Now with the eclipse excitement settling down it’s time to return to the night time world! Back at Orion’s Belt for the holiday weekend we have arrived at a critical point in the installation process for the newly acquired 16″ telescope. Time for optical testing which means we have to take an image! I guess technically it’s sort of a first light but I don’t really count it as such because it’s just star testing. However it is kind of a big deal because if we take this image and the stars are totally jacked up either we have to start collimation from scratch which means we have to buy more collimating equipment or in the worst case scenario there is an optical problem which needs repair! After all the scope is shipped from overseas. Who knows what could have happened. There is also the issue of focus, if it can be reached at a point somewhere in the middle of the focuser travel so we can do automated focusing. There are no “spacers” with this system. We had to get the right adaptor with just the right amount of backfocus. Hopefully we did the math right!
To get to this point it took the last 2 months slogging through the installation of the accessory equipment on the scope: the focuser, control system etc. You can see the blow by blow narrative in this page. I think overall it really went fine. Yes there were some issues but with this kind of stuff how can there not be? Mostly I was very anxious and apprehensive due to the huge expense of this equipment, every step of the way worrying about something breaking or malfunctioning. But thankfully no disasters yet and I got through it and learned a bunch in the process!
All the operating components are now in position. ‘A’ is the USB hub. ‘B’ is the focuser. ‘C’ is the camera. The OS bus controller is on the other side of the scope. Cables are secured to the holes in the telescope frame with the use of cable ties.
Looks more like a NASA space probe than a telescope, but then again we are able to “travel” to the far reaches of the Universe with it!
So now the first ever image taken with the RiDK 16″:
First ever image taken with new set up!
What we see are defocused star images but still pretty round all the way from side to side. Yay! We probably don’t have to send it back! The 2 lines in the image are called “column defects” and are present in the ccd sensor. These do occur with the standard “class 2” ccd sensors (class 1 sensors with no defects are generally used for research). The column defects do process out pretty easily with dark frames
Near focus is reached somewhere in the middle of the travel.
Next we rack out the focuser to close to focus position and see it does lie somewhere in the middle of the focus travel.
Conclusion so far anyway is that 1) We are close to decent collimation and 2) We can reach focus pretty easily with room in front and behind. That is a huge relief! Now onward and upward!
The 16 is powered up with covers off, ready to work!
Thanks for reading!
Finally we began installation of the long awaited 16″ telescope. It took 6 months for the manufacturing! Every telescope is built to order. I spent years researching which design and configuration to go with. 10 years ago the “RCOS” Ritchey Chretien was all the rage. They have since gone out of business, but they are still wonderful telescopes. After all the Hubble utilizes the same optics. However they require additional external field flatteners to get a flat uniform image. They are also notoriously difficult to collimate. Much more difficult to manufacture so this is reflected in the cost. Another option was an imaging newtonian. My first telescope was a Cave Astrola newtonian reflector for those of you old enough to remember those. When I got into imaging in the early 2000’s I converted the old telescope into an astrograph and it worked pretty well but there are limitations. The main one is the lack of backfocus restricting your imaging train options. Can’t have too much stuff back there. Accurate collimation is also difficult. However I honestly believe the newtonian is a very close second. You can’t beat the beautiful razor sharp diffraction spikes seen in their images! I may decide to try a medium sized version one day. The design I ultimately decided on was a CDK or corrected Dall Kirkham. The CDK employs 2 mirrors like the Ritchey but the secondary is spherical. The primary is aspherical. There is a corrector lens group placed before the focal plane. This arrangement provides the widest, flattest, error free field with the added bonuses of relative ease of collimation and very generous backfocus. Naturally I have looked at tons of images taken with these by the top imagers in the world. I don’t know that there is a discernible difference between, say an RC , a CDK or newtonian in the hands of skilled individuals. So I could not base my decision on that. The final choice was between a CDK manufactured here in the US vs one that was made by a company in Italy known as Officina Stellare (workshop of the stars). Their version is actually called “RiDK” or “Riccardi Dall Kirkham” named after the optical designer Riccardi Massimo. Their optical design is slightly different with respect to where the corrective lens is positioned and the shape of the primary (“aspherical”) as opposed to ellipsoidal. The result is a somewhat wider field based on the numbers I have read. I also felt the Italian version produced better images than the US version. Additionally I just got the sense that the OS scopes were produced with a little more attention to detail. Each one is custom made, not mass produced. They build them for aerospace and the optical designer is better known (Riccardi Honders fame). So that was my choice!
The “RiDK” 16 inch arrived in a crate you can see to the left, bottom. While the telescope itself weighs about 90 pounds the entire package was over 400! I had no idea this was the case. Thankfully I have a good friend who helped drive it up in a trailer to the observatory
The RiDK is shown with roof closed, mounted on the Paramount MEII. It does sit pretty high, but this is OK because it can park flat with plenty of clearance for roof closure
The journey to first light begins again! This time way more challenging. Not being an electrical or mechanical engineer, it does seem daunting to install and operate a high end professional instrument, especially a foreign one! For this reason I have created a separate blog page entitled “Installing and operating a high end professional telescope…for the rest of us!” This basically will chronicle the installation from the arrival to first light.
Thanks for reading!