Peter Drew

They may not have any, some binoculars are factory set and that's it! Do the front objectives have eccentric lens retaining rings? , this is another method of adjusting collimation. 🙂

Good luck to anyone who sets off for Mars. Things are bad enough here but it's said that the best day on Mars is worse than the worst day on Earth. I'll stay here and watch. 🙂

I agree with Chriske's comments and would try the 3 blob silicone approach at the next attempt. 🙂

I don't really know to be honest, small stalks seem to be commonplace these days with no general problems reported. I've always preferred to make backplates the same size as the secondary mirror, specially large ones. 😀

Looks like classic astigmatism to me rather than any collimation error. If you use a ring of RTV to attach the flat you should provide a hole or gap in the ring, otherwise differential cooling of the air trapped by the ring can cause distortion of the flat. Regardless of differing opinions about OOUK I think it highly unlikely that they would supply an astigmatic flat, as they are easy to judge for flatness against a known reference.

Whilst a binocular is a good recommendation, I feel that most people who rent holiday cottages are likely to already have one and would be attracted by an instrument that extended the views further. A short tube refractor or 6" Dobsonian both have their merits. I would support the red dot finder and a zoom eyepiece as being ideal, goto would be too complicated for non astronomers on a short stay. "Stellarium" would be available on the inevitable phone or tablet or one of the astro apps. 🙂

I've found that careful attention to interpupillary setting and individual eyepiece focussing has more affect on the image than outright optical quality. Binoviewers, along with binoculars are the most difficult visual optical systems with which to provide perfect results. Both take care and patience to achieve. 🙂

I became a vendor for the Meade 2080 shortly after their introduction. I was attracted by the overall look and colour compared to the Celestron C8 at the time. 🙂

Wish our clouds were that thin! 🙂

Perfectly reasonable approach if the clips bother you. Use 3 blobs of silicone equally spaced. Remember to place something like 3 coins or washers in between them also equally spaced, this will ensure level settling and provide spaces to allow cutting through the silicone when/if the mirror needs recoating. Remove the spacers when the silicone has set. 🙂

Pretty tough comparing an 80mm to a 250mm telescope hoping for some similarities in performance 🙂. The aspects in favour of the ST80 are cheapness, wide field which displays many open clusters best even if the stars are fainter, can easily be used for sunspot viewing and is a good grab & go telescope due to low weight and cool down time. It can make a great finder for a 250 Newtonian. 🙂

I can't say that I've ever seen an MDF based commercial Dobsonian ???. My self built 30" Dobsonian is definitely MDF. 🙂

Only double transit here is a double thickness of cloud! ☹️

Which Dobsonians use MDF? All my commercial Dobsonians, Orion USA and Skywatcher are chipboard covered with a sort of melamine coating.

Or vice versa which is why some achromats can be ideal for Ha work. Some users re-space the lens components to optimise the effect. 🙂

I also think a Quark could be a better bet, other options are going to involve significant irreversible modifications to the Takahashi which would not go down well if resold. A budget achromat would be perfectly suitable for this monochromatic application. High end refractors don't necessarily have the best correction for H-alpha. 🙂

Good job you're used to the sight of blood! 🙂

Like most, I've "done my back in" a few times. I found that the most likely operation that causes it is placing a heavy OTA on to the back seat of a car. The final motion of placing it far enough in tends to leave your back inadequately supported. Sometimes it takes another day before the result kicks in! 😱

The text says 600mm. ? 🙂

I have 40mm, 80mm, 100mm, 120mm and 150mm Ha telescopes. Due to high costs, only the 40 mm is a commercial unit, the rest are PST mods. Regardless of this, a comparison can be made. As with conventional telescopes, small incremental increases in aperture present small changes in resolution, as resolution increase is linear it takes at least a doubling of the aperture to make a significant improvement visually, the Sun is similar to the Moon in the respect that both look good at almost any aperture. My 80mm lives in Tenerife, I use my 150mm exclusively here in the UK, both give excellent views on a good day but the larger model provides greater detail and higher magnification, 150x is the lowest available due to the optical layout of the optics to make binoviewing possible, binoviewing the Sun is as beneficial as that to the planets. 😎

I agree with the title. Managed to get a five minute view during the only clear patch today. The rain must have cleared the air somewhat as the transparency was excellent, the only spoiler was the gusty wind, I actually had to hold on to the telescope to reduce the buffeting. 🙂

I built a mirror mount for a self built 102mm binoscope using two 102mm F5 Startravel refractors. I used a 260mm x 275mm first surface mirror from an early Xerox photocopier. The views at 20x were fantastic, I really must rig it up again this Winter. Large mirrors are available from Vacuum Coatings Ltd on occasion. You usually need a mirror slightly larger than the width of the binocular and around 1.5 x for the major axis for full coverage. It is possible to use two smaller mirrors, one for each objective amd mount them on a common base with one of the pair adjustable to merge the images. The rock steady image is a joy to behold.

Your last post arrived just as I was sending mine which mainly negates it. Still worth rotating the primary to eliminate the culprit before looking further along the system for a solution. 🙂

I'm happy to agree with everything that @Piero says as it saves me a lot of typing. Production methods these days ensure that native astigmatism in optics is rare, most observed cases are mechanically induced. An easy tests is to rotate the primary, which should be free to do so, this would show if the astigmatism is in either component, I also think the secondary attachment is suspect. 🙂

I have an Orion 8" Intelliscope Dobsonian. The optics are excellent, I bought it second hand based on the views of Saturn that I saw with it at the time. The "push to" facility is also excellent if carefully set up, you are still obliged to "dotrack" once the object is located. 🙂