ollypenrice

I don't like the idea of sand escaping near optical surfaces so I'd go for sawdust myself. Olly

Don't know yet, Tony. I'm trying to find a manual for dismantling it. It won't be much - just a broken wire or something. It's not the motherboard for which I have a spare. Olly

Each to their own, but I wouldn't touch a Hyperstar with a ten foot pole. If you read enough owner accounts, and look at their results, a pattern emerges: a few people get decent results, most don't. I agree absolutely with your earlier point, though, that a RASA should be bought only from a very reputable dealer with good returns policy. Nothing like enough FL. The RASA is a widefield instrument, pure and simple. Olly

I love the RASA 8 but it isn't perfect. I'd still refuse to swap it for anything else. Firstly you need to match a camera to it. A DSLR is too big to fit in front of the corrector without obscuring it. We use a ZWO ASI 2600MC Pro, which has a fairly large chip. We don't get perfect stars to the edge but can 'fix' them in post processing. A smaller chip would reduce this problem at a cost in terms of field of view. Our image scale is about 1.8 arcseconds per pixel, which is not very demanding in terms of mount/autoguiding tracking accuracy. You need an RMS of about half that, so 0.9" RMS. When our more upmarket Avalon Linear packed up recently I chucked a very old EQ6 under it and and, quite honestly, there is no loss of quality. You might also want to check out the issue of tilt... Olly

I do know that there are paints made with pigments and cheaper paints made with dyes. Those made with dyes are not absorbent of all wavelengths, so are reflective just outside the visible spectrum. Heat proof paints for stoves, barbecues, etc., use pigments and are not reflective in this way. This came up as a topic a few years ago regarding the shooting of flat field frames in astrophotography. How relevant this will be in visual observing, I don't know but the blacker (the less reflective) the better has to be true. My wife is a professional painter and, of course, uses top quality pigment-based paints. The density and intensity of their colour is mesmerizing. I found this fascinating and did a series of macro photos of her palette in use. Make no mistake, there is paint and there is paint. Olly

All orifices invaded at the same moment! lly

I suspect that it's because they were massively advertised at one time, and over-sold to boot. The manufacturers pushed them for deep sky imaging when, in reality, they were pretty poor for this and people wanting to go into imaging sold them and went for alternatives. The arrival of the tiny-pixel DS camera has made their long focal lengths even less attractive. I don't think they give much trouble. I've had four and all have been perfectly reliable. The spherical primary is easy to manufacture and collimation is simple. The long FL is restrictive but they are pretty nice as long as this is accepted. In a nutshell I just think they are too numerous and not suited to DS imaging. Olly

Can't we just dump this thread and get straight to the heart of the matter - polygamy!!! lly

SCTs have a low resale value at the best of times, compared with most other types of scope. Although this probably won't affect the view, it will massively affect the resale value. I don't know what a used C5 goes for these days but, whatever it is, I would not pay more than a third of that price for this one. Olly

As usual, capture and pre-processing by Paul Kummer with my post processing. RASA 8/EQ6/ZWO2600MC Pro, based here at Les Granges. 131 subs of 3 mins, so about 6.5 hours. The Fireworks galaxy has been gently enhanced by the blending of my existing TEC 140 rendition. Processing: a little Pixinsight, Registar for the high res blending and mostly Photoshop. Fullsize is here: https://ollypenrice.smugmug.com/Other/Galaxies/i-CcqZKsR/A Olly

If you were to ask me about the cosmetic condition of any of my telescopes, I'm happy to say that I can give an absolutely precise answer in every case, without leaving my desk. The answer is, 'Dunno., I don't look at them, I look through them.' As for this, ...vomitworthy. How embarrasing is that? Olly

I doubt you'll beat that. Mods, might this get a sticky since it would be so helpful to Tak owners? Olly

You could ask for an American member of SGL to buy the paint for you, perhaps, and send it on. Olly

The bloat is also quite magenta, so green is low - for whatever reason. Olly

I've had 8, 10 and 14 inch SCTs and still have the latter two. They do need dewsheilds but they need them a lot more than a refractor needs them! Whatever you use to combat dew, on a dewy night an SCT will get shut down before a refractor. Long before - and I live in the south of France, not Norway. Camping mat makes brilliant dewsheild material, by the way. Olly

