ollypenrice

On days when everything in our 4-scope observatory is wringing wet there is never any moisture of any kind on our RASA8 corrector. That's with a short, home made dewsheild which extends just to the back of the camera. Olly

What's your difficulty in cropping and sizing in Ps? Maybe we can help. Olly

If you've shot the Leo Triplet you'll have collected a good number of quasars near the Hamburger galaxy. These are seriously distant. Olly

This is why friction drive is so good. The mighty Mesu has no backlash. Newcomers reading this might not know that the Dec equivalent of east-heavy loading is running slightly out of polar alignment and guiding only in the direction needed to correct for this. Again, the disabled direction has to become the active one after a flip. Olly

I say 'backlit' because, under a very hard stretch, the nebulosity of medium brightness outshines the densest, darkest dust to such an extent that my eye-brain thinks the light source must be behind the object. If the source were also in front of it (as I think it usually is, being starlight from several sources) the darkest parts would also be illuminated. Very highly stretched dark nebulae make beautiful images, no doubt about that, but I think they risk becoming deceptive. I may be entirely wrong about the physics, here, in which case I'll stretch away with the best of 'em! Olly

I'm always fearful of stretching dark nebulae so hard that they look backlit. However, I decided I'd been too cautious on this one. The data had no problem with going a bit brighter. OK? Too much? Olly

2 panels, here. I don't have a good planetarium for these. It would be good to find one. Olly

Again, Paul Kummer drove the scope and gave me a pre-processed image for post-processing. RASA8/Avalon Linear/ASI2600MC. About 3 hours per panel. Really sweet data to work on. DBE, BXT and SCNR green in Pixinsight, then over to lovely Photoshop. I see @gorann has taken this field over to join the Iris for a great resut. Since I have an Iris to Ghost an extension would seem obvious. There's a small gap to fill in. I love it when you get these little bonus galaxies like NGC6951. It's only 3.19 arcmins across but shows nice detail. Distance is about 75 million LY. Olly

No, it's fine but it's an OSC camera and we don't have a dual band filter for it. I'm not keen on the idea of having an on-off-on-off filter arrangement for it. A second RASA rig would be a different matter. Olly

Wallace and Grommet are regulars at my place. They were here over the weekend, in fact, making new Samyang hardware... lly

We had this with a Starlight Xpress OAG which could rock considerably once tightened up. Our solution was to run an alloy strap from the top of the guide camera to the scope. I dare say this would also work for you. Olly

Good going! I don't have an operational rig capable of going for this, at the moment, which is rather a shame since adding S-D155 would be a nice touch. I'll have to speak sweetly to one of my robotic clients to suggest a collaboration! Olly

That's an absolutely beautiful image and I think you've realized your intentions superbly. As we seem to be concluding, we cannot 'have your stars and not have them,' and a compromise in star emphasis is not as good a solution as is having two renditions. I think I'll have a go at processing without SXT and see what I get. Following my conversation with @old_eyes I tried a very different approach with my data since I didn't feel the original got all that it could out of the faint background. Knowing that I could still de-star it, I tried the Ha stretch I use for Ha destined for blending with red. It's very aggressive: What it does do, of course, is give an extereme stretch and extreme contrasts at the darker end of the image, at the cost of large stars. (Not a problem with a 3nm Ha filter or with SXT available). I then de-starred this and found that I had, indeed, found more dusty activity near IC447 and mild advantages in one or two other places. In general, though, the result was remarkably similar to the first. As a long term believer in blending different renditions, as per Martin B's suggestions) I combined the two and came up with this: https://www.astrobin.com/viugy5/B/ As old-eyes said, there really must be significant differences between his data and ours, despite the similarity in equipment and sky quality. Olly

A really interesting comparison. Yours is far more punchy and dramatic. I'm tempted to revisit ours from the linear stage to understand where these differences come from. I really like your rendition. Olly

A man should resist everything - except temptation. Olly

Much nicer. The change in 'look' is very similar to the changes I get on these return visits. What a luxury to process nebulosity without trying to maintain the stars. Your dust is full of subtleties. Great stuff. BTW, Monique has just said 'Hi Martin' after asking me who I was writing to! Olly

