billyharris72

Afraid not. I eventually went for the Skywatcher flattened, which is okay across maybe the central 2/3 of my ASI1600 field, but bad beyond that. Had horrible problems with chromatic abberation at the blue end (not fixable by refocusing, but okay with a DSLR and no filters). Resolved the CA issue with a more aggressive cut off filter between focus wheel and OTA, but the tube has so little in travel on the focuser that it would not then come to focus with the correct tubes between the focus wheel and the cameras. In the end I sacked it and went back to the 130 P-DS. I think the more aggressive Astronomik "DSO" filters would fix the issue without adding to the optical train, and thus allow focus, but I've spent twice what the scope cost on trying to get it working and am not minded to spend more. Hopefully you'll have better luck than me with yours! Quality control does seem to be quite variable Brst of luck. Billy

No expert on platesolving but I know Astroart does it (used it occasionally and works okay). Astrotortilla looks like a good option and well worth considering. Billy.

We would definitely notice, but the point is a fair one in the abstract. Gasses in space at very low pressures can be at over a million Kelvin, yet the space itself could be (hypothetically) interpreted by us as "cold" if there isn't enough of that gas. The Sun's Corona is an example of this. At about 1 million K it poses comparatively little threat to the Parker Solar probe, which will be travelling through it. What that is "worried" about is the 5800K photosphere - less hot but an awful lot more of it. But for us - I have not actually thought it through in any detail, but I'd imagine the radiation and solar winds from a red giant would strip the atmosphere and turn every living thing on Earth to a crisp quite some time before any of this became a worry. Billy.

Agree with the above. I used to have both - of the two, the Newt was miles better on planets. The short focal length should not be a problem, since 5 inch f5 mirrors seem to be of invariably high quality. It should just be a matter of getting a suitable eyepiece (something about 4-5mm) or using a Barlow to get the required magnification. Don't be tempted to push too high - remember that, given typical seeing conditions (down to about 1 arc second), the human eye can resolve all accessible detail at somewhere between x60 and x120. The other things to check are collimation and expectations.The images in that video look like processed "lucky images" to me. To get a visual view like that is a rarity. Seeing conditions make a huge difference (though there are things you can do to minimise these a little). Making sure that the planets are at a high elevation (certainly over 30 degrees) is essential to a good view, though not possible every year (Mars is fine this year though). Other things I would check are that the scope has fully cooled, that you're not observing from a concrete or other radiative surface and that (if possible) you're not looking over buildings. Anything that radiates heat and causes convection will really mess up the view. Stick with the Heritage though - it's a fantastic little scope. Best of luck. Billy.

I'm with Craig. I'd sell it. A 10 inch Dob is quite a big beast if you're living in a city and want to travel to a darker site, and you seem to be happy with the ED72. Sure, a time may come in future when a larger scope makes sense, but that's not now. You might in future consider something like the Heritage Dobs (great scopes - ironically given the advice I'm giving I regret selling mine) on a simple alt az mount (portable, usable from a balcony, but decent light grasp) but for now I'd just stick with the frac. The best scope is the one you use. Billy.

I'd tend to agree with Ricochet. Personally, if your budget is under, say, £40, I'd recommend Plossls as by far the best option. While the field isn't wider than the stock eyepieces, optically they are pretty good. That includes the Skywatcher ones, which are pretty cheap. The only thing I'd add is that a 4mm Plossl is not a particularly comfortable eyepiece to use - eye relief is pretty tight even without glasses. I have one (a Celestron Omni) and quite like it, but it takes getting used to. With that in mind, something like a 32mm, a 9mm and a decent Barlow lens (the Celestron Omni is good for the money), while it will set you back a little more, would be a pretty good set of eyepieces. Might be worth checking out what they have on the Astroboot website - they often have Plossls on there at good prices. Best of luck with whatever you go for. Billy.

