ollypenrice

Why not calibrate close to the pole? Just think of the size of the circle described by a star up there during one sidereal day: it's tiny, meaning the star hardly moves in a day, let alone in the time taken to calibrate. That means that the calibration can obtain very little information about the tracking error since it is compressed onto a tiny circle. If you calibrate near the equator that circle opens up into what is approaching a straight line from the mount's point of view so it has much better information about the effects of tracking error. If you wanted to see if the stars appear to move with naked eye and chose Polaris, you might think they didn't. If you chose Betelgeuse you'd soon see that they did. Olly

Basically it turned out that there were different types of Cepheid. In the usual rendition of the story, this discovery is credited to Walter Baader and dates from the 1940s. (Given his many collaborations with Fritz Zwicky and the bad blood which grew up between them, I'll say clearly that I don't know whether this particular priority is disputed or not.) I've certainly read that Hubble was less than pleased to find his distance estimate doubled but he did not dispute the findings so far as I know. Curiously, perhaps, Hubble never adopted the term 'Andromeda galaxy' himself, sticking with 'nebula' to the end. Nor did he entirely accept that what he had discovered in the redshift-distance correlation was the expansion of the universe. He was confident in the measurements themselves but remained agnostic as to their cause. Olly

I think lots of discussion of piers is over complicated. For around ten years one of my Mesu 200 mounts has been standing on a pretty light weight Mesu steel pier. It has a large diameter main tube made of thin steel and then, at the bottom, has tripod feet which are just threaded bolts with plastic pads at the bottom. I drilled the concrete so I could trap these feet onto the ground with strips of wood just to stop an accidental kick from moving the pier. There is nothing massive or 'industrial' about this setup but it has never been touched or adjusted in all this time. Imaging with dual TEC 140 or dual Tak 106 or 14 inch ODK between 0.6"PP and 3.5"PP, it has never dropped a single sub exposure to tracking error. Seriously. So if I were you, vlaiv, I would just demolish the failed concrete pier and put a steel one in its place. It would just need three widely spaced feet to miss the hole where the failed one was. (I also use a really horrible steel pier for my other Mesu mount. 😁 It's one I welded up quickly to carry a cheap visual refractor. When I had the chance to buy a second Mesu without a pier I quickly cut the top of this pier off and welded up a load of steel scrap I had lying around to mount the Mesu on it. My intention was to make a proper one later. However, the horrible pier worked fine so... I still use it!) I believe many pier designs are solutions looking for a problem. Olly

This is the price I paid for a TEC 140 indistinguishable from new. Olly

I think that anyone who had not read the book but had read your reply might get the impression that the biography was openly hostile and disrespectful towards your father. Sincerely, that is not the impression I carried away from it. I'm an amateur reader of astronomy history and have come across the cliché portrayal of Fritz Zwicky plenty of times. I've never been persuaded by this portrayal because it smelled of the easy and oft-repeated joke or even of the cheap joke. For me the book demolished all that and presented a man whom I would love to have met. Perhaps it didn't go far enough in doing so? You're in a far better position to know that than most people. As for inaccuracies, I'm afraid that I'm not in a position to know. However, I don't like to be misled and am happy to read your corrections respectfully. I posted an endorsement of the book precisely because I thought it re-positioned Fritz Zwicky into more favourable light and I'm both sorry and upset to find that my endorsement might give you the opposite impression. I regard him as one of the great astronomers of his century - and it was a century with many outstanding astronomers. Best wishes, Olly Penrice.

An observatory. The first was a roll-off 'sentry box' which is still going strong,18 years later, over a visual-only scope. Observatories seem to be good breeders because there are now six of them, though not all mine. To walk out, roll off a roof and get going jusslikethat is a totally different experience. Other favourites are Telards, Mesu mounts and, certainly, SGL. It's the best astrosoc in the world. Olly

First for me too. The second, as barbula says above, is tinged with green and perhaps has more noise. Oly

You're not trying to save it at 16 bit? I'm pretty useless on these IT details I'm afraid. Regarding M33 colour, it's often presented with very dominant blues in the spiral but I think an honest processing simply gives a low colour intensity pretty well everywhere on M33. I went back to mine after looking at the Hubble Team's rendition along with a conversation about galaxy colour with Vlaiv and dropped the colour significantly, particularly in blue.

