ollypenrice

Ah, something new! A wonderful image. Olly

Thanks Maurice. I just used the panels Paul had run through ABE and they seemed fine, so I settled for them. A bit lazy but... I'm a very old man now! 😁 Olly

Indeed, but there are three notably black background patches running across the image which are interesting. Because their star count is low I guess that they are patches of dense obscuring dust not illuminated by any nearby bright star. Yes, that's the charm of these dusty sculptures shaped as you describe. The scale of many of them beggars belief. Olly

You're right, Goran. Indeed I'd already un-flipped it at one stage but obviously did it once too often! It's now corrected. Actually the present version is a full reprocess because Paul wanted to see f would could preserve more fine scale detail. There is a little more in the large version, now. Olly

I think you'd be disappointed because it would just be like perfectly empty space. The density of particles is lower than a laboratory vacuum on Earth. These are the kind of objects we can only see because they are distant. Olly

More dust from up north, about 10 degrees from Polaris in the Cepheus molecular cloud. Another project with Paul Kummer, who set up the robotic sequences from the UK for a rig based here. (Paul provides a Celestron RASA 8 and ASI 2600MC and I provide an Avalon Linear mount.) Paul also did the stacking so all I did here was the post processing. It's a 4 panel mosaic, about 3 hours per panel in 3 minute subs. ABE from Pixinsight, mosaic made in Registar, processed in Photoshop including StarXterminator to remove the stars before they were put back at a softer stretch. Olly

It's twenty years since I observed anywhere other than at a dark site but the first thing to say is that a dark site isn't dark. You can walk around without difficulty from starlight and the Milky Way (which is, of course, starlight.) I can't read a star chart that way but I can do so using a dim red light kept on for only moments and sometimes a magnifying glass. This is dimmer than any dimmed screen I've ever used and I've also tried red acetate over screens but I consider that useless, to be quite honest. It is only dark at a dark site when it's cloudy, and then it really is totally dark and you can see absolutely nothing. Olly

Before I ever saw a Mesu mount I was told by Maurice Toet, 'Lucas Mesu does his homework.' He does, as well. Olly

Yup, and he's taken his bat and ball with him. Olly

You say 'No astrophotography' but, speaking as an astrophographer first and visual observer second, I'd say it was hard to capture the visual sparkle of the globulars in a camera. It's not like the faint nebulae, many of which cannot be seen at all at the eyepiece. Starrry targets are routinely better at the EP than at the camera so I suspect you might want to look at your collimation, and/or cooldown. Olly

Surely your best bet would be to try it yourself? To my mind, screens of any kind have no place at all near a dark sky observer. The very idea is absurd. I'd also try a dark cloth over the head, or snorkel mask without glass, or all the other tricks folks use to make the most of a compromised site. You can't be sure that other people's findings with match your own. Olly

My my, this individual is more abrasive than the previous record holder! He should think about inventing his own focus mask so they could lock antlers over which is best. 🤣lly

I've had a number of Decathlon USB head torches and wind-up lamps. (Here in France you are never far from a branch.) They have been consistently excellent and very reliable. When choosing one for astronomy, the thing I'd watch out for is whether or not, to go from On-Red to Off, you have to scroll through White-On. Obviously it is far better to be able to go directly from On-Red to Off, as I can with my present one. Huge French sporting goods outlet, Dave. There was a branch in Derby when I lived near there. I don't know how widespread they are. I'm going back 20 years but, back then, the English branches I saw were very lack-lustre compared with the French ones. They were the same size but in England the shelves were half-empty and stocks were poor. Maybe that was a start-up period issue but, here, they are good shops selling decent quality goods at prices between 'Good' and 'Downright bargain.' I am currently sporting a pair of their shorts but will spare you the photograph... Olly

I'm not persuaded by the theory that the Bayer Matrix significantly reduces resolution. When I had both mono and OSC Atik 4000s I looked for such a reduction and couldn't find it. Of course, in strict terms, the matrix does reduce resolution, more in red and blue than in green, since there are two green pixels per red and blue. However, the debayering algorithms interpolate what is likely to be missing in between filters of a given colour and restore it. The edge of an Ha structure in a nebula will be picked up on one pixel in four but interpolation will fill in that edge. Not all debayering programs are equal but I think that, in reality, they are so good as to bring the result to a standard imperceptibly inferior to monochrome luminance. If the system is over-sampled, as is becoming increasingly likely with tiny CMOS pixels, there will surely be no possibility of distinguishing between the resolution of OSC and mono. I've long advocated mono over OSC in CCD days but this was on the grounds of light reaching the chip. I always conceded that they were effectively equivalent in resolution. All the images I've posted from the RASA have been resampled downwards. It is not oversampling on paper but, when you look closely at the data, it very clearly is oversampling in reality and there is nothing to be gained by finishing an image at full size. Also it might be worth thinking about the stunningly high resolution we obtain easily from DSLRs. They are nearly all OSC chipped cameras... Olly

