87 replies to this topic

[Scott in NC]

An excellent condition Astro-Physics Traveler from the last run in late 2003 just fell into my lap a couple of weeks ago.  This is probably the smallest 4" apochromatic refractor that you'll ever see, and it fits into a case smaller than the ones in which I keep my 60mm Tak and 80mm SV LOMOs.  It has oil-coupled triplet optics with 105mm clear aperture, the ED element of which I believe is FPL-53, and it gives pretty stunning apochromatic performance considering its fast focal ratio of f/5.8.

 

I've already had the opportunity to use this for both daytime solar observing with a Herschel wedge and nighttime observing, and this little scope failed to disappoint.  Not that I expected otherwise.  I owned one of these gems 4-5 years ago and made the mistake of reselling it so I could use the funds for other projects. Lately I'd found myself wanting another one, and was absolutely thrilled when this one became available.  And of course I was even more thrilled once I got the chance to put it to the test.

 

Here's what it looks like set up on my optical test bench (a.k.a., dining room table).  Don't you just love how my wife has it set up for Valentine's Day?

 

[Scott in NC]

Now let's get to the test images.  It took a bit longer than I thought it would, as while processing the images on my laptop I realized that the intrafocal and extrafocal images looked nearly identical, a physics-defying impossiblity.  Now I know Roland Christen is a master of his craft, but even he can't defy the laws of physics!   Too bad I figured this out after putting all my gear away.  So I unpacked everything and started again from scratch. 

 

Green inside/at/outside focus:

 

 

Red inside/outside focus:

 

 

Blue inside/outside focus:

 

 

White inside/at/outside focus:

 

 

 

[Scott in NC]

Green and red appear to be extremely well corrected for spherical aberration.  Blue has a bit of overcorrection, but I'm still amazed at how closely all three colors focus together at such a fast focal ratio. The white light images do show some blue fringing at the ends of the Ronchi bands, but once again pretty amazing for f/5.8.

 

The optics appear pretty smooth, and I've been told that the shallow concentric circles at the 20-50% radii positions are indicative of aspheric corrections applied to the optics rather than zonal defects.  

 

Please note that some of the marks on the images are either reflections or small scratches on my 8" optical flat (especially the ones seen near the edge at the 12:00 - 2:00 positions). These are not defects on the scope's objective.

 

I'm pretty pleased with the way this gem of a scope performs under the stars and tests on the optical bench.

[Maciek_Cz]

Hi Scott,
The perfect telescope!

[PhotogTom]

Wow! 

I'll have to send a link to this test, to my friend in Ohio. He's got himself a nice Traveler. 

[Scott in NC]

Wow! 

I'll have to send a link to this test, to my friend in Ohio. He's got himself a nice Traveler. 

Please do.  While I cannot say for sure, as this is the only Traveler that I've had the opportunity to test, it would not surprise me one bit if this were representative of the majority of the line.  But who can say for sure without objective evidence? I hope someone else will be able to test a Traveler at some point and post the results on CN. 

[Scott in NC]

I've now corrected several important typos, the first of which an astute reader pointed out to me, leading to my carefully proofreading everything once again. So if anything I said above didn't seem to make sense the first time you read it, hopefully it will now.  And if any of you see any more glaring errors, please let me know!

[Joe G]

Nice job.  Looks like it was figured in red. 

[Scott in NC]

[CHASLX200]

No wonder they are 5k or more.

[dawnpatrol]

Congratulations, Scott. It was looking through a Traveler back in the mid 1990s that got me hooked on astronomy. Back then I had no appreciation for what a truly remarkable instrument the Traveler is. It's not an exaggeration to say that every telescope I've bought in the intervening decades has been chasing that first night looking at the Double Cluster through the Traveler.

 

I know the legend of Traveler optics bubbles up regularly on CN, but one thing that gets a less attention is just what a fine instrument it is beyond the optics. Last year I bought a refractor with some truly excellent optics, and as much as I enjoy that scope, the mechanics are a far, far cry from the Traveler, despite one being made some 30 years later. It's something that can get lost in DPAC tests. 

