ollypenrice

A very nice, natural-looking processing job. Olly

I think you're safe. It's been so wet... Olly

What about relocating your gear to a remote hosting facility? I realize that this would leave your home observatory out of a job but not the rest of your kit. (For transparency, I do some hosting but have no availability. Places in Spain are available, though.) Olly

Don't look at a stretched version of your flat to decide. It tells you very little. What you should do is read off the ADU value of the unstretched flat (ie the linear flat) in the corners and in the middle. I've found that it was perfectly possible to ask flats to correct a 25% drop-off in brightness between centre and corners, so you need to know what your light drop-off is. It may well be that your drop-off is greater than that but, before spending, it would be worth a check. Is there any way in which you might get your filterwheel closer to the chip? You don't have any spacers between F/W and camera? Olly

None of this makes any difference if you adjust your true and final image scale at capture and then processing to what the seeing and guiding can realize. If I went for a flatfield SCT I wouldn't use the reducer, I'd capture in superpixel and/or resample before processing. This would mean I'd get the extra light per pixel onto the target and not onto background sky which I'd later crop out. Olly

The image in the link is mighty impressive. There are reds very close to, and within, the cluster which I think are ERE, Extended Red Emission, rather than Ha. UV illumination of dust produces luminescence in the 500nm to 1000nm range so it will pass through an Ha filter at around 656nm, though I guess in very small quantities. A broadband red filter will pass it far better. However, the reds on the left hand side of your image, between the pincer-like extensions from the cluster, look like Ha pure and simple. Olly

An absolute cracker of an image! The blend was certainly the right way to go - which I would say because I do that all the time. Hat's off for the Ha. The received wisdom is that there isn't any and the received wisdom is clearly wrong. You have the deep satisfaction of having brought something new to a familiar target. As for the rest, stars, background, dust, nebulosity - flawless. Take a bow! Olly

First off, it's a very clean and workmanlike image of M51. Background and stars are excellent and spiral detail is well resolved. It's very good, surely. The faint extensions are there and would show with more data. 5.5 hours has done a good job on the brighter stuff and has caught the blues in the extended tip of the 'bridge of light.' To my eye the colour balance is a tad high in green and more significantly short on red at the brighter end, though the background looks good. I'm not suggesting it's miles out, it's just where I'd be looking if the image were mine. SCTs tend to be very tolerant on reducer-to-chip distance but the true FL does vary considerably. Your variation from the nominal 1260mm is not remarkable and your intention to experiment has to be the right way, I think. While you are tinkering with this, bear in mind that all the arguments favour an OAG with this scope so it might be easier to fit one before agonizing over spacers. Regarding vignetting, I think it's to be expected on this setup. The thing is to measure it. This is easily done on flats. If you measure the centre brightness in ADU you can compare it with the corners. I found that I could live with a 25% fall-off with my Tak 106 rig so, if your uncropped corners were at 75% of centre brightness you should be OK. If your corners were darker than that you could sample the flat on a line from corner to centre and find the point at which it reached 75%. That would indicate your largest workable field. (The reality of galaxy imaging is that you rarely need a large field anyway, at least in my experience.) If I were you I'd be delighted with this as an opening result. Olly

The roof behind the bushes is pretty sharp. So, interestingly, are the fence and some other items in front of the bushes. The obvious conclusion would be that the unsupported branches of the bushes were moving in the breeze... Olly

I'm sure you wanted your list to get shorter rather than longer but there is a conspicuous absentee in the form of the MN190. https://www.firstlightoptics.com/maksutov-newtonian/skywatcher-explorer-190mn-ds-pro-mak-newt-astrograph.html This has both the right FL and an excellent aperture for high res imaging using a modern CMOS camera with small pixels. The faff factor is hard to predict and I've never owned one of these, but I think it would be less than with the RC. (I'll restore the list to its original length by saying that efforts to help one of my customers with an 8 inch RC flagged up a 'Never Again' alert in my mind. We gave up on it.) The MN190 weighs 10kg so I don't know if you could stay within payload with that but I think you might. Why all this talk of reducers? Just make your effective pixels bigger by stacking in superpixel mode and/or resampling downwards before processing. Reducers are best seen as field of view wideners and my experience of imaging at high resolution (about 1"PP, say) is that I ended up cropping almost every image I shot in order to present it at full resolution without the need for click-to-zoom. The last thing I wanted was a wider FOV. (Ironically, the shorter the focal length, the more often I do mosaics with it.) Refractors are certainly the easiest in what is a tricky business at the best of time. I have lots of nice results (I think) from my TEC140 F7 at 0.9"PP but I would shoot about 20 hours per galaxy. The MN190's extra 50mm of aperture would almost halve that exposure time. If you factor in what you will really capture, aperture may outweigh pixel peeping perfection... A big refractor 'plus' used to be the high quality stellar images but, with modern processing, you can get decent stars out of other systems as well. Olly

