ollypenrice

19 hours ago, wimvb said:

Today on astrobin:

https://www.astrobin.com/nxatl6/?nc=all

I'm going to be cheeky and say that this image has a better core than ours but we have the uppermost spiral arm showing a full extra section which is not seen in this one.  

Olly

8 hours ago, gorann said:

I am going in the opposite direction, having taken down my 14" Meade ACF and will set up a dual Esprit 150 rig when astrodarkness returns. Even if I have a dark sky, I have realized that seeing here is almost never good enough for allowing the 14" to resolve more detail than a 6" refractor.

Exactly what I found.

Olly

4 hours ago, tomato said:

Indeed it does Wim, and I would keep my RASA8 for that reason. The trouble is, I've always had a longing for a big RC, it was initially my scope of choice when I got back into AP 10 years ago, but I came to my senses after I saw @ollypenrice's galaxies work with the TEC 140s, and went with the Esprit 150s instead. While I'm still a "hands on" imager and not too doddery to handle a big RC, I think I will have to have one just to see how it compares to the refractors. It's not  a rational decision, but there you go, at least someone will get a bargain somewhere down the road.🙂

I understand this and think that, on occasion, you might find very slightly more fine detail with a big RC than with a 6 inch refractor. Purely personally, I'm inclined to leave fine detail to the professionals and am more motivated by the stuff they can't or don't do.  My own Wish List machine would be, without any doubt at all, a 14 inch RASA. I think that it has the focal length and optical resolution to get most of the gettable detail and the speed to bring in features not normally seen. That might even go so far as  being not previously seen.  Even with the 8 inch RASA I think Paul and I found a spiral arm extension in the Sunflower which I haven't seen elsewhere, though it's more than likely that somebody had it previously.

I guess I now just want light on my pixels, above all and bar none!

Olly

Congratulations!  Of course things would be so much easier if your valet were to appoint a cook, a nurse and, later a governess for the nursery. (I'm reading Tender is the Night at the moment so such people occupy every page. Does seem like a good idea, though.  😁)

We've just received an AM3 mount for the Samyang 135 rig.  This is so compact that a permanent 'observatory' for it would be nothing more than a wooden box with a footprint of about a square metre. Our plan is to squeeze it into the 4 scope robotic shed as an extra but it might give you a near cost-free observatory...

Olly

1 hour ago, Marvin Jenkins said:

Ford Probe!!! Why? Anything with the word Probe in it, can only be medical.

'Probe...'  Now don't pretend you don't know why a car maker in search of a, shall we say, thrusting, name might choose Probe.  I remember my English Department being in hysterics when Ford introduced this name. They were making the media analysis part of our jobs too easy.

lly

2 minutes ago, vlaiv said:

But you can take larger sensor and make it if with the FOV you are interested in - by changing FL, and if you couple that change in FL with change in aperture size - then you get faster system which larger sensor allows for.

In that sense - it's not just the FOV.

 

This would require the question to be, 'Does taking a picture with a bigger scope and a bigger chip make a better picture?' to which the answer would be 'Yes,' provided all the other ten thousand parameters 🤪 were adjusted to provide parity!

Olly

21 minutes ago, vlaiv said:

Sensor size affects one very important thing - total amount of light collected. How well is that light utilized - that is something else.

 

The total amount of light collected is of no consequence at all if it is from parts of the sky which don't interest you. If they do, then yes, but that is the same as saying that sensor size affects FOV - which is what I did say!

21 minutes ago, vlaiv said:

Pixel size and sensor size are directly related by simple equation

 I was disappointed by the equation which followed: I was hoping you were going to go all relativistic on us and prove that pixels got larger or smaller depending on how many neighbours they have!

(I do find it irksome when daytime photography writers use 'resolution' to mean pixel count. Grrr. They should be made to place a wet mackerel in a hat and wear it for twenty minutes on a warm day. And that's being lenient!)

Olly

I'm afraid I think it's dead simple:

The size of the sensor affects absolutely nothing other than the field of view, but your optics' image circle needs to be able to cover it.

The size of the pixels decides the resolution up to the limit of the seeing. Pixel size and sensor size are , in principle, unrelated.

The noise is determined by the camera's electronics, cooling and software.

The final framing depends on the imager's crop. There will be more to crop on a larger sensor but this is of no consequence. Ironically, I have found over the last 15 years, that I nearly always crop long focal length/small sensor images and nearly always use short focal length/big chip setups for making mosaics. This might strike you as the wrong way round but that's how my imaging works in practice.

