Peter Drew

There is always a potential problem but it is usually avoided by using very low vibration fans and attaching them in a manner that isolates vibration. 🙂

Good all year round for solar enthusiasts. 🙂

And yet, the Mewlon has a rolled over front edge to their tubes that closely defines the primary mirror aperture. ??? 🙂

One good start to mitigate tube currents is to have a decent clearance between the tube and the lightpath to the mirror. The OP mentions millimetres clearance, I would prefer centimetres. 🙂

Visually you should be able to see most of the details visible on the GONG solar site. There will be some representative images on the solar images section of this forum I expect. 🙂

Nothing to worry about (if used properly as intended), it's only the magnification that keeps multiplying. 🙂

An interesting topic. What has intrigued me over the years is the sheer variety of methods used by owners to address the issue. You would think by now a consensus would have been arrived at to define the solution. So many times I have read of an approach being advocated only for others to say that their experiment with it was a disaster. There is also a definite school of thought that you shouldn't actively cool optics but rather to insulate them to maintain their ambient temperature, mainly for closed tube designs.. There are several small firms making a living supplying gadgets and materials intended to help matters. 🙂

If you go to our website <astronomycentre.org.uk> and click on "Instruments on site" there should be a photo. 🙂

The mount moves very smoothly and takes no more power to run than an EQ6. Slewing is manual and overrides the motors through clutches. 🙂

I went from a 102mm to a 220mm but I had to make the scope, the mount and the observatory to house it. 🙂

Single frame animation? 🙂

I was just getting first light through the 120mm PST mod I've been working on. Lovely detailed view of the filaprom at 120x with binoviewers. I too, hadn't noticed it on Gong first thing this morning so was surprised, and pleased to see it. 🙂

WD40 is good for cleaning or releasing seized components but should not be relied on as a lubricant, it is a water dispersant (WD) and eventually gums up the "works" 🙂

We had a small fire indoors when the magnifying side of my sister's makeup mirror on the window sill set fire to the curtains. 😱

There is quite a difference in the perceived out of focus residual colour comparing imaging and visual, it is less noticeable visually and even varies between observers. 🙂

I don't see how objectives can be at risk from using a Quark with or without an ERF. At the position of a Quark the reflected focal point would only be in front of the filterby the amount that the filter was inside the focus. The objective would be only at ambient sunshine temperature at most. 🙂

The 35nm Baader filter is of the reflection type rather than absorption so doesn't get particularly hot. 🙂

Good zooms are possible but you have to build your own! I made myself a 80mmED unit that takes a pair of Baader 8-24mm zoom eyepieces giving a range of 25x to 75x. They will take 200x, or would do if I bought another 3-6mm TV zoom. 🙂

Worm movement up and down isn't backlash, it's end float. This too is adjustable and needs to be adjusted. 🙂

Using my kit makes me happy, if it's kit I've made myself it makes me happier, but what makes me happiest is sharing it with others. No worries about what happens to my kit when I am gone, it just carries on without me. 🙂

I have a 8" mirror with a polished finish on the back surface, it does look at first glance that it has been coated. Although a frosted rear surface could be applied to a scratched polished surface to eliminate the scratches, the more usual reason is to flatten the back surface of moulded blanks. 🙂

Turning the thread full circle, if it was my problem I would fibreglass the existing structure, the one you slaved over and were rightfully proud of at its completion. I somehow can't see replacing it being any less of a hassle. Not wishing to rub it in but the obs housing my 8.5" refractor cost less than £2K in aluminium and took me two weeks to make and one day to install. 🙂

WARNING! (Contains OTA cutting and drilling) During the initial lockdown and being confined to the house I used a cobbled together solar telescope made from a Coronado 60mm etalon and BF15 fitted to a SW ST80. Much better than nothing but leaving a little to be desired. Now back at the Centre, albeit on my own, I decided to build a replacement G & G version that would address some of the previous shortcomings and add some further versatility. The new setup is based on a Bresser 90mm F10 achromat and the same Coronado etalon and BF15. Several inches were cut from the tube as I want to be able to use binoviewers with or without a Barlow. I upgraded the focuser by fitting the R & P from the ST80, yes it really was an upgrade from the plastic Bresser original. Some holes were drilled in the tube to accept a pinhole projection solar "finder". The final result is an instrument that I can use for Ha, white light with a HW, with or without binoviewers up to 100x and with little effort, night time as well. A very brief try out confirmed that the performance was up to expectations. I'll try and get a photo together once I can put a bit of lipstick on it. 🙂

Are you sure there is a coating on the rear face?, if the substrate that the mirror was made from was some form of float glass then it could well be that it had a polished surface on both sides initially. In that case, you would be able to see the rear surface of the optical side through the back of the mirror. If it actually has been aluminised on both sides it will have no detrimental affect on the performance, in fact it has been proposed in the past that doing so could improve the rate of cooling. I've never known of this being done however, maybe the added cost was not in proportion to the benefit. 🙂

I bought a used 1.25" Lunt HW for a good price, I had the chance to compare it to a Lacerta, if I was buying new I would buy the Lacerta. 🙂