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- Comparison of the Boltwood II and Sky Alert Cloud Sensors
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CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.
Aries 16" Modified Newtonian
Here I like to do a little review of my personal largest backyard telescope. A similar type of telescope is available from INTES MICRO in Russia , called MN165 ( 16" Maksutov Newtonian for US $ 22,900)
In 1994 , where I have had first contact with ARIES/Ukraine we decided to start an own apo production run, due
the big demand of apo's all over the world.
After 1995 we have delivered already larger Fluorite Apos up to 10" and got an order for an 12" Fluorite Apo. At this time I thought about the possibility to order for myself an 16" Apo.
Aries checked the possibilitys to get such large Blanks and after some time he confirmed, yes it is possible, but the price, man, this troubled my pocket too much. So together we thought about an alternative project, which allow me to see similar planetary details as on an 12"~14" Apo. At this time my russian Partner INTES MICRO have manufactored Maksutov Newtonians up to 8" only. Aries did recommend to me not to go with an larger Maksutov Newtonian, since he told me, such large Meniscus lens will have big cool down problems and due the power of this lens, I am getting troubled to much with quality change. I could not fully follow this thread, but decided to hear on Aries at this point.
So we came out with an modified Newtonian design, a standart 16"F/5 Newtonian with an 59 mm secondary ( small axis) which provides a 15% central obstruction only. Matched together with an extremly high quality flat optical window with an central hole to mount the secondary mirror. So I have had the same closed system as in an Maksutov Newtonian, no spiders, no dirt problems on my countryside for the main mirror. The disadvantages have been: coma of an F/5 newtonian, which is absence in an Maksutov Newtonian, this can be compensated by using modern eyepieces for widefield observing , designed by Al Nagler, the Naglers. For small fields, coma is not a issue.
Second disadvantage is possible straylight from the optical window, which is absence in an curved Meniscuslens. Here we checked and found that a modern super broadband coating from an german company on both sides of the winow and our clever baffle design , makes this straylight at least invisible. The coating itself have cost me another $ 900.
Now we thought how to design and optimize the mechanics. CAO ( Crimean Astrophysical Observatory) , the place where Aries Optics are being made, have its own mechanical enginners, who doing even Russian spaceprojects. One of this designer, became after one of my visits my friend and offered me his help in designing the mechanics.
A half year later, this designing was done. The Mirror support was a special quite heavy, but ultrastable floating cell with 3 outer collimating screws, used only by my fingers, no tools required. The back of the tube was added with an special mounted cooling van. The designer told me, we must prevent the tube inside to load on my bodyhead, so he recommend to glue inside the tube fully of corklayers. Against straylight we used a matched inside baffle system, similar to todays known INTES MICRO baffling.
The front of the tube comes with the same cooling holes, as they are used today on all INTES MICRO MN Telescopes.
The best scope, need the best focuser, so we decided to go with the Starlight Instruments Feather Touch dual speed focuser. Due trouble of focuser position on Newtonians pointing to different places of the sky, we designed an larger 20 inch wide ballbearing supported tube rotating system, as used in very expensive scopes from ASKO. The tube itself got on outside a complete system of tubebalance systems and some handle to move and turn the tube during using easily. A dewcap was designed with inside baffles and also with corklayers.
As finder I decited to go with the 2 best known to me finders in the world
a, simple Telradfinder
b, ASTRO Japan 14x80 straight version errect image finder with an build in 2 inch helicoid focuser, a illuminated widefieldeyepiece 1.25" which is exchangable for other 1.25" eyepieces.Such finders are today still available and running for about $ 1,000.
After 1.5 years waiting time, my optics have been finished by ARIES/CAO and supplied with Sitalmirrors and Interferomtrical testreport showing local errors of 1/8.7 wavefront p.t.v. and a strehlratio of 98,3 % , measured for the whole system, a superb result for such large piece of optics.
After knowing this results, Aries checked the performance on Zemax and we came out, that the contrast is the same as in an 14" Fluorite Apo with 1/6 wavefront. So I expected impressive images.
