ollypenrice

Firstly I would only add star colour to a NB image which was aiming to approximate natural nebular colour in the first place, probably HOO. Rather than try to 'fill in' the star colour on the HOO you could use Photoshop like this: 1) Process the RGB, the Ha and the OIII and align them to fit each other. In processing the RGB concentrate on the stars, keeping them small and colourful and don't worry about the nebula which will be coming from the NB layers. 2) Add Ha to red in blend mode lighten, making sure your Ha stars are smaller and fainter than your red stars. (Use multiple iterations of a star reduction routine like Noel's actions or whatever on the NB layers.) save three copies of this. Call this Ha to red. 3) Add OIII to green in blend mode lighten in one of the copies and call it OIII to green. 4) Add OIII to blue in blend mode lighten in another copy and call it OIII to blue. 5) Make a three-layer stack like this: OIII to blue OIII to green Ha to red. Now you can choose opacities for the top two layers which give you the most natural nebular colour. Your RGB star colour should be unaffected. As you can see, this method does not work by replacing star colour so it gives a more natural look, yet the NB contribution to the nebulosity is the same. Olly

I'm intrigued by this as well. I have a very dark sky, sometimes reaching SQM22, but the seeing is predictably variable. I have never found E and F 'easy' though this may be me. I'm not a double or multiple specialist. Sometimes I'd call E reasonably easy but never F. Possible but not easy. I've used 10 and 14 inch SCTs, 20 inch Newt, TEC 140 apo, and F has never been 'easy' for me. Olly

Deep and sharp. Good job. Olly

Cropping included? This seems odd to me. Mind you I don't know the routine at all but I'd have thought that stacked image borders had unique artefacts of their own. Olly

The TEC140/Mesu/Atik 460 has been busy this year. Bubble in HaOIIILRGB An insane amount of effort went into catching a hint of the fossil accretion loop around NGC5907. Please tell me you can see it! A widefield from the Twin Taks in Vulpecula setting M27 in context. (High res M27 data blended in.) As with the image above, the interesting NGC7129 below was done with guest Paul Kummer: And finally a comparison of two planetaries, the Owl and the Cat's eye at the same scale: Happy new imaging year to all. Olly

It seems to me that the camera manufacturers are imposing on us a kind of mental double negative which isn't very helpful. I have had to look this thread up again since I'm back in the reducer spacing jungle! Groan. I'm going to follow Don Goldman and add 1mm of metal to the hardware connecting flattener to camera. That is, I'm going to make it an 86mm separation rather than a filterless 85mm. Olly

I find I can't do darks on the scope at all and that's that. I have to do them with the camera out of the system and the metal screw-on chip cover fitted. And this is on refractors with fully sealed electric filterwheels. How does the light get in? Not a clue - but it does. I compared 30 minute darks done on the scope and off. They were certainly very different from each other. There do seem to be a lot of threads discussing reflections in CMOS cameras. Olly

No, a rare sign of sanity by SGL standards! Olly

And does the shed at right angles on the right contain a conveyor belt of instruments ready to feed into the observatory in the event of a target needing a small change in resolution, aperture, field of view, etc??? How splendid! Or, more seriously, this really does look great. Olly

This is the processing solution. I have the process saved as an action - indeed I have three versions of it for different sized stars. Use the magic wand to select the star and then Start recording. Select, modify expand (by x.) Feather (by y) Filter, blur, radial blur, spin, best quality. (Put this command in twice.) Deselect Stop recording. The values for x and Y you have to find by experiment and the larger the star the larger the value, which is why I have three saved. If you save the action to a function key all you have to do is click on the star with the magic wand and then hit the key to run the action. It is one star at once but not many will be affected so the whole process is quick. You could experiment with the best stage in the stretch to run the action. Olly

The resolutions were 0.66 for the big scope and 0.9 for the small one. Realized detail was honestly about the same. The test was complicated by the greater sensitivity of the small pixel camera. In fact the smaller telescope with smaller but more sensitive pixels was probably faster but I didn't have the original raw data to explore this side of the comparison. In priniciple I agree with you, though. Olly

