Peter Drew

Not really suitable in my confined space. I am a fan of dual types for night use though. 🙂

+1 I've unscrewed a few, not always easy! 🙂

I think the main difference is that my telescope works in a fairly cramped observatory which is too angular to easily cast an accurate shadow. 🙂

Although I largely avoided these problems in the first instance, it underlines the importance of concentricity and as all machinists know, this depends on items being machined, if possible, in one operation setting. Adding subsequent components machined subsequently leads to errors, I've often seen portions of worms turned separately, bored and then grubscrewed on to shafts with subsequent run out. It's quite difficult to rectify an inaccurate wormwheel as you never know if the gear teeth are concentric to the the bore or the rim unless you try it. It's a bit like judging the quality of a mirror just by looking at it. I think I would would make a "top hat" bush that was a good fit on the shaft but well undersize of the gear bore which would have had to be overbored. The bush would have to have a lip wide enough to accept screws to hold the two firmly together. This composite unit could be trued up on the lathe to a reasonable degree. If the gear was now mounted back on the shaft and the pressure of the attachment screws was relaxed enough to allow the gear to be tap adjusted, it could be manually rotated by the worm to determine the high and low portions of the full cycle. This should initially remove the backlash and finally the mesh by noting the feel of the worm as it is turned. "Feel" is a very good measure of accuracy. Lastly, the screws would be tightened and the feel checked. Once satisfactory, the gear could be doweled to prevent further movement. 🙂

Interesting viewpoint. I made one of these originally and I found that you still had to wave the telescope about or use the shadow to find the Sun whereas my current unit simply made from a piece of flat aluminium stock, ends bent up at 90 degrees, pinhole in the front and translucent target at the rear seems much easier to use. The targeted solar image can be seen from the front, back and side angle without having to go anywhere near an eyepiece. Weighs and costs almost nothing. 🙂

Putting my "poor man's Es Reid" hat on for a moment I could confidently say that it is not astigmatic, does not exhibit any mechanically induced artifacts, the extrafocal rings appear to be expanding evenly without obvious zones, the outer ring fuzziness could be due to seeing considering the rest seems to be in order. A complimentary inside focus image could add to this appraisal. That will be 5 guineas. (How am I doing Es.) 🤣

Apologies to Suiter!. I have looked at the book and to be honest, apart from the type of errors I mentioned, the majority of the finer points of reference take an experienced eye to offer a reliable diagnosis. At the end of the day (night?) if your telescope is giving you the best images you've seen, does it count for much what the book or vendor claims? 🙂

For most amateurs, I think star testing best serves the checking of collimation. There are far too many variables in play to show much other than gross errors like astigmatism and severe zonal or correction issues. A definitive assessment calls for the controlled conditions of bench testing and examination by someone experienced in the nuances of the displayed image, many of which can have an impact on the performance. We're not all Es Reids! 🙂

I spotted this on GONG this morning but as usual the part of the sky occupied by the Sun was cloudy. Not long after I got to the Astronomy Centre the Sun appeared, I quickly fired up my solar telescope which has its own observatory and was just centering the image when a huge bank of fog appeared from nowhere and that was that for the day. No more Sun forecast until Thursday. ☹️

A possible problem could be caused by using the Moon as the alignment point. The Moon is the hardest thing for the goto to go to, the complexity of its motion compared to the fixed stars means that it's not an accurately recognised object as far as position is concerned. I doubt if you are entering any data wrong being as you are so close to the target. 🙂

Always good to share equipment with others. Unless you wish to use the telescope for full disc imaging, the B600 will be adequate, a B1200 will provde a wider field of view but no change to the solar image. Binoviewers are great with solar telescopes but most non astro users tend to have difficulty with them due to the varying adjustments needed for a good view. 🙂

I just noticed that there is a video showing the motion. Yes, removing the cover will show the problem. It would appear that the provision for adjusting the gear mesh has become loose allowing the unit to back away from the driven gear. 🙂

Probably more of a shame for the livelihood of local communities due to reduction in direct employment and associated tourism to the immediate area. There appears to be a consensus that replacement rather than repair would likely be more economic in the long run. All long term high tech equipment eventually gets superseded by improved technology to the point where maintaining a resource through retrofitting becomes more expensive than starting from fresh. The Arecibo facility has enjoyed a long and illustrious history but these days things like computer power etc has advanced way beyond the dreams of the times of its launch. Alternative methods are now possible, things like multi-aperture synthesis on a large scale that would be impossible without modern supercomputers. 🙂

Unless you already had some WD40 it's much better to use a proper penetrative oil such as Plusgas. If the shaft shown is the motor shaft, it seems to have a flat on it suggests that would be a grub screw to bear on to it. 🙂

It is to some extent but more so to focal ratio, lens complexity and glass types. As the lens gets larger these factors increase in importance. 🙂

There was no spring loaded bracket involved as I took the trouble to ensure that the o/d and bore of the gear blanks were concentric and an accurate size, no real problem if these dimensions were machined in one operation. There was a back stop plate with adjustment screws to prevent the worm bracket from backing off under load. Never had any complaints or returns! 🙂

I don't do imaging but I visually use a 150mm Ha telescope at a minimum of 150x magnification. As with most telescopes, on a good day I get a good image, on a poor day the image is poor but still acceptable. Ha is a little more forgiving of seeing conditions than in a standard telescope. You can always stop a larger telescope down! 🙂

Definitely an Auroral display. Many are missed by being too faint for the naked eye but show up on a photo. 🙂

Yes Andrew, that is the principle. In practice it's not so reliable as material hardness, accuracy of the tap used for hobbing the gear teeth and having a "R" in the month all conspire to create plus or minus a few teeth from those required. Gears for DEC drives are not so important but RA gears are. My usual procedure was to lightly engage the tap to produce witness marks on the gear blank, these would show whether the teeth were going to match up during a 360 degree pass. If a large RA wheel was to be made, specially if in an expensive material, I would gash teeth position with a fly cutter having mounted the blank on a rotary table. When remounted on the lathe, the tap would accurately follow the marks. 🙂

Eeeek! 🙂

Try swapping the adjuster screws.

That's odd, the tab detail that is cast for adjustment purpose is internal so I would expect that the adjustment screws must contact it within the alignment limits.

That sounds promising! Next I would suggest that you manually set the mount to your latitude and then carefully replace the adjusting screws until they come into contact without disturbing the setting. 🙂

I was observing Mars at 17.30 this evening with a SW 150ED and a 16" SCT and noticed a light streak bisecting the darker area at about 250x on both telescopes. The seeing was fairly poor but the occasional better moments showed it to be quite obvious. I did wonder whether it was the widely reported and imaged dust storm, it seems as though it was which is pleasing. The appearance was easier to see in the refractor due to the dimmer image providing better contrast, the SCT image was a bit on the bright side but did not improve with a ND filter. The seeing rapidly went downhill and I closed down by 18.30. 🙂

I don't know the answer but I would suggest removing both adjusting screws and then see if you can manually rock the head to 21 degrees or if there is something internally preventing full movement. 🤔