Second Time Around

Thanks, Gavin.

Thanks, Gavin, I'll have a proper look shortly. Are these better than the cheaper models that Joko and others sell? Any other suggestions? I'd need one that will take the Televue 55/67mm Plossl as well as narrower eyepieces.

IIRC, there was a (Japanese?) zoom available late 60s with a focal length of 8.4-21mm. I almost bought one around that time.

What smartphone adapter would you recommended and why? If it makes any difference it's for an OVNI-M. Cheers.

It may be worth looking at the tiny US made Photon Freedom Micro lights that are available in different colours, including red. Go to http://www.photonlight.com The Micro model can be dimmed down really low. It can be put flat on a table, worn round the neck or clipped onto a variety of objects. There's also an optional fingertip attachment available. I bought the covert model to get the narrowest beam, but found it has uneven illumination. I don't know whether the standard version is the same. Can anyone help?

For those who haven't seen it, the link below will take you to a topic where I post the results comparing the accuracy of 6 (now 7)cloud forecasts, including Clear Outside. https://stargazerslounge.com/topic/376745-a-record-of-the-accuracy-of-my-local-cloud-forecasts/#comment-4189743

I'm always worried that any cloth could have a small piece of dirt or grit on it that could damage an optical surface. I therefore prefer Zeiss single use lens wipes. These come in a sealed packet so you can always be confident that they're uncontaminated. I'd particularly be worried about an expensive main mirror. My own second-hand 10 inch OOUK mirror looked so dirty I opted for the safe option and sent it to them for cleaning. It turned out it was so bad it needed recoating.

Dark-adapted pupil size can vary hugely from person to person to say the least. I'd therefore suggest you measure your own at your observing site. It isn't difficult and there are several methods that a search will show you. This is what I did. I got dark-adapted for a few minutes to allow my pupils to dilate (there's no need for longer as full dark adaption is a chemical process). I then got my wife to take a flash picture whilst I held a ruler just above my eye. The flash is so fast that your pupil won't react. Make sure though you haven't got red eye reduction or pre-flash on. As Stu said, your pupil size will allow you to work out the maximum focal length eyepiece you can use without effectively using a smaller aperture scope. Unfortunately my maximum pupil size is only 4.5mm at my Bortle 4/mag 20.87 site. I too have a 10 inch f/4.8 Dob. I use an Explore Scientific coma corrector with mine that increases the focal length by a factor of 1.06. So the maximum focal length eyepiece I can use without effectively using a smaller aperture scope is 4.5 x 4.8 x 1.06 = 22.9mm. As there are few if any 23mm eyepieces, plus my pupil size is likely to get even smaller with age, I use a 22mm. I'm further constrained as I have astigmatism and much prefer to use a Dioptrx to correct this rather than wear glasses to observe. This does restrict the eyepieces that I can use though. However, a longer focal length eyepiece is also useful for a wider field of view despite the loss of aperture - I use a 28mm/68 degree Explore Scientific, that also accepts a Dioptrx.

I'm not qualified to write reviews on astro gear, but I have had a large number of reviews published in UK fishing magazines. I can say categorically that many of the UK fishing magazines were and probably still are influenced by their advertisers. For instance, I once wrote a very unfavourable review of a reel from a well-known brand. The reel wasn't very free-running, and in cold weather it almost froze up completely. I submitted the review to several of the magazines I wrote for regularly. Not one published it, although they published all the other reviews and articles I sent them! That reel was quietly withdrawn from the market. However, that was after a lot of people (including me with my own money) bought the reels based on brand reputation.

I use and recommend one of the inexpensive Black Diamond range. Most of their models offer infinitely variable brightness down to very dim, plus separate buttons for red or white light. Best of all they can be set to always come on with the dimmest red light first whatever button you push - so no accidents! You do need to avoid the higher priced ones that have a battery check on starting up though. This is because they light up an intense blue that'll ruin your dark adaption. Additionally, those with the more costly Powertap feature can be knocked on accidentally. For astronomy just look for models without a battery check and without Powertap technology. BTW, the so-called Astro models aren't suitable for astronomy as they don't have a red light! https://www.amazon.co.uk/Black-Diamond-Mens-Spote-Headlamp/dp/B07MP9KNNZ?ref_=ast_sto_dp&th=1&psc=1 https://www.amazon.co.uk/Black-Diamond-Unisex-Adult-Cosmo-Stirnlampe/dp/B07S2ZMGMV?ref_=ast_sto_dp&th=1&psc=1

Gorgeous!

