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Friday, July 12, 2024
I love my telescope.
If the sheer existence of this site itself isn't enough proof, there's also the fact that practically all of my astrophotos, outreach events, and personal viewing use it. I have a Celestron Nexstar Evolution 8. All things considered, especially given my current proficiency in this kind of stuff, this telescope is great! The optics are stellar, the mount highly portable for an 8" scope, and the collimation is comparatively easy for a beginner like me. I've been happy with this scope and have been using it for over a year.
But there's a problem.
My Evolution 8 is what is known as a Schmidt-Cassegrain telescope. It is a reflector, which means it uses curved mirrors to bounce the light back and forth inside the tube until it comes out through the eyepiece with lots of zoom. I initially opted for a reflector because I heard refractors had lots of chromatic aberration (which sounds annoying) and were often much heftier. The main attraction of reflectors, especially SCTs, is that they compact a lot of zooming power into a small space.
The main issue arises from that high level of zoom. With a focal length of 2032mm and a base magnification rate of 51x, my telescope zooms in a lot. This is amazing for things like planetary astrophotography since these planets are often quite small in the sky, but with deep sky objects like nebulae, it gets annoying very quickly.
Astrophotography is a balancing game between how much light you can gather and how much time it takes to actually take the photographs. As a high schooler (who tries way too hard), I normally can't afford to stay up past midnight without seriously risking flunking my test the next day. An 8" scope can get a decent amount of light, but zooming in essentially stretches out the same light over a larger area, therefore having a dimming effect. Compound that with my local light pollution levels and lack of time, and you end up with depressing, dim photos.
The Orion Nebula at my telescope's base power - Feb. 1
To make matters worse, I struggle to find objects that I can even fit into my field of view in the first place. With a 51x zoom, I can easily capture planetary nebulae. Zoom out more, and I can comfortably fit some smaller globular clusters and a few decent nebulae. However, anything larger and I risk the object falling out of the field of view. I have an alt-az mount, which means that field rotation becomes a real issue with my crop sensor DSLR, meaning I end up cutting out a decent chunk of my photos in post-processing. Even with a focal reducer, I still have the same issues.
So. . .
How did I fix this?
I designed a piggyback mount!
A photo of Celestron's Product
I am an ex-robotics kid and was a member of the design team. I have experience with CAD software, specifically Onshape. I knew it was well within my capability to make one myself, especially since I have a friend, Cody, who owns a 3d printer who was willing to help out.
Celestron already offers a piggyback mount design built for Celestron telescopes. I felt lazy and thought it would be fine to buy one.
Then I saw the price tag.
And the reviews.
Turns out, this is a universal mount, built for different sizes of Celestron telescopes. That means it never perfectly fits one and breaks. I don't care how lazy I am. I am not paying $40 for a piece of fragile plastic!
Designing it was surprisingly easy. I loaded up Onshape, and in a few hours, I had the file for my piggyback mount! I sent it over to Cody (who managed to salvage the printer breaking last-minute with minimal damage) and I had my part by the end of the week, right on time for the new moon that Friday. I bought a few screws and attached it to my telescope for the first time. IT FIT!
In hindsight, it seems strange that something so easy to design costs so much from Celestron, especially given how often it seems to break. Celestron normally makes pretty good hardware, but I guess that's what happens when you try to make a universal mount.
Either way, I now had a piggyback mount that worked.
It was time to test it.
My piggyback mount
The night of July 5, I took my telescope out to attach my beloved mount. My target: my goal for this summer.
The Rho Ophiuchi cloud complex.
Rho Ophiuchi is not exactly a nebula. It is a wide-field object in the constellation Ophiuchus just above the bright star Antares. I say "object" loosely because it's more like "objects" with an "s". Rho Ophiuchi is a combination of many different deep-sky objects: an emission nebula, a reflection nebula, the crab globular cluster, hints of the Milky Way in the corner, and bright stars. It's an astrophotographer's playground. I chose a spot atop the Jollyville Plateau overlooking the southern horizon. I began photographing, and. . .
(A not very good) Rho Ophiuchi - July 5
Ugh.
Yeah, it didn't turn out so great. (please don't look up the real one)
Here is an itemized list of issues:
My tracking was off
The stars are unfocused and display comas and field curvature
There was a ridiculous amount of wind for most of the time
The light dome from downtown Austin created some unholy gradients, and removing it created a lot of noise.
I only had about 35 minutes of integration time.
That one streetlamp next to me that would not stop randomly getting brighter
The botched flat frames probably just made everything worse
You can glean hints of nebulosity just above Antares, but otherwise, the test was a complete failure.
Here's the thing: the mount itself worked like a charm. Sure, there might have been some downward tilt due to the slight flexibility of the material, but overall, it was incredibly stable even with the ridiculous wind. I also figured out how to connect an intervalometer to the scope, so I could relax more between changing settings.
The issue wasn't with the mount itself. I just happened to incur the wrath of Murphy's law that day.
I know my next steps, though.
Obviously, most of the photography issues stemmed from my lack of experience doing pure DSLR photography, especially when it comes to focusing. My technique during processing could also use some work, especially when taking flat frames.
I also designed a version 2 mount that I'm going to print soon. It has more surface area under the camera for better stability, including a part that sticks out more than the last time. It's also better aligned with the telescope's orientation since I made the top parallel to tangent with the circumference of the optical tube. The holes are in slightly different places to position everything better. I don't know, maybe I'll actually get a good photograph next time!
Piggyback Mount V2
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