79 replies to this topic

[Scott in NC]

I found another nice sample of an Astro-Physics refractor to test, this time an AP155EDF f/7. This one is an oil-coupled triplet with a center element made of FPL-53, created by Roland Christen and company in 1997. As the EDF (not S) version, it has a humongous 4" AP focuser with Starlight Instruments Feather Touch dual-speed micro focuser. 

 

Here's it set up on the optical testing bench (a.k.a., dining room table, which my loving wife has temporarily donated for the cause ).

 

 

But OTOH if you guys are getting bored with all these optical test reports, I guess I can just stop right here and keep the results to myself. I have to run off and do some household chores at the moment anyway.

[Scott in NC]

Okay, I'm back. Since no one has yet voiced their objection to yet another boring DPAC thread, let's proceed!

 

Green inside/at/outside focus:

 

 

Red inside/outside focus:

 

 

Blue inside/outside focus:

 

 

White inside/at/outside focus:

 

[Scott in NC]

It looks pretty smooth, with very little chromatic aberration.  There's slight overcorrection in green, and I think maybe a touch less so in red. Maybe Maciek can analyze these images with his AOS program and give his input. This overcorrection is more apparent in the extrafocal images than the intrafocal, and I suspect that that's because I had the focuser set a little closer to the focal point when I captured the extrafocal images than when I captured the intrafocal images.  The closer you get to the focal point the more sensitive this test is to picking out small amounts of spherical aberration that might not otherwise be noticeable.  Blue is a bit more strongly overcorrected, but less so than with my faster 105mm f/5.8 Traveler. There's a hint of a possible edge aberration seen here, but as I previously mentioned when I tested my TOA-130, I think that much of this may be an artifact from my 8" optical flat.  When I re-tested the TOA-130 with my best optical flat (a 6" flat created and tested by Zygo), the edge looked better than with my 8" flat.  Unfortunately, my 8" flat is the only one that I have large enough to test the AP155.  One day I'll be on the lookout for either a more perfect 8" flat or a larger 10" flat.

 

Now I'll welcome any comments!

[Scott in NC]

I know you've heard this from me many times before, but this scope looks like a keeper!

[rgsalinger]

I was really happy to see how well this one performed because I have the EDFS version (2.7" focuser). It's hard to believe how well these scopes work after so many years of use. 

[Scott in NC]

I was really happy to see how well this one performed because I have the EDFS version (2.7" focuser). It's hard to believe how well these scopes work after so many years of use. 

The EDFS version is a few pounds lighter, and if I had had a choice of buying the EDF with 4" focuser vs. the EDFS with 2.7" focuser, then I might have chosen the one with the smaller focuser purely for the weight savings.  I only use this visually, so don't need a humongous focuser to allow full illumination of a large chip camera.  But OTOH I do like how the heavy focuser on mine balances out the otherwise front-heavy scope, so I can set the rings a little farther back, keeping the eyepiece end higher above the ground.  Regardless, when you decide you want to buy one of these, you take what's available, and I'm happy with what I ended up with.

[Mike Spooner]

Nice!

 

For the record you can count me as one who doesn’t get bored with these tests.

 

Mike

[The Ardent]

This is what CN is supposed to be .

[rgsalinger]

Indeed. I learned about my scope one Saturday morning on this site. PM'ed the owner and within 3 hours I was at a parking lot in Orange County about 60 miles north of my house with as much cash as I could muster, a check, and my zelle app. I've wanted a 6" refractor since I saw the Unitron 6" in the late 50's but they were out of reach given my $3 dollar allowance and the money I earned on my paper route. I called AP and they sold me a flattener which they still had available. I use it with my ZWO ASI2400 and it does, indeed, produce essentially perfect stars across the full frame. Amazing to me for such an old scope. 

 

Rgrds-Ross

Edited by rgsalinger, 10 February 2024 - 01:17 PM.

[Scott in NC]

Ross, how long have you owned yours and do you know what year it was created? And please feel free to PM me if you don’t wish to post that info here.

[Scott in NC]

Here’s the front lens, which looks quite nice. There are a few tiny spots which I couldn’t remove, probably from past dew exposure, but I know better than to overzealously scrub the optics. I doubt that their presence or absence would make any difference to the superb views that this scope has provided me with so far. I’m not going to bother with removing the optics to try to clean the back side. Maybe one day I’ll tackle that project, but I really don’t see any need. I’m pretty happy with the appearance of the objective lens, given that it’s seen 27 years of use. This scope is in very nice shape, even though on close inspection no one would mistake it for a scope that someone received brand new back in 1997 and then locked away in its case never to see starlight for the duration.