 

I look forward to reading (and living vicariously through) your reports of the Traveler under the stars. 

[PhotogTom]

Please do.  While I cannot say for sure, as this is the only Traveler that I've had the opportunity to test, it would not surprise me one bit if this were representative of the majority of the line.  But who can say for sure without objective evidence? I hope someone else will be able to test a Traveler at some point and post the results on CN. 

Seeing Saturn through his Traveler some 15-20 years ago lit the spark that eventually got me to start toying with astronomy. I haven't been at it particularly long, but I'm learning every time I go out with a telescope.

 

The image of Saturn, crisp and clear, with the ability to see the Cassini division. Excellent views that night. I couldn't begin to tell you what eyepiece he had in there, but I imagine it was something in the 5 mm range. 

[PhotogTom]

Nice job.  Looks like it was figured in red. 

Infrared.

[Erik Bakker]

That is an excellent Traveler from that last production run Scott. I think it is safe to say these 2003 scopes were the best incarnation of that wonderful classic with superb optics.

 

Enjoy under the stars!

[Scott in NC]

I look forward to reading (and living vicariously through) your reports of the Traveler under the stars. 

I know that lately I’ve been posting more DPAC testing reports than observing reports, but I certainly don’t want people to think that I buy these scopes just to test and then pack them away, never to see starlight again. It’s just that plenty of people post observing reports, and this is something different that I can do, that’s a little more objective.

 

But the truth is that I rarely DPAC test a scope before I’ve had the opportunity to observe through it, unless the weather just isn’t going to be conductive to observing for a while after I receive it. I’ve had this scope for about a week and a half now, and I’ve had the opportunity to use it for white light solar observing with a Herschel wedge as well as nighttime observing. And so far I’ve been just thrilled with it. Yes, it’s pretty expensive for a scope with as little aperture as it has, but I don’t regret my purchase one bit.

 

Using a Herschel wedge with solar continuum and polarizing filters gave nice sharp sunspot views without a hint of CA, although admittedly I was using fairly low magnification under poor seeing conditions. But for solar viewing I usually prefer to use low enough magnification to achieve a full disc view. And if I want to get better detail on a particular spot, then of course I can always use a shorter FL eyepiece for more magnification. For this observing session I used Vixen LVW 8-22mm eyepieces, giving 28-76x.

 

During my recent nighttime observing session I was astonished at how much nebulosity I could see in M42 despite only having 105mm of aperture. It had been a while since I last viewed through a scope with oil-coupled optics, and I’m wondering if that feature of the Traveler is one factor that gives it such exceptional contrast. Then again, it had been a while since I had last looked through any scope made by Astro-Physics, so there’s that too.

[Scott in NC]

Here’s a pic of it set up last weekend getting ready for nightfall.

 

 

 

[Paul Hyndman]

My 25+ year old Traveler is one of my favorites, going from low power star-field sweeps, detailed lunar/planetary observing, and as a capable solar (90/90/30 Coronado) platform. It has done it all, from visual to film to digital imaging from a Canon Cool Pix to a monster sized SBIG ST11K, is easily setup and ready to roll without any huffing or puffing. It will be one of the last scopes pried from my aging hands.

[weis14]

Nice writeup Scott!  I've long lusted after a Traveler, but I've never owned one.  After getting a brand new Stowaway in 2020, I had a chance to buy one locally, complete with AP400GTO mount and tripod.  Sadly, I couldn't justify spending $8-9k on that setup, so I let the owner sell it to someone else.  

 

Your comment on being surprised on how much you can see with 105mm in that scope is something I think almost every time I look through the Stowaway.  There is some sort of special sauce that Roland uses with all of his scopes, but it is especially present on these smaller ones.  

[fate187]

Like for the valentines table. The test is perfect and boring  .

[RichA]

Now let's get to the test images.  It took a bit longer than I thought it would, as while processing the images on my laptop I realized that the intrafocal and extrafocal images looked nearly identical, a physics-defying impossiblity.  Now I know Roland Christen is a master of his craft, but even he can't defy the laws of physics!   Too bad I figured this out after putting all my gear away.  So I unpacked everything and started again from scratch. 

