Overdue First Light: Astrotelescopes 152 f/5.9
Posted 14 October 2012 - 10:40 PM
Luna without chromacor.
Posted 15 October 2012 - 07:02 AM
I have one and looked thru a similar scope
Here are my findings:
Mine Celestron 150mm F5
- On moon CA free up to about 75x
- On moon acceptable to 100x anything over purple creeps in alot
- Planetary high contrast but have to look passed the purple! views are not very pleasing
-Bright stars Vega etc show CA slightly even at 27x at really low power no CA shown 14x
-Very specific scope wide field sweeper low power 100x and under. Best views ive seen of the Veil and double cluster and others.
Looked thru Canadian Telescope 152mm and basically same results! These big achros pretty much act the same.
I tried my scope with a chromacore and the views really cleaned up as far as CA however still thought the views of planets were just ok.
Posted 15 October 2012 - 07:07 AM
Posted 15 October 2012 - 08:51 AM
Dunno, Steve. Perhaps the large swath of defocused portions of the visual spectrum affect the "tightness" of the in-focus stars. Perhaps the optics are a bit rough. Perhaps there's some attenuation happening. Perhaps the baffling isn't as effective as it should be. Lots of possibilities. It's not a bad scope. It's actually a very entertaining scope, but there are several liabilities that come with it that I suspect would irritate many users.
From my perspective there were no surprises. I expected false color, and received it, expected mass and length, and received them, and expected decent optical and mechanical quality, and received them. On the value front, though, unless someone is Hellbent on having a 6" fast achromat, there are other 5 to 8 inchers that would likely be easier to live with and more well-rounded, for the same or less money.
Hi, Jim. I had one of these AT 152' s for about a year. I found the false colour to disappear on stars fainter than mag 3.5. On the overwhelming majority of objects there is zero CA. Zero. Globulars, nebulae, galaxies, planetaries - no false colour. Typical Struve double stars with both components below 4th mag -zero colour and perfect diffraction patterns - and there are a couple of thousand of those to look at...
Not a planetary scope? The views of Jupiter, Mars and Saturn through a #58 Wratten (green) filter were crisp and showed remarkable levels of detail.
I would still be happily using the AT 152 to this day if I had not fortuitously found my current 1988 AP triplet APO at a very good price.
Posted 15 October 2012 - 09:37 AM
Jim, don't tell me you didn't look at Jupiter or the moon with this scope?!?
Since I have today (Monday) off, I left the AT152 set up (just covered with a new BBQ grill cover) and got up at 3am CT this morning to view Jupiter and The Pleiades. The Pleiades has a small amount of CA using Siebert 24mm SWA's. Jupiter showed no CA whatsoever with my Pentax 8.5mm XF's.
I must say I am impressed with this scope and the view of Jupiter it presented. I should have pushed the power up higher to see the results, but honestly it was chilly out and our Shih Tzu was talking to me and urging me to come back to bed.
Posted 15 October 2012 - 10:14 AM
personally, one of the most fascinating things i've discovered on CN is the fact that optics really are subjective, that an individual's satisfaction with an astronomical image is not something a ray trace or point spread is going to predict or even adequately describe. i thrill when, for example, someone like marcus ludes says something like "overall impression of the chromatical correction is better then I hoped for, from the optical design." the optical design always omits your idiosyncratic eyes.
So what do you say to the reviews by Warren Maguire on the CT152 and Larry Carlino on the AT152? Are you saying they are wrong? As usual with your review and the other 2 reviews they are merely self opinions which don't necessarily reflect the views of others.
and then there is the "don't disrespect my lady" response of people who own an instrument that has been negatively reviewed. seems to me like people at some instinctual level understand the subjectivity of the image, and therefore rely on group consensus opinion to anchor the ambiguity, and become upset when consensus or received opinion is challenged.
as you and several posters have stated, even a 6" ƒ/6 achromat is good for *something*, and maybe even very good. and better good, if used in the right way (e.g., with a filter). skill and expectation matter: if you know what to expect, and you expect it won't matter for what you want to do, then the only remaining issue is build quality and price, which you appropriately spell out in component detail.
Posted 15 October 2012 - 10:39 AM
True! This certainly happens when the views about build quality or anything other than positive mention is made about a Tec or AP or other high price scope.
Posted 15 October 2012 - 10:39 AM
Posted 15 October 2012 - 10:52 AM
Posted 15 October 2012 - 10:59 AM
When the D&G arrived, it did indeed have some false color, as you'd expect, but I found that there was not enough false color to make me want to hassle with moving the MV-20 filter around between eyepieces. The MV-20 sat, largely unused (other than one night with my Antares 105/1500, as an experiement at very high magnification), for years.
