Peter Drew

I have three ST80's, two as a binoscope and one as a finder on one of my large telescopes. As Stu, and others have found, the accessories tend to limit the performance of the comparatively good objective. Another interesting experiment would be to use the supplied basic accessories on a higher end refractor to see by how much they diminish the performance. 🙂

I could have a look at them for you at the Astronomy Centre. 🙂

For future reference, for small incremental increases in aperture, the most noticeable improvement in performance is the quality (usually luck of the draw) of the critical components. I have had 40mm PST's that outperformed some Lunt 60's. 🙂

Easiest way is using a Herschel wedge for "white light" for sunspots etc, or as Stu says, a Quark for H-alpha. The cheapest conversion is a front mounted solar film filter for white light only. Slippery slope financially! 🙂

There are, however, plenty of small inexpensive entry level refractors that have good optics even though the supplied mounts and accessories are of poor quality. The generic 60mm F11-ish objectives are usually surprisingly good, the ones I used for my binoscope easily supported 120x and were full aperture. 🙂

I strongly suspect that the reduction in effective aperture is to further control aberrations. I have seen many such instances in entry level refractors. Interesting that at least the box recommends use for terrestrial and bright astronomical use, areas where the reduction in image brightness would be least noticeable. 🙂

I always blow on my chips, never suck. 😀

In retrospect, I thought this may be the case, hence the ? I was aware that certain mediums pass unwanted radiation despite attenuating the brightness. I'm not surprised you know better but one can't be too careful with solar observation. 🙂

"Safe" in brightness but not necessarily safe in other radiations? 🤔

52 degrees seems a little low to me for Bury, we are nearer 54 and we are only just "up the road" from you. 🙂

Just had a look as well with my Meade 90mm Mak. Front mounted glass filter and Leica zoom eyepiece. The umbra of AR3190 looks like the silhouette of a hovering raptor. 🙂

Pinched optics can also produce astigmatism. If the cell is oval, pinching due to cold shrinking the cell will pinch across the minor diameter. 🙂

Always worth detuning Ha views as it can accentuate as well as diminish features. I have noticed similar strange filamentary appearances during detuning and thought it might be due to Doppler effect. 🙂

I also agree that it looks like a classic case of pinched optics. No doubt a consequence of the current low temperatures. I seem to recall similar issues with Esprits in the past. 🙂

I was never a major dealer but during 35 years as a professional telescope maker I had an optical bench which utilised a 12" parabolic mirror and an artificial star at the focus, telescopes were collimated against this image. Nowadays, I would use an ordinary artificial star at the appropriate distance. To collimate my personal refractors I would first of all determine that the focuser was square to the objective by shining a laser collimator through the eyepiece holder and making sure it exited through the centre of the objective. In order to avoid decentring due to slop in the fit of the eyepiece holder I made a 2" to 1.25" adapter that had a firm fit on both dimensions. 🙂

I'm not familiar with this mount but there will be some way to adjust it. First of all though, determine whether there is end float causing the problem. When you rock the mount, look to see if the worm is moving side to side. 🙂

Could be end float of the worm. 🙂

I managed a brief solar view in Ha today and also caught the small flare. 🙂

Yes, as mentioned, a mobile phone adapter will fit on to the eyepiece and you will be able to take photos of the Moon and planets or birds and wildlife during the day with your phone. Anything much else will need a completely different set of equipment. 🙂

The basic construction looks pretty good and worth refurbishing. As a mechanical engineer I would favour retaining the steel structure, a wood worker may differ. 🙂

I noticed gradual image improvement in PST's following initial solar exposure. Airspaced etalons are tuned either by pressure or tilt, in each case temperature can have an optical effect. The Quark etalons are intentionally temperature controlled so the variation in performance due to the temperature reaching its optimum level is to be expected. 🙂

I've made several Schmidt cameras and was halfway through making a 18" F3.5 photographic telescope with just a Newtonian primary similar to what you are proposing. I have to ask you the same question as I eventually asked myself before I abandoned the project, "What was I hoping to achieve?" My initial thought was to avoid the cost of a secondary and also to increase the light throughput. Further research showed that, for a photographic instrument. the light gain was not enough to warrant the mechanical complexity. Regardless of this, a single Newtonian mirror will still have the optical characteristics of a Newtonian, nothing like the corrected RASA or its variations. If you do decide to continue I would recommend a primary mirror adjustment for focusing. This can be achieved by fitting a 2" plug to the rear of a backplate of the mirror cell and fitting it to your focuser. The focuser itself would be fitted in a fixed position on the telescope backplate. Compression springs between the cell and the backplate would take up the weight of the primary mirror and produce a light focusing action. 🙂

Don't be disheartened, I'm sure there is nothing wrong with the telescope, just something not quite right with the setting of the focuser. As already mentioned, the shiny silver tube should not protude into the main telescope tube, as photographed it is too far in. Wind it back out and try to see something in the daytime. If this doesn't work then the eyepiece might be too far out. If so, then there may be a piece that unscrews between the eyepiece holder and the eyepiece, removing this would shorten the length of the moving tube. 🙂

I have a lathe and could do this. 🙂

I believe it is a combination of one's eye getting accustomed to the view and the Ha etalon warming up to achieve its optimum band width. 🙂