Peter Drew

Put wheels on an EQ platform and you would have a dual purpose unit. 🙂

Just think of a polar axis shaft perfectly aligned but on its own suspended in space. You could then place everything around it, mount, tripod, pier randomly within reason and it would make no difference to the accuracy. 🙂

Polishing a lens is the last stage of its optical manufacture prior to any subsequent coating. Polishing now will either damage the coating or alter the figure of the lens. I think you have probably done as much as can be done. 🙂

The paint chips appear to be at a similar spacing to the rings spacing. They may have been caused by the screws to attach the rings to the mount being too long. If this is the case, the rings could be moved to cover them, even if it means having to rebalance the tube. Self adhesive felt could reline the rings. 🙂

Fortunately, most mechanical shortcomings can be addressed whereas poor optical optical quality remains. Sounds like the mirror on this one is a peach rather than a lemon. 🙂

I don't buy much really high end stuff but what I do buy from the likes of "quality" manufacturers like Vixen, Baader, TV etc I buy with confidence and positive expectations. For less popular brands, for me, seeing is believing. To be honest, although by no means perfect, I get the most pleasure from using equipment made by myself. 🙂

Not hot enough then, your image showed that the Quark was not yet "on band". It also showed Newton rings which can be eliminated by tilting the camera or by using a camera that is not susceptible to them. Quarks are seldom "plug & play". 🙂

There is no specific tuning point for a Quark as they are all individuals. The mica chip which forms the etalon is a natural component, it is what it is, you can't change it or improve it, hence the variability of the Quark. The mica chips in the Quark are ones that failed to make the grade of the much more expensive research grade models. Getting the best performance from your Quark is a process of experimentation. 🙂

My understanding is that you scoop off the dob of sealant from the retaining plate, unscrew the plate, drop out the filter and pop in the new one. Keep the old one as they can be cleaned, it will be a spare if you have to repeat the process in the future. No idea currently on the other questions. 🙂

My largest refractor so far. 8.5" F12.5, scope, mount and observatory all self built, apart from the optics. 🙂

The Ra worm assembly incorporates a slip clutch in the aluminium connector between the motor and the worm shaft. There is a nylon disc situated under the grub screw nearest the worm to form the slip clutch, they were designed to be useable without disengaging the drive but if you decide to operate it manually it would put less strain on the motor gearbox if you do disconnect it. The worm shafts should be 5/16" diameter so will need a control rod that size. 4" mirrors are uncommon today and re-aluminising can be quite expensive, it might be more economic to find a used 4.5" OTA with mirrors in good condition. 🙂

Sure do, I'm one of them! 🙂

I have a large Dobsonian family as well, too extended to photograph collectively! 114, 150, 200, 250, 300, 425, 500 and 750. 🙂

I too have a 32mm Erfle as well as a 28mm RKE, a 16mm Clave' Plossl and three 44mm "Palomar" giant Erfles 🙂

I you really want to see the difference between a small and large telescope, have a look at a globular cluster. 🙂

First of all, I think it is highly unlikely that the primary mirror is cracked, the material is far too thick, mirrors can easily be chipped or completely smashed but not cracked. Expectations of a larger telescope are often too high initially, it takes time to fully appreciate the improvements. You say that this is the first time you have had the chance to use it, I'm sure with practice you will find the push-to system easier and more accurate to set and there will be better nights to enjoy. The eyepiece selection is going to be an issue though for best performance at F4.7 🙂

Yes, I (and others!) were certainly underpaid financially but the skills I learnt set me up for life in an occupation that I enjoyed every minute of. And still do after "retirement". 🙂

Just to clarify, the ST102 and the rest of the ST refractors have achromatic doublet lenses. It is their F5 focal ratio that limits the magnification performance as the higher end reveals the effect of chromatic aberration. These are best suited to low power, wide angle viewing. A review of posts asking for advice about telescopes shows that the majority want to know the maximum magnification possible for wide field models and the widest field possible for long focus ones more suitable for high power use. The best advice is "horses for courses". 🙂

I don't have experience with any of the listed binoculars but what I do know is that there are many aspects that conspire to reduce the pleasure of using a binocular and the more you spend, within reason, the less these aspects will arise. 🙂

As a 2 quid a week engineering apprentice in 1958 I couldn't even afford a used telescope let alone a new one. Ended up having to make my own, still look where that got me! 🙂

If that is a correctly photographed image of a centrally positioned star then I would say that the optics are significantly out of collimation. At that far out of focus even a perfectly looking concentric image can still need adjustment by the time it is at focus. You need to have the image almost at focus under at least 200x and in good seeing conditions to improve it. Adjustments will be minute tweaks of the collimation screws. Most poorly performing SCT's are good ones just waiting to be properly collimated. 🙂

Post it on bookFace for alternative opinions. 🙂

Yes Stu, a pentaprism performs constant deviation so the orientation of the view is the same with or without it other than the "bending" through 90 degrees. 🙂

Yes, Paul, uncorrected astro image. 🙂

Don't forget that although the PST's eyepiece is a right angles to the line of sight, the prism used to perform this is a pentaprism so the orientation is that of a refractor without a diagonal. 🙂