 

 

 

[rgsalinger]

I don't know how old mine is, sorry. There doesn't seem to be any serial number on these, but I know that there must be one somewhere. I've owned it for about 6 years and I was the third owner.

 

There was an old thread (seems to have disappeared) where a couple of the usual refractor forum suspects plus the owner did some observing tests against some other scope (maybe TOA-150?) and concluded that it was every bit as good. I wish I could find that thread but it's been archived (or lost).

 

I have never had the nerve to clean my objective so it's full of dust. Maybe it's time to do it, I don't know. There's a tiny flaw in the coating, though, and I have no memory of when that popped up. Here's a link to a shot I took a couple of years ago with a full frame CMOS camera. 

[Erik Bakker]

They are numbered by hand on the outer glass edge of one of the lenselements. Scott’s image shows it clearly in his sample  between the 8 and 9 hr mark. And with software, you can mirror reverse it to easily read it.

[Scott in NC]

Thanks, Erik—I was just getting ready to post that. And AP keeps very good records, so Ross if you're ever interested in finding out the year that your scope was created, you can just email or call AP and give them your serial number.

[Scott in NC]

Here's a link to a shot I took a couple of years ago with a full frame CMOS camera. 

Wow—that’s a beautiful M13 image, Ross! Extremely detailed.

[Scott in NC]

 

There was an old thread (seems to have disappeared) where a couple of the usual refractor forum suspects plus the owner did some observing tests against some other scope (maybe TOA-150?) and concluded that it was every bit as good. I wish I could find that thread but it's been archived (or lost).

 

I don’t know if this is what you’re thinking of, but here are a couple of comparisons that Ed Ting posted a long time ago on his Scope Reviews site.

 

AP155 vs. FS-152:

https://www.scoperev....com/clash.html

 

AP155 vs FCT-150:

https://www.scoperev...com/clash2.html

[rgsalinger]

Thanks! My SN is between 2 and 3 o'clock, but unless I clean the objective I'll never have a chance at reading it. I tried using my phone to take a picture and all I got was the dust. I just don't want to scratch that objective. 

 

I've seen the Ed Ting reviews, what I was referring to was a thread here on CN in refractors. I remember now trying to read the SN soon after I bought it and then gave up. Maybe if I rotated in in the rings I could see it better. 

Edited by rgsalinger, 10 February 2024 - 02:04 PM.

[Scott in NC]

I wouldn’t worry about the serial number too much, as it’s not really a big deal. I just like knowing everything I can about the provenance of scopes that I buy, especially classic ones like this one. And I’ll bet if you took an air blower bulb you’d get enough dust off of it that that’s all that really needs to be done.

[CHASLX200]

Looks like it should for a $15K+ OTA used. I would expect no less.

[Scott in NC]

And lest any of you think that I buy these scopes purely to DPAC test, the answer is a resounding no. I buy these scopes to observe through, but of course can’t resist testing them as well. I got first light though this AP155 last week on February 2, and was quite impressed despite the fact that Astrospheric rated the seeing as below average. The Trapezium E and F stars were easy picking despite poor viewing conditions. I’m looking forward to a night of above average or excellent seeing, but those nights are few and far between.

 

Here’s the scope set up and cooling down for its first light last week.

 

 

[Scott in NC]

Looks like it should for a $15K+ OTA used.

Fortunately nowhere near that. My pockets aren’t that deep, LOL!  And I do thank those of you who recently bought scopes from me to help me fund this gem.

[CHASLX200]

And lest any of you think that I buy these scopes purely to DPAC test, the answer is a resounding no. I buy these scopes to observe through, but of course can’t resist testing them as well. I got first light though this AP155 last week on February 2, and was quite impressed despite the fact that Astrospheric rated the seeing as below average. The Trapezium E and F stars were easy picking despite poor viewing conditions. I’m looking forward to a night of above average or excellent seeing, but those nights are few and far between.

 

Here’s the scope set up and cooling down for its first light last week.

 

IMG_4320.jpeg

Be fun to play with for Jupiter.

Edited by CHASLX200, 10 February 2024 - 02:21 PM.

[CHASLX200]

Fortunately nowhere near that. My pockets aren’t that deep, LOL!  And I do thank those of you who recently bought scopes from me to help me fund this gem.

Maybe i am thinking of another AP 155. 

[Scott in NC]

Maybe i am thinking of another AP 155. 

You might be thinking of the AP160. Those are a bit rarer and also way more than I’d want to spend.

[Scott in NC]

Be fun to play with for Jupiter.

Jupiter did look nice, but the seeing conditions weren’t very good on 2/2 and I’ve seen better views of Jupiter through an FS-128 and TOA-130 on nights with much better seeing. The quality of the optics is definitely important, but the seeing conditions remain the great equalizer.