Second Time Around

Anyone else from the South East Kent Astronomical Society (SEKAS) a member of Stargazer's Lounge? If so what name do you post under if not your own? My real name is Steve Burke.

Edit note: Rob, I'd assume the wavelength is likely to be 620-630 nm. If not I'd guess they'd highlight it as I found some other manufacturers of specialist torches as opposed to headlamp makers do.

Here's a link to the 2019 Black Diamond European headlamp page: https://eu.blackdiamondequipment.com/en_GB/headlamps-and-lanterns . All the 2019 models are on here. The 2019 Cosmo 225 is described in full here: https://eu.blackdiamondequipment.com/en_GB/cosmo-225-headlamp-BD620642_cfg.html#start=9. I've linked separately to this one as (except on the mobile version) there's a table comparing specifications and a link to videos on this page. According to this table the only 3 models that have dimmable red lights but don't have the battery check (usually bright blue according to the video) when turning on are: Cosmo 225 Cosmo 250 Spotlite 160 The least expensive is the the Cosmo 225 that I bought from https://www.wiggle.co.uk/black-diamond-cosmo-225-headlamp/ and is priced from £21.99 depending on which colour strap/body you choose. Here's a picture: Don't forget to make sure you get a 2019 model with 2 buttons (1 large + 1 small) as shown in the picture.

At the IAS Steve from First Light Optics asked me to post the following on SGL after I showed him my recently bought Black Diamond headtorch. I've used a lot of headlamps over the years, including many that have separate switches for red and white light. Even so, I've all too often pushed the wrong button and ruined my dark adaption. Additionally, all the lights have been way too bright. So the ability to dim the lights is an important feature. However, whilst there are many good torches that dim right down, there seem to be few such headlamps, that I prefer when observing alone. The best I've found are some of the 2019 Black Diamonds. Confusingly, although the model name (but not the number) remains the same, many have been totally redesigned for 2019 with two buttons instead of just one. One of the great things about them is that only the larger button turns the headlamp on; the smaller button just changes from red to white, but nothing happens when you press it if the headlamp is off. Additionally, they remember the last setting you used before turning off. For instance, if you finished with the red light at its dimmest setting, that's what you get when you turn it back on. Set up like this it means that it's impossible to turn anything on at the start but the dimmest red light - whatever button you push. Not all the 2019 Black Diamond two button range are suitable for us though. Some of them have battery check LEDs that light up when you first switch on. The problem is they're bright blue! Also note that the poorly-named Astro model doesn't have a red light. I started by buying two models, the Cosmo 225 and the Spot Lite 160, that use 3AAA and 2AAA batteries respectively. The numbers represent the max. brightness in lumens. Surprisingly, the red light on the Cosmo 225 goes dimmer than that on the Spot Lite 160, although this may just be a sample variation. The former is also on special offer at the moment because a new model, the Cosmo 250 has just been launched, that seems to be identical but has a higher output. I've just tested this, and comparing all 3 with fresh disposable batteries the 250 is indeed slightly brighter on full power white light than the 225, but there isn't much in it. On the dimmest red light they're exactly the same. So any of the 3 models are fine for astronomy.. There were complaints about older versions of these products having a weak closure on the battery compartments. This appears to be rectified nicely in the new models that have a firm, precise click action. I'd add that, here in Europe at least, these Black Diamonds have a 3 year guarantee. That doesn't of course prove anything, but they're expected to last at least that long. These headlamps should also be suitable for my fishing and camping as they have a waterproof rating of IPX8. This means that they can work for at least 30 minutes submerged to a depth of 1.1 metres (3 1/2 feet). However do note the battery compartment itself isn't waterproof and will need drying out. So for the first time I'm satisfied with a headlamp for astronomy and can thoroughly recommend these 3 Black Diamond headtorches. They're also very reasonably priced. Do check though that you're buying the latest 2 button models. Many outlets are still selling the similar 1 button type that's not good for us. For instance Amazon UK even has a picture of a 2 button Cosmo but the description suggests it's the old 1 button model. Hopefully FLO will stock them so you can buy them from our sponser!

I dropped off a very dirty 10 inch mirror to Orion Optics UK to be cleaned and if necessary re-coated. I also bought a few accessories, but was most pleased with this beautiful picture from Carl Gallagher of Light by Night. It's number 8 of a limited edition of 10, but the reason I bought it was to give me some inspiration to try some wide field Milky Way photography with my dSLR.

Hi, my wife Peggy and I have just arrived at the nearby Bungalow Farm B&B and will shortly be having a meal at the King's Head in Cubbington. We hope to meet some of you tomorrow. Steve

As you say, probably not for a fast Dob. However I'm very pleased with my Baader Hyperion Zoom. The only downside is the narrow field of view at low powers, which of course is what this new wide angle eyepiece is for.

I mentioned earlier in this topic about https://www.bbastrodesigns.com/diagonal.htm as a way to calculate diagonal size. What I should have added that inputting the parameters into the calculator is easy except perhaps for one - the distance from the centre of the secondary to the focal plane. Apologies if I'm teaching Grandma to suck eggs but the focal plane is where the image from the primary mirror is in focus. To determine where this point is take the eyepiece out and rack the focusser in as far as it will go. Then point the scope at the moon. Take a piece of white card and gradually move it away from the focusser until you can see the moon in focus. Then measure the distance the card is from the tube of the scope. Add that to half the diameter of the tube and that gives you the "diagonal to focal plane distance" to enter into the online calculator. It sounds more difficult than it is. If I can do it anyone can!

Thanks, Louis and Paz. I'm somewhat disabled so am limited to short observing sessions thus I imagine comfort is going to play a big part. It also means I'm limited to this particular scope for my light bucket. I found that with the Orion Optics UK Dobs I can manage a 10 inch, but am limited to an 8 inch with other makes, due to both weight and bulk. I'd therefore like to get the best quality views I can, and so cost is well down the list of considerations. Due to inexperience I don't yet know what I'm looking for - eyepieces have certainly come a long way since Ramsdens and Kellners my first time round! I suspect that I'll end up with the 22mm Nagler, but I'd like to try lots of other candidates. Thanks again for the input and please keep comments coming - I've got a lot to learn!

For easy calculation of diagonal size plus lots of useful info on the subject I use this: https://www.bbastrodesigns.com/diagonal.htm

Many thanks for the advice and all the trouble you've taken, Louis! Luckily I don't have presbyopia, just myopia. I've found the most practical way for me to observe is without my glasses as I can then also focus on a tablet showing Sky Safari as well. I keep my glasses on a cord round my neck and put them on for a naked eye view. The 20mm Pentax has now arrived - I just need a clear night to try it. Thanks for the heads up on the AstroTech and the APM; I'll certainly look into these. Does anyone any experience with these plus a Dioptrx? Has anyone tried a 21mm Ethos with a Dioptrx? Given that the Dioptrx reduces the effective eye relief will there be enough? Any other suggestions gratefully received.

Hi, apart from buying from the classifieds this is my first post here. I've recently returned to astronomy after several decades and, amongst other things, just bought a used 10 inch tenth wave f/4.8 OOUK Dob and an Explore Scientific Coma corrector. I've measured my dark-adapted pupil size at 4.5mm, so I'm after trying various wide field 20 to 22mm eyepieces, but as I have astigmatism will be using a Dioptrx. I've got a 20mm Pentax XW on the way, and have also shortlisted a 22mm Nagler and 22mm Vixen LVW to try if I can find them secondhand. Any comments on the above 3 would be appreciated. Are there any other eyepieces I should consider in this focal length that'll take a Dioptrx? Many thanks.