In my view these conversations spend too much time on the weight issue and not enough on the accuracy which, at these pixel scales, can be the dominant factor. Olly

Why are you keen to add resolution via focal length and then reduce it via binning? It really doesn't matter whether you fill the frame or not. What matters is how many pixels (single or 4 pixel superpixels) you put under the object's image as projected by the telescope. It is this which determines the object's image's final size at full size (1 camera pixel = 1 screen pixel.) * Earlier in the year I did a comparison in Astronomy Now between a 14 inch scope (2.4M FL) with large pixels and a 150mm scope (1M FL) with small pixels on galaxies. I found that the level of resolution and the size at which the images could be presented on screen was effectively the same. It seems that the considerably greater optical resolution of the larger scope was not translating into more final details. In both cases the mount was running with an RMS of less than half the image scale. Personally I'd look for a scope with a FL which will give you about an arcsecond per pixel or a tiny bit less and make it the kind of nice simple design that you know you will find productive. I've struggled with one of those RCs with a guest and got nowhere. The theory is one thing but this example did not behave according to the theory. Olly *Not the best sentence I ever wrote!

The 'flashlight test' makes anything look horrible. Ignore it. Nice one from Dave here! Olly

You'll get one from any country still so primitive and misguided as to be using imperial threads. No further comment, but don't mention Mars landers... Olly

To be honest leveling really makes no significant difference. 'About level' E-W will set your reticle 'clock' to an orientation which will be good enough. Leveling N-S is meaningless anyway since you're going to tilt the mount to the angle of your latitude and the angle of your tripod on this axis matters not. (Avalon mounts have a good bubble level but it operates only on an E-W axis. You only need to level mounts N-S as well if they are alt-azimuthal with Go-To and tracking.) Olly

Yes, and the only critical reason for leveling your mount is to set the polarscope 'clock' onto a horizontal surface so you get a true reading. Have you checked that your polarscope is parallel with the RA axis? To do this you set the mount up so the polarscope's central marker sits on a distant point like the tip of a church. You then rotate the RA axis. When properly aligned the marker will stay on the steeple tip. If it's out it will describe a circle. It can be adjusted with its three radial screws. Olly

I'll be studying this with interest, Steve, since I have never been able to get any sense out of deconvolution (other than with a small format 8 bit system in an old copy of Astra Image which I once had.) Thanks for posting. Olly Edit Corrected the name of Astra Image.

Yes. It was incredibly difficult for plate film photographers to manage the dynamic range of M42. Olly

Within my own lifetime this would probably have been the best M42 ever taken. AP has made pretty incredible progress. Olly

Spot on. A fine image. Olly

Until reading this, the best job I ever heard of was, 'Fish warden on the upper reaches of the rive Wye.' This beats it! Olly

There are two positioning systems used in astronomy. First there's RA and Dec, in which an object's co-ordinates never vary because the scales are 'printed' on the celestial sphere, so to speak. RA and Dec are the setting circles of an equatorial mount. The other co-ordinate system is Alt-Azimuth in which the scales are locked to the observer's location. To use Alt Az co-ordinates you'll need a planetarium software into which you've keyed the time, the date and the location of your setup. Your object is always moving relative to Alt and Az, the more so the further from Polaris you stray, but the planetarium will, at any given time, provide you with the Alt Az co-orodinates for the object. They are of temporary value but they will tell you the compass bearing and elevation of the object so that you can find it, after which you'll need to track it by hand. Steve's system is very elegant. I missed that article. Olly

I pick mine up on the Duster's roof rack. Just be careful to prevent the sharp edges from sawing through any tie downs that you use. This certainly happens, as I know!!! I've used flat steel sheet on our summer kitchen's fixed parasol but you have to bolt it down only at one end and hold the rest down under wooden or steel strips which allow it to expand without buckling. Why does corrugated steel not buckle along its length? Maybe it tries to but the corrugation simply prevents it. Expansion in the other axis can be absorbed by deepening the peak to valley, of course. This is a great observatory in the making. Olly

We looked at your videos, Steve, but the scope we were working on didn't follow the pattern. There were interactions between adjustments which sent us round in circles. Perhaps there was a maechanical problem somewhere. Olly