andrew s

21st century Regards Andrew

If you don't center the secondary then you won't get even illumination even if the rest is collimated perfectly. The secondary doesn't have a unique optic axis it's the only way to place it correctly under the focuser. Regards Andrew

Note well all filters must be after the Herschel wedge not before it as the might shatter in the full heat of the near focused Sun. Regards Andrew

Nice work Brendan the 21 C sight tube. Regards Andrew

That will keep me occupied for a while! Thanks Andrew

Most kind offer @JeremyS once established I will take you up on it. Regards Andrew

Hum, if you use a conventional Newtonian the it will always have a diagonal! Also close to focus angular wave front errors have less distance to generate linear errors. A prism in a low f system will generate chromatic aberration. I would like to see some quantitative evidence for these claims. Certainly straining your neck or viewing in a contorted bodily position will impact your visual system. Regards Andrew

I not sure they do one for f12. The ones you normally see advertised have s built I Barlow for f4 to f8. Regards Andrew

Should have got a Takahashi. Regards Andrew

The Lacerta Brewster angle. 1 1/4" and got good reviews. Regards Andrew

Well have you managed to observe the sun in the dark? Regards Andrew PS corrected

Not a windup and no I have not changed my mind. I would have preferred an off axis Gergorian (see Big Bear solar telescope as an example). However, that would have been at least one if not two orders of magnitude more expensive. I could use the Mewlon but I have always wanted to try a Herschel wedge which led, reluctantly, to a refractor. It also means I can keep the Mewlon cool during the day. Regards Andrew

@JeremyS if you are reading this you had better sit down. I have just ordered one of these as part of my back to basics kit for solar white light observing with a Herschel wedge. Its classic 80mm F15 Fraunhofer design is fully in keeping with the basics ethos. Regards Andrew

A change in colour to meet customer request for anything but black apparently! Regards Andrew

Nice work @ollypenrice, wanting CMOS and OSC. St Paul has nothing on your conversion. 👼 Regards Andrew

Quite correct, indeed there is no definitive model of turbulence in any setting. An outstanding problem in classical physics. The Fried number r0 ca be determined experimentally without recourse to any theory of turbulence. Regards Andrew

They may look flimsy but they are designed to work under tension. You could strengthen the tube with a ring if the tube is distorting. Other than that I have used steel 12" rulers to good effect.. Regards Andrew

...and a Sage is someone to eat with stuffing? 😵 Regards Andrew

It goes on the outside of the tube to stop it over cooling and creating a boundary layer on the inside. Look at the post just before your wind up in the thread "Science behind seeing (SCT C5 80mm APO)" and the linked paper. Regards Andrew

Yes quite. I will be selling off the excess at ££££ per square cm 😉. Regards Andrew

Low emissivity film (0.09) to wrap a Takahashi in. Also to be used inside and out of a new shield for Mewlon 180 to keep those nasty dew currents away! Regards Andrew

While he has to tune his SCTs he uses them as I am sure @Peter Drew and you know is because for resolution you need aperture and for successful Lucking imaging you need very short exposures which needs aperture. As well as quality optics. I agree refractors in relatively small sizes are simpler to use but in larger sizes they are not easy to handle (😜) even if you could afford to buy and mount one. I am sure @Peter Drew could modify a commercial SCT so that it held collimation just as well as a refractor it's a matter of mechanical design not optics. Each to his own as long as you enjoy the hobby. Regards Andrew

Similarly calibrated spectra can be submitted to the BAA spectroscopy data base. Regards Andrew

But had Peter checked the collimation of the SCTs 😜 especially at low altitude? Nice report Peter. Regards Andrew

Don't think much to your maths. 1 + 1 + (1 ×2) - 0.25 - 0.25 = 3.5 Regards Andrew