ollypenrice

6 hours ago, GalaxyGael said:

 

I do like the hint of blue giant light reflecting off the lower ramparts of the dust though

It's nice that you should make this point because I felt the same. It was one of the little nuances that made it enjoyable to process.

Olly

My co-conspirator Paul Kummer described this as a 'B list image' or even a''C list.'  I don't see this rendition sending it to the top of the target hit parade either. 

But... it's there and it looks like this. Trust me, there isn't much to work with, but 85x3 minutes in the RASA 8 gives data which can be stretched to screaming point. This job had more to do with torture than with processing.

Capture and pre-processing by Paul, post-processing by me.

Olly

BTW, the 'Crescent' name makes sense if you observe this visually. Only the bright outer rim is visible and it does make a crescent shape.

Olly

Good!

Olly

This is very classy imaging indeed. Sharp, clean, balanced, free from exaggeration and with totally invisible processing.

Chapeau!

Olly

Nice. Is that the full field at 250mm FL on the 2600 chip? It seems much more restricted than I'd have expected.

Olly

The Squid is outstanding, bold and smooth.

In your shoes I would go for more broadband rather than more OIII. Paul Kummer and I recently did an image of this region in one shot colour with a very fast system. The result is almost the opposite of yours: we have deep dust and reflection nebulosity but no Squid whatever!  We should collaborate! 

Olly 

Very good! Simple as that.

Olly

Lovely, and an inspiration for all who work from light polluted sites.

Olly

The great square is a famous test of naked eye observation and sky quality. A number of us, here, tested another guest, famous for his eyesight, and we were all convinced that he made mag 7, naked eye. This is not unprecedented, but t is rare, and we do have a good sky.

Olly

9 hours ago, Clarkey said:

I'm just wondering the difference between this and a mini PC? It's just a small computer. No hub, direct usb connections. I use a homemade power box and a mini PC on the rig and so far it has been bomb proof. Now I've jinxed it....😀

The difference is that I've swapped out a fair number of failed mini-computers on behalf of their owners, but never a full sized PC. This is anecdotal and doesn't suggest that all mini PCs will fail.  However, when setting up our jointly-owned rig in my robotic shed, it won't surprise anybody that we went for a destop, based on this experience.

Olly

48 minutes ago, Killpond said:

The "GOTO" worked once I disabled the feature that needs a main cam to plate solve so it knows the goto was correct. Polar alignment and plate solving using the ASI mini sounds cool but will PA work if the cam is offset to the right of the axis? I have the cam and guide cam left and right of each other and the mount rotated 90 from normal. Will this offset cause the PA to be out of line?

I'm also intrested to see how far off my focus has been. The focus on Fuji is by wire so I can store a focal point in the lens to quick snap too. Looking forward to seeing how far off it was once I put the mask in place.

It took about 200 years for astronomers to detect stellar parallax (shift in apparent position) when the Earth was offset by 2x its distance from the sun (ie when it was six months away from its previous orbital position. Call it 200 million miles.)  Even this offset was impossible to detect till they factored in the effects of changing atmospheric refraction. I think you can relax about a few cm of offset.  

Olly

Big second hand desktops with lots of USB ports are quite cheap. Put it on a trolley with damp protection, ditch hubs and mini-computers and live happily ever after.

Yes, I'm old-fashioned - but I also host six robotic imaging rigs so I have some insights into what actually works.

Olly

Just now, Elp said:

So the big Q. RC or SY?

More resolution in the Redcat but far less speed/depth/FOV. It's the imager's choice. On targets with fine detail the Samyang lacks resolution and is at its best making mosaics where each panel will be downsized so that this doesn't matter. With the Redcat you'd get more detail in more time. Is that what you want? I think that it takes a certain amount of experience to find out what you want and what will provide it. What I want is irrelevant. What do you want?

What I really wanted to say is that the Redcat's numbers are out there: Focal length, aperture, F ratio... The question remains, Does it do those numbers well?  The one I met today does them very well indeed, to my eye.

Olly

31 minutes ago, Elp said:

Think you've been missing out. Looking with interest at their Pleiades scopes later this year.

With a RASA 8 and a Samyang 135 I don't feel I'm missing out on widefield, but the Redcat strikes me as being damned good.

Olly

I'll admit to a lingering wariness when it comes to William Optics instruments, suspecting a risk of style over substance, a pretty finish over good mechanical engineering. Maybe I'm just out of date on this, as on many other things.  

However, today I processed some data taken here by a guest using a Canon 5D Mk3, so full frame, in a Redcat with a FL of 250mm.  These are, of course, great numbers for anyone wanting to shoot widefield. We didn't have flats and the image came out with a very red bias, easily subtracted using ABE. The gradient map was a flat sheet of red so there really can't be much vignetting and I saw no sign of any in the stretching. Better still, We ran the data through Blur Xterminator and the stars seemed tiny and tight, corner to corner. Once we started stretching, they remained tiny and tight. Star Xterminator produced a nasty grid pattern this time, as it occasionally does, but then we asked ourselves why we wanted to use it anyway? The image, centred on Sadr, had such small stars that we didn't want them any smaller and they were still perfect into the corners. Sadr itself was better than it was in my Tak FSQ106. It had the smallest of soft halos and was OK as it was or it could be tightened up in 30 seconds in Ps if preferred.

Frankly, I was mightily impressed by these optics. I'm already using two short FL systems, both F2, but, if I weren't, Id be raiding the piggy bank, I think.