I suspect that too much light brightens star colour towards white. The secret of your ED80 may, in part, be its small aperture. I certainly think smaller aperture helps star colour. Olly

I do big stars in Photoshop like this: Make a copy layer. Create a soft-edged eraser the size of the large halo and apply it at 100% over the halo and star on the top layer. This has no visible effect because the layers are identical. Keep the top layer visible, make the bottom layer active and open Curves. Put a marker on the curve just where the background sky or nebulosity is free from any of the bloat. Just alt-click on the background closest to the bloat. Put a fixing point below the first marker. Now grab the curve just above the background marker and pull it down. You can see the result through the 'hole' in the top layer. by playing with the curve and maybe adjusting the background marker you can reduce the offending star while looking where it's at in real time. I call this 'reverse processing' the star. Often this single Curve adjustment will work for more than one star in an image, in which case erase the top layer over the stars you want to reduce. You can adjust the saturation in the bottom layer while you're at it. Olly

All those CCD images posted 'out there' still exist. Have they all been demoted by new and better CMOS images? It's news to me if they have... Olly

I'd give the UV cut filter a try. I have both an FSQ106N (the old fluorite version) and a TEC 140 with TEC flattener. With the flattener (but not without it) the TEC produces tighter blue stars than the Tak and, indeed, tighter stars in general, but it has more aperture so it should. Some specific processing is to be expected in the case of all bright stars, I think. Olly

It would be slight movement via warpage that I'd worry about with wood,. You don't find this? It certainly looks better than concrete! Olly

I have the good fortune to know Dave and the less good fortune to be Dave to the six remote rigs I host! Honesty compels me to say that I'm getting a bit old for all nighters beside the handsets so I'm now robotic on one rig as well. But (and this is a big 'but') I have Paul doing the IT side of things! 😁lly

I like handset-controlled mounts... Olly

That would be the best way but it involves taking multiple images and stacking them. Exposures need to be long so you need to track accurately. It's a business... 😁lly

Galaxies are normally imaged at prime focus, so without an eyepiece. With an eyepiece the galaxy's projected image will be too large to fit on you chip. Olly

Two things stand out, firstly the dominant greens and secondly the excessive stretch. Inevitably a hard stretch of middle and high brightnesses reduces their colour intensity. I would go much easier on the stretch and preserve more colour and more contrast in the spiral structure. I always find that a careful DBE (not too many markers, even spacing over the chip, none close to the galaxy) gets my background sky neutral. However, a dose of SCNR green is often needed to subdue the greens higher up the range. I would not expect Ha to solve you red issue (if there is one. M33 is not very red.) What it will do is find interesting structiures in isolated HII regions in the arms. After DBE and SCNR green I prefer to go into Photshop rather than torture myself in PI. Olly Edit: Plate solving may be a minor convenience but Tom O'Donoghue and I did a 36 panel mosaic over 4 years without it. No big deal.

This is quite literally true. When I've had my F/W issues (before finding an alternative software to use when they won't connect) I would walk away and, in the morning, they would work. This was well and good when I was just imaging for myself but was not a workable solution with guests. Olly

Firstly I'll risk asking you why you used a focal reducer on this target? To speed up capture? It doesn't do that because it doesn't increase the aperture. Have a look at 'The F ratio myth' on Google. (On the other hand, maybe it's also a flattener which you do need?) The reducer is introducing extra glass into the train with an attendant risk of reflections which may or may not have a bearing on your bright centre. The reducer puts the available light onto fewer pixels but you can do that by software binning. The bright centre is odd because ABE, used on galaxies, usually has the opposite effect. It tends to sample the sky too close to the galaxy and pick up its outer glow which it then over-corrects into a dark region round the galaxy. I prefer DBE on galaxies and use as few markers as possible, certainly keeping well away from the galaxy. What's rather lacking in this image is colour. This is a very colourful galaxy and we also see little star colour. I'm sure it will be there in the data. I extract it primarily by using two Photoshop techniques, both of which avoid the saturation tool like the plague. The first is go into LAB colour mode and greatly increase the contrast in the a and b channels. The second is to create two copy layers, set the blend mode to Soft Light, flatten the top layer onto the middle one, convert the blend mode to Colour and flatten that. I'm sure the mono version of your camera would be a little faster because the luminance time is capturing all colours at once per pixel, but CMOS OSC cameras seem to be very efficient, far better than CCD OSC. Olly

Here here. Do nothing via computers that can be done without them. By far and away the most reliable AP setups based here (there are seven in all) involve handset-controlled mounts and manual focus plus ST4 guiding. The PC is limited to camera and F/W control and direct communication between guide camera, PHD and the mounts. The only thing I don't expect to work every time without fail are the filterwheels, which sometimes are not recognized. I have an alternative software for them if they refuse to connect quickly but would be happy to use a manual wheel if such were available. (They don't seem to be made in 2 inch.) Anyway, even the F/W issue is rare. As you say, the overwhelming majority of issues are PC and USB-derived. Olly PS Next year I hope to be able to congratulate my original Mesu mount on ten years without dropping a sub to tracking error.

I like AstroArt. I've used it for stacking and calibrating for over a decade and find it intuitive and fast. (The 'fast' bit really matters with CMOS cameras and their huge number of short subs.) It gives great results with an ASI2600C like yours, though in our case there is always a colour gradient which follows the camera, not the sky. It's a red-green imbalance across the chip which is easily dealt with using PI's ABE. Olly

A permanent observatory increases the good nights by a staggering margin... Olly

Death by drowning. Olly

The original wisdom was that PHD worked best with a soft focus, this coming from Craig Stark himself. However, I've read since then that the software now prefers a sharp focus. I think it's all to do with how the notional centroid of the star is being calculated. As ever, I'd give it a try and report back. Olly