From the BBC website (science pages): "Skywatchers have been treated to the first full moon of 2020 - known as a "wolf moon" - at the same time as a lunar eclipse." 🤔

Good choice. My final setup for grab and go with that scope (which I still regret selling) was the OTA on an AZ4. Portable and absolutely rock solid. Another option is buy a cheap second hand set of tripod legs from somewhere like AstroBoot and just bolt a sheet of plywood on top to make a collapsible plinth for the Dob base. Works well and should only set you back about 30 quid.

The heritage is actually easier to transport - it can be carried in one hand, but you're right about wanting something to put it on. Something like a 3 legged stool would do the job okay though and would not be too much more to carry.

I'd agree with banjaxed. While I don't think equatorial mounts are all that hard to get your head around, the lighter models are often not great. The EQ2 may not be all that stable. I also think the EQ scope you're looking at may have a spherical mirror - not the end of the world, but not as good optically as the Heritage, which is a great scope. What is it about your site that makes you think it may not be suitable?

Have you considered making your own dew heater? I have major issues with dew on the secondary, but loop of resistors drawing around 2 watts, wrapped in shrink tube and attached to the back of the mirror with electrical tape, solved the problem. Going the DIY route also let me use finer wire, so there is no real impact on the image. I imagine something similar could work for the primary? Billy.

Hmmmm, point taken - that's nice! Makes me wonder if I've got something else wrong with my setup. I seem to be able to go both sides of focus, so it's not that, but have bloated stars in luminance and in blue. We're talking really bad here, like a blue fuzzy ring around each star. Removing it in processing leaves the stars looking almost white. I fitted an additional Astromimic UV/IR cut filter, a bit more aggressive than the stock filters. That cleans it up quite a bit - but now I seem to have the focus issue you mention. Only way to get focus is to put the flattener way too close to the chip. Wonder if it's just a QC issue. Billy.

With an unmodded Nikon DSLR you should be fine with the 72ED, and it'd be a good match for the mount in terms of size. It struggles badly with RGB filters on a mono camera (below about 420nm it just doesn't focus), but the DSLR will not suffer excessive chromatic aberration. On the other question, it depends what lenses you have. With an 0.85 focal reducer/flattener you will get 357mm at about f4.9. Having used and compared a budget (c. £80) Sigma 70-300mm zoom at f5.6, my money would be on the Sigma. Yes, the zoom bit and the less than friendly manual focusser are a pain, but optically it's clearly better. Economies of scale - can't beat em! Billy.

Interesting, and makes sense. I've tended to the exact opposite (pointing up) but down does seem much more stable thinking about it. That might even work with the guidescope setup, as it would be opposite to the guide. I'm really tempted by an OAG though. Do you use one with that DSLR? If so it should cover my chip no problem. Billy.

Hi all: I've struggled a bit with getting a guidescope to work well with my 130 PDS/ HEQ5 setup. I've used three arrangements (all with a 120m as the guide camera). 1) QHY 30mm f4 guidescope, mounted in the finder shoe. Works well, but is a little short so pixel scale / performance could be better. Probably the best setup so far. 2) Skywatcher 50mm ED in the findershoe. Impossible to balance the scope in DEC with this setup - massively front heavy. I suppose I could put a counterweight of some sort at the back. 3) Skywatcher dovetail bar on top of the tube rings with an ADM clamp and the 50mm guider mounted on that. Worst setup by far - just terrible. First, it flexes. Second, the guidescope points straight at the camera unless I rotate the scopein the tube rings so it is out of the way. The scope is now out of balance in DEC (put it in parked position and loosen the clutch and it will move in the direction of the camera). Of these, option 1 is certainly bearable, and one improvement might be to try a guide camera with smaller pixels (maybe the ASI290MM). The other option I was considering was using an OAG. It would probably be the lightest and tidiest option, and it's cheaper. Does anyone out there have any experience with this combination? My main concern is with the illuminated field of the PDS. Will it be possible to illuminate the guide camera without having the prism protrude into the main imaging area? Thoughts and experiences much appreciated! Billy.