No flattened edging on either my 8 or 10 inch OOUK Dobs.

In case it's relevant, the 22mm/70 deg Omegon Redline takes a Dioptrx to correct astigmatism. IIRC, some of the others that are optically identical don't. Don or anyone? I agree with Don about it being a real bargain; in fact I preferred it to the much more expensive 22mm Nagler.

Mike, if you can find this petition, I'll sign it.

Mike, has anyone looked into whether Thanet Earth are breaking their planning permission?

Copied from my first post on May 1st: The forecasts were recorded roughly at sunset when I'd put my 10 inch Dob out to cool down if clear skies were suggested. The accuracy was recorded over a roughly 30 minute period from nautical twilight when it was dark enough to observe. This is approx 75 to 90 minutes later than sunset at this time of year. I now use the app Sunrise Companion to sound an alarm at sunset. If you long press on the date you also get the times of nautical sunset etc. www.timeanddate.com also gives these times plus moonrise and moonset, but doesn't have an alarm.

The Met Office is slightly ahead, perhaps because of its consistency. However, is this statistically significant? Although I've an A level in pure maths and statistics it's so long ago that I've forgotten most of it. To check whether the difference in accuracy of the forecasts is significant or not I seem to remember I'd have to do a student's t test (or is it a chi squared test?). Anyone? However, the results are so similar that I think it safe to say that there's no significant difference between the various forecasts. Short term vs medium term forecasts What is interesting from my research is that there are 2 methods of deriving forecasts. The one most of us will be familiar with is the medium term forecasts that we see on the TV and websites. These are computer models looking perhaps up to 14 days ahead. They're "driven by powerful numerical weather prediction (NWP) systems. By solving physical equations, NWPs provide essential planet-scale predictions several days ahead. However, they struggle to generate high-resolution predictions for short lead times under two hours." (My bold italics.) The other type of forecast is a nowcast. "Nowcasting is a technique used for very short-range forecasting. The current weather is mapped and then an estimate of its speed and direction of movement is used to forecast the weather a short period ahead (assuming the weather will move without significant changes). It takes time to gather and map weather observations, so a short forecast is needed to outline what the weather is currently. Nowcasts can be used as a source of detailed guidance on the location, extent and timing of imminent, often high impact weather events." "The Met Office produce a routine delivered service for T+0 out to T+6, for the United Kingdom, which blends our observations and UK Atmospheric Hi-Res model. At T+0 the blend is heavily weighted to observations and as time goes on the weighting of the UK Atmospheric Hi-Res model is increased, at T+6 the UK Atmospheric Hi-Res Model has the dominant weighting. The UK Atmospheric Hi-Res model is part of the Met Office flagship numerical weather prediction (NWP) model called the Unified Model. The resolution of the Nowcasting is comparable to radar data." Nowcasting is of course what we need to decide whether to get our scopes out. Unfortunately, nowcasting in its relative infancy. AI is now being used to enhance its accuracy, for instance in tests that the Met Office is doing with Google's Deep Mind. Hopefully, this will be of particular benefit to the likes of us. In the meantime I'll continue to use these 6 cloud forecasts (with Good to Stargaze being added from next month). However, as I've mentioned elsewhere, I also look at 2 other sites with satellite data. The first is Zoom Earth for current cloud photos. Unlike many sites it also shows cloud at night using infrared images, plus one can go back a long time. Bear in mind though that low cloud and fog doesn't always show up on infrared images. But it often correctly shows that the only cloud in Kent is over our area, and that it's clear just a few miles away! The other is Meteoradar as it extrapolates cloud satellite pictures to give nowcasts up to 3 hours ahead. Unfortunately it does so only for daytime hours. However, it's useful for soon after sunset, and also for solar observing. How accurate are the current forecasts? What will surprise many though is something I commented on in a topic where the OP was lamenting the accuracy of Clear Outside. Even now, the current forecasts are pretty accurate. Below are the figures for Clear Outside over the first 6 months of recording. However, as I said, all the other forecasts will be very similar. Correct 67% Partly correct/partly wrong 29% Totally wrong 4%

Above are the December results. Click to enlarge the image. Yearly analysis to follow.

