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SKYOPTIKST 114/900mm (f/8) primary + 25mm secondary mirror set
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Preamble
SKYOPTIKST 114/900mm (f/8) primary + 25mm secondary mirror set
4 months ago, I wanted to build my own telescope despite never owning or operating one. Most would consider it a stupid decision, and I would agree. I won’t go into detail about why I wanted to build one, but before I knew it, I was halfway into building the mount for it and had bought its tube, a 150mm wide concrete form tube. I figured I’d just go for it at that point. These were the cheapest commercially available mirrors in my region by a long shot (I live in northern Europe), and they had pretty good reviews. However, they are spherical, but due to the long focal length, the shape doesn’t deviate from a paraboloidal one by more than 1/8th wave. The mirrors come in a set that I paid 44 euros for, but the price varies from 20-50 euros/dollars/whatevers from what I’ve seen. I like viewing nebulae and galaxies over open clusters, and do some planetary from time to time but much prefer DSOs, but I have yet to see a glob. I also slightly prefer imaging over visual.
Visual performance:
Before the build was finished, I had the opportunity to look through a 14” SCT with a dirt-caked corrector plate (it probably hadn’t been cleaned for 30 years or something). The seeing was incredibly poor that night, and I can safely say that on a good night my telescope outperforms the SCT on a bad night, but I guess seeing is just that important. This mirror set continues to exceed my expectations and challenge the consensus that spherical mirrors are inherently bad. I’m not sure how they perform on magnifications above 90x, as the cheap 2x barlow I bought doesn’t work at all, so I haven’t brought out the full potential of these mirrors at high magnifications. However, I have been able to see the craters on the Moon, bands of Jupiter, and even some details on Mars with my 10mm eyepiece. As for DSOs, so far I’ve seen the Orion Nebula, Andromeda, the Pleiades and M44, all of which wow'd me the first time I saw them! However, I noticed very slight spherical aberration when viewing the moon but other than that there were no defects.
Imaging
I went down a bit of a rabbit hole and did a bit of smartphone astrophotography. I’ll post more in my gallery when I get the chance but here are the best photos I’ve got so far:
Moon
Jupiter
Orion Nebula + M43
Conclusion
This mirror set is an incredible bargain and a great option for anyone who wants to build their own telescope on a budget. If you’re on the fence, if you have some time to kill, are into DIY and want a nice entry level scope, get these mirrors. There is also a fully 3D printable truss tube dob available online with this mirror set’s spec which I didn’t build, but should perform similarly to mine.
Despite going against tons of advice, this telescope and these mirrors are a ton of fun, and I’m considering buying a 6mm goldline in the near future for higher magnification. That’s all, clear skies everyone!
- RichA, rfcooley, Eric Weder and 3 others like this
8 Comments
Refreshing to see the ATM spirit has not passed into history.
I'd have cleaned off the C14, made an off-axis cardboard mask 4.5 inches across then compared it to the mirror set. Otherwise, we can only take such a comparison as humour.
Oh hey! That's the recommended vendor for the Hadley 3d printed telescope. I bought one a year ago. Occasionally there will be a turned edge on them, but a 5mm stop down ring fixes it right up.
Absolutely a crazy bargain.
Having fun with my C114GT. Of course it is a Bird-Jones hybrid but for its size,114mm, it does quite well. A truss tube Dob sounds tempting for DIY project. Nice and encouraging article.
RF
It really saddens me to see this in writing. The willingness to go DIY is frankly of mark of good character in my mind. This especially when you get to the point of leaving established designs behind and start to produce your own. It isn't just personal satisfaction either because once something you have created has eyes put on it by the rest of humanity you add to the wealth of knowledge that the world has to work with.
Consider focusers, if Crayford didn't explore his personal interest and ideas one of the most popular focusers wouldn't exist today. The Crayford is only one design to come out of the DIY world. Consider what would happen if these Imagineers listened to the negative nannys and gave up on their creativity. The word Imagineers comes from Walt Disney theme parks and it is an almost perfect description of a DIY mind set. A person that pursues the DIY life style eventually imagines a better way and then engineers a device to do that better way. As for Telescopes themselves what would the range of possibilities be like without Dobson and the innovations he made to drive down costs.
The only other thing about this article that kinda suck is that you didn't post a picture of the finished device. Seems like that should be central to an otherwise really good article. I do mean the article was really good, just don't become a never nanny and dismiss the value in DIY.
Here is the thing, DIY isn't for everybody. I fully understand that we are all individuals after all. But if a person has something that is driving them to DIY (be it a house fix up, a car modification, router table build or whatever) they should pursue these builds and not pay attention to the naysayers. Even a DIY build that turns out to be a failure by some measure, does something positive for the builder.
It is certainly not a "stupid decision" from my viewpoint: the more ATM'ers and DIY'ers the better: and we get such a great sense of satisfaction from DIY!
My first telescope was a 10" f5.6 dob, which I ground and built from scratch- largely following Jean Texereau's "How to make a telescope" which I borrowed from my local Library. My first ever view of Saturn, the "Leo Trio" and even the Horsehead was through that scope: amazing!
I have built a range of other scopes since then, although the commercially available scopes are relatively a lot cheaper nowadays. I suspect though that to buy a commercially made 14" bino-scope equivalent to my latest project would cost me as much as a new car (WAY more than I spent!).
Likewise, accessories like a parallelogram mount, observing chair, solid adjustable wooden tripod etc. were not only fun to make and cheaper than the commercial versions but continue to give great satisfaction in use.
So, well done for going down the DIY route, enjoy making more discoveries with the scope, and keep up the good work!
- Dean
One correction - the Crayford focuser was invented by John Wall, who was a member here until he passed away. The focuser design was named for the Crayford Manor House Astronomical Society.
Hopefully this review encourages people to build their own scopes and not the other way around. Also, thanks for the aperture fever. Seeing the horsehead must have been incredible, I don't see much structure in anything but the ring and orion nebulae. Time to build a truss tube dob, and then when that's done I'll look at Mel Bartel's sketches and build something even bigger, and before I know it my bedroom has been converted into a telescope...