It was purely as an afterthought that I put it in the eyepiece case when I loaded the AT152 for its first light voyage. On Rasalgethi at 224x the filter did a great job restoring much of the color contrast of the pair and darkening the split. I think that with one of the even more modern MV filters, these scopes are suitable for higher magnification targets if the user is tolerant of the reduced amount of false color that will remain.
I'm not in a hurry to off the scope at this point. As I said earlier, it is pretty much what I expected it wold be. I do plan on following through with my original idea of picking up a new alt-az mount capable of carrying it, and using it as a Peltier-esque "comet seeker".
It also occurs to me that a 40mm 2" 68 degree eyepiece would help counterbalance the front-heavy scope. 6.8mm exit pupil, 3-degree TFOV, 22x, on a solid alt-az mount would make a diabolical giant monocular setup. What an intuitive, easy to use, hands-on hoot for public outreach, with an RDF. Also, what a stunner from a truly dark site where the 6.8mm exit pupil might actually be usable.
These are my first impressions of the scope. I do feel that it is a niche scope. I'm in that niche - always wanted the Peltier experience; drooled over the big Jaegers RFT achros as a cub, etc.). Not every observer will be as enamored with such a scope, though. My comments are intended as "fair warning". That's all.
I'm looking at padded tripod and lighting gear bags for OTA transport.
Posted 15 October 2012 - 11:23 AM
That's an easy one, Bruce. The eyepiece would be at the wrong end of the OTA.
On a more serious note, I don't feel my review was "negative" but rather "factual". "Negative" is an interpretation of those facts. "A lot of false color on moderately bright targets at modest magnifications" is a fact. I dub chromatism as a "deficiency" not as a personal judgement, but rather based solely on the fact that chromatic aberration is defined as, well, an "aberration". I suppose aberrant behavior isn't always bad, but...
I should also probably dig a little deeper on the C6 versus AT152 front. When I say that I believe most observers would be better served with a C6 (the f/10 SCT, not the C6R achromat) rather than this scope, it has more to do with the three "Cs" (convenience, comfort and cost) than it does with the actual performance of the two scopes at the eyepiece.
In comparing a 6" SCT to the AT152, there is a certain qualitative difference between how an large CO instrument and unobstructed instrument of a given aperture render star images. Using the MV filter in the big achro, there was still plenty of false color at high magnification even on fairly dim stars (Rasalgethi B, for example, is just magnitude 5.4, yet at magnifications north of 200x, shows plentiful false color, even with a MV filter in place), but stars retain that "crispness" systems with large obstructions seem to lack. Stars in the C6 (and other large-obstruction systems) are little quasi-discs rather than points, to my eye. Both systems (SCT and filtered achro) will show the same details (native star color, separation gap), but the way they present has a distinctly different appearance, disregarding the CA. I prefer the refractor's "style" of star rendering, but that is just a personal aesthetic preference.
Even with such a predilection towards refractor weenie-ism, I gotta think most folks would look at the two scopes, think about the relative magnitude of the trials and tribulations involved in living with each, and run screaming from the big achro.
Posted 15 October 2012 - 11:43 AM
Instead I'd steer you quickly to the $400 Celestron C6 OTA.
After looking through 6" achros at star parties I would have to agree with this, even my ST80 f/5 refractor throws up too much color for me at 22x on mag 2 and brighter stars which is kind of odd because a past ST80 f/5 refractor I had did MUCH better than the current runs of ST80s offered for whatever reason. I really like refractors and am working on finishing off a 60mm f/11.7 project now but I'd have a hard time using a 6" f/5 - f/6.5 achro, my vision is just too good and I notice a LOT of optical defects and spherical aberrations in these scopes, not to mention the color errors. I'm not knocking them and think they are useful but they are not for people with exceptional vision as they will drive you nuts with imperfections without a filter or perfect optical alignment.
Posted 15 October 2012 - 11:48 AM
First, I can't recall the last time I saw a quality or performance related criticism of a TEC, Tak or A-P in a forum. Whining about expense, snobbery and the like are plentiful, but complaints about performance are rare. I don't think that the scarcity of bitchin' about quality in these scopes had anything to do with elitism any more than I think every owner of an affordable scope who cannot afford one of these brands has a chip on his shoulder or suffers from "sour grapes" syndrome or has a Napoleon complex.
Sure, there are snobs who buy fancy stuff out of chauvinism, and not for the genuine quality advantages such stuff carries with it. Likewise there are plenty of petty folks who secretly covet what they can't have and adopt a sour-grapes attitude toward it as a result. But neither of those behaviors alter *facts* about the characteristics of different optics.
There are objectively really good quality affordable optics and really poor quality ones. The instances of really poor quality expensive optics, however, are rarer than instances of really poor quality affordable optics. It's not elitist to say it. Rather, I think it's kind of logical to assume that a manufacturer building a scope to a price (say $1000) doesn't have the leeway to put as much work into it as a manufacturer building a scope to a higher price (say $5000).