Coming our way, too. We had a good dump of it last week, though not as bad as in your image. OK, I think that one's nailed it! Olly

Thanks, I think that answers my question. The payload will be very small - a Samyang 135/cooled CMOS camera - so it looks like bolting the AM5 down onto a flat plate should be easy. Olly

Thanks. Sorry, but what I still can't work out is how to attach this mount to a home made pier. If my pier top consisted of a flat steel plate with access from beneath, could the mount be placed securely on that and bolted down onto it by bolts from beneath? Is the bottom of the mount drilled and threaded to receive bolts from below? Drilling the mount top plate is no problem since I do have a large pillar drill. Olly

Hi all, does anyone know what would be needed to fit the AM5 mount to the top of a generic concrete pier like a Todmorden? I can't see what's going on under the bottom of the mount or the standard pier adapters. If I put a flat steel plate on top of the pier, can the ZWO AM5 attach to that? And, if so, would it need access from beneath? Cheers, Olly

These old ellipticals don't have much by way of interesting structure and, since we're looking out of the plane of the Milky Way, there's nothing much in our own galaxy to provide foreground interest. 'The Eyes' galaxies probably provide the most rewarding detail, with their tidal interactions. Paul Kummer and I have it in an 8 inch RASA, so comparable with the Hyperstar. It's a wider field mosaic so it's on the enormous side as an image but here it is. You can do the clicks for the full res if you have the patience. I think the interest in this region lies in cruising the field in search of little surprises like irregulars and little spirals. It will never be attention-grabbing eye candy, so to speak. https://ollypenrice.smugmug.com/Other/Galaxies/i-kTDJC88/A Olly

A famous portrait painter once had a very dissatisfied customer who strongly insisted that the likeness was false. She had a more than averagely asymmetrical face and the artist realized that she was used to a mirrored view of herself, so he altered the painting to a mirrored view and she was satisfied. I'd much rather not have the moon mirrored but put up with it because the rather basic erecting prisms I've tried really clobbered the image resolution. I've never tried a good one. Olly

Nothing wrong with that. René was here, he said, to see it and photograph it, perhaps for the last time. He was in his eighties and had too much LP to see it from his home on the other side of the country. Olly

Lovely shot. I had the pleasure of being host here, for a week, to Dr René Dumont whose doctoral thesis was on the zodiacal light and whose article on the subject is the very last in Moran's Astronomy and Astrophysics Encyclopedia. It was a delight to be enlightened on the subject by a professional astronomer and world authority, especially since he was such a truly nice man. (He and his wife were particularly attached to our affectionate dog and asked after her on subsequent Christmas cards. ) Olly

I hadn't thought of actually venturing down the tube to do this. An input fan on one side and an output on the other would be more comfortable... lly

Have you tried blowing air across the surface of the mirror? There's an argument which says that this is the best way to break the boundary layer. I've never tried it and no longer have a Newt. Olly

That's great, packed with things rarely seen. Paul Kummer and I had fun in this region in broadband. Olly

For an objective measurement I checked the background brightness per channel in two places using the Ps Colour Sampler Tool (eyedropper menu.) I check these values regularly when processing. It gave R40 G30 B19 and R38 G29 B19. A neutral sky would have parity in all channels though personal prefences also apply. However, the numbers do say 'red high and blue low.' Olly

Super project. Your background sky is looking decidedly brown on my monitor so a background calibration might be in order. Olly

Whatever they are (and I can't help with that) they are extremely interesting. I wonder if the circular loop, probably a spherical shell, above SNR G206.9 2.3 is associated with the much larger loop which no doubt continues above the region you've already captured. Keep going! Olly

Nice. Certainly a conversion issue, then. Olly