Whirlwind

For WO products you generally measure from the base of thread (when screwed all the way on) to the location of the sensor. It's not the camera that needs the backfocus but the flattener. Most cameras/filterwheel/OAG set ups are designed with this length because it matches standard DSLR distances. The small amount of extra scope for adjustment is to allow filters to be included (which increase the optical distance between the reducer and sensor).

I don't think it has been mentioned but another reason for a high quality rotator is to allow you to position accurately for flat if you image multiple targets over a night. This can be more or less pronounced dependent on where the rotator is located and the optical arrangement of the telescope. Otherwise you would have to fix the position at the beginning of the night and then leave it there regardless of what objects you image for that night (so you maintain the same rotation for the flats before/after the imaging run.

As noted above it would be the returns system that will be most awkward as if you need to return something that would require customers to complete forms etc. Getting others to pay in advance (like ebay) of the customs duties makes me wonder how cost effective that would be when they will still be paying customs/VAT/shipping hassles/exchange rate risk and then the companies premium (staff costs) on top of this. Part of me wonders whether it would just be easier to pay the cost 'at the door' as it were if you were going that route (as it removes some risk costs). It largely depends on how reasonable postal companies for managing customs vs businesses. It will also be interesting to see how rules of origin will work that will need to be evidenced as well (so something available in the UK that can be bought but might bring higher tariffs in the EU if bought direct, and vice versa) as the trade rules have been deliberately designed to stop these backdoor shenanigans. This might apply to the StellaLyra/StellaMira range for example.

Yes, the email I have indicates London.

When I recently purchased something from Astrograph, Rupert mentioned that they have the ability to manufacture custom adapters as well.

I think the Royal Mail guidance was anything posted after 28th December should be as they need to be compliant with any extra red tape on the day they arrive in the country. With everything transpiring together they couldn't guarantee that they would be able to deliver before the 1st after this date. I think now we have to consider any extra customs duties (plus the mandatory extra shipping charges that companies will apply) when that happens.

Just remember that anything to the EU will now have to be sent with customs declarations form (that isn't a letter).

Yes there are plenty of battles to fight both large and small. However, the point I am trying to make is that disposable items as a product needs to be a thing of the past. In the same way we view drink driving - it doesn't matter if you are slightly over the limit or hugely over the limit. Yes the latter has a much bigger risk but neither are acceptable. I go back to an earlier point that if we, to an extent, shrug our shoulders and say it is just a few items that doesn't change our mind set as a species (and also those that don't get that exemption will cry foul). To save the planet we need to view the same activities all in the same way. Yes, the drink cans disposal a huge issue to deal with. To some extent though we can have a bigger impact in the astronomy market as it's not huge and a small number of people are much more likely to have a big difference, as the market would have to adapt if a relatively small number decided it wasn't acceptable - if that is then replicated across many small markets (model building etc) then those trickle effects can be a torrent, just like the largest rivers start from very small rivulets or springs. For the drinks industry you need millions to change their habits (or be driven by governments) - that is not to say that change isn't needed.

That's not really what I meant and it sounds like I did cause offence, which wasn't intended. The "straw man fallacy" arises when another tangential topic is used to justify an argument against another. In this case whether it is acceptable to have some disposable items because other industries do it elsewhere in larger quantities (and perhaps worse). The problem with this argument is that it pre-disposes that the principle of pollution is acceptable as long as it is in small amounts, but it is the accumulation of small amounts that could be larger overall compared to specific larger industries. That there are food packaging issues is a real issue but that doesn't mean we shouldn't be reducing environmental impacts elsewhere even if they have relatively minor impacts (as the accumulation of the improvement on all minor items can have a big impact). Fair point. Plastics aren't necessarily all bad though. It's been a bit of a myth in the last year that *all* plastics are bad. It's more how they are disposed. The problem is that a lot of plastics are of poor quality (cheap) or mixed types which makes recovery difficult/impossible. However, high quality easily recoverable plastics can be better environmentally than card, metal, glass etc as these can introduce more environmental costs than we realise (for example we cut down by far more trees in the world than we grow, the weight of such packaging is higher so transport environmental costs increase, extracting new metals and glass and is very energy inefficient; card/paper can rot generating methane etc etc). Thinking of plastics as a 'pariah' isn't really the way to go but shoudl be thought of as a tool to be used appropriately.

In the politest way possible (as I'm not intending to cause offence), this argument is a "straw man fallacy". It is relating two different issues. The solarcan product is designed to be disposable. Drink cans and other food cartons for wet or degradable food *have* be disposable (or recyclable) as reusing them risks food contamination / food poisoning / rapid food degradation etc. Therefore for a lot of food products there is a need for them to be disposed/recycled to protect society (with the exception of some dry foods which you can use reusable containers for). As such food packaging is designed to keep the food safe. The solarcan on the other hand is designed to be disposable - it would be very easy to design it to be reusable (with only new photographic paper being needed). Secondly the principle of exceptions is why I think that we have a very long way to become sustainable. This one product might not seem much but then if this small product is given an exception then why not another, and another, and another, and then the large multinational companies want an exception. Ultimately this line of thinking leads us to no change at all.

This assumes that any such event actually occurred at the time. It is more likely (in my view) that it became a myth from an event that did happen but was probably uncorrelated. Hence it is quite possible that the star being referred to was observed by Chinese star gazers - it is just that it was much later or much earlier than the mythological timeframe.