Outstanding!

Yep, at our latitude the earliest sunset was on December 12th, the latest sunrise will be on December 31st. The winter solstice will be halfway in between. Doesn't make any difference to the almost perpetual cloud though!

What an excellent report! My own brain has frostbite and I may not be reading it correctly. Does your OVNI-B not have gain control?

Here's the November results. This has been the worst month for observing here since I came back to astronomy 3 years ago. It was often clear at sunset, but night after night it clouded over before it got dark! Frustratingly, the satellite photos showed it was often clear just a few miles away! 🤯 The only properly clear night we had was on the 2nd November, and December has started in the same way.

Sorry, I've got that a bit wrong. My hands are playing up tonight and I thought that was the problem I'd found. Rather it's that with the NPLs the eyecup is either up or down. I prefer it in an intermediate position and the hairband allows this. I find this especially important when solar observing with my Quark when eye position can be critical. Thanks for flagging this up.

Having tried several Plossls in the 30-32mm range, your 30mm Vixen NPL is my favourite as it's so comfortable to use. I like the twist up eyecup but it does has a tendency to slip down, especially with use. I've solved this by putting a hair band/elastic band round the barrel, and this holds the eyecup in the best position. This will of course vary from person to person, but can be easily adjusted

The only XW I've owned was the 20mm. I didn't directly compare it at night with the BHZ as I rarely use the latter at 20mm. Rather I normally use it at 8-16mm plus at 24mm. However, despite having high quality fixed focal length eyepieces, I use my Baader zoom a lot more often. The zoom plus a Barlow lens and a low power, wide field eyepiece is often all I use the whole evening. I have several Barlows of different powers. The one I use the most is a dual 1.5/2x, and most nights the 1.5x is best matched to the seeing conditions. Additionally, at a given magnification the field of view will be bigger with 1.5x amplification. This is because the vast majority of zooms have a wider field of view at the high power end. I agree with AGS. Fixed focal length eyepieces may be slightly better corrected when compared with a zoom at the same magnification. But that's not always a fair comparison as that magnification may not be the optimum for a given object. This is because one of the many advantages of a zoom is to be able to dial in precisely the best focal length. For instance, this may be 13mm or even 13.1mm, which may actually show more detail than shorter or longer fixed focal length eyepieces - even better quality ones. I particularly like the ability to increase the magnification to make use of brief moments of good seeing (a steady atmosphere). It takes more time to swap out an eyepiece, and the opportunity may then be missed. You can't see anything if you haven't got an eyepiece in the focuser! Having said that, I also agree with Ricochet that there's a place for high quality fixed focal length eyepieces. There's not much difference on axis, but it becomes apparent as you look away from the centre of the field of view. So it depends on what object you're looking at. Ernest Maratovich in Russia does lab tests on eyepieces. This is the text taken from a review of a Mk IV Baader zoom (not the earlier used Mk III he described as "battered"). This is how Ernest described the image quality: "Based on the results of star observations under conditions of a 1: 5 apochromat. {i.e. at f/5} At all focal lengths, the main field aberration is the curvature of the field of view. Curvature is more pronounced at long focus - reduces image contrast from about 60% of the field of view. At a short focus, the curvature is noticeable only in a relatively narrow (20%) band adjacent to the edge of the field of view. In the center of the field of view, image quality is limited only by defects in the observer's eyes. There is no glare. Light scattering is negligible. Distortion is not striking. When changing the focal length (the effort is quite adequate, there is a soft lock at 5 values), the focusing goes away quite a bit, but you still need to refocus."