The Celestron C90 Maksutov Cassegrain Telescope
Mar 02 2015 05:00 PM by skyaddict
William Optics Zenithstar 71ED and Twilight I M...
Feb 28 2015 10:53 AM by Ahab
If you want to Master your craft, read Lessons...
Jan 07 2015 11:29 AM by AstroDad
Celestron Ultima 80
Dec 16 2014 05:54 PM by Gianluca67
Categories See All →
- CN Reports
- User Reviews
- How to . . .
- Observing Skills
- Astronomical History
- Optical Theory
- Vision and Related Experiments
- How to Gain the Support of your Family for your Astronomical Pursuits
- Evaluation Tips
- Special Events
- The Elements
- New Articles in [!monthname!]
- Telescope Articles
- Submit a Review / Article
- Monthly Guides
- Behind the Scenes
- About Us
- Copyright ©
- Terms & Conditions
- Tiny Eyes on the Skies
- From the Editor's Desk
- What's Up . . .
- The Light Cup Journals
- Who is this Super Light Cup?
- Cloudy Nights T-Shirts
- Imaging Contest
- Small Wonders
- Previous Imaging Contest Winners
- This Month's Skies
- Mike's Corner
- The Cloudy Nights Friends and Family Discount
- Uncle Rod's Astro Blog
- Fishing for Photons
- Binocular Universe
- Article Submissions
APO MAX 130 f/12 refractor
The topic of what is an APO MAX refractor and how it perform has been asked recently on the newsgroup sci.astro.amateur. I have also received some personal emails asking my opinion of this rare scope. What follows will be an ongoing commentary and review of this superb instrument. Such an instrument begs to be compared to other apos and we hope to setup several evenings of comparisions. The first such evening was a wash due to clouds and poor seeing.
Click on the pictures that follow for the enlarged version.
The APO MAX 130 is an 5.2" f/12 SuperApochromatic (their term) triplet ED refractor. The APO MAX literature states the lens design is distinctly different then other apo designs. Here is a quote from the paperwork that came with the APO MAX.
"APO MAX consists of a unique three-glass combination that not only brings four distinct wavelengths to a common focus, but also maintains extraordinary control of aberrations at all wavelengths between the widely spaced "crossings".
The scope comes with a 4" focuser, custom hard case, dew shield and incredible lens cover. Find some pictures below with comments.
In the first picture above is the large dewshield that is held in place with 6 red nylon screws. In the second picture is the legendary focuser. Yes, it really does make a "whoosh" sound when you move the focuser as air escapes through the seal.
The lens cover (and all other aluminum parts on this scope) was contoured on a CNC machine and is held in place by three thumbscrews. Weighing approximatly 35 lbs, the scope is not as heavy as it looks. The G11 can carry it easily but I will need to add a 1/2 pier extension for more comfortable viewing.
That's all for now. I will add additional material as I gather it and will place an "update" stamp next to the article title on the scope page.
I've received a number of private emails over the past month wondering why I havn't posted any updates. The simple answer is the weather. This has to be the worst summer of observing I have ever experienced. I can count on one hand the number of clear nights I've had over this entire summer. I've even taken to looking out the window in the middle of the night hoping the clouds have cleared! As soon as it clears, I'll post my observing reports here.
The Losmandy 1/2 pier extension worked wonders with this scope elevating the entire OTA to a very comfortable viewing level. For those not familiar with the Losmandy 1/2 Pier extension it is a 14" mount extension that sits between the tripod and the mount head. Near the horizon I can actually stand at the eyepiece while at zenith I am seated normally on my piano stool. Damp time is right around 1 second while either focusing or slewing the telescope. My compliments to Scott Losmandy for creating such a fine mount at a relatively inexpensive price.
I was able to complete two planetary observing sessions with the APO MAX and was delighted with the results. It is a bottomless pit of magnification, keeping up with whatever I threw into the diagonal. Combine this with it's medium sized aperture and it has the wonderful ability to give CONSISTENTLY high quality and high magnification views of the planets. This is the heart of the reason why many people prefer APOs for planetary viewing, it always gives the best images balancing aperture against the limitations of the atmosphere. Living in the northern climate, I can't stress the importance of this. There have been so many nights where my larger aperture telescopes are outperformed by much smaller apos due to relatively poor seeing. It's easy to forget when telescope shopping that it takes very little atmospheric disturbance to degrade planetary views.
I've written before that I typically use lower magnifications then many others when observing. As an example, I find I see more when at 180x with a 4" apo then at higher magnifications. This phenomena has been debated at some lengths on many astronomy chat groups and I've concluded that it is a combination of the skies above where you live and your own personal observing style and habits. Use whatever magnification YOU feel you see the most at and don't let others tell you otherwise.
I bring up my personal planetary viewing biases as a context for the magnications I find useful when viewing with the APO MAX. Before I do I'd like to make a comment on the "scale" of the image in the eyepiece. It goes without saying that the higher the magnification, the larger the image of the planet will be in the eyepiece. While I feel I "see" more at 180x in a 4" apo, I feel much more satisfied if I can maintain that level of detail in an image at 300x. To me (and perhaps me only), planets become interesting targets at 300x and above IF they can maintain the level of detail and contrast that I view at 180x in a 4" apo.
