Peter Drew

The "tuner" is a pressure chamber. Screwing it in compresses the air which in turn increases pressure on the Ha etalon. The etalon is two glass discs separated by a precise air gap, the increased pressure varies the air gap which varies the bandpass width of the etalon. The bandpass determines what Ha detail is optimised. 🙂

Despite the mew in Mewlon, it's not a CAT it's a Dall-Kirkham Cassegrain. 😀

I don't think this will work. The optics in the Hyperstar correct the aberrations from the F2 primary much as the corrector plate and secondary mirror combination do for the native F10 system. Without the Hyperstar the images are likely to be horrible. 🙂

I don't have these details but presume so. I do know that the equipment was insured so hopefully that will soften the blow.

This is exactly what I used to do when I made Maksutovs commercially. The screw -on larger disc was used for terrestrial purposes where contrast reduction due to sky flooding would be noticeable with a small obstruction. The only practical way to eliminate this problem for both astro and terrestrial use was to employ the Dall modification that included an erector transfer system into the primary mirror support baffle tube. This enabled a much smaller CO without any sky-flooding. 🙂

I thought I said "decent size" that's only a 16", can't Takahashi make big telescopes? 😀

For visual I would go for the extra aperture of the 9.25" 🙂

Probably best me via a PM and I can pass the info on.

A local astronomer had his observatory broken in to recently, the following items were stolen:- TV NP101 with 90MM CORONADO ETALON ATTACHED 80mm REFRACTOR with 40MM CORONADO ETALON ATTACHED STARWAVE 102 CANON 20D CANON 20DA Please be on the lookout for such items being offered in unusual circumstances.

The further away from the eyepiece is from the diagonal then the further into the focal point the diagonal will need to be to achieve focus. Therefore more of the diagonal optical surface will be in use and better the diagonal quality needs to be. 🙂

I'm sure you'll enjoy a decent refractor, I certainly do as I have several including a 150ED and a 220mm achromat but anything less just doesn't cut it for me on DSO's. You can't change physics and light grasp is the name of the game for DSO's

I personally wouldn't buy any refractor primarily for visual DSO observation, they are far too small in the affordable price range. A good setup would be a 10" Newtonian for visual plus a 80ED for grab & go and future AP. 🙂

Thanks for the info Jonk. Just caught it in time, hope I didn't jinx it! 😱

How to watch this live?

I can see a dual purpose emerging, something for the cloudy nights? 😀

But what if you want a decent size telescope? 🤣

What size of mirror are you considering? I've had several OO mirrors over the years and even the lowest spec ones have been good. I can't have just been lucky every time. 🙂

The assembly looks ok so it must just be the adjustment. I suggest trying backing off the central screw and tightening the ones either side of it, small increments. If this doesn't improve matters it may need the reverse, slackening the two outer screws and tightening the central one. What's needed is to reduce any clearance between the shaft and the flat on the focuser drawtube. 🙂

All good advice, however if it's a Takahashi they are indestructible I hear , so a Brillo pad and Ajax are all you need. 😀

Well it's one of our favourites at the Astronomy Centre during our outreach sessions. Keen sighted visitors can usually see Alcor presenting a naked eye double and are then amazed to see in the telescope that Mizar is itself a double. A graphic example that there is more to astronomy than meets the eye!

Yes, I've often used a pair of non click zooms on a binoviewer. I found is surprisingly easy to judge when the magnifications matched. 🙂

Yes I have. None of my usual mounts, not even a Fullerscopes MkIV, was really up to the job of carrying a 12" F8.5 Newtonian so a "Cross-Axis solution seemed a worthwhile project and one that I had been mulling over to try out a motion damping scheme. Being experimental it was floor standing and the mainframe was in 3" x 2" wood. There was no South pillar, just an angled bearing plate. The base was an "A" frame and the North pillar was a braced "goal post" carrying the top bearing. The polar axis was a length of 4" square 1/4" wall steel tubing with stub axles at each end. The friction damping discs were 18" diameter made from MDF faced with aluminium, variable friction was supplied by adjustable PTFE brake pads. The cross-axis was a stub axle on one side of the polar tube carrying the telescope and a counterweight shaft on the opposite side. The main object of the exercise was to try out the damping scheme which worked well, the construction has since been dismantled pending a final engineered version when it comes to the top of the "to do" list. Photos of the mount are currently locked on a defunct computer. ☹️

Too much!

As has been said, give it a try, you may be surprised how little affect it will have on the performance once the damaged area is blacked out, it will certainly be usable. A piece of card cut to the shape of the damage and glued to the corrector should do the trick. It may be possible to obtain a replacement corrector, the ones for Maksutovs of that class are spherical as far as figure is concerned so matching shouldn't be an issue. The overall value will be impacted in its current state of course. Most unfortunate. ☹️

The symptoms suggest , that for whatever reason, your Quark isn't coming "on band". I'm sure you've gone about testing it correctly which leaves the Quark a faulty suspect. Time to contact Daystar I think. 🙂