Olly

2 hours ago, Louis D said:

The Ford Fiesta name is a blast from the past here.  They were discontinued in the US after the 2018 model year.  I never did see very many of them in Texas, despite the name sounding like it would have been a favorite among Hispanics, they tend to favor full sized pickup trucks to double as work vehicles.  The Ford Fusion was about as small as most Americans wanted to buy.  It has also long been discontinued in the US market.  Ford hasn't sold any sedans in the US since well before the Pandemic.

After a five week cycle tour down the west coast I hired an American Taunus which looked like our Ford Mondeo of the nineties. Then one day a stylish, but smaller, sedan pulled up alongside and I thought, 'That looks vaguely familiar.' Then I realized that it was a Jaguar XJ6, and that my 'Ford Mondeo' was a monster compared with the European Mondeo of similar shape but not size. Clearly my sense of scale had been 'Americanized' during my stay!

lly

1 hour ago, TiffsAndAstro said:

I can't see me getting a Rasa 8, when I can get a similar result from a edge hd and hyper star.

Don't bank on that. The RASA is purpose built with a high success rate showing among users. The Hyperstar is more controversial.

Olly

1 hour ago, TiffsAndAstro said:

Thanks both. Putting hyperstar on a edge hd gives me Rasa like speed and focal length though, so in theory I could switch between full focal length for galaxies, x 0.7 that with a reducer and then like f2 with 500mm ish with a hyperstar? 

I'm certain it won't be that simple as I've heard reference to mirror flop and other difficulties, but I'll look into those. Also cost but I'm ignoring that for now

My experience of operating an F2 system - in this case the RASA 8 belonging to Paul Kummer, is that when you have it giving tilt-free, collimated images, you will want to touch  nothing, ever, under any circumstances!

You are not (believe me) going to say to yourself, 'Well, having spent nights under the stars and days on the bench with a tilt jig to get this close to right, I think I'll just tear it apart for a quick visual pop at the moon tonight.'  In my estimation, only a minority of users report success with the Hyperstar and, of those who do, none of them swaps back and forth between configurations.

Reality is a terrible thing.

lly

1 hour ago, TiffsAndAstro said:

Looking for reasons why, at sometime in the far, far future, an Edge HD would be a terrible idea for astrophotography?

Yes will need better mount and oag or maybe that weird looking zwo 2 cameras for the price of 3 camera thing. 

But it looks like a good flexible scope with maybe Rasa conversion for just £1000 more ?

The RASA isn't a conversion, it's a dedicated astrographic telescope. There is a Hyperstar conversion for the standard SCT, though.

In terms of what they do and how they do it, the standard SCT and RASA are at opposite ends of the scale, one long focal length and one short. The RASA 8, for instance, does not compete with an 8 inch SCT, it competes with a refractor of about 80mm, since both have comparable focal lengths.

The argument against the standard SCT for imaging is that you can usually reach the resolution limit of the seeing with a focal length of only about a metre. Pixels have become small enough to make this possible. This gives you the option of a far wider FOV for other targets while capturing all the detail you're ever likely to manage in anything.

Olly

4 hours ago, Rodd said:

The data set is compromised somehow, which is not unusual for data from there.  I’ll have another go at it and see if I can get the wrinkles out 

Maybe 8 hours without luminance just isn't enough with the 11 meg Kodak CCD. It only has a 50% QE.  I've done hundreds of hours with this chip and like it in all sorts of ways, but it isn't fast. I'd always shoot luminance on a target like this.

I wonder how the data are calibrated. On mine it was best to use a bad pixel map and a master-bias-as-dark.

Olly

The blues look odd to me. The background seems a little colour-cold and the stars tend towards cycan. There's also a lot to like in the image and its a unique target.

Olly

3 hours ago, andrew s said:

While I admire the thrift of sgl members would not buying new have rewarded the author for his excellent work?

Just a thought. 

Regards Andrew 

 

Fair point. My Kindle edition cost a tenner (in £) and will partially reward the author as well as helping Bezos maintain his minor-continent sized yacht.

Monique and I are now wary of buying second hand books online because, unless they are hardbacks, we risk finding the font too small to be legible, even using magnifying specs.

