AG12 first light (M55)

Paul Haese · #1 05-09-2018, 04:23 PM

Well, lets say first colour image. The scope has taken lots of hours of tinkering so far and I am far from happy with it at present.

Something I have learnt is that a fast Newtonian gets harder to collimate the faster it is below f5. Tilt of the secondary, centring of the secondary and rotation of the secondary are all hyper critical.

To add to the above the way the Wynne is seated and positioned can be extremely difficult to get right. This is the closest I have gotten it so far, which required a feeler gauge, some shimming and a set of digital vernier. There are still some weird stars off to the right of the image, which I hope to fix one night when I can get down to the observatory for final collimation.

The image is of Messier 55, which is a globular cluster in Sagittarius. I thought this would be a good litmus test for this scope. I must have imaged it over 30 hours in the last month. The image is a 100% crop.

The good news is that the star shapes remain the same both sides of the meridian and no matter where in the sky the scope is pointed.

Click here for larger image.

RickS (Rick) · #2 05-09-2018, 04:53 PM

Looks much improved, Paul. Stars still a little off at top left (eccentricity of 0.4 or greater is visually round) but otherwise very good.

I don't know if you've been following my experiments with fast lenses but you're doing better than me

Cheers,
Rick.

troypiggo (Troy) · #3 05-09-2018, 04:58 PM

Looks great. I like this glob - bit of variety in star colours.
I wonder what that purple star is bottom of glob - a planetary?

gregbradley · #4 05-09-2018, 06:38 PM

Hmmm, how much did you pay?

Great on your progress but as you say for a perfectionist like yourself more to go.

Lovely colours in the stars.

Greg.

alpal · #5 05-09-2018, 08:33 PM

Hi Paul,
that's a nice first pic.

It's hard to tell what's going on after it's been processed.
How do the stars look in the raw FITS in separate LRGB when
you use Maxim DL in 3D mode by putting a box around the stars?
The pic you've presented looks like many stars are flat topped mountains
maybe due to reaching the well depth.
They should be pointy conical shaped little mountains.

cheers
Allan

Placidus (Mike and Trish) · #6 05-09-2018, 09:21 PM

Beautiful Paul. The stars at the edges look excellent.

Quote:

Originally Posted by alpal

… The pic you've presented looks like many stars are flat topped mountains maybe due to reaching the well depth. They should be pointy conical shaped little mountains. …

We think Allan means "Gaussian in profile". A conical profile would be very abnormal.

Although it is true that filling the quantum wells can produce flat-topped stellar profiles that look a bit like fuzzy-edge sequins, for us the biggest cause of flat-topped stellar profiles is trying to demonstrate, in a single 8 bit image, the bright stars in the core and also the faintest features in the corners, such as the half-dozen or more galaxies that you've captured. The process of applying a nonlinear stretch in order to make the super-faint features visible causes an extreme loss of contrast between brightest and almost-as-bright features. That is not the fault of the optics; it is not the fault of the camera chip or the exposure duration; it is not even the fault of the human doing the processing once the decision has been made to show the faint stuff.

The engineers at work used to say, "Price, Features, Time to Market, pick any two." The same applies to processing an image like this. "Bright detail, faint detail, truthful relationship between them. Pick any two."

We'd say that you've done a superb job. And the scope is working superbly.

Best,
Mike and Trish

alpal · #7 05-09-2018, 09:39 PM

Yes - I meant Gaussian in profile.

Ryderscope (Rodney) · #8 05-09-2018, 11:55 PM

Good to see that your hard work is starting the pay off Paul.

Andy01 (Andy) · #9 06-09-2018, 10:19 AM

Your perseverance and patience is admirable in light of what one would expect from a premium product that was far from premium in reality.

However, you're the kind of guy who will eventually tame that beast, and it will surely deliver the goods as expected then

Well done - looking forward to some spectacular images soon

multiweb (Marc) · #10 08-09-2018, 08:32 AM

Not bad at all. You don't have much at all in term of tilt and collimation is pretty spot on. All you have to sort out now is your corrector. Your field is very even and symetrical but not as flat as it could be yet. I suspect corner aberrations can be fixed by tweaking spacing. It's great news it's holding in various parts of the sky with weight shifts though so it's 99% of the work done right there. Keep going.

PS: btw the contrast is amazing. It's picked up loads of background galaxies in that shot so no doubt your figure is top notch.

Ross G · #11 08-09-2018, 08:53 PM

A beautiful photo Paul!

Looking forward to many more from your new telescope.

Good luck.

Ross.

Bart · #12 08-09-2018, 09:42 PM

That looks quite nice Paul. Keep chipping away, you'll get it.

topheart · #13 09-09-2018, 11:16 AM

Well done Paul - I hope you soon become totally satisfied with the rig!
Cheers,
Tim

Paul Haese · #14 11-09-2018, 04:31 PM

Thanks guys for the comments. Things are progressing along now. I have done a lot of work since this image and I think I am getting very close to final commissioning.

Quote:

Originally Posted by RickS

Looks much improved, Paul. Stars still a little off at top left (eccentricity of 0.4 or greater is visually round) but otherwise very good.

I don't know if you've been following my experiments with fast lenses but you're doing better than me

Cheers,
Rick.

I found that it is tiny little tweaks to the collimation and the spacing of the corrector. It is frustrating because the scope is 90km away from home and I cannot just simply walk out and get it sorted. It's closer than these figures now.

Quote:

Originally Posted by troypiggo

Looks great. I like this glob - bit of variety in star colours.
I wonder what that purple star is bottom of glob - a planetary?

I thought the same thing Troy. I have not found it on my charts.

Quote:

Originally Posted by gregbradley

Hmmm, how much did you pay?

Great on your progress but as you say for a perfectionist like yourself more to go.

Lovely colours in the stars.

Greg.

I paid way too much for this scope. Landed was around the 14-15K mark. Optically it is fine but the way it arrived made it hard to sort it out quickly. Better instructions on getting the secondary in the right position would help. You only need to be a millimetre out from centre and this upsets the whole system. Not to mention that rotation needs to be near perfect. I'll write a review at some point.

Quote:

Originally Posted by alpal

Hi Paul,
that's a nice first pic.

It's hard to tell what's going on after it's been processed.
How do the stars look in the raw FITS in separate LRGB when
you use Maxim DL in 3D mode by putting a box around the stars?
The pic you've presented looks like many stars are flat topped mountains
maybe due to reaching the well depth.
They should be pointy conical shaped little mountains.

cheers
Allan

Stretching would have created that flat top look. Stacking certainly evened out the shapes of the stars but fortunately I did not need to do a lot of work to the stars.