The Cocoon Nebula (IC 5146) is a mirrored image and emission nebula that lies 4,000 light-years away in Cygnus. The writer captured this picture with HαRGB filters and exposures of six, three, three, and three hours, respectively. Credit score: Tony Hallas
The Cambridge Dictionary defines magnificent as “deserving to be admired.” I had no hassle doing that after I walked into the workplaces of Stellarvue to get an extension ring for my SVX140T and to go to my good friend and Stellarvue proprietor Vic Maris: Whereas there, I witnessed an SVX180T 180mm f/7 refractor being ready for cargo to some fortunate buyer.
Till that second, I had been pleased with my Stellarvue 140mm f/6.7, however the energy of 180mm dwarfed it by comparability. Fully captivated, I put a deposit down on a 180mm and waited — these hand-crafted devices can take months to assemble. Happily, Stellarvue was in full manufacturing and simply 4 months later I obtained the long-awaited name saying “Your scope is prepared, come decide it up!”
The time has lastly arrived
The very first thing you discover whenever you see this telescope is that it’s large. No effort was spared to make this the final word refracting telescope. For instance, though the target is 180mm, its absolutely baffled tube is 8 inches (203 millimeters) throughout. This aids in thermal stability as warmth currents usually tend to keep out of the optical path. The dew protect can also be massive sufficient to present the entrance of the target room to breathe and ample space for dew management. The 180mm scope has three choices for the focuser; I selected the Starlight Devices 3.5″ focuser, which is extraordinarily rugged and properly made. Stellarvue constructed an enormous subject flattener for imaging — as an non-compulsory add-on — that fastens on to the focuser and covers any dimension digital camera with the fitting adapters.
To see how properly a telescope baffles mild, do that experiment: Place a white, well-lit board in entrance of the telescope, take away the eyepiece and diagonal, and look by the scope. What do you see? A well-made refractor ought to present you nothing however the vibrant white circle of the lens surrounded by a black void, whereas a poorly made refractor will make a vibrant star seem like a colourful blur. While you carry out this take a look at on the Stellarvue 180mm refractor, a transparent, vibrant level is strictly what you’ll see. The scope is extraordinarily properly baffled, so any spurious mild is blocked from reaching the eyepiece or digital camera.
A complete new view
My unique intent for buying this telescope was for visible use, as I personal a big corrected Dall-Kirkham reflector for astrophotography. And for a number of months, that’s how I employed the 180mm. As anticipated, the distinction was superior, the illumination was fantastically even, and the smallest stars have been mere pinpricks. The planets and the Moon appeared the perfect I’ve ever seen them throughout moments of fine seeing.
One occasion actually stands out: One evening I used to be wanting on the craterlets within the lunar crater Plato. As I checked out one of many craterlets, it appeared to separate into two. Unhealthy seeing? Thermal results? However the extra I appeared, the extra I used to be satisfied I used to be seeing an actual double craterlet. The subsequent day I appeared up a NASA image of Plato and lo and behold, there’s certainly a double craterlet there. It was the primary time I noticed this with any telescope. I used to be additionally stunned at how properly the 180mm dealt with deep-sky objects. It was good to see M81 and M82 in the identical subject of view with an added Pentax 40mm XW eyepiece. The views by this positive instrument are wonderful.
However Vic was curious how the scope would carry out photographically in my arms — and so was I. With the help of some associates, I pulled my reflector from its imaging mount and put in the 180mm as a substitute. For the following a number of nights, I ran the scope by a number of assessments with my complementary metal-oxide semiconductor (CMOS) digital camera and famous how delicate the scope was to temperature adjustments. I made a decision to additionally add the automated Starizona’s Microtouch focus motor, with built-in software program for temperature compensation, to the rig.
The facility of an APO Lens
Credit score: Tony Hallas
One of many questions I hear concerning the 180mm is whether or not it’s a true apochromatic (APO lens), the place all the colours focus in the identical spot. This query highlights a traditional distinction between a reflecting telescope and a refracting telescope. A reflector brings all of the mirrored mild to the identical level, no matter wavelength. However a refractor bends the incoming mild by a lens, so the colours come to a spotlight in barely totally different positions. In conventional refractors, photos of vibrant stars typically produce a purple-red ring round them. This “false-color” concern actually turns into an issue when utilizing narrowband filters, notably when pairing these with extra disparate wavelengths.
