andrew s

@JeremyS is an extender significantly different from a Barlow? If so what are the advantages and disadvantages? Thanks. Regards Andrew

But, but but... ...I bought it as it did not have an automation path to tempt me. Regards Andrew

A rough calculation for you Tec 140 shows they need to be help within 0.7 micron to keep any shift to 0.3 arc secs, assuming the rings spaced at 50% the focal length. Not an issue for field matching more of a challenge for guiding. Regards Andrew

The residual flexure might not be due to the saddle. The two telescopes could be at different temperatures, the mirror cells with slightly different tensions (as @JamesF said above), variation in tubes thickness and any number of similar small differences could contribute at this level. Miracle mount or not you can't beat the laws of physics. Regards Andrew

Starting at 7:00 PM. Go to the BAA website for zoom link or YouTube. Regards Andrew

The sumo squats should come in handy. 🤼‍♂️. A diagonal is on order. Regards Andrew PS I just remembered I did have to cancel a software demo as an earth quake in Wales took out the electricity at the ICI Runcorn site.

New clutch bolt in place and sitting on a slightly over engineered pier with the Mewlon ready to go. Still have to add the DSC. It took a while to find some bits to add an eyepiece as the Baader diagonal js yet to arrive. Fun time ahead. Thanks to FLO and Rowan for fixing the issues. Regards Andrew

At high resolution active optics is the only realistic solution as @ollypenrice noted on PG's system. That's what the pros use on segmented mirror telescopes to keep the segments aligned. Mechanics have to deform under varing loads and the tolerance is extremely small. Maybe just having multiple mounts and scopes would be more cost effective or, even more radical, don't spend capital spend revenue and move to remote hosting site with more clear nights. Regards Andrew PS possibly the most cost effective solution is to use CMOS cameras in low read out noise configuration and take exposures short enough to avoid and sign of differential flexure.

@Alkaidhe best discussion on this I know is by Thierry Legault, a world class astro photographer, here http://www.astrophoto.fr/technique.html Regards Andrew

...but, for the same money you can get an obstructed SCT or Newtonian with a bigger aperture who's Airy disk is much more intense than the unobstructed refractor. Regards Andrew PS sorry but it's a hobby horse of mine! 😜

The super nova SN 1987A was naked eyebright but not visible from the UK as it was in the Large Magellanic Cloud. Regards Andrew

Both are correct. The by area gives a feel for how much light is blocked. The by diameter is related to the impact on resolution. They are related by simple geometry and the size of the telescope and secondary diameters. Regards Andrew

I built an auto collimator using an old 50/50 beam splitter some years ago. By injecting an artificial star in the side beam you could have a plane mirror as near as the scope as you liked and then collimate it. The unit just plugged into the focuser. Edmund optics made something similar for ££££££ Regards Andrew

I often get stuck in a gumption trap. I blame Prisig and "Zen and the art of motorcycle maintenance " Regards Andrew

..for that titan of Takahashi, that behemoth of Berlebach, the man how made SGL a lifestyle forum our very own @JeremyS is giving the BAA webinar this Wednesday 1st July at 7:00pm on SS Cygni a star even more eclectic than he. Don't dare miss it. Regards Andrew

Thank you for your response. The worm extensions look to run true but will check again carefully tomorrow as I have just had a long drive. Thanks again Andrew

Where @JeremyS keeps all his Regards Andrew

Thanks, FLO have sorted it out for me. I did not examine the Rowan site as I did not see any need to. Interesting to note that the altitude clamp is bent in the unpacking photo. Regards Andrew

If everything clears and the slit alignment/ width ok then why worry? Regards

Thanks for the information note sent to FLO. Regards Andrew

I just noticed the altitude clamp on my mount was bent. I initially thought it was by design to avoid fouling the scope, but then I noticed a blow mark on the grip. Is it bent by design or has it been damaged. Regards Andrew

Drink more think less. Regards Andrew

Mark you it's a much better problem to have than sales at zero and laying off staff. FLO have shown that when mistakes get made they fix them which is all you can ask when they are under pressure. Regards Andrew

Think about shinning a light through a slit. You get a pattern on both sides as well as the central peak. The spider gives an inverse "pattern" - bright be comes dark etc. Regards Andrew PS I have glossed over the technical details.

We all live and learn. Regards Andrew