ollypenrice

Any filter blocks light. That's all they ever do. What the dual band filters provide, like equivalent mono filters, is the isolation of the Ha and OIII structures. I'd be aiming to make a 'host' image in RGB from the unfiltered camera and before applying the more aggressively-stretched filtered data in a lighten-only mode. This is how I work with LRGB + Ha/OIII. Where it wasn't appropriate, say on dusty targets, you could run the second camera unfiltered. Equally, OSC and mono for NB would work but I'd be wary of expecting L on one side and OSC on the other to be productive. I tried it with CCD cameras a good while ago and found that the OSC signal would not support the addition of much luminance. It was not as strong as RGB from a mono in the same time. I found it harder than expected to align two scopes and ended up sourcing the discontinued Cassady T-GAD alignment device (at prodigious expense even second hand!) This would allow you to set the two fields of view up with an overlap in order to shoot two panels of a mosaic simultaneously if you so wished. Olly

Shorter subs would give the cores more colour saturation because the brighter they get, the whiter they get. I'd experiment with some very short ones - 10 to 15 seconds, to see what they give, but the present image is nice. When the stars are bigger their outer parts get nearer to each other and that makes the colour difference show well. It's like observing Albireo slightly out of focus, which many people do to enhance the colour contrast. The background's a bit dark for my taste, though. Purely personal. Olly

I've always used mono+mono but, these days, I'd be very tempted by OSC unfiltered + OSC with dual or tri-band filter. If you're fighting severe LP then mono+mono will always win but, if not filtered and unfiltered OSC would be very productive, I think, especially at fast F ratios. Olly

I agree that 2 minutes of arc is not a big ask. I think an EQ6, unguided, might have an error of 30" of arc, or so. Is your exposure ruined by being briefly lost from the slit? I know nothing about photometry. Olly

Project with Paul Kummer, who persuaded me that this was worth a try. I was doubtful, thinking it too low from Lat 44.19, but I'm glad he persuaded me. This had 2.8 hours in 3 min subs from a RASA 8 on an Avalon Linear and with ASI 2600 MC (OSC) camera. Paul managed the capture and pre-processing from the UK but the scope is located here in our robotic Observatoire Per Frejvall. This is my post processing. We could find no way of using DBE or ABE since half of the image has no background sky, but I compared it with good images from lower latitudes and concluded that our colours and brightnesses were in decent agreement without severe gradients. This version was de-starred in StarXterminator after a partial stretch and the stars replaced at a softer stretch. I think our latitude basically cost us contrast because there is nothing in the field requiring high resolution. Olly

It's rare to see an image you'd want to describe as perfect but this is such a one. It deserves a standing ovation. Bravo. When I read that this was done with a 40mm camera lens I was amazed, because those powdery stars do not look as if they came from a short FL. The image looks telescopic. Brightness range and colour balance are spot on and the mosaic is seamless. Ha blending is tasteful and unobtrusive yet thoroughly effective. My dismal internet won't let me see the full res but I'll be delighted when it does. Olly

That is a sensational result and, bravo, well done. Resolution of spiral detail is just brilliant. There are High Dynamic Range techniques which would let you fix the small, circular saturated core, probably, though you might need to shoot a handful of short subs for that. The background isn't perfectly flattened but, hell, nobody is going to begrudge you a bit of leeway from NW England (land of my birth! ) This is the most remarkable image in terms of quality-from-location that I've seen in a long time. Olly

I have a 14 inch LX200 for visual and it's nice - though very wobbly. Years ago, in my first steps in imaging, I tried a wedge-mounted 10 inch LX200. My conclusion? That the exercise was a total and complete waste of time. I was advised by Ian King not to waste time on it and I should have listened, but instead I went ahead, bought a wedge, faffed around with it and tried imaging. The mount can deliver about 10% of what's needed. What's more, the days of the long focal length instrument for amateur imaging are over. You simply don't need these focal lengths because pixels have become smaller, making the resolution allowed by the seeing available to much shorter focal lengths. (There are exotically high-end imagers on vast budgets who are using long focal lengths, certainly, but from remote mountain tops with superb seeing. Down here in the real world you can do anything possible with a metre of FL.) The LX200 is not an imaging mount. Olly

