ollypenrice

Popped out for a quick nature call before going to bed last night, looked up and there was a nice little bolide in all its glory, streaking towards the SW. It fragmented neatly at about 45 degrees above the horozon. No colour but still very nice. It makes you wonder how many we miss! This was at about 8.30 pm UK time, 9.30 pm here in France. Olly

All of this is a shame and if FLO/Celestron will help you out, then I'd follow Steve FLO's advice and await instruction. On the other hand, removing the corrector of a Schmidt is ludicrously easy, the thing being to mark the orientation of the corrector in the tube using a bit of tape or a marker. I just cleaned my Meade ACF this morning, taking out and replacing the plate. Sure, the collimation of the RASA will probably be affected because anything affects it at F2! But it will probably need collimating anyway. Some arrive collimated, others don't. Ours did need it. In any event, relax, it's no big deal. Olly

Yes, good detail. Blues are tending towards magenta on my screen, suggesting a lack of green signal. Olly

I'd have thought that, if you used a blowtorch on a spring, you'd change its metallurgical temper and, potentially, ruin it. I'm sure someone with metallurgical knowledge could give us chapter and verse but I wouldn't be too casual about heating a spring, myself. Olly

As a pragmatist I always try both options till I know the gear. Olly

I thought the 383L was marginal regarding the need for 2 inch filters but look this up. My memory... Personally, I think Baader LRGB are fine and sensibly priced. I've processed Astrodon LRGB data and not felt I was missing anything. I'm also a bit biased against Astronomik, having been stung by their totally trashy and disposable flat panels. The Baader 7nm Ha is also OK but I also have an Astrodon 3nm which is much better. As it bleedin' well should be at the price! OIII is always tricky. I've had two Baaders and two Astronomiks and none of them was really much good. Halos... Safest all round bet at normal prices? Baader. Olly

This is to do with amp glow, I guess? In which case, yes, for sure. Olly

For many years, and maybe still, my favourite camera was/is the very noisy and low QE Atik 11000. Why did I/do I still love it? Because it produces gorgeous data which you can't kill in processing. And do I use darks? Nope. Dither? Nope. Just defect map and bias-as-dark. Darks are the most over-rated item in the history of digital imaging, in my view. Olly

Yes, manufacturers quote a cooling performance in degrees below ambient. You get away with it by taking much longer to produce an image and, sometimes, by accepting a lower standard at the end. You can also go for the brighter targets rather than the faint, dusty ones. DSLRs do thrive on fast F ratios, too, as Maurice Toet demonstrates. with his DSLR-Tak Epsilon images... but an AP mount, Tak Epsilon and 5DMk4 no longer constitutes a budget alternative! It's a very portable one, though. https://www.mauricetoet.nl/DeepSky/ Olly

For the benefit of those too young to know what 35F means in sensible units, it's 1.6C! (I've just been faffing around trying to find imperial sized bolts for my Meade SCT so this is a sore point!! 🤣) Those temperatures will certainly help an uncooled camera and narrow the gap. I also think scotty38 is right in saying that the need for stable temperatures is diminished in modern CMOS cameras. For all that, given the cost of the complete rig, I'd go for cooled. Olly

Yes, true. One thing's for sure, though: small, fast, budget achromats are the worst of all photographic instruments. Conversely, eye-wateringly expensive small, fast apochromats are among the best. Olly

To my mind an aperture of less than 70mm for visual use is best left to binoculars because it ceases to deliver a truly 'telescopic' view. Regarding the 'ST ' series Skywatchers, the 'Short Tube' versions are obviously more compact but the slower F ratio versions do deliver a much better image, especially on the moon and planets. I rather like them and I'm an inveterate refractor snob! Olly

In my head only, I conceived of a sliding counterweight system to reduce the gravitational pull on the focuser to as little as zero if that's what you wanted. It would not be all that difficult to make. - Start with a tube mounted parallel with the optical axis of the scope and behind the focuser's knobs. - In this tube is a cylindrical weight of the right diameter to slide up and down in it like a piston in a cylinder. - A cable (fishing line?) goes from this weight forwards to a pulley on the back of the scope, which it loops around, and then back to the camera. That's it. Pointing at the zenith, the camera is pulling down, a counterweight equivalent to the camera's weight is also pulling down by the same amount, but the direction of the counterweight's pull is reversed by the pulley so it neutralises the camera's pull. Both pulls diminish proportionally (bar minor differing effects of friction) as the scope approaches the horizontal (and the problem ceases to exist anyway.) An industry capable of producing so many excruciatingly bad focusers should have no trouble making a tube, a pulley and weight. Olly