One of the few things I miss, living in France, is the chance to browse second hand bookshops in which you turn up random, but fascinating, reading material. How else would I have come to read I Sailed With Chinese Pirates by Aleko E Lilius, or Kabloona by Gontran de Poncins, or Ice Palaces by Anderes and Agranoff?

Olly

On 23/05/2024 at 14:23, JeremyS said:

Yes, there are few videos of Dirac speaking in later life. I wanted to hear his Bristolian burr, that the book made much of, but it’s barely detectable to my ear.

Norr to moyne....

(Forgive me, I haven't been to Bristol since the eighties and my recollections of the accent are unreliable! Great city, though. One of the best.)

Olly

11 minutes ago, vlaiv said:

How so?

Just what I've found to be the case. Bright tends towards white when I process data.

Olly

Yes, I think that being cautious not to over-expose in RGB pays off. The higher you go in the brightness the less colour you have. It is also possible to use the RGB as a 'short exposure' set to use in layer masking short and long exposures when the target image requires this. (HDR imaging.)

For me star removal and replacement is now an obligatory aspect of processing in which all you need for the stars is a gently exposed RGB layer. They will be small, tight and colourful. Bingo.

Olly

On 21/05/2024 at 16:18, Captain Scarlet said:

I received mine in the post today. Previously owned it seems by someone called Ruby Stockham who’s signed its inside cover.

I’m a few pages in and already ruing the things I’m not going to get done as all I want to do is get back into the book. I’ve developed a habit as well of diverting off into Wikipedia on many things that get mentioned in passing.

M

I also look on Google for interviews with the authors and, where appropriate, with the subject of the book. Because authors do promotional tours there is usually an interview available and it's nice to have a better idea of who a writer is, I think.

Olly

The thing to remember about our passions (I hate the word 'hobbies') is that they're not compulsory. I felt ridiculously guilty over cutting right down on my cycling but the emotional need for it had just gone. So be it.

Enjoy the music making!  Erm, I like singing. Would you like to hear me? 😬👹🤪

Olly

I agree with Elp in that it's target-specific. There is no point in chasing faint tidal tails in RGB, so put the time into the luminance. Where you're not chasing faint stuff it tends to be easier to combine the L and the RGB if you have a similar total exposure. Pixel by pixel, though, L still gives more light  per pixel than RGB combined - and that's the whole point. Time saving is the reason why the LRGB system was invented.

My focus with Tak FSQ106 and TEC I40 did not change perceptibly between LRGB so I shot RGB, RGB, RGB etc. I also used Lum flats for everything, again with no perceptible consequences. Quite a few of our expert guests do likewise. The L channel is going to define RGB brightnesses anyway but if you do have a problem you might need flats per filter. I didn't so I just got on with it!

Olly

Re backgrounds, I wouldn't hesitate to use the 'add noise' filter on special occasions. You can feed a bit of texture into an over-polished looking background.

Olly

Wow, a feisty image, Rodd, with lots to say for itself. Very impressive indeed, the main spiral looking more contrasty and dramatic than we usually see.

One of your best in my view.

Olly

12 hours ago, gorann said:

Why not just try an SCNRgreen and see what happens?

Thanks, Goran. I never think to use SCNR green on non-linear images but your suggestion worked perfectly. It gave me complete control over the green-blue balance, so here it is more towards blue. I could have taken it further but I'm a believer in baby steps!

Olly

40 minutes ago, Xiga said:

The method I used is a little different.

I first processed the Ha by removing the stars and applying a bit more N-XT than usual. I tried sharpening it, but it was already quite faint and couldn't really take any. Then I added it as a new layer and double-clicked on the layer to open the Layer Style menu. From here, I changed the blend mode to Screen and de-selected the G and B channels. Then I used levels and Curves to really darken the Ha layer a lot, so that it wasn't affecting the sky background. Once I was happy with it, I changed the opacity of the layer to 80% and then made a copy of the layer, only this time I de-selected the R and G channels and changed the opacity to 20%. This way, I was able to weight the Ha 80% to Red and 20% to Blue, which seems to be the consensus for how the Pixel Math brigade do these things. 

Nevertheless, I always trust my eyes over anything else, and I admit I did like the effect. It made the Ha less of a fire-engine red, and gave it a slightly magenta hue, which I really liked, so I think I'll do it this way from now on 😃

That's interesting. The argument for adding Ha to blue arises from the fact that the fainter H-beta line, which is blue, traces the same gasses as Ha. I used to do this in the early days but seem to have got out of the habit. I'll take another look.

Olly