Although it's expensive, I find Registar to be a great boon. It is a super-accurate aligning-resizing-mosaic-making software. I use it all the time. Say I've reached the stage where I do a final crop and apply it. Then I have a bright idea for a processing refinement which involves using an earlier, uncropped layer. I just open the cropped and the uncropped in Registar and use it to align and crop the old image to the cropped. Likewise I can add new data in the same way. It's just one of those tools I use time and time again. Applying luminance: Wim mentions the problem of luminance overpowering RGB if applied at 100%. This is certainly a problem. I address it in Photoshop by applying the Luminance in partial opacity, starting at about 20%, giving the result a slight blur, increasing the saturation, flattening and re-applying the luminance to that. I carry on with this several times till, in the end, I can apply the luminance at 100% and not give it any blur. This final application prevents any residual blur. It might also be worth resisting the temptation to take the luminance to its highest possible stretch. Leave a bit of potential stretch unused before combining with the RGB. Then go for the final, ultra-hard stretch with the LRGB. There are theoretical arguments against this technique but I find it can simplify life. Olly

Who told you this? You shouldn't have believed them! 😁 The RASA needs not only excellent collimation but excellent chip orthogonality (freedom from tilt) and this tilt can come from the camera or the alignment of the optics or the attachments or all three. The whole system is insanely sensitive and, after a year of effort, we are still not fully sorted with ours. The key test of guiding is easy with a RASA because it can catch so much signal so quickly. On the same target at the same time, just take a set of subs, getting longer as you go. 10 secs, 30 secs, 1 min, 2 mins, 3 mins. Does the quality of star shapes alter much? If it doesn't, it isn't your guiding (and I don't think it will be.) Another RASA thing: with regular optics, being slightly out of focus means having slightly larger stars. With the RASA it's more subtle: a tiny fraction out of critical focus either way will hardly affect your FWHM (star size) but it will affect your star shapes in the corners. The world of F2 is a strange one. You need to try it to know this. Olly

When I started photographing the night sky some fifteen years ago I followed the advice of Ian King, now associated with FLO, and went straight into mono CCD with a short FL refractor, autoduided from the start. This is not the standard advice but Ian King was not a standard imager. Even though I had no IT skills (and believe me, nobody today has so few IT skills today as I had fifteen years ago) I was soon up and running. And I was not up and running down a blind alley, which is how a number of my guests have described DSLR imaging. Using an astro camera is easy. I sometimes wonder if those urging that it's complicated have ever actually used one. I know of only one imager who has gone back to DSLR from CCD (now call that CMOS) and that's Maurice Toet, who is very expert indeed, who uses the screamingly fast optics of a Takahashi Epsilon and who wanted a PC-free mobile system. But here's the thing: Maurice has the expertise to make it work. My argument is that this requires more expertise, not less, to compete with CCD/CMOS. A screwdriver is a simpler tool than a chisel... until you need to use a chisel. At this point a chisel becomes simpler than a screwdriver. Olly

Go To in AP is not like GoTo in visual observing. It saves the commodity in shortest supply - which is time. You don't just save time at the start, you save it when things go wrong and you lose your target - and there are plenty of ways to do that! Once you have your target framed you can note or save its co-ordinates and be back in business in no time. Reframing by eye takes a long time. You have to scan the edges of the image to be able to relocate the previous edge stars. Tilt screens? It is so much easier and better to capture with a laptop. You have a bigger image at higher resolution which is a boon for focusing. Focusing a fast lens in AP is not like focusing in daytime photography. The quality of focus will not only impact on the sharpness of the image but on the quality of star shapes towards the edge. I wouldn't want to focus the Samyang while peering at a tiny camera screen. Both DSLR and CCD capture software offer assisted focusing usually using Full Width Half Max. (This will Google.) Back to 'easier' DSLRs. If you take the whole process from start to processed finish, DSLRs are harder. Their output needs a lot more processing in order to get to a decent standard. You have more noise and more artifacts to deal with. It is pretty much obligatory to dither between subs. (Shock horror, I don't dither when shooting with CCD.) When framing, you can, with a CCD, get a clear view of the objects in the frame in very short exposures. No chance with a DSLR. There is 'perceived easy' and 'real easy.' They are not the same. Olly