I hope so. I'm also hoping to fix an Altair Astro 80mm triplet to the top in order to have a widefield alternative view. Olly

Slightly nerve-wracking but it went well. I gave some thought to the order in which to do things and started off by putting the forked scope on a bed for safety during the de-fork process. If you aim to re-use or sell the mount, mark the position of the Dec clamps against the fork tines before you start. The critical thing is to be able to loosen one of the tines. On the 14 inch it is done by removing the four bolts below on the GPS side, but at this stage I just gave them a turn to loosen them. Doing it in the following order proved perfect. Next I removed two of the three bolts which hold the OTA to the mount's altitude clamps. The one I didn't loosen at this stage on either side is the one shown here. This would be accessible later when the others wouldn't. (To get to the others you need to swing the fork upwards. I wanted the tube stable in the clamps at this stage, hence leaving the two accessible screws till last. Next I went back to the four big tine bolts in the second image and removed them. I could then free the tine completely and under good control when I removed the last of the three bolts holding the tube to the clamp (as per image 3). I could lift the tine away without its being under any stress. The last bolt to come out was the single remaining one of the three OTA bolts on the other side. It's all pretty obvious but if done in the wrong order might have the heavy mount bashing and scraping the OTA. Once cleaned up it is almost impossible to see where the mount attached to the fork on one side and on the other it literally is impossible. This scope, over twenty years old and a veteran of observatories in Britain, Italy and France looks no more than a gnat's crotchet short of brand new. I'm now awaiting a dovetail to mount it on the Mesu and am working out how to attach a nice Altair Astro 80mm triplet to the top to give a widefield alternative to the big scope's 3.5 metre focal length. To be continued. Olly

Slipher didn't know that his spiral nebulae were galaxies, didn't know their distances and, therefore, didn't know that their redshift-distance relationship was linear or that this relation held good in all directions as viewed from the Earth. It's vital to have all that information before you can conclude that the universe is probably expanding. However, Slipher opened up the observing program which led to the missing information. As well as Leavitt, Hubble and Humason, we must also credit Harlow Shapley who found a way of calibrating Cepheids and turning them into useful tools. (Don't expect Hubble to give Shapely any credit for this! Think Robert Hooke and Isaac Newton. ) @Marvin Jenkins I agree with nearly everything you said but how dare you say anything about Chip Arp. The Patrick Moore book noted at the beginning of this thread clearly says Arp is one of the finest observers in history and his observations cannot be questioned. I wouldn't dream of saying anything against Halton Arp since, as a culture of doubt, science must have its doubters to challenge all forms of lazy orthodoxy when they appear. As for the idea that Arp's observations cannot be doubted, we must define 'observations' as distinct from 'conclusions.' As I understand it (and I'm not well read in this), Arp was interested in galaxies which showed visual signs of interaction while having radically different redshifts. The visual interactions Arp observed have been reduced to line of sight effects by most of the professional community and most certainly are questioned. In all truth we are dealing with scientific discoveries by human beings. The latter part of that statement means anything is possible. Does that mean Penzias an Wilson are wrong? Oh no what have I said About what might Penzias and Wilson be wrong? That a radio signal with an effective temperature of just below 3 deg. Kelvin can found found in all directions? That's very unlikely! They found it without knowing what it was and were enlightened by Robert Johnson whom they'd unwittingly scooped. And, remarkably, I've read that none of them was aware of the work of Alpher and Herman who'd predicted the presence and temperature of the CMB from theory many years earlier. If you want to hear real heresy, I'll give you this: Patrick Moore is not an entirely reliable historian of Astronomy. Olly

I'll take this a step at a time as I do it, because there is some dire misinformation out there in Netland. Whether I've got to the bottom of it will be seen as the project continues! Stage one is Google Homework. Most 'de-forkers' unscrew the tube from its Dec carrier-brackets and then abuse it as they try to drag it out between the fork tines which are too tight for it to pass. It ends up gouged or scratched. Some create more space by spreading the tines with a car jack! Now hang on, did Meade assemble the thing by spreading the tines with a car jack? This makes no sense. A better class of U-tuber discovers that one of the fork tines, despite all appearances, is not integral with the other but can be unbolted, creating removal-space. Now we're talking. However, different variants of of the LX200 have fork arms which detach in different ways. The 14 inch has only the upper end of one tine which detaches. I didn't find a video on this but a close look at the GPS arm showed how it should come off. The take-away, however, is that one of the fork tines detaches and you don't have to scrape the OTA out between un-separated tines. Olly