An apochromatic refractor makes use of plenty of lenses to take away this concern and get all wavelengths of sunshine to come back to a standard focus. Stellarvue makes use of Ohara S-FPL-55 super-low-dispersion glass in a novel lens design to realize this, creating a real apochromat. Throughout manufacture, the goals are repeatedly examined with a Zygo phase-shifting interferometer to detect irregularities — if any are discovered, the opticians fastidiously take away them. This course of can take months, as every goal should be examined time and again after every correction. Stellarvue doesn’t cease till the lens is as excellent as might be. The telescope can then ship a closing determine centered on the inexperienced wavelength of sunshine and displaying a generally recognized projection impact, a Ronchigram.
The 180mm — with its fashionable lens design and use of the best supplies — transmits RGB and slim bands such that that all of them come to a spotlight on the identical level.
One-of-a-kind telescope for one-of-a-kind photographs
Credit score: Tony Hallas
Not like mass-produced telescopes, Stellarvue telescopes are customized made within the U.S. on the firm’s Auburn, California, amenities.
All this perfection can be ineffective if the lens cell, which holds the big lens parts, have been constructed from an improper materials corresponding to aluminum. Aluminum expands and contracts with temperature, that means lens parts might be pinched in colder temperatures, which adjustments the form of the lens and impacts the standard of the picture. To keep away from this, Stellarvue makes the lens cell from metal that has a low coefficient of enlargement, thereby avoiding any strain on the lens parts even because the temperature adjustments.
The Stellarvue 180mm f/7 APO triplet refracting telescope represents the best massive refractor obtainable to the discriminating client. With restricted decisions for shade correction obtainable available on the market, this air spaced triplet has been constructed with no compromises by devoted opticians and machinists. It’s the results of years of telescope constructing, analysis, and experimentation within the quest for perfection. A big refractor is extra than simply wonderful optics — the complete telescope has to work seamlessly collectively to create a unified entire. And that is what you expertise with Stellarvue’s magnificent telescopes.
Reaching the best imaging setup
As soon as I made the choice so as to add Starizona’s Microtouch focus motor to the rig, subsequent got here the problem to connect it. The closely geared telescope motor fastens on to the main target shaft, eliminating any likelihood of focus backlash — not like much less highly effective motors that connect by the ten:1 discount gearing. After putting in the main target motor, I ran the easy-to-use temperature compensation “studying characteristic” (included in motor’s software program), which calculates the main target shift in relation to temperature drop. The main target motor regularly retains the picture in focus by adjusting each 0.18-degree-Fahrenheit (0.1 diploma Celsius) drop in temperature. Utilizing the motor permits me to run my rig all evening with out having to refocus, and stars keep the precise sharpness from the primary picture of the night to the ultimate picture, even with an total drop of almost 22 F (12 C) by the evening.
One of many latest recreation changers in astrophotography has been the arrival of small-pixel CMOS cameras with low noise and good quantum effectivity. That final merchandise means the photograph sensor captures a big share of the photons that hit it. Not like their older, bigger 9-micropixel CCD predecessors, these 3.7-micropixel CMOS cameras can resolve extremely positive element. This performs on to the strengths of huge, razor-sharp, high-contrast refractors.
I began a typical imaging run by organising the scope simply earlier than sundown so it had time to succeed in thermal equilibrium. As soon as it was darkish sufficient, I slewed to my chosen goal and framed it, getting into its place into the mount reminiscence. I then generated a V-curve with an autofocus software program utility to realize pinpoint focus. At this level, I opened the main target motor management and turned on temperature compensation, permitting the motor to watch the temperature and alter the main target accordingly. Subsequent, I began up my picture acquisition software program utility to discover a information star and begin monitoring. My closing step was to arrange the imaging sequence and begin imaging.
I preserve my mount on an analog timer each to stop it from operating the telescope into the pier and to close off the ability when the session is full. Though there are lots of automated packages that may do all this for you, I’m nonetheless a bit old-school.
