ollypenrice

The ST80 is utterly hopeless for imaging. (I have two and use them for autoguiding, which they do brilliantly, but that's an entirely different task.) There are three problems. 1) The chromatic aberration is extreme. Different colours come to different points of focus. This will affect your camera particularly badly because, being one shot colour, you cannot refocus between filters so some of your colours will always be out of focus and you'll get big blue halos around stars. 2) The focuser is too primitive for imaging. It will not hold your camera chip square to the light beam so one side may be in focus while the other is not. This is called 'tilt.' 3) The lens has significant spherical aberration and your camera has quite a large chip. Stellar images away from the centre will be distorted. It's a worthy little scope, good value, but for budget imaging get a Newt or the Evostar. Olly

The green bias is overwhelming but can certainly be fixed. Olly

No, it's easy. It's basically the same as holding your daytime camera horizontal so it's aligned with the horizon. If you don't do that you can end up with a picture of The Leaning Horizon of Pisa if you're not careful. 😁 Images which are orthogonal are simply ones which will be parallel with the earth's horizon when the object transits the meridian. Olly

It would be helpful to know the orientation of the image and its trails relative to RA and Dec. It's good practice to have your chip aligned orthogonally, meaning RA and Dec aligned with the edges. You can set this roughly by eye and then tweak it by taking a short sub while slewing slowly on one axis. This will produce trails at the angle your camera now is. Troubleshooting is then easier, identifying the problem axis if it is just one of the two, and you can add data to an image easily in the future. I try to shoot orthongonally and when I dropped your image onto mine it fitted like this: Unfortunately I can't be sure that my image really was orthogonal but, if it was, your trails don't arise from an error on a single axis. However, they are very systematic in being linear, so whatever was causing the problem was doing the same thing all the time. Olly

Aha, when you have the Ha posted onto the red in blend mode lighten it's important to be sure that the background sky level of the Ha is just below that of the red or it will, indeed, turn everything red. This is easy to do. Blink the Ha on-off in layers and if it's lifting the background you can bring its black point in a bit so it no longer does so. You can also put an S curve into the Ha, lowering it at the bottom and raising it further up. Olly

Why not a proper parallelogram mount? Bulky but they do everything. Olly

On emission nebulae it would certainly be the filter, for me. Olly

That really is a fine image. Very well done indeed. Olly

Very good result. Have you considered an Ha layer? It's quite strong in this target. Olly

I like it very much but think it's presented at a scale beyond one which the data will fully support. I'd accept a smaller galaxy on screen, with a reduced grain from the noise. I also wonder if it was worth stretching quite so hard. The outer regions, which are interesting, would still be visible and informative if they were left considerably closer to the background sky brightness and, as a result, would be smoother. However, it is great when someone has the courage to go after the small targets like this and you have my hearty congratulations. Olly

A small sensor will not vignette as much as a large so that's a plus. You can mark the camera for orientation but the best trick is to fit it a closely as you can to orthogonal (aligned along RA and Dec) and then take a roughly 5 second sub while slewing slowly in just one axis. This will produce star trails which show your present camera angle. Adjust and repeat till your trails are horizontal or vertical. It doesn't take long and is entirely repeatable, which is a bonus. Olly

Lovely. And what a result from 130mm aperture! OK, they're good millimeters but even so... 😁lly

In a permanent setup in which you leave the camera in place there is no need to do flats every time. I find mine usually continue to work well for several months. Darks and bias do evolve over time but very slowly from my experience. I'm not sure I agree with Alacant on the use of a coloured T shirt with an OSC camera. If its filtering effect is blocking a certain colour the OSC pixels filtered to pass that colour will get little light and risk being noisy as a consequence. In a mono camera, even with colour filters in place, you could simply increase the flat exposure time for the light-starved colour. Olly.

The smallest workable observing shed is almost certainly of the 'rolling sentry box' kind because the sentry box in question is too small to accommodate the observer and must be rolled off to expose the scope. Once rolled off it can have a drop down desk and bench, or a protruding pod, which can serve as an office for star charts, mugs of tea, pints of foaming ale or whatever. I've built three of these and been pleased with them. Here's one of them about to be moved to a different location (a secondary advantage of this design) Open the doors, roll it back and the scope's inside. But I missed a trick when I made this and went to the bother of welding up a steel space frame then claddng it in timber. There is a MUCH easier way which I'd use next time... Construct your rails and pier, buy a piece of good strong marine ply the size of your chosen shed's footprint, screw 4 wheels to the bottom and place this as a rolling platform on your rails. Cut a slot half way into this base so it can roll forward till the pier is in the middle. Now simply assemble your bog standard garden toolshed on the rolling base. It can be a nice wooden one or a nasty but practical plastic one but the choice is yours. It can even be a lovely garden chalet style structure such as Singlin's (in this section, I think.) This is just so easy. If you don't want a pier but just a concrete block for a Dob then just make a concrete block and let the rolling base run up to and away from that. If the block or pier has protrusions just above the height of the rolling base it will serve as an anti-lift device - which is essential. Please read that twice! Olly

When you add Ha in Blend Mode Lighten you can save yourself the guesswork by adding it at 100% and saving the result. Then open the HaRGB and paste it onto the RGB original so you adjust the opacity to give as much or as little of the Ha modification as you like. Signed, Layeroholic.

I host two 10 Micron GM2000s and I think they sound pretty much the same as yours. Olly

Did you add your Ha as luminance? I'll guess that you did. The problem with this is that the entire image is illuminated in fairly monochromatic red light, which denies the other colours the chance to take their place. Towards the middle of your image there is a big bright star surrounded by some blue reflection nebulosity - so it shows mostly in the blue channel. If you illuminate this in red light, in which it does not shine, you kill it. I'd have a go at splitting your RGB channels and adding the Ha to red in blend mode lighten. That will keep your red Ha data where it belongs - in red. Olly

He doesn't want his eyebrows infected with Covid19. Do you? I have great faith in Vlaiv and have modified my face mask according to his model. Olly

A last resort might be to delete and re-download DSS. Olly

Not really anything I'd call 'an idea' but have you tried rebooting the PC? DSS may simply have failed to heed your instruction to move onto new files. Failing that you could copy and paste your galaxy files into a new folder and try again. Olly

So what emerges as the key factor is that the Ha emission from the moon is scattered far less than for shorter wavelengths. We might also want to add that there are plenty of objects which are strong in Ha emission, strong enough to be able to produce a workable S/N ratio in a reasonable time. I guess we wouldn't, in reality, be shooting in Ha if our objects were no stronger in Ha than they are in, say, SII. So it's a happy marriage between the behaviour of the atmosphere and the behaviour of the objects. Olly

The polarscope on the Mk1 iEQ45 I reviewed was very good. I'd certainly start with that. Olly

I wouldn't over-estimate the number of people who bin colour. I never do and I'm certainly not alone. Since you're using a CMOS camera I gather the advantage from binning is not what it is with CCD but I've yet to use a CMOS first hand. What is your pixel scale? There's a calculator here: http://www.12dstring.me.uk/fovcalc.php I can't help on the software problem, not using APT. Olly

Is this the version of the mount with the spring loaded worm gears? These can become very under-sprung after a while, leaving a lot of room for sponginess in the drive. It's not exactly backlash, which is free movement, but it's certainly a lack of stiffness. I think later mounts were made differently. Olly

That's a pretty determined effort to keep things stiff and aligned! It deserves to succeed. Olly