I'm comparing any scopes of different focal length, I think. Long FL scopes have smaller FOV's than larger. My point was that this is the downside of the SCT. There are a great many excellent objects which require a short focal length, after all. Olly

Well, I had a 20 inch F4 and could see large swathes of the Veil with with a 26 Nagler. Now, with a 14 inch SCT, I'm too boxed in by that 3.5 metre FL to be able to do that. Surely it's a simple matter of focal length? Olly

I'd beware of solutions which are looking for a problem, a quip once aimed at Vincent motorcycles. A simple, thin-gauge but large diameter steel tube has good strength in compression, plus high resistance to bending and twisting. It can be triangulated against tilt by using cables in tension (as per Astro-Physics) which require less metal and less volume than struts in compression. Since this design ain't broke, I wouldn't try to fix it. The exercise is interesting, though. Olly

The flex tube dobs are reasonably compact but they are heavy. I don't know how you feel about price but, if only for the fun of it, I'd have a look at David Lukehusrt's website. https://www.dobsonians.co.uk/ He also makes equatorial platforms which allow a period of motorized tracking which is both relaxing and a great practical boon if sharing the view with others. His compact Dobsonians really are very portable for their aperture. There is no one point at which a fundamental change in the view suddenly occurs in rising aperture. Not for me, anyway. However, I would be unlikely to go for anything less than 12 inches if I had the means of using one. Olly

I have a Meade ACF and it's pretty darned good. I should use it more! Olly

Running an astronomy gite for nearly 20 years, I have some experience of trying to impress the non-astronomer. On the planets, it's easy, in almost anything. On the deep sky, it's almost impossible - even with a 20 inch. And... I live at a very, very dark site. I recently introduced some absolute beginners to the deep sky with a 14 inch and found some objects which I think they really enjoyed, but they were seriously interested and had booked an astronomy holiday. For many, most things remain faint fuzzy blobs. M42 is a common exception, as is M31, but that's a winner in binoculars guided by a laser pointer (not in London!) So, as already suggested, I would concentrate on yourself. The SCT is compact but the long focal length, in many cases, defeats the object of the exercise by cramping the field of view and excluding many targets you might enjoy. (Rosette, Veil and many, many more.) Personally I'd go for a collapsible Dob as big as possible. Olly

Glad you liked it. I haven't seen it on paper yet. Olly

Io, Europa, Ganymede and Callisto are, respectively I, II, III and IV. Olly

It's great, especially for such short integration time. Have you processed the halos to reduce them? If not, they don't look bad to me. Small telescopes will always produce larger stars and 51mm is a pretty small aperture. There are some bright stars in this field. Since you have Noise X, have you considered StarX? You can remove the stars and replace them with stars given a much softer stretch. Olly

Our horizons are variable. There's a huge lime blossom tree to the north but this doesn't really matter because the circumpolar objects always rise above it and are at their best when they do. In the south we can go to horizontal in one place and to about 10 degrees around that. The western horizon rises to 20 degrees but that just shortens the imaging time available on an object. It doesn't exclude anything. With proper planning you can leave red till last and catch that at lowest elevation where you don't really lose much of importance. Depending on the target, this also applies to Ha, certainly in the case of galaxies where the Ha tends to be fairly blob-like at best! 😁 Olly

I agree that the EQ mount only makes sense, these days for imaging. If you want motorized tracking you can have it in alt-az mode with more convenience, thanks to the inboard computing available. I don't think the sales bias towards imaging has much to do with the rarity of large Alt-Az mounts. Rather, it's the efficiency and economy of the Dobsonian Alt-Az mount which has undermined the engineered, metal Alt-Az. For my money the Dobsonian Alt-Az is both better and cheaper than many metal-and-balbearing alternatives. This set me thinking that most solar observers at mid and high latitudes could make a variant of the Dobsonian for refractors, since the range of elevations would be quite limited. No need to approach the zenith. Edit: I've used a GEM in Alt Az simply by pointing the polar axis straight up, as you would polar align it at the north pole. After all, that's what an Alt-Az mount is: an equatorial aligned for N polar observation. (As for N. Polar observation, all I'll say is, 'After you!') 😁 Olly