With respect to this scope, the fact is that it puts up loads of obvious false color, and there is not super-s3cr3t formulation of gnomish fairy-glass that would allow it to behave otherwise for its price. When I read folks claiming not to see it, with all due respect, I think there are three possibilities: (1) they don't know what false color looks like, (2) due to a physiological condition (color blindness, cataracts) the literally can't see it, or (3) they know their lady's butt is big, but for other reasons wholly external to the merits and drawback of a big butt, claim that it it not.
"I like big...er...achros, and I cannot lie." On the other hand, I'm willing to accept that the vast consensus of scope performance characteristic preferences is on the other side of the fence.
Posted 15 October 2012 - 11:56 AM
Posted 15 October 2012 - 12:40 PM
I like to display the facts out on the table too for people looking into buying one of these larger short tube Achro.
CA you will see and a MV or a CC will help reduce CA but REDUCE is the KEY word!
Ive compared with a MAK and a Triplet APO spliting stars at around 150-200x and well the Archo does poor!
When compared side by side the Achro shows more CA than you think than if you were just viewing with the Achro without anything to compare to.
However there is a great side to these is the resolving power for WF views! Resolving M11 at 15x-30x is wonderful
Pleades is awesome and other views are just stunning!
Too me its the best scope for paning around the sky at low mag.
There really isnt one scope that can do it all!
Posted 15 October 2012 - 03:22 PM
I don't think that the scarcity of bitchin' about quality in these scopes had anything to do with elitism any more than I think every owner of an affordable scope who cannot afford one of these brands has a chip on his shoulder or suffers from "sour grapes" syndrome or has a Napoleon complex.
folks who secretly covet what they can't have and adopt a sour-grapes attitude toward it as a result.
To me it's not a question of money. I could buy a much higher price scope. But I won't. I would find it hard to spend 4 to 8 thousand dollars on a scope that would show no CA and be perfect so to speak. The views I want I get from the scopes I have. I have nothing against those that do spend big bucks on scopes. To each his own. It's their money and they can do with it what they want. It's like that with other things besides telescopes.
I'm in this hobby for the enjoyment of looking into the heavens. I'm not one to pick fly$hit out of pepper for that last photon. As long as you are happy, great. As long as I'm happy, that's even better.
Posted 15 October 2012 - 03:57 PM
The combination of loads of context (i.e., lots of surrounding sky) and partial resolution of a bright globular courtesy at low magnification of the extra aperture, is really nice. Unless you happen to have a second magnitude or brighter star in the FOV, you likely won't notice the false color at low magnifications on DSOs.
That's the magic of a 6-inch scope with a 3-degree TFOV. I suspect folks with NP-127s experience a similar effect on such targets.
Posted 15 October 2012 - 05:11 PM
Jim, Your star test sounds like you have some SA that I have not seen on mine. I mentioned in another thread you could clearly see the CA as a tight line on the Lunar limb and crater shadows in my photo without chromacor. I find that niether a 6" SCT nor an 8" SCT were a match for my AT 152. I hope the quality controll has not changed since the 1.5 years since I purchased mine.
Luna without chromacor.
Were you just comparing views of planets and the moon with your AT 152 against 6" and 8" SCT's? Or was that for several deep sky targets as well.
Posted 15 October 2012 - 05:27 PM
Yup thats the magic of the 6" short tube the larger apeture resolving power in combination of the WF views.
Ive looked thru a 120 Achro and a 111 APO and they had no where near the resolving power punch of the 6" Achro.
The way to get rid of the CA on brighter star with higher mag. is to use a CC but they tend to $$$ so i usually sweep at around 27x 3 degree FOV in the 28mm WO UWAN which is really corrected at F5.
Posted 15 October 2012 - 05:55 PM
Posted 15 October 2012 - 10:54 PM
Jim, you certainly have a way with words.
When I read folks claiming not to see it, with all due respect, I think there are three possibilities: (1) they don't know what false color looks like, (2) due to a physiological condition (color blindness, cataracts) the literally can't see it, or (3) they know their lady's butt is big, but for other reasons wholly external to the merits and drawback of a big butt, claim that it it not.
"I like big...er...achros, and I cannot lie."
Posted 16 October 2012 - 12:40 AM
If you're going to use a f/4 newt., you'd better have a Paracorr available. Coma would be really bad without it.
actually ... for what it's worth ... my cheapo AT 10" yields extremely nice views with a 22mm LVW (1.25" barrel). that's a 5.5 exit pupil, just about right for me (my pupil stops at 5.9mm). i've tried it with a coma corrector and didn't see much difference.
like i said ... diff'rent strokes. all types make the world go 'round. et cetera.