Here is where the APO MAX performed admirably, maintaing the high quality image that I liked so much at 180x in the 4" while at 300x in the APO MAX when viewing Jupiter. Pushing magnifications beyond this didn't degrade the image, but robbed valuable low-surface contrast from Jupiter. Banding, plums and swirls were apparent and beautiful while the edge of the planet contrasted starkly against the velvet black background of space. While I have often commented on the price/performance advantage of a sem-apo or achromat, there is simply no way to describe the high quality planetary views through and APO while using a high quality Orthoscopic eyepiece. It is beautiful in it's own way inviting the observer to sit and stare and stare and stare. . . . .
Chill out . . .
Over the years I've read different folks claim wildly different cool down times for apos and other telescopes. I've been called "cooldown finicky" by several observers so read this within that context. The APO MAX takes 1.5 hours to cool down to a temperature where it can sustain 300x on the planets. This is coming from an unheated garage to the outside. It's interesting to observe the cool down process as every 15 minutes or so I can increase the magnification by another 30-50x and maintain a solid image. It's sorta like I'm sneaking up on the planet if I observe while waiting for it to cool. The star test will completely smooth out in 2 hours but I find I can't detect any degradation in the image for that last 30 minutes. Perhaps if I were a more skilled planetary observer I would see it but as of today, I can't.
Two are Better then One
Other then the top 30 most interesting binary stars, I have yet to develop an apprecation for the subleties of binary star splitting. Having said that, I found the APO MAX gave some of the best binary star images while using Orthoscopic eyepieces. How can a binary view be judged as "best"? Easy, the stars presented as hard points of light. Let me emphasis, HARD points of light. No flaring, no elongation, no dancing around due to seeing, simple hard points of light. Like planetary images, it is easy for other telescope designs to compromise the binary image if seeing conditions are less then perfect. Even then many telescope optics fail to show the stars as hard points of light.
So if so wonderful, why only 3 observing sessions in the past 2 months?
I thought others might benefit from reading my experiences with a large telescope to help them in their own purchasing decision. Once again, to give context to my comments, both my wife and myself have full-time careers in addition to two small children. Compound this picture with a beautiful neighborhood full of stately and old trees in which the telescope must be moved to view anything outside a small "window" between tree branches. Add to this the size and bulk of the Losmandy G11 ( the best mount for the money in my humble opinion) and you begin to get a glimmer of my situation. The APO MAX is not being used very often.
Those rare times in between bi-weekly established observing sessions when I can observe I may have only 20 minutes total to observe. Since the G11/APO MAX takes around this long to setup, I find I pull out a pair of binoculars or a short tube achromat on an alt-az mount. For those night I have established observing sessions and half the night to view I find I take my 12.5" Portaball to take advantage of the dark site skies. As the weeks rolled on it slowly began to dawn on me that I can own the most optically perfect telescope in the world, but it it's not used it does me no good.
This is not to imply that one shouldn't buy large telescopes/mounts, simply benefit from reading my experiences by pausing to reflect on your own personality, habits, and lifestyle before buying your next telescope. If you live a hectic life and have short, and unpredictable viewing sessions, then by all means focus on the smaller, easier to setup telescopes. However, if your life is relatively settled and you have time for established observing sessions with plenty of time for setup and breakdown, the get the largest telescope your back can handle.
Lastly, I've read others more experienced then myself comment on this and it is a comment I agree with completel y - it's not the telescope that dicates your setup and breakdown times, but the mount. If you have or are contemplating a large mount such as the G11 or above, it's inconsequential whether you purchase a short focal length APO or a long focal length apo unless you are pursuing astro-photography. It is sad to see the decline of the long focal length refractors due to the impression that the setup time is longer then the short focal length refractors. Long focal length APOs are a no-compromise design in which the designer eeeked the last drop of performance out of that aperture. This may not appeal to everyone, but for some, it is rare and invaluable.
I've been surprised at the amount of interest the APO MAX article has generated in other amateurs. Not a week goes by without several email inquiries about the APO MAX and potential future APO MAX runs by the company that created them. I see this as a positive sign for long focal length refractors. Perhaps pundits have been premature in declaring the market for long focal length APO refractors dead. Today's serious amateur astronomer appears more discriminating then ever before and the pursuit of the best possible image is one dear to the hearts of many of them.
I've had a number of requests from folks wishing to read the original paperwork that came with the APO MAX. To this end I've scanned them in and posted them below. Simply click on each of the small images to read the full size document.
Figure #1 Introductory letter from Yeier Optics (reseller of the APO MAX)
Figure #2 Optical design details
Figure #3 Optical design details #2
Figure #4 Mechanical design details
Figure #5 Strehl Diagram
Figure #6 Lens cell diagram
Figure #7 APO MAX Picture
Figure #8 Spot Diagram
#1 #2 #3 #4
#5 #6 #7