 

Green inside/at/outside focus:

 

IMG_8995 green inside.JPG

IMG_8979.JPG

IMG_8996 green outside.JPG

 

Red inside/outside focus:

 

 

One product where you truly got what you paid for.

[bobhen]

 

During my recent nighttime observing session I was astonished at how much nebulosity I could see in M42 despite only having 105mm of aperture. It had been a while since I last viewed through a scope with oil-coupled optics, and I’m wondering if that feature of the Traveler is one factor that gives it such exceptional contrast. Then again, it had been a while since I had last looked through any scope made by Astro-Physics, so there’s that too.

The exceptional contrast is likely because the optic is so well corrected and with a super smooth polish. And of course, it's a refractor.

 

Nice scope!

 

Bob 

[R Botero]

Great scope Scott!  Make sure you keep it   I still regret not buying a Traveler matched to a 400GTO mount which was offered to me a few years ago locally.  I have a number of Astro-Physics telescopes and mounts but I should have bought that outfit...it was a real looker  

 

Roberto

Edited by R Botero, 05 February 2024 - 07:32 AM.

[Scott in NC]

One product where you truly got what you paid for.

There have been more, so not just this one.
 

[Eddgie]

 

Using a Herschel wedge with solar continuum and polarizing filters gave nice sharp sunspot views without a hint of CA,

By its very nature, you will never see chromatism on the sun when using the Solar Continuum filter. 

 

The real test of color correction is to see the sun without the Solar Continuum. 

 

Because imaging has become so popular, the right decision is to optimize somewhere in the 620nm range.  Had the scope been optimized for 55nm, the blue would have probably been near perfect but again, for imaging, it is probably much better to be optimized towards red. 

Few "Apos" will show the sun color free in white light when no filter is used. The sun in white light is (to me anyway) the ultimate test of "Apo-ness."  Even a fast achromat won't show chromatism on the sun when using the Solar Continuumm filter so saying that it worked well with the filter doesn't really say anything. 

 

I would be interested to see how it works on the sun without the filter though. I would expect it to not be totally free of blue, but I do suspect that it would be near the very top of the stack for solar white light.  Solar white light is the ultimate test for spherochromatism control. 

[Jeff B]

I know that lately I’ve been posting more DPAC testing reports than observing reports, but I certainly don’t want people to think that I buy these scopes just to test and then pack them away, never to see starlight again. It’s just that plenty of people post observing reports, and this is something different that I can do, that’s a little more objective.

 

But the truth is that I rarely DPAC test a scope before I’ve had the opportunity to observe through it, unless the weather just isn’t going to be conductive to observing for a while after I receive it. I’ve had this scope for about a week and a half now, and I’ve had the opportunity to use it for white light solar observing with a Herschel wedge as well as nighttime observing. And so far I’ve been just thrilled with it. Yes, it’s pretty expensive for a scope with as little aperture as it has, but I don’t regret my purchase one bit.

 

Using a Herschel wedge with solar continuum and polarizing filters gave nice sharp sunspot views without a hint of CA, although admittedly I was using fairly low magnification under poor seeing conditions. But for solar viewing I usually prefer to use low enough magnification to achieve a full disc view. And if I want to get better detail on a particular spot, then of course I can always use a shorter FL eyepiece for more magnification. For this observing session I used Vixen LVW 8-22mm eyepieces, giving 28-76x.

 

During my recent nighttime observing session I was astonished at how much nebulosity I could see in M42 despite only having 105mm of aperture. It had been a while since I last viewed through a scope with oil-coupled optics, and I’m wondering if that feature of the Traveler is one factor that gives it such exceptional contrast. Then again, it had been a while since I had last looked through any scope made by Astro-Physics, so there’s that too.

Scott, it's a really neat invention called "contrast" and is addicting in use.  

 

I note the lack of sharpness and contrast differences between the inside and outside of focus green images.  Both are well defined and sharp which, IME, has always been associate high contrast, low scatter optics.  Another subtlety that can be gleaned by well done DPAC that is validated visually.

 

Good Lord, you have a reference optic.

 

Well DONE!!

 

Jeff