Olly

There is a lot you can do in post-processing to reduce star bloat.

If you use Star Xterminator you'll get to the stage where you are ready to replace the stars and have them as a top layer over the starless image. Simply increasing the contrast on the star layer can drop the bloat below the level of the nebulosity in the bottom layer so it won't show. The stars themselves become brighter but then you can adjust the global brightness of the star layer. The key thing is contrast in the star layer, which you can adjust using Photoshop's contrast slider or have more precision using an S-Curve in Curves.

Olly

3 minutes ago, vlaiv said:

@Swoop1

Did you use UV/IR cut filter? If not - star bloat can be because of that. ASI290MC does not have one inbuilt.

That would make sense.

Olly

2 hours ago, Swoop1 said:

@ollypenrice- transparency wasn't perfect and, later in the evening, when I switched to lunar, there was a definite softness to the sky.

In which case I'd give the rig another run under a crisp sky.

Olly

Hmmm, I'm a little dubious. What seems odd is that, the bigger the stars are, the softer they are. Yes, this is normal enough but, here, it seems exaggerated. We seem to jump from small, tight stars to large soft ones. Was there any haze when you shot this?

On the basis of just this image I wouldn't, personally, sign off the optics as all OK just yet. I'd try another dense star field.

Olly

On 04/09/2023 at 12:20, JOC said:

I believe science on the curriculum would be far more interesting for students to study if only the teachers would include the 'why' when they teach something.  The numbers of practical science experiments I carried out at secondary school without ever understanding 'why' we had done it, until 10+ years later it dawned on me out in 'industry' why that particular experiment had been important, were many and would surely have added to my enjoyment and perhaps even have captured the imagination of more students.   It is a hole that I really try to fill when I go into schools as a STEM ambassador.

What you are describing doesn't just apply to science teaching, but to all teaching. It's sometimes called 'decontextualized teaching,' and leads to something fairly useless called 'school knowledge.' That's to say knowledge which will never play a part in students' lives outside school. It is, as you suggest, the enemy of real and useful teaching.  But...  it is very important not to misunderstand this problem. It is not resolved by finding cutesy little applications of what is learned in class. (I'm not suggesting that you think it is, let me stress.) There is no value in conducting a decontextualized chemistry lesson and then tagging on, at the end, the assertion that 'This is how we make nail varnish.'

Personally, I think that a contextualized lesson is one which delivers the pleasure of truly understanding something.

Olly

10 hours ago, OK Apricot said:

Well I must say chaps, thank you for the impromptu optical theory lessons 😅. I've tried to have a good read through to understand what you're debating but sadly it is above my intelligence level! 

Could you summarise what you're saying here in layman's terms? 

@ollypenrice I didn't know guiding RMS has to be <half your sampling rate. I was under the impression that as long as the RMS was under your sampling rate, you wouldn't notice any tracking errors. Please could you explain why that is?

Cheers chaps 😊

I think Vlaiv has answered that far better than I would.

I also think it's worth saying that undersampling may not be a problem at all on some targets. Large, diffuse nebulae, for instance, often contain little fine structure to resolve. Galaxies, of course, contain a great deal and these are the subject of your thread. However, galaxies also produce tidal tails and streams which are inordinately faint.

Arp 94: I imaged this, or tried to, in the TEC 140/CCD rig at 0.9"PP. In the end I gave up. The interest in the image is the tidal streaming and I just couldn't get this to separate reliably from the background. I had nice detail in the galaxy cores but they were not what I wanted.  When I tried again with the RASA 8 I could not resolve fine core detail at 400mm FL but the tidal streams were plain sailing.  With finite resources there will always be compromises.

Olly

On 19/12/2022 at 08:38, Karl Perera said:

I shall surely be returning to this page as a reference because Photoshop is what I am using and I need to improve.

It remains a wonderful program for astrophotographers. I refer to it as 'civilization,' to which I return after carrying out adjustments in more barbaric environments!

lly

2 hours ago, tomato said:

Nice to see this lively thread maybe ending on a remarkable image of M51, although I have to say it is not to my tastes. The faint nebulosity looks a bit over processed to me and has a painted on look but perhaps that how it is in reality. 
I prefer images with (dare I say it) more detail in the actual galaxies. 
I agree with Olly that amateurs can really only break new imaging ground by going deep and off the beaten track, but if your favourite objects are galaxies then you can only strive to get the best detail you can with the kit and location you have.

And I’ve obviously not got the message as I have just ordered a camera with 2 micron pixels….😉

Interesting! What are you going to put it in?

Olly

18 hours ago, George Jones said:

Several years ago a colleague asked me to write a short homage to physics that emphasized fundamental curiosity-driven physics. Writing to order, I produced the following hyperbolic passage, which my colleague has used several times in presentations.

"Why study and research fundamental physics? Why study curved spacetime and general relativity? Cosmology? Elementary particle physics? One possibly selfish reason for me and many other physicists is "Because it's fun!", but other reasons exist. Science, including non-applied fundamental science, is part of who we are as a species. Fundamental science is as much part of our culture as music, art, and literature. If we lose the desire and ability (possibly through politics) to ask fundamental “Why?” questions of our world, we have failed as humans."

 

Bravo. Ten times bravo.

As for the 'justification' of science through technology - no.  There is a hell of a downside to technology but to science there is none.

Olly