My own reading of astronomy history makes it very clear that Hubble continued the observations of Vesto Melvin Slipher, who is regularly cited in astronomy history. To be honest, almost everything I've read on the matter makes this clear, so I think you've been unlucky in your choice of texts if you have only just met him. You're certainly right to note his contribution. However, the story is convoluted because Hubble was happy to ride the tide of fame which followed Einstein's interpretation of the linear distance-velocity relation Hubble discovered. But we must moderate our view of Hubble as the the 'discoverer' of the expansion since he never entirely believed it - or never even believed it at all. It is for professional historians of science to get to the bottom of all this but my own suspicion is that much of the story hangs on Hubble's troubled personality. He craved adulation and spent his scientific life searching for discoveries that would immortalize him. When Slipher ran out of aperture, I think Hubble spied an opportunity and went for it with the Hooker. And I suspect that his reluctance to accept the expansion of the universe as the explanation for his distance-velocity discovery was that this explanation wasn't his but Einstein's. He hoped to find some 'new physics' to explain the phenomenon (as did Fritz Zwicky with his 'tired light' hypothesis.) Maybe the last knockings of this quest for a new physics found their final expression in Halton Arp, who continued to challenge the redshift-distance theory to the end. Anyway, I hope that all readers of astronomy history agree that the expanding universe has two fathers, Slipher and Einstein. Hubble and Humason (don't under-estimate Humason) might be considered the midwives. Olly

That's interesting. Thanks. Olly

Does anyone know this eyepiece? It would be used in a 14 inch SCT and would open up the view from the 0.6 degrees of the present 26 Nagler to 0.76 degrees. That's not a great deal but works out as a roughly 20% increase and the dropping of the magnification from 137x to 85x might brighten up the fainter targets. Exit pupils are 2.6 for the Nagler and 4.2 for the Vixen. The 41 Panoptic I'd probably have gone for is just too expensive at the moment. Olly

You won't break an EQ6 by putting a 12 inch SCT on it. Since it's in balance, the gears and motors will scarcely notice any difference and the overload is hardly going to break a bearing, assuming they are not misaligned or overtightened. The issue is just one of stability. I was using our 10 inch Meade on an EQ6 visually, quite recently, and it was fine. It wasn't rock solid but the original LX200 fork was a springy as a trampoline. In fact I'm currently de-forking a 14 inch to put on our Mesu. As for the scope itself, I've had the 8 inch, the 10 inch classic, the 10"ACF and the 14 inch classic. In my experience the quality of the view goes up with the aperture (no surprises!) but it does so at more than the rate you'd expect. In other words I think the optical design works better with more aperture. The 8 inch was a so-so 8 inch scope but the 14 inch is a good 14 inch. So the 12 inch should be good as well. The scope is compact for its aperture, sealed against dust, easy to collimate and maintain and you look through the end! You'll need a dewheater and dewsheild but the obvious drawback is the long focal length. Wide views are impossible. On looking into eyepieces to give the widest possible field I've come across the Vixen LVW42 which gets close to what's possible, is rated as optically good and comfortable to use, and the price is reasonable. TeleVue have priced themselves out of my range of late, or I'd have the 41mm Panoptic. Another positive from the shortness of the tube is that the eyepiece does not vary as wildly in height when used on a GEM. Olly Edit: In built counterweights? Where are they??? You can see most of the interior of the OTA from the front so, if they exist, they can't be very big or very heavy. I'm not buying it.

I'll never know because I won't be buying them! lly

Since the imaging is now done with a robotic setup based here, I've decided on a marriage between our 14 inch Meade SCT tube assembly and our venerable Mesu 200 mount, to have a great visual observing setup. The LX200 Alt-Az mount is handy but wobbly and has now started acting the goat electronically. It's over 20 years old and I think that, even if I fixed it this time, it would most likely act up again. This is no good in my circumstances. Stuff has to work. The Mesu observatory is small for visual but the SCT is nice and short. We'll lose the convenience of alt-az but gain the convenience of a Moonlite Crayford which we can't use on the fork mount for fear of collision. So, Mesu, do you take this 14 inch SCT to be your lawful wedded wife? We'll find out when the Losmandy dovetail for the Meade arrives and I've de-forked it. (Nearly 300 euros for a dovetail? Better than over 1,100 euros for two tube rings. Not a misprint!) Olly

This absolutely is not a poor M13. It's a very good one. Stars are resolved to the core, are in focus and are nicely distinguished by what looks like accurate colour. The Propeller shows beautifully. I demand that you apologise to yourself immediately! lly

I attached an arm to the mirror box, in the same axis as the optical path of the telescope, and had a sliding counterweight on that. It pointed down just below the bottom of the box but clear of the ground. Olly