I started to have a play with these data but ran into a problem with ABE creating contour lines. I don't have the time to try to sort this out because a robotic shed issue is all-consuming at the moment. However, I saw no reason for the background to become blotchy and I really saw no vast amount of noise to deal with. Is this because I may be stretching differently? I've seen lots of stretching videos where the imager keeps on stretching and then pulling in the black point, over and over. This seems crazy to me. Once the darkest part of your image has reached the brightness value that you want it to have, why stretch it any further? Why not pin it in Curves and stretch only above that? Why pull your dark signal up above the noise floor? In the case of this image, there is dark, sooty nebulosity well below the brightness of the more transparent background sky so, once this sooty stuff was up around a Value of 17 in Photoshop, I pinned it and stretched only above it. It all looked pretty good to me. I don't go for any of the bought-in, sliced cheese stretches with began with DDP, years ago. I'll use a standard log stretch till the darkest signal is where it needs to be then I'll only stretch above that. Olly

I've had that as well! Grrr. Olly

Where is the artificial intelligence in all this? It is just a regurgitation of numbers already out in the public domain, with one vitally important number replaced by the adjectives 'average' and 'good.' Since these are the numbers which define everything that the system will produce, what are they and where are they? I would rate this answer average to poor. lly

Lovely stuff, Maurice. I see that people are shaking off their sleep in Lagrand and putting the coffee on! Olly

I'd have to ask what criteria he uses to define 'reliably get 30-second exposures with his DSLR on his old driven equatorial mount.' My fear is that, in upgrading to a better camera, he would be wanting to upgrade his images and would, very quickly, find himself re-defining what he found to be acceptable tracking. 30 seconds, unguided, at well below an arcsecond per pixel? Science doesn't work by proving negatives but, no, I would need a lot of persuading. Olly

Yes, I understand this argument but the OP has wisely started out with binocular observing already. The problem with starter scopes, which is common to starter products in other arenas, is that the buyer risks finding, 'Yes, I like this,' and will almost immediately want to take the next step. When they do, the starter setup will be obsolete for them. On the other hand, many seasoned observers have a 4 inch (ish) refractor along with all sorts of other, more extravagent, instruments and they keep it because it remains a particularly useful tool. Personally, I have given up on 'starter products' because I invariably find that they have a very short role in my activities. This may just be me, of course. Olly

For me a small telescope with a very long focal length misses out on what a small telescope can do and a big one can't, which is deliver a very wide FOV. That's why I'd prefer to avoid Maks and SCTs. I also think that, in Norway, you will also want something which does not attract dew. SCTs and Maks are bad for this. I do like the look of this, mentioned above by Vlaiv. https://www.firstlightoptics.com/stellamira-telescopes/stellamira-110mm-ed-f6-refractor-telescope.html I didn't know about it. Olly

Aperture is important in visual astronomy but inevitably comes at a cost in terms of portability. Bigger is - well - bigger! Robustness is another aspect of real portability. For many, the 4 inch refractor hits their target. This one is an old established favourite. https://www.firstlightoptics.com/ed-pro/skywatcher-evostar-100ed-ds-pro-outfit.html It has a longish focal length for its aperture so isn't going to give as wide a field as a faster 4 inch, but it is very well colour corrected as a result. Being a refractor it is robust and won't require collimation. For visual observing, alt-az is nice and intuitive, does away with polar aligning and needs no counterweights. This would be one option. https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/astro-essentials-alt-azimuth-fork-mount.html On a suitable tripod it would make a kind of budget replica of the Televue 4 inch used by Steve O'Meara to write his classic observing guide to the Messier objects. You'd be on budget for a couple of reasonable eyepieces, too. ( Eyepieces stimulate a kind of mania among astronomers, many of whom have twenty or so. I use two, almost exclusively. Better two good ones than four poorer ones, in my view.) This is a setup you would pull out of the car, place on the ground and get started. A red dot finder would also be good and you'll need star charts but you could print selected regions from a digital planetarium. Olly

Yes, if you have a little backlash in RA, then running slightly east-heavy will leave the driven gear resting against the drive side of the driving gear rather than oscillating across the backlash. It does mean that you need to reverse the imbalance after a meridian flip. There is an equivalent procedure to reduce Dec backlash but which doesn't involve balance weights. You can deliberately polar mis-align the mount slightly then activate only the guide direction which corrects for that. You don't run the guider on the other direction. Trial and error decides which inputs to disable and, again, they need to be reversed after the flip. While I've had reasonable success with both methods, this was only as a stop-gap measure prior to fixing the problem properly. Olly

I like them all. BTW, cropping, of itself, has no effect on resolution. In daytime photography there is a careless tendency to confuse pixel count with resolution but they are not at all the same thing. Olly