TELESCOPE Crayford Focusers: A History And Demonstration (How It Works) ( by
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- Опубликовано: 1 окт 2024
- The Crayford Focuser is everywhere in astronomy. Few people know that it was invented by a modest engineer who gave it away for free...
#crayford #telescope #focuser #reflactorguy
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Questions Answered:
1) Who invented the #Crayford #focuser
2) Who was John Wall?
3) How do I take apart and fix a Crayford focuser?
#astrophotography
#astronomy
#dobsonian
#reflector
#reflactor
#dobsonian
@reflactor
I would submit that you, sir, are carrying on John Wall's legacy by sharing your knowledge, experience, and insights freely with us via RUclips. Thank you very much!
Thank you for the kind words, but I haven't created anything new or unique like Mr. Wall did. He is a true hero to the community.
Looking for help with my Dob XT8 and I've sent an email to you. Hopefully you can help me out!
Got your email. Will reply directly.
@@reflactor really appreciate it!
Love this appreciation of the Crayford Mount and the great John Wall. If you can find it I highly recommend watching Equinox: Earth Calling Basingstoke from 1989.
John Wall's story is a pretty fascinating one. I'd like to visit the Crayford House building some day. Thanks for the Basingstoke tip!
You should do a part two on this taking apart the Dual speed crayford as I would love to see how that functions
That's a great idea! I've also been curious how those work!
I did not realise the Crayford focuser was invented so close to where I live. Closer to where I live is Ockham, the birthplace of William of Occam (inventor of Occam's Razor), and home of Aida Lovelace, chiefly known for her work on Charles Babbage's proposed mechanical general-purpose computer, the Analytical Engine.
From what I've read, they astronomy group now meets at a different building, but they still by the same name.
When I retract my crayford all the way in, it looses its grip during the last few turns. When I back the focuser out turning the knob, I need to lift up on it a little, help it engage, then it works great. What might you suggest? It’s an Orion XT10 stock focuser that I got used.
Might take the hatch off and take a look.
First step is to adjust the tension screw (the center bolt, sometimes it is a set screw). That will push the roller tighter against the focuser tube. You can see me do that in this Crayford restoration video: ruclips.net/video/NknmBk7qKcc/видео.html
@Reflactor This is an excellent video describing how the Crayford focuser works and a Great tribute to John Hall!
I use his invention almost every day. :)
Great video! Sounds like John Wall was an intelligent, yet humble man.
He certainly made a huge contribution to astronomy. Clear skies!
Your voice sounds exactly like the history that deserves to be remembered guy, are you related?
Haha, thanks, but I don't know anybody famous.
Neat!
I'm thinking of getting a Synta (Skywatcher) 2" Crayford for my 200/1000 Newt' to replace it's Synta/Skywatcher 2" Rack & Pinion (still single speed).
I see all over the 'net that it's smoother but can anyone tell me whether it also eliminates or reduces the sag that a camera exerts onto a rack & pinion please?
I've found that when I put my smartphone camera on the Crayford, it sometimes slides back in (I adjust my Crayfords to be light on the touch), so I sometimes have to use the locking screw. It's no big deal. The nice think about Crayfords is that they don't have the side-to-side slop when adjusting in or out of the telescope (like rack & pinions do). Clear skies!
@@reflactor I'd forgotten I posted the question but thanks. In the meantime I eliminated my R&P sag by sticking some thin (beer can) aluminium onto the focuser tube.
I wouldn't say crayfords were running wild since 1971. Other than a premium upgrade aftermarket focuser, and early william optics telescopes, they didnt start to become ubiquitous until 2005 when GSO started making them, and shortly after synta followed suit. Yours are syntas.
I started buying scopes in 2004,.and they all had rack and pinion focusers. My friend got a 12" dob the same year, rack and pinion. Then when i got my 10" dob in 2005, they had just changed to the crayford, a nice machined aluminum one too, but single speed. So it has been less than 20 years that crayfords have been an industry standard rather than a premium upgrade only made by a few companies, starlight feathertouch, moonlight, jmi and william optics. Technically the meade microfocuser is a crayford design but only electronic with no knobs. I have an older JMI that is the same. A crayford mechanism but only electronically controlled.
