ollypenrice

R ,U, indeed? Y would that B? Oh gawd, I'm turning into a teenage texter. Of course, to do it properly I have to be driving a car at the same time... lly

I suppose an English speaker shouldn't growl too loudly since we have a word with six consecutive consonants.* At the other end of the scale I live near a French village called Eyguians which I consider to be an example of irritable vowel syndrome. Olly *Kinghtsbridge. We're used to it but imagine a rational being looking at ghtsbr in the middle of the word and preferring Svbony any day.

Heh heh, it makes little difference to me! Svbony Sbvony, Schvbony, Schbvony, what's the difference? 😁lly

'Sbvony.' OK, I'll ask: how do you pronounce this??? lly

Something else to consider: when I looked at GalaxyGael's lovely Gamma Cass rendition, I was reminded that you can get a certain 'look' from the modern CMOS OSC cameras. Very natural. It doesn't have to be about going insanely deep by adding NB data (though you can with Tri band, we know.) Tom O'Donoghue and I went depth-mad on this region and produced the picture below but, quite honestly, I do love the one posted above for different reasons. We don't all want to be doing the same things or it would be repetitive.

Yes, this idea of 'Documenting as you learn' is very prevalent at the moment. It baffles me entirely but, hey-ho. Olly

I only use plate solving on one setup, the other two having non-ASCOM compliant mounts, so it really isn't a necessity. GoTo, look at a test image, frame up. It's easy. I sometimes can't focus my Astrodon 3nm Ha filter in my target either so, as you did, I just go to a bright star to focus. Once you have your Ha, I'd suggest being careful over what you do with it. Using it as luminance is a bad idea in principle. It means you light your whole image in the light of deep red. Why would you do that? It will subdue any blue and green signal for one thing and it's entirely false for another. OK, on purely emission targets I'll use up to 15% Ha as luminance just to tighten up the structures in the gas but, if you use more than that, you'll turn the image pink and create blue stellar halos. A nice way to use it is to add it to red in Photoshop's blend mode lighten. That way it will brighten the red channel only where the Ha is brighter than the red. It will leave the stars and the background alone. Olly Edit: I had a look at the Trevor Jones HaRGB tutorial and thought it was floundering. He adds the Ha to the red in blend mode normal at a random percentage like 35% or whatever appeals. He then points out that this reduces the size of the stars in red, which is why you shouldn't do it! For the same reason, you cannot just replace the red with the Ha. It also means that the contribution of your best emission detail is applied at 35% of red. What happens to the other 65%? It's lost. I stopped there but, judging by his final image, he also used Ha as luminance with the consequences I mentioned above. For better tutorials look at for Adam Block, Warren Keller, Rob Gendler, R Jay GaBany and others.

Thanks, yes, it has a certain glorious logic to it! I need to try it on old data, as you suggest. Certainly L-(R+G) ought to equal B. Olly

Tell us more!!! 😁 Olly

With 190 subs from an inherently low noise camera I don't see dithering being very significant. Its importance is proportional to noise so, for a guess, I'd say you probably wouldn't notice much difference. Anyway, running unguided you'll be getting a bit of natural dither anyway. Your stars also look tight so, with these short subs (at no cost in terms of read noise) guiding wouldn't make the difference it usually does, either. It's an excellent image and would go deeper with more integration. For such a simple approach it's more than excellent and nicely processed. I might be tempted to throw a slight blur into the stars set aganist the right hand part of the nebula since they are rather hard-edged. Alternatively a small clone stamp set to 'Lighten' might let you grab a bit of adjacent nebulosity to pop over the stars. It will only affect any dark ring around them. Olly

You're assuming that non-parfocality comes from filters but I don't think it does. I think it comes from optics. If you don't refocus between filters with mono (and I usually don't) you are in the same focus situation as with OSC where you can't focus per colour. You need to refocus regularly anyway, so it's no big deal. Flats: I use luminance flats for everything, 95% of the time. But, with the demise of CCD, I like OSC! Olly

I continue to insist that, contrary to popular belief, mono is faster because it can capture luminance (all three colours at once) which OSC cannot do. If this is not correct, please tell me why. The LRGB system was invented to save time. However, it doesn't save frustration if you're deprived by cloud of a critical filter's subs. As Dave says, mono is better for narrowband, better as in faster and having higher resolution, which makes it better at beating the moon and other severe LP. However, the new CMOS OSC cameras have changed my mind about the usefulness of OSC. They are far better than OSC CCDs, of which I've had two and sold both. I'm now using an ASI 2600, which I certainly won't be selling, a) because it isn't mine and b) because it is downright excellent! The arrival of dual and tri-band filters for OSC also opens up a new world of exciting possibilities. Conclusion: personally I would seriously consider OSC CMOS but not OSC CCD. Olly Edit. Don't be fooled by the parfocality debate regarding filters. Most of them are parfocal, the non parfocality coming from the optics. These remain non-parfocal when you're using an OSC but you can't do anything about it. You have to choose the compromise focus.