Here's our new mounting setup following the total failure of the abominable Wega mounting bracket, which continued to fall apart. As we are desperately trying to finish a project on Orion I wanted to use only bits of hardware I had in stock or could make. So... A Losmandy to Vixen adapter holds a Vixen rail to which two hefty Altair Astro guide rings are attached. These carry the scope-camera. Bolted to the front of the Vixen rail is a homemade piece of alloy angle with slotted holes for tension adjustment as it carries the focus motor. The belt which came with the Wega has the same pitch as the ribbing on the focus barrel so there is no need for the Wega pulley, which also fell apart. In practice the fine tuning of the belt tension is best done using the adjusters of the Altair guide rings. An old Vixen rail is then bolted to the guide rings and carries a Skywatcher finder guider. I'm not a fan of guide rings but this, so far, is nice and stiff and I've used the Altair guide rings for several years on another rig so I trust them. There will be cone error using guide rings but, on an Avalon M-Uno, there are no meridian flips so I don't expect it will matter.

I suspect that your star replacement layer has slightly subdued the faintest signal in your starless. This is something you have to watch out for very carefully. In Photoshop, at least, once you have your star replacement layer on top of your starless you need to blink it on and off in order the check that this is not happening. It's something I spotted when first using StarXT. I often find that my star layer is clipping my faint signal and I use Curves to adjust it so it isn't. (You can use Curves directly or use it via Brightness and Contrast or Levels but it is all the same thing.) If you're using Pixinsight you'll have to work out how to adjust your pixelmath values to prevent it. However, you also say that this is the starless 'before pulling the levels down' so that might be the stage at which you lost the extremities of your faint tidal extensions. But you did lose them. Look carefully. Olly

I had another look at star size and came up with this, which is also more magenta, true to the real colour, I think. Sometimes I think two versions is the only way! Olly

Oops, my mistake, IC447. It's also vdb77 in this present image. Thanks for the heads up. Olly

It does depend on the target and total integration time remains the key thing. However, with your Kodak chip I would aim for at least 10 minutes and maybe 15. Certainly 15 for narrowband. Going for 30 minutes with a mobile rig and a limited time window would be a risk likely to bring more cost than benefit. A friend using your chip was advised by a well-known imager to use shorter subs. She tried it and rejected the idea, returning to longer ones. (I can't remember the precise details.) My own experiments gave me the same results. Olly

Yes, I think the local contrasts in emission gasses are much more visible in NB. Another thing, though, is that in this image there is a need to devote quite a lot of dynamic range at the dark end to the dusty features around IC443. We need to separate the dark, obscuring dust from the slightly brighter reflection dust around it. The entire Cone region is much brighter than this, meaning we can only make the darkest parts of the Cone's gasses brighter than the brightest dusty regions. In a crop, we could make them much darker and, therefore, more contrasty. I've only started to think about this since using the RASA. In going so very deep on the faint stuff it makes me want to bring out those faint distinctions which, previously, would all have been compressed into background sky. The price paid for this is a reduction in remaining dynamic range once you've done it. Still, a nice problem to have. Olly

My honest (but perhaps misguided) opinion is that, while you are wading through all this stuff, you could be doing something more productive if your aim is to produce good images at the end. I really do not believe that the difference between good, bad and indifferent images comes from whether or not they have been made using optimal sub lengths. Two hours well spent on learning something new in processing will give you a benefit worth 10x the difference between a reasonable and a perfect sub length. This is particularly true with CMOS sensors of low read noise. Prior to that, using CCD, it was more of an issue: the critical thing in those days was to ignore all the tech gurus who told you that there was no point in doing 30 minute subs in search of faint stuff - because they were wrong. Experiment and, above all, learn about processing. Olly

So this is from an unguided, driven Dob? Give that man a medal. I hope mine won't be the only reply. Olly

Colour and resolution are really punchy and will stand a crop. It's the faint stuff I'd be wanting to revisit. The background sky is dark and flat which makes me think that the faint outer extensions will have been slightly clipped. From what we can see of them, I'm inclined to think they'll be there in the data awaiting a bit of a coddle! Olly