12 replies to this topic

[Jeff B]

First I want to express my thanks to a fellow CNs'er for being willing to let me test it, let alone up and shipping it to me for an extended period.  I sincerely appreciate your trust in me Rakan.  

 

So it arrived in great shape, even the case looks good.  

 

This is a solid "little" scope with impeccable fit and finish (though, like my sample Stowaway, the dew shield stickers are a little fragile so be careful taking it in and out of the case).  

 

 

Attached Thumbnails

• 
• 
• 

[Jeff B]

One of the first things I do with a refractor is check the focuser alignment using a paper mask with a small hole in the middle over the aperture and a Glatter laser in the focuser.  The laser should fire trough the mask hole.  In this case.....

 

Boom!  Dead center perfect as you see in the photo.

 

The Cheshire eyepiece showed a single, well defined reflection dot in the middle.  Alignment wise, it does not get better than this folks.

Attached Thumbnails

• 

Edited by Jeff B, 21 November 2022 - 01:49 PM.

[Jeff B]

Then preliminary DPAC with a green LED with 133 LPI screen.

 

More later.

 

Jeff

Attached Thumbnails

• 

[SandyHouTex]

In your first post, the third pic, what's all of that junk on the lens?

[Jeff B]

In your first post, the third pic, what's all of that junk on the lens?

Some dust.  We're looking at it very obliquely, under a strong source, and I hyped the contrast up.  

 

But I'll clean it before it goes home. 

[Jeff B]

Here are some additional DPAC images, first the "white" light images taken with a single LED whose white light is composed of three LEDs, being red, green and blue.  I have to note the bit of blooming from my cell phone sensor in the out of focus image.  You can see this as a thinning of the ronchi lines and brighter area both towards the center.  Yes, a small amount of the effect is due to the mild center zone, but I get this if the LED is just too bright and saturates the sensor, particularly in blue, but it spills over into the other colors too.  It also seems to happen more so with fast refractors and outside of focus.  Visually looking at the outside of focus image shows only very uniform lines out to the edge, just like with the inside of focus image, which was taken after I had considerably dialed back the brightness of the LED.  I'm also just too lazy to redo the outside of focus image.

 

With either the inside/outside of focus images you can immediately notice the lack of red & blue fringing around the outer ronchi lines and the uniform white tint to the areas in between the lines as well.  This indicates excellent color correction from red to blue.   The objective seems ever, ever, so slightly overcorrected overall....maybe.

 

But, but, the at focus image is a kaleidoscope of color!  

 

Yes, it is, but that's completely normal, even with the best APOs as, they are, after all, refractors and DPAC will readily catch that out.  I've also attached a similar image from one of my excellent 100ED F9 doublets that shows the same story.

 

The other thing you readily see is the mild donut zone and the very smooth polish (there is basically no fine micro-ripple, which you can catch out with the 100ED).  And don't sweat that zone.  Again, remember this is brutal DPAC that doubles everything.  I've run across only a few objectives that don't have zoning detectable in DPAC (though they may have other issues).

 

Jeff

Attached Thumbnails

• 
• 
• 
• 

[scoale]

Why can't you live next door to me

[Erik Bakker]

Thanks for sharing that DPAC Jeff.

 

Surprised me to see what only looks like 3 spacers in the last picture. My EDF had 6 of them:

 

[Jeff B]

Thanks for sharing that DPAC Jeff.

 

Surprised me to see what only looks like 3 spacers in the last picture. My EDF had 6 of them:

 

44722DA8-B161-4B95-8DA7-ED66E281994F.jpeg

Erik, you are welcome.

 

The spacer shadows you see in that last photo are in the 100ED objective, any in the AP 130 GTX are outside the light path.

 

Jeff

[Jeff B]

Here are my usual color montages, generated from the white light shots above by isolating the individual red, green and blue channels.  The yellow images are generated primarily by cutting the blue channel and a tiny amount of the red until it just looks very yellow.

 

Judging by the number of Ronchi lines and their positions, especially those faint lines at the R/L edges, the images indicate to me low longitudinal "CA", meaning the blue through red seems to come to a common focus position or very close to it.  

 

You can see the sphero-chromatism at work in the red and blue images as the Ronchi lines curve a bit and they curve in opposite directions from each other while the green and yellow are quite straight. 

 

This says to me any "CA"  this sample has to due mostly to spherochromatism.  

 

The level of spherochromatism seems quite well controlled for such a large, fast (F6.3) APO with the blue (which is ~470 nm in my phone) being right at or really close to the diffraction limit and the red (close to the C line) better than that.

