ollypenrice

Here's a corner crop in luminance from my elderly FSQ106N on a 45mm diagonal chip resized up by the same amount as I did yours. (Atik 11000 camera.) It isn't perfect but I think it's significantly better. I never have any channel alignment issues arising in RGB. Olly

OK, here's the stretched lum, top left. The other corners show the same sagittal astigmatism effects. I think that they may be exaggerated by the wavelength (blue being the worst) but that might be expected, maybe? I think Takahashi should speak out on this. The chip we are dealing with does not reach out into the limits of their claimed corrected circle. Anyone trying to use a 36x36mm chip in this scope would be doomed. When the stars are distorted differently at different wavelengths the software will struggle to align channels. I think Registar did as well as could be expected but, when we see all visible wavelengths captured together, as here, the distortions are still present and have nothing to do with channel alignment. The scope is not working to spec in my opinion. Olly

But if there is an optical aberration it might well vary with wavelength? In other words it might be chromatic to some extent. I'm still trying to download the L. That will decide it, I think. Olly

Potentially it depends on the colour of the star, perhaps? My attempt to download the Lum failed so I'll try again. Olly

I've been speaking to Ken via PM and don't think the primary problem is channel alignment. I suspect that alignment is a secondary problem arising from lens distortions inherent to the data. I aligned the channels in Registar which, as well as aligning images, will resize them to fit a selected channel. I chose red as my reference channel because, though common sense might suggest green (mid spectrum) I've found that red is the most effective reference channel when problems occur. Here are two upwardly resampled crops from the centre of the image. I can see no reason to doubt Registar's alignment and I don't see anything much wrong with them, though there are some probably unrelated pixel oddities. However, the stars in the corners show classic elongation as if they were all part of a large circle. This is something we see with incorrect chip to flattener distances and other lens issues. I'll just post two diagonally opposed corners here because I sent all four to Ken and the same patter is sustained, theough the bottom left corner is much less severe. I expect this pattern to be clear in the luminance as well but I've yet to download and stretch this. I'll do this later. The distortion seems to be called sagittal astigmatism according to this website. https://www.lonelyspeck.com/a-practical-guide-to-lens-aberrations-and-the-lonely-speck-aberration-test/ Anyway I'll have a look at the lum. Olly

Nice. Why would you not want to crop for presentation on a forum like this? It just saves people from doing a lot of clicking. There's nothing artificial about it, any more than there is in walking towards a picture in an art gallery. Olly

For imaging your mount needs to be more than 'go to,' it needs to be equatorial go-to. Alt-Az go-to is not what you're looking for. Olly

In that case you'd be well advised to keep the focal length as short as possible because your tracking accuracy won't support high resolution. (Don't be fooled by the 'round stars test.' Round stars will arise from errors in tracking which are roughly equal in both axes but resolution is still compromised.) Olly

Are you autoguiding? This is by far the most important 'first question.' Olly

There's no hard and fast definition and there are two worlds, visual observing and astrophotography. What they tend to have in common is that 'widefield' means 'a large swathe of sky containing several or many objects,' as opposed to a field of view featuring a single object. In truth the terms overlap. Olly

Absolutely true. It's also highly applicable in the case of motorcycle front suspension where the telescopic fork, under braking, has its inherent 'stiction' greatly increased. Olly

It's from David Kriege's book that I first came across the idea that static and kinetic friction should be equivalent and it struck me as a good insight. When I once ran out of Turtle Wax for my 20 inch Dob I used a different brand of polish, chemically similar but available in France. It was an absolute disaster. The mount would stick-stick-stick then luuuurch past the target. I no longer have the big Dob but Turtle Wax is still the best vehicle polish I know of. 😁 Olly

Yes! Olly

We've been here before but it seems to me that the useful unit would be one we never see: area of aperture per pixel. This unit would clear up the confusion sowed by the term F ratio and would work nicely with the useful term arcseconds per pixel. Olly

I'd have thought that the key attribute is not the absolute level of friction but the similarity between the static and moving friction. When they are the same the mount doesn't stick then over-respond to pressure. Perhaps this is the main advantage of the textured surface? Olly

I can only comment on the 6.3 reducer in a number of Meade SCTs I've used. Like Jeremy, I much prefer a good wide angle 2 inch EP over the reducer-and-1.25 option. There is no point in using the reducer with 2 inch widefields because the baffle tube limits the FOV anyway. Olly

They're not! The EM200 Temma Junior was my worst ever astro-investment. Despite its exorbitant price it came without GoTo, other than via a primitive planetarium to which it frequently failed to connect. It was more reliable running in TheSky6 but non-connection remained a permanent anxiety. Sometimes it would guide very well indeed and sometimes it wouldn't, with no rhyme or reason, in a permanent setup. With use its nylon gears developed backlash and I sold it on, fully declared, at an eye-watering loss. When working well it was more accurate than an EQ6, when not working well it was less accurate. It is not a patch on the Avalon Linear Fast Reverse or the Mesu. The one thing I really did like about it was the polar alignment system it employed. Olly

There is no point in going for more focal length if it takes you to a resolution (in arcseconds per pixel) beyond what your tracking under guiding will allow. I can't see any point in going for the 150 over the 130, quite honestly. Olly

Wow that's good going from this latitude. Tree skimming! Lovely filmy-looking dust and gas. Nice. Olly

This really has come good. Great stuff. I have two thoughts on the image. 1) the core (but very selectively) will certainly take more sharpening and show more structural detail. 2) A deep Ha layer would bring all-new features into play, far more so than on most galaxies. It wouldn't just bring in a string of rubies in the arms, it would find a fascinating little jet at right angles to the disk. If you really went for it you might find even more Ha structures but those are seriously exotic. Check out R Jay GaBany's M106 for inspiration! Olly

No, but future archaeologists studying the town of Wirksworth will wonder why curious concrete circles had been cast in a number of the town's gardens during the late 20th Century... 😁lly

Context is always interesting and Registar is such a great tool. Olly PS the house made me jump: it's a dead ringer for our last house in the UK, right down to the balcony for the dormer!

That's nice and it's well balanced. As ever, it's just a matter of time. With more data you'd find the reflection nebulosity would grow to surround the Ha, the golden milky way would glow more strongly and you'd be able to sharpen the details in the gasses. You clearly can capture enough to make this into something special from your latitude. Why not go for it? I've never done a high resolution Trifid, only ever a widefield with the other components of the Sagittarius Triplet, but I'd like to do so because it is one of the most beautiful nebulae in the sky. Olly

Ooh, careful! If there is one phrase which will never, ever, apply to astrophotography it is this one. It is an activity in which the main endeavour is stopping things from going wrong! It is also a very counter intuitive activity in which what one might reasonably think to be the case is not the case... Olly

I'd forgotten that Sara had tried one of these. I know of only three people using them and the one who posted most recently was Peter Goodhew. Peter was finding it impossible to avoid effects of differential flexure in his dual 6 inch refractor rig so, if I have this right, he installed an AO unit on the 'slave' scope and now finds that this is the one which actually gives the lowest FWHM. Autoguiders don't react fast enough to follow the seeing so, in theory, the advantage should be more or less equal whether guiding on encoders or on stars, I'd have thought? My 'digest' of what owners have told me about these units is that when they work they make a difference but getting them to work is often a pain. By far the most positive experience is Peter's. In effect it allows two parallel scopes to be independently guided. Our dual TEC rig does sometimes suffer slight trailing on the slave side but my low tech solution is to use that side for RGB. Olly