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Thanks for the suggestion, Jack. I’ll take this issue to Council. I’m not sure it should be solved in the way you suggest; maybe relocating the event to a venue with bigger capacity, or holding another similar event elsewhere is the way to go. It certainly seems to be a victim of its own success.
Yes. The idea of carrying an f/11 4-inch refractor on an adequate German equatorial mount up and down stairs doesn’t seem like a realistic option to me.
I don’t recall ever looking through a Mewlon, but everybody says they are superb. However, there are advantages to the closed-tube cats, and I don’t think you should dismiss them out of hand. They stay clean inside, they don’t have spiders (either the animal or the optical kind) to affect the image, and the coatings do not corrode rapidly (this latter factor I find to be a huge issue in a polluted city for open-tube scopes). Dewing of the corrector is an issue, but can be greatly slowed with a dew shield, which can be a flexible piece of plastic. The ‘large central obstruction’ is a bit of an over-done preoccupation of some people, in my view. The great telescopes of the world (and in space) all have obstructions of 30-40% of the diameter, and no astronomer ever thought that made them bad telescopes. Contrast comes from many factors, including cleanness of the optics and darkness of the tube (baffling). SCTs tend to score well on these. The central obstruction throws a bit more light into the first diffraction ring, and if observing close double stars in fantastic seeing it is an effect you might possibly detect, but it doesn’t seem to damage planetary detail. I’ve been happy enough with Celestron SCTs to have owned 5 different ones.
My other thought on all this is that, to save weight to be carrying, you could consider: do you really need a German equatorial? As Peter says, they imply that annoying counterweight. There’s an increasing selection of altazimuth mounts, manual and driven, available now. Most of them, again, I haven’t tested, so how well they might do in your context I don’t know. But another correspondent of mine is currently having a lot of fun with a Skywatcher GTi altazimuth GOTO (but only with a 75mm short-tube refractor).
As far as the 2nd hand market goes, I’d recommend UK Astronomy Buy & Sell for bargains. I’ve bought loads of things off there over the years, and rarely had any problems.
Bresser is a German company that is associated with Chinese manufacturer Jinghua Optical Electronics Co. (who also now own Meade), so that probably gives where they are actually made.
One thing that’s not clear from your post, Bob, is whether you are looking to purchase a whole package: mount and telescope. If you are, we should be talking about the mount at least as much as the telescope. The mount of the Messier AR-102 looks too small for the telescope to me, judging by the picture on the tringastro site. If the telescope and mount are separate, for a manual mount, I recommend spending at least ⅓ the budget on the mount. For a GOTO mount, at least ½.
A separate 102mm f/11 OTA is sold by Altair Astro: their Starwave 102mm f/11. This looks different to the Bresser offering, and got a good review from Sky at Night magazine. I’d say a telescope of this size should not go on a smaller mount than the Skywatcher EQ5, or similar. Unfortunately, we may be getting to the point here that you would have difficulty getting this setup up and down stairs to your first floor flat, unless you disassembled it into several pieces each time.
A 150mm SCT or Maksutov would have similar image quality to a long 100mm refractor, but work with a lighter mounting, and the setup would be more stair-capable.
I agree with Peter’s comments. That graph he gives is very useful in judging what to expect with achromats. I would expect the chromatic aberration in the 127mm f9.5 to be quite intrusive, making it rather non-ideal for lunar and planetary work.
I haven’t tested these Bresser telescopes, but generally Bresser have a lower reputation than Skywatcher and Celestron – deserved or not – and much lower than Vixen (whose style they look to be imitating with their white paintwork).
I have some words to say on this subject in the December Journal, which will be out shortly!
Yep, this is the kind of thing that really needs a dummy run on an earlier night to get a feel for the difficulty of the problem. Glad so see some observers got something, if nowhere near 0.2s cadence.
This reminds me of the visit I recently made to Berlin, for the European Planetary Science congress. On the last day there was a visit to the longest refractor in the world, the Archenhold Telescope, which has a focal length of 21m and aperture 68cm (f/31). The longest eyepiece they have is 100mm, giving x210. This is the power they nearly always use. The telescope is in regular use for public observing, particularly by school groups. The eyepiece is the green bit in the photo.
The meeting has been organised in collaboration with Wessex Astronomical Society, and they chose the venue. We are dependent on the knowledge and contacts of local societies in organising such meetings, and the results are usually excellent, as I fully expect they will be in this case.
Indeed, but if importing yourself you’ll have more difficulty and expense if something is wrong with the product or it goes wrong later (which is common with solar scopes as they are delicate and precise things). This after-service is what you pay for by buying from a local dealer. As the US is a much bigger market, and most of these products are actually shipped from there, it is inevitable they will be more expensive here.
In the last year I have been showing Jupiter to the general public with a 100mm ED glass refractor with a magnification of 80-160, and when the GRS is on the disk, and it has been pointed out to them, 95% of them have been able to see it. This would be in the poor seeing we have been getting at the low altitude we have for Jupiter. So this gives a measure for people with no experience of looking though telescopes at all.For more experienced observers I have little doubt a 75mm refractor would be enough, under typical conditions, with a magnification of 80.I would say the GRS is easier to see now than it was in past decades. I think in the past a 100mm refractor or 150mm reflector would have been the absolute minimum, with good conditions.I do have 80mm and 66mm refactors as well, so now the question has been posed, I’ll see if I and others can see the spot with those this year.I covered many possibilities in my book “Setting-up a Small Observatory’, (Patrick Moore’s Practical Astronomy Library), still available from Springer, with descriptions and photos of methods of construction various people have used.