 

In DPAC this is a very well corrected objective.

 

Jeff

 

 

 

 

 

 

Attached Thumbnails

• 
• 
• 

[Scott99]

nice, but I'm thinking late-model AP scopes are probably a good way to test the accuracy of your DPAC setup, not the other way around!!

[Jeff B]

Something I've sometimes noticed with in my DPAC images of fast refractors, especially in green, is what appears to be a very narrow edge "issue" in some outside of focus images.  This AP 130 is an example. 

 

Is it a real jog in the glass at the very edge?

 

I believe not.

 

I believe it is some sort of diffraction thing.  Why do I suspect this?  Well, because I've seen this before with other fast refractors, and like the others, I do not see it on the inside of focus image. 

 

Also, if it were real, I could could mask it out right?  So I repeated a set of outside of focus green images with a 120mm stop over the objective.  As you see in the shots, it is still there.  

 

Place the cursor over the images to read their titles.

 

Thoughts?

 

Jeff

Attached Thumbnails

• 
• 
• 

Edited by Jeff B, 25 November 2022 - 11:21 AM.

[Jeff B]

Last week I was able to take advantage of some very nice weather around here for this time of year to get in some quality observing time with this scope.  I did not make any comparisons with other scopes save one (more later)

 

Short version:  Truly excellent.

 

Longer version: 

 

Mono-vision: Once thermally settled (more on that later), Vega displayed no real "CA" during steady seeing with a very white airy disk at high power (185x with a nice barlowand an AP 2" diagonal), scatter was very low.  There was no hint of astigmatism or coma.  The double-double was two sets of beady eyes staring at me from the blackness of space with very faint first diffraction rings. 

 

Jupiter was a "hard" disk with plenty of belt and festoon detail, the moons little balls.  Similarly, Saturn produced that "etched in space" quality I see with high quality optics.  Unfortunately Mars was behind a neighbor's tree during the sessions and by the time it rolled into view, the seeing had gone to hello, even at 5" aperture.  

 

Bino-viewing:  My one quibble.  With the stock AP visual back, the scope is not "bino-friendly" even with my Baader MK V and Baader Zeiss Spec prism diagonal.  I had to swap out the stock AP visual back for their special thin one to use the viewer sans GPC elements.  With that visual back, I could get to focus with all of my eyepiece pairs except for my Celestron 35mm Ultimas.  I could just barely get to focus with my APM 24mm UFF pair and M45, M31 and double cluster were magnificent, even in my moderately light polluted skies.   Switching to my Baader  MK V/BBHS T2 mirror diagonal/1.7x GPC/quick changer viewer configuration I swung back to Jupiter and Saturn.  Very, very nice with a pair of my good old U.O 7mm orthos.  I saw even more contrast and belt detail on both planets compared with mono-vision.

 

Cool down:  It did take the scope a good hour to settle out thermally when going from my 67 degree F basement to the ~50 degree F outdoors with the ambient decline being two degrees per hour.  During that time the objective went through an interesting optical "ballistic" (and my Stowaway was very similar).  Initially there was the quite noticeable undercorrection which got better with time but there were color disturbances too, showing a decidedly reddish tint prior to thermal settling .  Also, there was what I called "transient thermal astigmatism" which would come and go before leaving the building all together once the lens was thermally stable.  I've  seen this before.  

 

The interesting thing is that once cooled down, the objective seemed subjectively a trifle "warm" visually, no matter the viewing configuration, but more so with the bino-viewer set up.  This was noticeable in comparisons to my 10" LZOS stopped to 7" aperture and trying to match exit pupils as best I could.  It was most notable and best seen on Jupiter with the planet seeming a tad "warm" with the NEB standing out in the view compared to the LZOS.  I actually rather liked it and I imagine it will serve the owner very well on Mars.  It kind of reminded me of my TEC 200ED in that the warm tint spoke to my heart, while the "cooler" tint of the LZOS went straight to my head.  Now all prism based bino-viewers I've had and measured in DPAC show a degree of filtering in the blue, especially the MK V.  This does indeed impart an extra mild "warmth"  to bino-viewer images for me.  The only viewers which don't filter the blue in my experience are the CZAS viewers, especially the older ones with the older style coatings.  I was using that one with the LZOS. 

 

The LZOS of course showed more detailing with its bigger aperture and image scale, but the 5" AP was no slouch, delivering a completely satisfying image all on its own with plenty of detail.

 

This sample is a wonderful visual scope.

 

Jeff