ARIES/CAO gave to INTES MICRO the mechanical drawings and 3 month later I received from INTES MICRO the matched tube. It was interesting to see, that both, optics and mechanics, matched perfectly and assembling was done after 2 hours only. I have to add , that my tube arrived in an ultralarge wood container with approx. dimensions of 120 inch long, 40 inch high and 40 inch wide. So I have had to recycle a quite large woodbox.
In the mean time my mount, designed and manufactored by a 65 years old guy arrived with an simple stepper motor dual axis drive system. The mount weight was about 350 pound and loading just enough to keep my 330 pound tube safetly.
Later I sold my mount with an 16" Aries Cassegrain with optical window to an USA customer, where it is still operating and I ordered a much larger mount, ready to hold Cassegrain telescopes up to 36 inch size. Just some future thoughts have been the reason.
This mount weights about 600 pounds, carrys for visual purposes about 1000 pound telescopes and for photographic work about 700 pound telescopes. This mount , using our german FS-2 Gotocontrolling system arrived last week , spending about 8 hours with 5 people and a crane, my telescope was assembled again and ready for observings. Here you can see now some pictures of my again born backyard super planetary telescope, waiting the planets.
The whole set up, mount, telescope, counterweights without pier weights about 1200 pound.
What do I see with such an big scope ? I must say, I used in the years before I got this scope a Carl Zeiss Jena custommade 16"F/10 Maksutov Cassegrain and early last year for about 6 month an Meade 16"F/10 SC LX 200.
None of this both scopes have had that image brightness, sharpness and contrast even close to my real backyard
scope, the 16" newtonian with optical window.
I still remember the very impressive images, of Saturns ring system, the clouds, spokes and colordetails on Jupiter and all the channels on Mars. Central Star in Ring Nebluae was never a problem with my 16"F/5 , but most time invisible in my 16" Zeiss and never real clear visible in my 16" Meade.
Limited power on Planets in my 16" Meade have been about 500 without image degradation and about 600 power in my Zeiss. My 16"F/5 handled with same sharpness easily 800~1000 power.
Most impressive diffrence between my 3 different 16" scopes I saw on bigger globular Glusters like M13, where the 16"F/5 showed more than twice resolution and more than double amount of stars. Also brighter Nebulaes in the 16"F/5 are much more impressive due the much larger field and much better contrast.
Two reasons are the main deal for this much better contrast a, the only 15 % central obstruction ( of the diameter)
b, the much better optical quality of my system.
My 16" with the small C.O. support also much better douple star observing, since the sintelation is much smaller and I can see much easier airydiscs with faint diffraction rings, which have been all the time a problem in my both other 16" scopes, where I could see them only in very seldom super nights or with maskings.
The much larger tubevolume of my 16" supported more inside turbulences, which i could and can fully, real fully eliminate by using my cooling fan. Using the cooling fan, I can see in any good night, diffraction airydiscs and rings.
Today my 16" scope have just one disadvantage: Pointing to the Zenith, I must observe staying on my mount or on an ladder. Anything else is perfect on this scope, the mechanics, optics, quality, drive system, it can be beated only if you invest 10 times more money in an apo of similar size.
In the last few month I thought about exchange this scope against my already ordered 12" Fluorite Apo which I will use as an Coudesystem ( in USA called Springfield-design), but now where my scope was last 4 night operating again and showed me nice details on moon, using my binoviewer with up to 1000 power and some galaxies in early evening, I decided not to sell it anymore and keep it as an second scope for deep sky and planets if the seeing permits and using thew12" Apo as an Solarscope and planetary telescope only.
Some might think, man whats the price volume of such an scope ? The answere is : less than an modern 10" Apo optical tube, about US $ 36,000. Not a bad deal for a scope, which show planetary details like an 14" apochromat.
All you need is an backyard observatory and dark skys. Here I am lucky, on our countryside in my small village we have a 900 people popullation and in best nights in zenith a 6.3 mag.
Everybody who ever come ever to my area is welcome to do a together observation with me.
- Jon Isaacs, Berny and Mechanizoid like this