But those were a few exceptions, and only on the LX200 GPS which came out in the early 2000s, so only a few years before every dob and just about every refractor with a 2" focuser had them.
Very cool! I was curious about how it worked.
Thanks for watching. I'm about to post a restoration of a really wrecked Crayford forcuser. Might be an interesting followup.
I went outside for the first time with my 8 inch dob after weeks and weeks of cloud i found that it was out of collimation so tried to collimate with my laser collimator and was successful which I was happy about.i put an eyepiece in and the focuser didn’t work.i had no instructions with scope so played with the two silver thumb screws with no joy.i was getting rather angry and gave up.after watching a 40 second video i now know how to do it but wasted an clear evening.please be clear tomorrow🙏🏻
Are you saying that the Crayford focuser is working okay? Or is it still broken?
@@reflactor yes a simple 40 second video showed me how to do it.took a minute to sort it working fine now.its a gso(stellalyra) 8 inch dob but no instructions came with it.easy when you know what to do! Thanks great channel only just found it so catching up on your content.
Another really enjoyable video.
Thanks for watching! I've got a bunch more planned. Just need to find the time. :) Clear skies!
Yeah thinking cardboard tube to hold everything
Very interesting topic. Thanks!
Thank you for watching. Clear skies!
Excellent video 👌
Thank you for the kind words. Clear skies!
Excellent video!
Thank you for the kind words - I'm glad you enjoyed it!
thx for shared!
Thanks for watching!
AWESOME
Thank you for watching!
always a pleasure@@reflactor
Where can the initial drawings be found? I searched some on the web and had no luck. Thanks!
I believe the originals are hanging on the wall at the Crayford Astronomical Society, but you can see some scans here: en.wikipedia.org/wiki/Crayford_focuser
@@reflactor Thanks for the link to the plans!! BTW I just purchased the full 1972 year off eBay to get the September, 1972 issue. I have looked through it a few times and did not see anything about the focuser. Was it just the article published? If so maybe that is why I missed it.
@@centaurus777 I too read through the September 1972 issue of S&T(twice), and failed to find anything about Wall’s Crawford focuser. I even looked at the September issues for adjacent years, in case the year was incorrect, but found nothing.
Nice, thanks. btw i enjoyed your books
Wow! Thank you for reading the books. I hope these videos are helpful.
Yes it was, but i decided to purchase motorized focuser.
I liked the history and honuring mr. Hall atribution to astronomy. Would love to see the dualspeed crawford insides as well, if You will go for it. What is Your newest book name? Good luck
I actually dissected a dual-speed Crayford focuser in my Orion 14G Dobsonian restoration: ruclips.net/video/voSzgNB8QoI/видео.html
Great video I knew John and its good to see a video out there telling his story. I would add I too worked for Vickers - Vickers Instruments (in York, England) successors to T.Cooke & Sons/C.T&S and 'you do not drop out of education' to do an apprenticeship, if any thing education is ramped up and an apprenticeship back then was was equivalent to a degree, theres a lot of snobbery in this world. John always worked on his CEM much earlier than 1969 and theres mentions in BAA Journals in comments about CMHAS astronomy shows.
Thank you for your comment. I really do apologize for minimizing the importance of an apprenticeship at Vickers. It shows my ignorance of the British educational structure. Researching this video was bit tricky, but I was able to get a few resources that were helpful. Trying to pinpoint the date that it came to life was very tricky.
No probs @@reflactor if you want to know any thing else about John and his 'evile werkes' (his words) let me know. I was the last astronomer to see him when I visited him in hospital the week before he passed away. We had a good laugh about UFO's, Satan and religion ;o) best wishes from the UK
That is a well presented expose on the Crayford. Delivery and content is pleasant on the ear. Perhaps you have heard other astronomy/astrophysicists on YT, but if not, you might consider David Butler (ruclips.net/user/howfarawayisit). Some of his content is definitely challenging but it is always served up with the Walter Cronkite style of engagement.
His series "How Far Away Is It" is very thorough - he has a Carl Sagan aspect to his presentation style.
