchi lines. This indicates very good control of the spherochromatism present in refractors.

[Jeff B]

Michael, right on and well done!.

 

Using the white light LED and then software to isolate the primary colors is a very powerful technique, giving you directly semi-qualitative information concerning longitudinal color focus differences (as you said any subtle shifting of the bands) but also spherochromatic differences (curving of the bands).....all from one picture.

 

The results of your LZOS 130/F9 don't surprise me one bit as one of Thomas's goals with that lens design was to have basically NO spherochromatism at R,G and B.   Actually, I'm major impressed with the CFF 185 objective results for such a large aperture, fast, oil spaced triplet.

 

Jeff 

[fate187]

In my initial post I wrote, that I would do measurements of the telescopes in combination with optical accessory like prism diagonal, barlow, flattener, etc. I have had no success testing the prism or barlow. I do not get a good image. However, I tried the TEC140ED in combination with the dedicated 6x7 field flattener, which itself is a large piece of glass. From an aperture point of view the Tak FC100 is jealous I guess .

 

Some people may know, that when using the TEC140ED for astrophotography the telescope can show bloated blue stars. This is due to the correction, that is optimized for visual, but not so much in blue. This effect will only be visible with cameras, that are very sensitive in blue like the Sony ICX 694, that can be found in an ATIK460. Kodak KAF 8300 will not show this effect. Additionally, it may depent on the filters you use. Filters cutting more of the blue spectrum even using sensitive cameras may not show blue bloat.

 

I will list the results and compare them to my initial post on the TEC140 from this thread ( https://www.cloudyni...ent/?p=10620636 ). You can always hover over the images for filenames and desciption.

 

TEC140ED with TEC-flattener:

Red:

Green:

Blue:

RGB:

 

Null:

RGB

R/G/B

 

In my initial post I deduced, that the TEC140ED is overcorrected. Now with the flattener there is shift towards a undercorrection. This can be seen from the different bowing in the inside/outside focus images:

Red inside without/with flattener:

 

In blue you will notice the improved correction, as the bars are less strong bend. I assume, that this will ultimately lead to nicer stars in images.

Blue outside without/with flattener:

 

For completeness let us look at green:

Without flattener inside/outside

with flattener inside/outside

 

Judging by the images in green I am inclined to try this flattener for visual. I do have difficulties with star testing and seeing differences, because I lack expierence there. Maybe a dedicated star test in double pass will help

 

best wishes

[25585]

Bumping this thread as it has some interesting scopes tested.