To an extent we likely have to consider that the Bible is an amalgamation of myths and references to events that might not necessarily be connected. They are probably based on some actual event but then distorted over time. A bright comet is perhaps an option for the "star of bethlehem" not only because they can be very bright if close but also have a tail which could point in a direction (and hence referencing that it is pointing to a location). Some comets are one off wonders which we may never see again (or have such long periods no humans will be left to see it again). On the other hand if my understanding is correct (I'm by far not an expert) if the Saturn/Jupiter conjunction signals the second coming doesn't that imply the beginning of the apocalypse, which with COVID, climate change, anti-bacterial resistance, draining of the earths resources may not be that far from the truth!

The problem I have with these products are that they are designed to be used once and thrown away. Given we should be moving to more sustainability I have a general opposition to things that are designed to be thrown away after one use. Hence all the packaging, transport, fuel costs etc are substantial for a one use item. Now if they were designed to be reused that would be much better.

It really depends on how wide you want to go - have you checked what sort of field of view you want? The one thing to note is that large refractors can be burdensome on the mount and perhaps more so than a C925. This is because the they are long and have large moments (especially when you add on the cameras). Another thing to note is that many have flatteners or reducers but these have very limited backfocus so limits options for focusers/rotators/fwheels and OAG etc. Did you also definitely want a refractor. There are also things like the Tak Espsilon (130, 160, 180 all fall in the price range) which have pros and cons. Other refractors that might be worth considering is the Vixen AX103S. Yes it is only 4" but has a large backfocus of 130mm from the end of the drawtube. It also has a dedicated reducer (it naturally has a flat field). The FSQ85 has already been mentioned. The Tak TSA120 will also fall just in your budget (but the reducer would take it over the budget). The TEC140 second hand as mentioned but are as rare as hens teeth. Astrophysics 130ish or Tak106 scopes occasionally come up second hand as well.

I wasn't clear whether you wanted to look for variable stars visually or via CCD. I believe (though have never undertaken the exercise myself) is that you can see the change in magnitude of Algol. Its period is just shy of 3 days so if you check when the eclipses are you may be able to see the change visually (weather permitting).

It's perfectly fine to do this as it increases the signal to noise. For example the Kepler the space telescope (may it rest in peace) had six second exposures that were combined to create 1 minute and 30 minute cadences. It's mostly used on fainter objects, but as noted above it can be limiting in short variable objects if you only observe one period - if you observe multiple periods this becomes less of an issue as it is unlikely that the exposures will exactly align with the objects period.

There's also the short back focus (especially for the 8" which makes things tight if you want to add a filter in). The idea of the waving around a filter drawer in the cold and dark in front of a optical glass makes me go cold!

In perfect conditions mono will always be faster because of the reasons above. However, in the UK conditions are far from perfect. With a colour camera even if you get an imaging run of an hour you have all the data you need for a colour photo. With mono you can find that you have the R and G but clouds affected the B so you can end up with a partial image. As such sequencing is important in the UK so that you run L-L-L-R-G-B set of images. However, for a lot of set ups you might find you want to refocus per filter which adds more time setting up. With colour cameras you also can utilise some of the very fast RASA telescopes on the market that aren't particularly suited to mono imaging. However their large apertures/short focal length matched with an appropriate colour camera can then offset the reduced sensitivity. However you are correct that mono does give you more flexibility but these can be worked around to some extent. You can still use narrowband filters (or dual band filters) to get the Ha for a HaRGB. You can still use software to extract the Luminance from a colour image etc. Hence it largely depends on how you see your hobby progressing in the long term. I have mono cameras because I prefer imaging nebulae over galaxies or clusters for example which was one my prime drivers for which style to go for.

Given the way things are going we might not be allowed to do either as well....!

Halo's are a result of reflection within your imaging train. It is likely that the filter is reflecting some light back up the imaging train and which is then reflecting off the reducer back towards the camera. You won't have seen this before because if any reflection did occur it would be from the main telescope lens which would have by that point been so out of focus you would never notice it. Some filters/reducers don't have great anti reflection coating (especially at the Near infra-red and given that you are getting red halos I would guess it is around this wavelength that the light is being reflected. Sometimes flipping the filter the other way round can help (some have a 'shiny side'. Otherwise it may just be finding a better filter.

Not in the UK we don't...There are places in the world that a bit more friendly to Astronomy (until satellites fill every possible space above anyway).

The weather gods appear to work that if you are on annual leave it is cloudy. The day after you get back it miraculously becomes clear and you can't take the opportunity. I've concluded that we need to relocate the country completely.

This all depends on what you are intending to image. No filter is a miracle cure. If you look at the pass band for the filter here:- IDAS D2 Light Pollution Suppression Filter | First Light Optics then you can see that it does filter out to an extent the LED light but not all of it. Inn particular the 550nm - 650nm band there is still quite a bit of light pollution that is let in. If we ignore the bayer matrix impacts for ease explanation you then have to consider the targets you might be observing. If you are imaging in a heavily light polluted area and reducing a high background will reduce the background but may still be much brighter than the faintest of objects. On the other hand if you imaging bright galaxies, globular clusters etc then it may well be OK. Faint objects are likely to still be washed out. This is why you get different views because people like to image different things. If you want to image faint nebulae then you would want to focus on the multi-narrowband filters as these will cut out the light pollution as much as possible whilst allowing you to maximise the signal from the nebulae. On the other hand if you are planet/moon imager then you don't have to worry about light pollution at all because they will (barring the outer reaches of the solar system) will always be brighter than the background light pollution (assuming you aren't imaging under a light column).

One of the few trade agreements that has been rolled over is that with Japan (with a few extra benefits for Japan) so in theory it should have less impact (assuming that it isn't an EU distributer that we get all our Taks from?)

Yes it would be good to see some UK dealers with this scope as it is intriguing as a fast system for the UK (and you want to use filter wheels etc) which a RASA doesn't allow for and is by far cheaper than than OS RH200. Closest comparator appears to be Vixen R200SS with PH corrector (excusing the other epsilons).