5" F/14 Solar Scope, one of two...

[Astroman]

First light on a 5" F/14 solar scope today. No mount as yet, but after collimating it last night, I couldn't wait.

For those unfamiliar with the design, I'll outline it here. (There's also a page on my web site on construction.) An ordinary Newtonian reflector telescope, with the silver stripped off the main mirror. Secondary can have silvering or not. With silvering, it gives wonderful unfiltered views of the Moon. Unsilvered, it's only for the Sun and bright Moon. A green welders glass is cut to fit a standard filter holder that screws into the eyepiece. #11 for silvered secondary, #8 for non-silvered. The idea is that only 4% of the light reflects off of an unsilvered mirror. The welder's glass filters out infrared and ultraviolet harmfull rays, leaving a high contrast green Sun in the eyepiece. This is the third scope I've built like this and the fifth I've observed through. (A 4.5" F/4.5 Tasco Newt I got for free, a 6" F/4.5 I'm currently taking on the road, this 5" F/14 and the inventor's 6" F/9. Plus one Astroscan setup (4" F/3?))

The views of the Sun were simply fantastic through the new scope! Granularity across the entire face, with amazing resolution near the limbs. Details in sunspots were astonishing, showing detail in the umbra as well as rich interior structure in the umbra and penumbra both. A 32mm EP barely showed the entire disk. At 1750mm focal length, the 32mm gives ~57X, 25mm=70x, 15mm=117x and 10mm= 175x. I didn't get to go higher power yet, but watching the Sun drift through the ep at the resolution I saw was spectacular. With a mount I can only imagine it to get better.

I'll try to post some pics when I get a chance, both of the scope and through the EP. I have another, nearly identical mirror made that once silvered will be the main optics for the spectrohelioscope. Should be fabulous! 8)

[Ant]

Never thought about using un silvered mirrors, excellent idea! So if an unfiltered mirror only reflects 4% of the light then having both mirrors un silvered your effectivly only letting through 0.0016% (blocking99.84%) of the light.

Clever idea, I can imagine that the first person that tried that had his/her heart in there mouth's whe they first looked through the scope...

Could a scope like that be used for imaging?

Ant

[Astroman]

It's extremely important to use the welder's glass to block harmfull rays. :!:

As I said, I know the inventor and this design works famously! I have indeed taken pictures of the Sun through this scope. Well, actually, through the 6" F/4.5, but I will be taking pics through this one soon.

[AndyMac]

Sounds very inventive Astroman. Your description of the resultant images also sounds very encouraging.

It would be great to see some images posted when you get the time. Good luck!

[Astroman]

Finished a Dob mount for the scope last weekend. Extremely poor performance. Given the OTA is 6' long, and the center of mass is 34" from one end, the mount had to be much too high to be stable. The moment arm of the telescope twists the base when touched and the whole thing takes seconds to settle down. In the mean time, the Sun has moved from the FOV, given the high magnification. Rubbish! Guess I'll have to design a new equatorial mount for this long scope.

[AndyMac]

Sorry to hear that Astroman. Hope the new design fares much better.

[OXO]

Yeah sorry to hear that Astroman, could you not implament some sort of dampening pads?...

James

[Astroman]

Thanks for the suggestion, James, but the box itself is twisting and needs to be stiffer. Adding dampening would most likely limit motion in altitude. Making it stiffer would require heavier, thicker sides. I'll try to take some pictures tonight or by the weekend so you can see the problem.

[OXO]

Look forward to the Pics Astroman. Does sound rather hard to sort out from what your saying..

James

[Astroman]

Here are a couple images of the solar scopes I've made. The yellow one is a 6" F/4.5, the wood one is the not-yet-completed 5" F/14. Se the problem? The 6" has the balance point much farther back, toward the mirror cell, which allows the mount to be made to a convenient height. The scope isn't very heavy, being made of cardboard, so there's little torque applied to the mount.

The F/14 on the other hand, balances nearly in the middle, and places an enormous amount of torque on the overly-tall mount.

Any ideas, besides redesigning the optical tube?

[OXO]

Would this Help at all? I cant think of anything else sorry Astroman..

James

[Ant]

What about just shifting the centre of gravity closer to the mirror ewnd - with some weights. This would mean that the mount could be shorter and may provide a more stable view.

Ant

[Astroman]

James: Thanks for the idea, but that wouldn't work.

Ant: That would work, but more weight would still cause high moments on the tube. Worth a shot, though...

[OXO]

Hows the Solar Scope getting on Astroman? Hope you have manage to sort something out matey.

JAMES

[Astroman]

James: Haven't had time to work on it. I have observed through it quite a bit though, just getting used to its limitations. It's a really fine scope!

[Adrius]

dob mount yes? add springs to where the tube sits on the mount, pulling them togeather, and make sure you have farsen'd tefflon or bearings between them. tight springs often solve the issue of tube and dob mount weight problems and backlash etc, after you have a spring system if it still causes weight problems all you need to do is stick alittle velcro peices over your tube, and stick a bean bag wherever you need the weight adjustment. simple but affective

[Astroman]

Thanks Adrius, but the problem is twist in azimuth in the rocker box itself, not backlash in either axis.

I've decided to try mounting it on an old fork mount from my C8. I can put it on the pier in the rolloff and see how that works, at least temporarily.