ollypenrice

This is a good one for comparison. https://www.cloudynights.com/topic/616189-m51-how-far-can-i-push-until-it-breaks/

Olly

29 minutes ago, murwille said:

Hopefully all of this was a hoax!  Is Alyn Wallace Dead : “Alyn Wallace: Alive or Dead?” – County Local News  I don't know yet what to believe.

I trust any hoaxers are feeling proud of themselves and are happy to have reached their personal peak on the food chain where they will be a happy find for any passing slugs and snails.

Olly

It's a total non-issue if you have a decent number of subs and a good outlier-rejection algorithm, as others have said. Now that I'm working with CMOS in 3 minute subs, rather than CCD with up to 30 minute subs, sat trails no longer exist, despite the increase in the wretched things.

Olly

Super resolution in the galaxies but is the black point slightly clipped? It's very flat and black. I wonder if you could trade a bit of noise for a bit more faint stuff?

Olly

I'd put it on a Skywatcher AZ EQ6. AZ (Alt Az) is much nicer for visual because eyepiece position and orientation are more consistent and this is OK for planetary imaging, too.  It's quick to set up, with no polar alignment. But... when you want EQ orientation, you have it. Finally, you will not be under-mounted, which is just so nice.

For Ha viewing I would just buy a dedicated Ha scope at whatever budget suits your pocket.

Olly

For focus,  your capture software should give you a Full Width Half Max reading on either a chosen star or an average across the chip.

https://en.wikipedia.org/wiki/Full_width_at_half_maximum

This means that it looks at the bell curve of brightness going from one side of the star, through the middle, to the other side and it measures the stellar width half way up the curve. It can't accurately measure from one side of the full stellar image to the other because the faintness of the edge of the star makes it impossible to be sure just where it starts and ends. If using this FWHM facility in your software, the star must not be saturated. If it is, the top will be chopped off top of the curve and this will then have a flat top. To avoid saturated stars you can choose fainter ones or shorten the exposures, but 3 second-plus exposures average out the seeing and give you more stable FWHM readings. Do expect them to vary, though, at each reading and keep the lowest reading in mind.

In practice, I would use the B-Mask in live view on your bright alignment star, frame up the image and then check FWHM just before starting the run. The thing about FWHM is that you'll find a focus star without having to leave the target whereas, with a B mask, there might not be a suitable one in the frame. So... initial bright star focus with B mask and then FWHM on the target region after that. Check focus regularly - as ever.

Olly

10 hours ago, Gerr said:

Hi Olly,

I see your point and it is easy to overdo the saturation in processing without too much effort!!  I had another go at this and maybe this image shows where you are coming from better but to my eyes it is a fine line indeed to tread.

The M101 core re-done (better hopefully)??

Geraint.

 

For me, way better. We can now trace spiral detail much further into the core.

Olly

13 minutes ago, Gerr said:

Hi Olly,

Core isn’t saturated in the linear data. I guess I like the centres bright as long as I don’t obscure the dust lanes. A number of processing connotations can be followed dependent on your ‘artistic’ side. It’s what makes astro processing so difficult as there is no hard and fast rule to follow - whatever looks good I suppose!! 😂

Thanks,

Geraint.

I'm not sure I agree. Not destroying information in processing is as much scientific as artistic and going from unsaturated to saturated does destroy information.

Olly

I agree with Elp. This would be great with the colour balance eased away from red in the bright parts.

Olly

An attractive nebula, nicely done.

Things I might look at would be 1) noise - StarXterminator is so effective. 2) Colour noise in the background sky. It's quite 'colour busy' and just selecting the background and reducing saturation might make a difference.

Olly

On 20/02/2024 at 10:54, JOC said:

 For viewing the heavens the key seems to be the apparent magnification from the EP.

I wonder if the active ingredient here is the exit pupil?

Olly

I'm not a fan of mini-computers on the scope. I host six remote instruments and have replaced a lot of them for their owners. For long term reliability I like an observatory desktop with a lot of USB ports and I gather the cables at the dovetail and at the top of the counterweight bar and let them hang from there. Clearly this isn't a portable solution.

Olly

1 hour ago, Rodd said:

Thanks Olly. You hit upon a couple of the plethora of problems with this image-hence my frustrated post. Here is the final version of this image. better?

Yes, lovely. I'm going to see if I can find my old linear TEC140 data and see what difference modern processing tools make. 

Olly

I'm surprised this hasn't piqued more interest. It certainly doesn't look like near IR in your data.

Olly

That green glow... I bet you could be persuaded... 

These are great galaxies.

Olly

It's very good and the colour is far more accurate than the bright blue spirals which we often see with M101.

The core is saturated in the first one and still saturated, though less so, in the second. The first thing I'd want to do is look at the core in the linear data. Is that saturated?  If it isn't, there is no need for it to become saturated during the stretch. You just need a better stretch, or a blending of two stretches. Maybe just a hand-shaped stretch in Curves would do it. What does the linear core look like?

Olly

For me, this image didn't seem exceptional until I clicked for the largest size - and then I found that the central bulge and dust lane were absolutely stunning. Unfortunately the last one seems to have been posted at lower resolution, or am I giving it the wrong clicks? It needs to be seen in large format to show its class.

What I do think is that the fainter outer regions are noisy, with a pronounced grain. I'm sure Russ Croman's Noise Xterminator would fix that easily and might allow you to give the lower brightnesses a bit more of a stretch. I wouldn't apply it to the brighter parts or dust lane. Those are superb.

Olly

Ultra-promising.

Olly

5 hours ago, Budgie1 said:

Good question, I assumed it was Oiii in there as I imaged the nebula back in 2022 with the Askar Duo-band filter (7nm) & ASI294MC Pro camera and got a more pronounced central area.

I've also included the Oiii stack from this session, stretched and nothing else done to it.

 

Interesting. This is the blue channel from our OSC camera.

I'd probably vote for reflection, but who knows?

Olly

4 hours ago, TiffsAndAstro said:

Apologies for the title but it's hard to describe what I'm trying to search for.

 

With limited visibility in backyard  say roughly west I can see Orion as it drops, followed by other stars at same distance from ncp

Is there a way to sort of take mosaics as they pass by and then stitch them together?

Cos it might look cool

The answer is 'yes.' This is a mosaic combining 42 individual images.

I can't tell you how to do it in five minutes, though!

lly

Look at that tail! Go for it!!

Olly

On 20/03/2024 at 12:18, Budgie1 said:

The Ha is quite strong but I was a little disappointed the Oiii in the centre of the Christmas Tree Cluster isn’t more pronounced.

 

Is it OIII or blue reflection?

Olly

Very hard for imagers to capture the globular sparkle but you have it for sure. Great image.

Olly

2 minutes ago, gorann said:

Thanks Olly!

Feels like I just got a RASA 11 for 500 pounds!

How well will it hold focus, do you think?

Olly

That looks very promising.

Olly