My 2p worth - I'd probably go for the 102. As you've said, it's a very compact instrument, light and portable, and still quite capable. More aperture is always good, but it is at the cost of bulk (not that the 127 is exactly huge, but the planned mount is lightweight). On quality, from experience with the 102 and the 150 Maks, Skywatcher can say what they like but mechanically and optically these two scopes are really very similar. There is not some kind of quantum leap in quality once you go above 102mm, just more light grasp (and the ability to use a 2 inch diagonal on the larger models). Optically, I'd say both are decent scopes, but not great - an f12 or f13 Gregory Mak is fast for that design - it will suffer residual spherical aberration, and it is obvious on both the 102 and 150 SkyMax at higher magnifications (c. x200). Neither will outperform a half decent Newt (including on planets or double stars) but there is not much of a loss and the ergonomics of these little scopes are fantastic. The slightly slower f ratio on the 102mm might actually play in its favour. I have not checked the baffle tubes on these scopes but have never felt the need to, as I've never had an issue with stray light. That said, I have (like kappy-kat) heard good things about the advantages of flocking the baffle tube, and my one look through a C90 with internal flocking was very impressive, so maybe there is room for improvement there. Vignetting should not be an issue with a small chip. At prime focus both scopes cover a whole Nikon DX (15.8 x 23.6 mm) chip. Light fall off towards the edges is easily corrected with flats. Cheers, Billy.

I think this sounds like a great setup - probably the most common "beginner" astrophotography setup there is these days, and for good reason. The other option (maybe a little more demanding, but with more light grasp, tighter stars and actually less expensive) is the 130 P-DS. To be honest, there's not much in it, and the 80mm ED is by all accounts a keeper. It involves a lot less fiddling around in the dark than a Newt. On the 72ED, I have one and have to say I'm retiring it as an imaging scope. The thing can't focus blue light. It's fine with an unmodded DSLR but on a mono rig the levels of CA are totally unacceptable. Add that to focus slop and a lack of in focus and to me that scope is just a dead end for imaging. That said, I may have a bad one, but I've not been at all impressed. Billy.

Hi Paul. I have the 300mm version of this (bought secondhand from Mr niall) and have been very pleased with it. I'd answer your questions as follows (as always, YMMV). Setup time for me is about 5 mins. I take the scope out in two pieces, put the tube on the mount and that's it. It can be taken out in one, but its heavy and better as a 2 person lift. You'd want to allow another 5-10 minutes for collimation, but do this after cool down. Cooling time will depend on what you want to observe. For planetary or double stars (you have a 120ED, so the use cases where the Newt would give any advantage are limited) you'd want to leave it a good hour, but for use at the lowest powers on fuzzies or wide-ish field half that would be fine - there's nothing stopping you using it right away, but this isn't really a "quick peek" or a grab and go instrument anyway. Portability. Pretty bad unless you have a decent sized car and don't plan on moving the scope far from the car. Though a trolley (or observing partner) could make this easier. I never move the thing more than about 20 metres from where it lives in the conservatory, nor would I relish doing so. It barely fits in my Toyota Yaris, but a larger car would handle it okay. Overall quality. Good - in fact really good. With an ES 34mm ep stars are pinpoint over about the central 2/3 - the rest shows moderate coma consistent with a 12 inch parabolic mirror; this could be cleaned up with a coma corrector (or you could put what you're viewing in the centre of the field!). Seems to cope with higher mags well, though with the low position of the planets I've not had occasion to push it. Overall, I've been surprised by just how good the scope is optically. Mechanically I've no quibbles either. The focuser is okay, provided you don't mind single speed, and everything is rigid enough. You'll need to collimate the primary each time (no getting round that with a 12' Newt) but the secondary is stable even given the flex tube set up. Overall, I'm very pleased with mine. Hope this is a help. Billy.

