x6gas

Wow - stunning.

1 hour ago, Elio_C said:

As I mentioned I'm looking into a new telescope and I've come down to two options, they are both refractors with an aperture of 70mm, one with a 700 mm focal length, and the other with a 900mm focal length (and a much better mount, albeit a bit out of my budget).

Is there actually any advantage to having the 900mm focal length when both of them have the same highest practical magnification (140x)? What's the benefit? 

I am aware that a longer focal length means a greater f/ ratio and apparently that's good for astrophotography, but astrophotography is not really my thing so that does not hold any appeal to me. 

Thanks!

Hello and welcome to SGL!

Longer focal length - for the same aperture - means a greater f/ratio and means that the system is 'slower' than a system with a lower f/ratio.  A fast system is usually considered preferable for imaging though it comes with problems (more difficult to get a properly corrected image and very precise focusing required.

For visual, the longer focal length scope will be a bit more forgiving all things being equal... but it would be worth posting the scopes you're interested in so that people can properly comment - we all love spending someone else's money!

On 10/05/2020 at 22:08, David Smith said:

Hello Richard, from a fellow Oxfordshire resident.

And from another one!

That's truly amazing for an unguided image.

All good wishes to you and your wife Vlad...  my wife and I have also had it.  I was lucky and was virtually asymptomatic but my wife was in bed for the best part of two months and fully four months after her first symptoms still gets fatigued very easily.  If you are unlucky it's a very, very nasty virus so do rest up... and then rest some more... and when you are feeling properly better... keep resting for a few more days!

Super image Olly and the bluntest tools can produce delicate results in the right hands which you have proved here.

I've delayed responding as I wanted to check my own data.  The subs I have at 860mm don't show the shock wave as it's just out of the frame but it is visible pretty clearly in the version I took with my FSQ85 and I didn't remember having to work too hard to drag it out... but going back to the original stack, it's pretty faint and gets a bit lost in the OIII signal that is pretty widespread across the field of view.  Here's a crudely stretched, and very noisy crop:

I wonder if you got a similar result?  If not, and if you did your trick of holding down the background noise when stretching the data, could that have suppressed this feature?

As I say, lovely image...

Ian

Beautiful.  Very nicely done.

Oh yeah.

Nice bit of turning your mate did on that adapter, Adam.  Cutting the threads "by hand" on a lathe (which means turning the lathe by hand) is pretty common as it gives excellent control.

And the image looks brilliant!  Clearly a nice piece of glass...

Steve - absolutely love your image.  That's one of the best M31s I've seen and it's very nice to see the Ha regions in deep red rather than the neon pink that is more common.

Lovely result, well done!

I can see in theory why you'd want individual RGB subs from a mono camera to be the same length as the luminance subs but in my experience it isn't necessary as you can stretch the colour data harder, give it a lot of noise reduction if necessary and rely on the lum for detail.

Lovely image, as ever, Brendan.  Very nicely balanced...

Well blimey that's a lovely image... and for a first SHO... well you wouldn't know.

Stars are a bit red in places - maybe a job for selective colour in Photoshop? - but what the heck... it's a fantastic image.

So much going on in that image Carole - well done.

Nice image Marv - well done.

The background looks a tad too dark to me but a great rendition nonetheless.

Great effort for a first processed image - well done!

3 hours ago, ramdom said:

Thanks! It looks helpful - I have been following the LVA tutorial except for using the PSFImage script to generate the PSF (I did it manually once and this script seems to do better) from Herbert Walker's page (it's a great tool if you've not used it before).

Yes +1 for PSFImage.  Like you I've done it manually and PSFImage seems at least as good and 100x quicker.

2 hours ago, Datalord said:

I think I'll have to disagree with this one. Decon is a seriously good tool to sharpen nebulosity. So much so that I sometimes go a little too far with it, but it definitely works on nebulosity.

Well fair enough - though I didn't say its doesn't work on nebulosity - just that it won't do much to sharpen it... which has been my experience.  Be interested to know if you use different settings on stars and for the nebula.

I agree with MarkAR - something in between maybe?

Nice image and a new one on me.

Anyone else she a lady's face in the blueish-white nebulosity surrounding the central target - nose just below the 3 o'clock position and a pony tail at abot 10 o'clock?  With the bright central object it looks a bit like an advert for a headache tablet to me!

Well if your processing skills are basic it's certainly not holding you back!

You've got some real crispness in the nebula without over-sharpening it.  Very well done.

Has a subtlety and moodiness about it Brendan and I like that you appear to have left a bit of green in the nebulosity...

That looks very nice.   Haven't tried starnet++ yet but I will definitely be doing so soon based on this!

That's a lovely image of a great target and you have processed it really nicely.  Very well done.

That colour mapping does work well and the star colour looks good to me.

On my screen parts of the nebula look over-cooked (both in terms of saturation and brightness) but that's a matter of personal taste.