Fabulous history there, thankyou again for wonderful content!
Would love to hear your thoughts on the linear rail focuser too!
Unfortunately I'm not familiar with that - looks like I have some research to do! Clear skies!
Thanks for the great content. Great video honoring the creator. I did not know this story, and now I do. Thank you. Clear skies!
Thank YOU for watching. I'm glad you found it interesting. I'd always wondered who invented the Crayford focuser and was not disappointed in what I found during all of the research. Interesting guy for sure. Clear skies!
A very enjoyable watch!
Glad you liked it. Clear skies!
Fascinating and informative. Thanks!
Thanks for watching. Clear skies!
An excellent and informative presentation. Thanks
Thank you for watching!
Helical, rack & pinion, and Crayford are three types of focuser. There is a fourth type that you have left out. I won't say what it is, since you don't want to promote it. However, it has no backlash, is non-rotating, has no gears, is very precise, and is easily made with hand tools.
I don't work for any of these companies, so I'll promote whatever is best for the user. Please let me know about the fourth type.
@@JJDreese That would be the Clement focuser, by Don Clement. It was patented, but the patent was dated 2001, so it is now expired. Uses flexure hinges to eliminate all hinge and bearing play. How could you k not know about this? Don't you live in southern California? Don manufactures these for Takahashi scopes, and his machine shop quality is excellent. But you could make a less pretty non-motorized version that physically would work just as well. Some people have made them out of printed plastic.
Hi Richard, that sounds very interesting! I think I know why I haven't heard about them - I don't live in California. From what I've heard, Takahashi's are some of the best telescopes made, but they are way beyond my pay grade. I generally only buy used/abused Orion, Meade & Zhumell telescopes. However, if anybody wants to sell me a used Takahashi, I'd be up for negotiations, lol.
Thank you for taking the time to present a fellow Englishman’s achievement in bringing a design freely to the masses. We English have a habit of giving great designs away! My only concern with this type of focuser is with slippage, has any manufacturer considered adding a rubber/ silicone sleeve to the cross bar to prevent this?
Mr. Wall was a remarkable guy for sure! As for the slippage, most makers have addresses that by milling a flat spot on the tube. That gives it much more surface area to bite down on. There is also a tensioned set screw which allows you to adjust the tightness. Thanks for watching!
I overcome the slippage by reversing the procedure. three flats on the tube. two at the top 60 degrees apart on the tube supported with Teflon adjustable pads the bearings at the bottom being pressured on the tube. three ball races engage the tube bottom flat. Two ball races space side by side the third at the rear between the two front bearings overlapping by a third of the diameter of the bearings.
The pin sits between these bearings with a fourth bearing centralised over the pin with adjustable pressure. This allows for a small diameter pin without pin deflection. The whole bearing train has pressure supplied to it separate from the pin. The test model was 4" in diameter and set on a bench that could lift easily a 6kg weight vertically without a fallback. I now use one on my rebuilt Jaeger 6" refractor very smooth in operation.
For many years I worked for a tooling company and visited Vickers at Crayford as I lived in Kent but now live in Western Australia.
We have wonderful dark skies here. At present, WA is setting up Astrotourism for astronomers to come and see our dark southern skies many are on farm stays or very small townships. Until you see the southern sky you realise you haven't seen anything like it so many stars and brilliant objects so bright you can read a newspaper under the Milkyway starlight. WA is so big you can be in summer all year round. WA state size is about a quarter of the USA's land mass with just 2.5 million people mainly in Perth. It is possible WA could become the Astronomy tourism state of the world. Starting with the Exmouth Hybrid eclipse on the 20th of April 23, this is the first hybrid eclipse in Australia for over a thousand years. The first in a western country in the photographic era, Is that special enough!!!!! I am going on a five-day cruise on the Pacific Explorer to see it.
What a great and informative video ! Thank you very much !
Thanks! It was a lot of fun to research this video. Great invention. Clear skies!
lovely
Thank you. Mr. Wall is a bit of a hero to me.
@@reflactor What about D. C. ?
@@richardnineteenfortyone7542 Hi Richard, I'm afraid I don't know what D. C. is?
@@JJDreese