m45

[alacant]

Hi everyone

Trying to decide if loadsa short frames are better than fewer longer frames. Any ideas/examples most welcome.

m45 en tauro, 72 x 1 min ISO800. Looks quite promising. The noise seems to be under control, even for a short exposure time.

Cheers and thanks for looking.

Edited December 6, 2023 by alacant

[Elp]

I think that looks good as it is. The issue with this one is if your optics cause star halos, the stack will show almost solid circles around the bright stars. My SCT does it so i've decided to do this with a refractor or camera lens instead when I get around to it.

[ollypenrice]

This is an unusual target. What you have is as tight as a drum, which is obviously a good thing. I think your stars are small and crisp, given their brightness. Spikes or not spikes is just one of those things. In any event, they are good spikes. There is also nicely structured detail in your nebulosity. For an M45 of this depth, it's very good. More than very good, in fact.

The question is, How deep do you want to go? There is an enormous amount of nebulosity not showing at this depth but going after it is not compulsory, it's just an option. All depths are valid, in my view, if the data are properly respected.

Olly

[alacant]

On 06/12/2023 at 18:51, Elp said:

do this with a refractor

Hi

I had a go with a refractor but it takes ages; 6 hours. I don't think an hour or so would get much detail. Do post your image and prove me wrong though!

23 hours ago, ollypenrice said:

if the data are properly respected.

I think that's important. Even with just 72 minutes, it's tempting to push beyond what's really there.

When to stop? Having to continue processing to combat artefacts -not just noise- you've introduced is perhaps a good time to decide where processing ends and over-processing begins.

Edited December 7, 2023 by alacant

[Elp]

7 minutes ago, alacant said:

I don't think an hour or so would get much detail

This is an interesting challenge.

[ollypenrice]

1 hour ago, alacant said:

Hi

I had a go with a refractor but it takes ages; 6 hours. I don't think an hour or so would get much detail. Do post your image and prove me wrong though!

I think that's important. Even with just 72 minutes, it's tempting to push beyond what's really there.

When to stop? Having to continue processing to combat artefacts -not just noise- you've introduced is perhaps a good time to decide where processing ends and over-processing begins.

Over-processing can introduce artifacts, certainly, but they can also be inherent to the system. Personally, I see post processing as an activity which involves 1) extracting what's in the data and 2) performing cosmetic correction of artifacts. This involves a negotiation between what's in the data and what's up there in the sky. I guess we'll all differ to a greater or lesser extent on where these boundaries lie, but my bottom line is probably this: if it isn't in the sky I don't want it in my picture. Then again, even that doesn't really work because all stars are point sources in amateur instruments. We are doomed to live in a world of compromises. 

Still, I agree with your definition of over-processing, I think.

You like imaging quickly. Have you considered a RASA? They do leave you with some cosmetic work to do, though.

Olly

Edited December 7, 2023 by ollypenrice

[alacant]

1 hour ago, ollypenrice said:

imaging quickly

Not imaging. Processing.

If it's not working out, it's only because you have poor or not enough data. Best to go and get more frames the next night than sit in front of a screen over processing data which will never yield.

No theory in support of my claims. Just lots of wasted time!

 

Edited December 7, 2023 by alacant

[alacant]

1 hour ago, Elp said:

interesting challenge

I once witnessed a side by side with an 80ed and a similar fl Newtonian. 150mm I think. DSLRs. For me at least there was a clear winner.

But that was five years ago.

[Elp]

My 1h with my C6+HS wasn't that eventful for me, but I was testing a new to me camera and I'm also bortle 7 so...

[alacant]

1 hour ago, Elp said:

C6+HS

Sorry, me being thick. I drew blank on Google.  Could you spell it out? TIA

[Elp]

Celestron C6 SCT with added Hyperstar lens (6 inch aperture scope imaging at F2).

[ollypenrice]

12 hours ago, alacant said:

Not imaging. Processing.

If it's not working out, it's only because you have poor or not enough data. Best to go and get more frames the next night than sit in front of a screen over processing data which will never yield.

No theory in support of my claims. Just lots of wasted time!

 

I agree. On the other hand, some processing tasks are inherently complicated even with good data. Mosaics are the obvious example because small gradients, insignificant in a single frame, add up in a mosaic. Very, very faint signal also tends to be tricky. I mean signal so faint that doubling the data will not significantly assist in the task. And then some systems just do throw up artifacts in need of cosmetic correction. I wish they didn't but they do, and I think that making a good job of them is rewarding.

Our cameras also have limited dynamic range, emphatically more limited in a single exposure length, so using multiple exposures or combining multiple stretches is a slightly involved process which can extend the range. I think this is perfectly valid and, again, enjoyable to do.

Olly