I used treated timber rails and guides and plastic rubber-tyred wheels, and, about 12 years on, this is the one part of my construction that has failed and needs replacing. The problem has been that wear by the wheels (even though there are lots of them, spreading the load widely) caused groove formation on the rails, which allowed water to stand, and the eventual decay of the rails. I build the shed in a modular fashion so it is not that difficult to replace the rails, as I anticipated this might be necessary. I can’t see any ultimate solution, other than using metal. Aluminium of the scale required however would be expensive, and steel is very heavy. I did try just surfacing the rails with aluminium, but that caused a different problem: water got capillarised in through the narrow gap. I intend to replace with new timber, but I may try varnishing with yacht varnish or something hard and hard-wearing, in an attempt to increase durability. But in the end none of these solutions last for ever, and 12 years is not too bad.
Anybody who studies or pursues astronomy in any dedicated way can call themselves an astronomer. I have met plenty of people who have ‘astronomer’ as their official job description who have not often, or ever, been in the circumstance described by Woolley. There is there a hint there of the kind of ‘macho suffering-cult’ that you often get in people’s definitions of their professions or hobbies in order to make them more exclusive: ‘You can’t call yourself an x unless you’ve done y extreme or uncomfortable thing’. Anyone with any sense rejects this stuff. There are a thousand ways to do amateur astronomy today, some of which involve extended physical contact with telescopes at night, but many of which don’t (solar observing, for example!), and in the BAA we value and encourage all of them.
Very sad news. I wonder how something good can be rescued from this.
I don’t think the BAA could commission something like the Yearbook, but we do already have our Handbook, and maybe that could be expanded, with the cooperation of some of the people who were contributing to the Yearbook, to include some of the most useful material from the Yearbook that it does not already cover. We could make the Handbook more pictorial and diagrammatic, market it more outside the Association, and charge an appropriate price to non-members. Maybe we could also pay something to contributors. However, that would require detailed consideration.
My method is to use tissues (one per wipe, then use other side, then throw away) plus de-ionised water, plus isopropyl alcohol. I alternate the alcohol washing stage and the water washing stage, going through a few cycles.
The main points I’d emphasise are being gentle, only doing a small arc each time, then lifting the tissue, and not rubbing in circles.
Also, don’t try to get it perfect. They’ll always be streaks. I do it maybe every couple of years, but my location is very dirty, with many diesel vehicles nearby.
Well it’s arguable that Council meetings are the equivalent of the meetings of a Board of a company. The minutes of these are not normally made available to shareholders, or members, of the company. I’m not saying I support this position, but it’s arguable.
David
To answer the other question, Council minutes are not available to members. I feel this is unsatisafctory, and I think they probably could be published, as could probably the minutes of the new, separate, Board of Trustees. This is just my personal opinion; there is nothing in the By-Laws to say they should or should not be available to members, but the tradition is that they are not, and that Council buiness is confidential.
David
Thanks David, yes that is kind of helpful.
It’s still a pity they haven’t done one Mercator projection (or similar) map for the whole planet. I have now worked out that their global mosics go from 180 deg to 180 deg longitude, not from zero to zero, which was confusing me for some time. It’s still a lot of work to relate these images together, as Mercury’s suface, like that of the Moon, looks completely different under different illumibation angles. Also they’ve made a problem by reproducing all these image really dark. You have to import them ito Photoshop and turn up the levels to see much.
One of the things I’ve been trying to establish in my reasearch is if there is any valid relationship at all between telescopic maps and drawings and what is really there. Peter Grego in his 2008 Springer book on Mercury and Venus still holds that the traditional maps do represent things that can be seen repeatably by good observers. Patrick Moore, on the other hand, after Mariner 10 visited, always said that the visual maps had been ‘hopelssly wrong’. My examination of the Messenger data tends to side with him – there’s no relationship whatsoever.
To ‘third’ these comments, I would say that Jonathan’s greatest achivement over these years had been maintaining the BAA and SPA combined comet webpage in a way that has made it perhaps the most useful and practical port of first call for anyone looking for up to date information on what comets are actually visible with amateur equipment from their particular location. Comets are coming and going all the time, and the fact that this page always seemed to be maintained reliably and was up-to-date with basic information, that could then be followed-up elsewhere, is quite remarkable in view of Jonathan’s work schedule with extended visits to Antarctica. It has always been very useful to someone like me who is not sufficiently interested in comets to subscribe to the specialised newslists, but wants to dip in from time to time.
From Edgware the occultation lasted 14.7s from 04:28:09.5 to 04:28:24.2.
I’ve placed the time-stamped video on YouTube
David
Yes, this is a common experience that the callibration frames are not quite right and create problems rather than solve them.
If you have a light-polluted sky at all then flats are much more important than darks; also if there is any vignetting (uneven illmination) in the system at all.
I’ve never had success with artificial flats (using a light box for example) but find the best method is to take flats on a clear sky at sunset or slightly earlier. The optical system needs to be focused and ideally pointing in the same direction as for the light frames (in case there is any mechanical slop).
With a DSLR it’s fairly important that the dark frames are taken at the same temperature as the light frames (to within, say 3 degrees C). I always note the temperature, and have built up a library of darks taken at different exposures and different temperatures.
Anyway that’s a nice shot. I’ve got an ED 80 and it’s a good combination with a DSLR.
David
I managed to get a similar result from Edgware in a claggy sky early on Thursday evening before it clouded-up. The disconnection is just about shown despite the LP gradient. R Ligustri’s image on Spaceweather is pretty stunning.