The European importer is Optique Underlinden. https://www.telescopes-et-accessoires.fr/ Olly

I didn't, Rodd. I teamed up with one of our gite guests and provided a mount and a location in our robotic shed. Paul provided the scope and camera. All this is very recent but I do like the setup. Olly

It might be time to try Russ Croman's StarXterminator which many say beats Starnet. It's on my list of jobs to do. Olly

I think premium refractors may go for slightly more than the 60% 'rule of thumb,' but it remains a minimum price, at least. Being without a 4 inch refractor at the meoment I can vouch for the claim that everybody should have one! lly

I don't know of anybody who does a set of short exposures for stellar cores. I've certainly never done so, but it doesn't stop us from getting strong star colour. Indeed, it is very exceptional for me to do short exposures for any part of an image. The obvious exception is M42 where it's necessary for the Trapezium region. Like many others I used sets of about 10 seconds, 50 seconds and then 15 minutes with a CCD, layer masked together in Photoshop. Exceptionally I may use my RGB as a set of shorter exposures for galaxy cores since the RGB has less signal and this doesn't apply in your case, but my point is that blending long and short exposures is an imaging rarity. It's possible to pull star colour from the fainter outer edge into the core. The easy way is to use Noel's Actions, Increase Star Colour, (now known as Pro Digital Astronomy Tools, I think.) Alternatively you can make a copy layer, blur the bottom layer, make a star selection (instructions available in MartinB's tutorial on here in the Imaging Techniques section) and erase a feathered selection of the stellar cores from the top layer. Increasingly popular is the use of Starnet++ or Star Xterminator to de-star a stretched image before placing the linear image on top in Blend Mode Lighten. You can then give it a gentle stretch and the stars will appear with less over exposure and more colour (which can be colour-saturated without affecting the rest of the image.) Olly

Although fine focus isn't critical for guiding, you do want to get it reasonably close. It sounds as if you need an extender, and you don't want the camera inserted by the skin of its teeth because that risks making it move a bit in the guide scope. One common 'extender' which people sometimes have lying about is an old or low grade Barlow. If you have one, simply discard the lens and use the body as an extender. Olly

Interesting. Does anybody know what the equivalent Skywatcher mount is? Or does the CGX lie between the EQ6 and the EQ8? I'm not up on Celestron mounts. Olly

I wouldn't run G out of focus. Rather, just increase the saturation in R and B a little to compensate. Olly

Excellent! Olly

I don't think it's a good idea to use a dewshiled higher than the back of the camera on this scope. At least, it isn't necessary, since the camera's heat and fanning of the air seems to kill dew easily. You need the camera to be able to vent fully, too, so I made mine end at the back of the camera. Olly

Great idea. It's odd that purpose built bins-with-filter-holders aren't readily available. Olly PS Love the dog!

The later stages of this post make better reading than the first because, in the early days, Avalon had a brilliant service reputation and the engineering of the mounts is lovely. I replaced mine only because a second hand Mesu became available and I recently bought a well-used Avalon for a new installation as well. I'll have to look at the belts on my used one! To my mind the Avalon would be an obvious choice if the price new were lower but, as it is, it is far too close to the Mesu, which easily beats it on payload, precision and stiffness. Of course, the Mesu is also a lot bigger to move about. For its size I still like the Avalon, though, and agree with David that the guide trace doesn't seem to do justice to the real performance which really is very good. Olly

Like vlaiv, I would go for a rack and pinion. I host a number of robotic scopes and find that the R and P focusers never give any bother but the Crayfords regularly do so, including reputable ones like Baader and Moonlite. When you're counting steps or supporting a heavy weight against gravity you want more than friction to keep things consistent. (Yes, I use friction drive mounts but they are in balance, not being tested against significant resistance.) Why it seems to be so hard to make a focuser is something of a mystery. Olly