Hi all. I'm trying to get my head around this, in the context of stellar physics, and how stars emit both thermal and line radiation. Most of the books I've read seem to cover electron energy level transitions and then talk about thermal energy and black body radiation as if there is no issue to explain as to how one turns into the other. I get the idea of electron energy level transitions, and (to some extent) of collisional line broadening, but I'm struggling to get my head round how these quantum energy state transitions relate to the translational (kinetic) energy necessary to raise the temperature of a gas. Presumably this has to happen or the gas in stars would not get hot. I've seen an explanation on physics stack exchange that suggests that, with the electrons in a higher state, interactions with other molecules become more likely and that kinetic energy can be passed on that way. But what happens in this process - does the electron de-excite without emitting a photon? If not, where does the energy that is passed on come from? And are photons emitted by atoms in other ways (e.g. does the translational acceleration of the atoms release photons, in a way similar to braking radiation)? Also, are there other ways a photon can heat an atom or a molecule? The same stack exchange thread has a post that suggests that radiation cannot directly heat a gas molecule. I could see (from the above discussion of energy levels) that such a mechanism might not be necessary, but what about cases like co2, where infrared imparts energy to an oscillating dipole? This doesn't seem to involve energy level transitions at all. Presumably, for that matter, neither does transmittion of photons through the at least the inner part of the radiative zones of stars, as it's presumably all plasma at those temperatures. Struggling a bit with this one. Any help (or suggestion for not-to-advanced reading) much appreciated. Thanks, Billy.

I don't use automatic platesolving that often, but when I have I've used the built in functionality of AstroArt. Overall I've found that to work reasonably well, though Astrotortilla looks to be more powerful. You can also set up Astrometry.net to run locally, though I have not had any joy with that. Billy.

Great post Dave - many thanks. I've been meaning to have another go at this with the ASI1600 but one thing that has been bugging me atmospheric correction. Do you have a view on how wide a field you can get away with in comparative photometry without doing corrections? I've seen some sites that suggest half a degree, but trying to find variables with decent range of comparison stars in a half degree field has proven tricky. My own attempted workings would seem to suggest that, for anything above 45 degrees, a field of two degrees would probably be okay, as the error would be only a few hundredths of a magnitude, but I could be wrong and have not seen this anywhere else. Thoughts appreciated. Billy.

I'm with alacant on this. The cheapest dedicated astro camera I could find out there with a half decent sensor size(still smaller) was the ASI1600, which was about £1200 (maybe a bit cheaper now). That's by no means a bad deal (you get a lot of camera for the money) but still quite a bit more than the DSLR. Add to that the greater flexibility (are you totally sure you'll never use it for anything else) and I still reckon it's the best way to start out. Bear in mind also that you don't need to mod it, though you might want to. Clusters, galaxies and a lot of nebulae don't really need it - depends how much you want to image the fainter Ha emission nebulae. Billy.

I've struggled with the same issues. I bought a collar type dew srtip from 365 Astronomy (wraps around the secondary stalk) but it tended to change the profile of the secondary mirror (which affects star shapes in images). I emailed Altair Astro to see if they have something that would do the trick (the ones on their site are too big) but that petered out. In the end I've gone for the DIY option, with a loop of 4 x 24 ohm resistors that is taped to the back of the secondary mirror. In testing it runs a bit hot, but I'll make a plug to connect it to the dew controller that I use for everything else and vary the voltage appropriately. Othr advantage is that can use thinner wire than commercial dew heaters, which won't unduly increase the profile of the secondary strut that I run the wire across. Not a lot of work and it should do the job nicely. Billy.

Yep - f5.8 so should be right in the sweet spot. I reckon it's usable with a bit more tweaking; it's proving a bit of a painful experience. On an altogether more positive note, I've just tested the Skywatcher flattener at 58mm and it's a massive improvement. Not perfect, but much closer. Billy.

I've recently purchased the Skywatcher reducer and I'm getting pretty bad curvature with 55mm backfocus. Thinking that it needs more space myself, so interesting to hear that 57-58mm range seems to work for some people. I can see a lot more fiddling in store before I get this right. I've been trying with the OVL flattener and have not been able to get an acceptable result - it performs oddly, with curvature bad at 53mm, getting worse at 55mm and then getting better at 58mm. Best performance I have got from it was with 38mm of t-extension tubes (so about 64.5mm back focus taking the filter wheel into account). That was getting there but there was still a little curvature, and the focuser does not rack in any further to allow additional spacers. Test shot attached is the best I have managed to date; could use people's views on that - I don't hink it's catastrophic but should I be aiming for better? Billy.