You got everything right with that capture - tracking and focus, most obviously. Nice processing, too, with a well-judged and flat background and small stars. Olly

As an astronomy provider I have some good optics available: Takahashi FSQ106, TEC 140, Meade 10 inch ACF, etc and, make no mistake, I would love to add a Samyang 135 to the lineup. This widefield lens is taking some of the best astrophotos I've ever seen. So I think that's a great choice. To get the best out of it you'll be introduced to the wonderful world of fine tuning to get rid of tilt and you'll meet the need to focus perfectly. This is good and necessary. I've never been a DSLR fan and, nowadays, older CCD cameras are appearing for sale at knock-down prices. They will trounce a DSLR, except on chip size. A set of RGB filters won't break the bank and if you add an Ha filter you'll have a killer rig in place. Or you could go for a colour CCD. The smaller chip will make getting the tilt fettled much easier. Don't expect many people to agree with this post! 🤣 I'm used to it. Olly

@ Ian B How do I see what the Servocat settings are? Do I connect it to a PC somehow? I've never done this. Or is the information on the AN controller display? Olly

I don't know how to give you a screenshot of the Argonavis settings but I can have a look through the parameters I've put into it. I won't be able to get to this straight away because I'm in mid project and we have guests but I'll see what I can do. The encoders are not very accurate. They are fine for finding a target but you cant note the RA and Dec positions, feed them in on another night and expect them to re-frame perfectly. My mount's first owner tried to get it to run from a planetarium but couldn't make it work. Since he's an IT professional and I'm an IT turnip farmer, I have never tried again. You'll get there. Olly

I've found that more aperture usually improves the view using a white light filter. Olly

J'aime les cookies! My wife and I were puzzled by a radio broadcast on artificial intelligence this morning. The expert kept talking about licornes (unicorns) but neither of us had a clue as to what this had to do with AI. Needless to say, Google came to the rescue. It was reassuring to find that billion dollar startup companies are les licornes and not les unicorns over here. (I probably only know the French for 'unicorn' because our grand children have an inflatable one in their pool. For some reason I never learned this useful term at school. 😁) Olly

Just for information in case anyone doesn't know about these things: https://www.amazon.fr/Neewer-Professionnel-Réparation-dOuverture-Inoxydable/dp/B00J5F73GA/ref=asc_df_B00J5F73GA/?tag=googshopfr-21&linkCode=df0&hvadid=227916778552&hvpos=&hvnetw=g&hvrand=4978925880824984634&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9054932&hvtargid=pla-405661153168&psc=1 It isn't a tool I use very often but when I need it I need it, and it's reassuring to know it's there. (Saying this made me go and confirm that I still know where it is 😬 and, glory be, for once I do!) Olly

Well I think you've won this one!!! Heroic. 😁lly

For what it's worth, I've updated my view after trying both Star X and Noise X. I found that noise X seems good at removing the kind of noise created by Star X, though this is based only on processing one image. NoiseX is certainly the most natural-looking noise reducer I've ever tried personally. Olly

I'm not proposing it, per se, but I was able to get my TeleVue Genesis onto flights as hand baggage. It was just possible on length after I made it a compact thin plywood case. I'm sure there are now dozens of fast (therefore short) refractors up to around 90mm which would pass. It's common, these days, to design them with very short main tubes which require lots of drawtube out to reach focus. Although this is a daft idea structurally, it does make them more compact. Olly

And platesolving always works and never acts the goat? My robotic clients will be delighted to hear this. When did this miracle occur? 😁 Olly

I don't know the TSA120 from experience but, in principle, a good 5 to 6 inch (ish) refractor is a very versatile choice, lovey visually and, with the right sized pixels, capable of getting much closer than many would think to the limit of resolution imposed by the seeing. We no longer need 2 metres of FL in amateur DS imaging. If it can cover a full frame chip it need not be all that limited in imaging field of view, either. My own incarnation of this formula is a TEC140 but the same principles apply. Olly

True. Olly