Knight of Clear Skies

Think the tripod was reasonably stable and I stayed well away from it for the longer exposure. I don't remember much wind that night but I could probably find some weather station data to confirm. I've used 135mm lenses on three other mounts before and while I've had streaks due to balance problems or misalignment I haven't had a flock of seagulls before.

Yes, it's certainly feasible, and stacking may not be required. Here's a few example 2-minute exposures taken with a 135mm lens at f3.5. In the dark they show up much better on the camera screen and its possible to zoom in to see quite a bit of detail. My Samyang f2 lens would be even better. The above is after a very quick process. Results will be greatly improved by shooting from a dark site, but an Ha filter is an option for light-polluted areas.

My Moon lens cost me £10 from a Charity shop, an old Prinzgalaxy 400mm f6.3. Exposure and stacking details here.

I tested out a newly purchased Star Adventurer for my Dad the other night, using a 135mm lens, and got these results: (2 minutes, 100% crop) (5 minutes, 100% crop) To me, this looks like serious periodic error. Things I checked: polar alignment (not perfect but fair), balance (pretty good, tried to make it a touch East-heavy), made sure everything was tight, put a weight on the tripod tray and stated well clear of the mount when it was taking the 5 minute exposure. Do people agree with me please that this looks like severe periodic error and that the mount needs to be returned?

Great images. Welcome to the forum from a fellow Cornishman. I live in Hertfordshire these days but have family down there still, so do most of my imaging from a dark site on the edge of Bodmin Moor.

Just to add, there are pros and cons to using camera lenses with smaller sensors. While much of the image circle is wasted lens aberrations and vignetting are less noticeable because the corners are cut off, sometimes the lens needs to be stopped down half a stop less which produces a brighter image. Also, depending on the target, the smaller field of view may not be important. The 1600MM Cool, with its small pixels, is a good match for lenses in the 135mm-200mm range. Even 135mm is enough to resolve good detail on many DSOs, note the dust pillar on the head of the Pelican in the image above.

The field of view with the 1600MM Cool is a bit smaller than a DSLR due to the smaller sensor, here's two images with a 135mm lens that shows the difference: (~20 minutes @ f2, 7nm Ha filter, 1600MM Cool) (22 minutes @ f2, 12nm Ha filter, 1100D)

The forum also censors the highest point in Cornwall (Brown Willy) and a number of counties (Essex, Middlesex, Sussex). Edit - or has that been tweaked now?

Yes, I thought my post was clear that my experience may not apply to everyone. It's something to be aware of but it may not be essential to support the lens.

Seems to work fine for me, I have the camera body on a ball-head mount so I can frame images to my liking. It's possible that the lens tilts a touch relative to the sensor (AP is much more demanding than daytime photography) but I haven't really noticed.

Given the huge volume of data I think that's a good guess.

Here's a HaRGB image of the Rosette and Cone. (2h22m RGB and 46m Ha, using the modded 1100D and 2 minute unguided subs. No flats (took them but they were overcorrecting so used GradEx to sort out vignetting), no darks.)

Not full frame, but here's a single sub on the Rosette and Cone with the 1100D after a rough colour balance. Taken unguided, so there is about 0.5-1 pixels of trailing in there. I believe it's f2, but there is a chance I accidently clicked the aperture to f2.4.

Kind of, but a typical Quasar is - if I'm remembering correctly - about 100 times more luminous. It's exactly the same process though, Quasars are just a super-luminous type of active galactic nucleus. 'Quasar' isn't precisely defined.

It's much smaller and less active than M87, despite being far closer the angular size is a lot less. (The apparent size of Sgr A* is only a little more than M87 despite being in our own galaxy.)

I believe the SPT was only used to gather data on Sgr A*.

Arguably, we already have. The effects of accretion disks are visible, there are plenty of Quasars within reach of amateur equipment (up to 12 billion light years away) and the M87 jet is resolvable. The EHT also relies on the accretion disk for its image but has the resolution to show the shadow of the accretion disk.

Very good summary, well worth watching. Thanks Ruud. Surprised to see the Sgr A* image there too.

It exceeds my expectations, I find the image both interesting and inspiring. It's encouraged me to learn about the subject and think about the implications of living with such a monster in your galaxy. M87 spits out a jet 5,000 light years long with the energy - If my math is correct - of 200 million, trillion Deaths Stars. Continually. What effect does that have on star formation, or any planets that stray across its path? Considering the educational value, public interest generated and that it's a test of fundamental physics I'd say the EHT easily passes muster in terms of cost/benefit. (The cost to myself is, at most, a few pence of my taxes.) There may be many applications for a radio telescope the size of the Earth. A couple of my favorite astronomical images are just dots. A single point of light in changed brightness in a predictable manner and we discovered the universe. The Cepheid Variable Edwin Hubble found in M31 proved that it was a separate galaxy rather than a feature of our own. Or the Pale Blue Dot. Not very pleasing aesthetically but as Carl Sagan said " That's us. On it, everyone you ever heard of, every human being who ever lived, lived out their lives." We been somewhat spoiled by Hubble images cosmic vistas and planetary images by probes parked on their doorsteps but there are other aspects to astronomy. Radio astronomy is often overlooked but, for example, observations of neutral hydrogen were an essential tool to mapping out the structure of our own galaxy.

I think it's pretty good for an object which has the angular size of a mustard seed - on the other side of the Atlantic.

Here's a cleaner image.

I know what you mean but I think it's OK to call it that as you can see the black hole's 'shadow'. From the BBC article: "The image shows an intensely bright "ring of fire", as Prof Falcke describes it, surrounding a perfectly circular dark hole. The bright halo is caused by superheated gas falling into the hole. The light is brighter than all the billions of other stars in the galaxy combined - which is why it can be seen at such distance from Earth. The edge of the dark circle at the centre is the point at which the gas enters the black hole, which is an object that has such a large gravitational pull, not even light can escape." Which is pretty good for a very short summary. I'm not sure it's quite correct though, as the dark circle isn't perfectly round and I'm not sure what that means. Also, I read somewhere that the apparent size of the black hole is 2.5 times its event horizon and I'm not sure why. Hopefully in the next few days there will be some more technical (but readable) articles from people like the Bad Astronomer and Ethan Siegel which will shed some more light on what the image means.

I think you're right. There was a lot of confusion over this as people were expecting to see Sgr A*, which has a larger apparent size. However, it's also a lot dimmer than the core of M87, so probably harder to image despite being much closer. Has anyone said when the image of Sgr A* is expected?

It's the M87 black hole rather than the one in our galaxy (the OP references Sgr A*), which the EHT is also imaging. The source of the em radiation is the accretion disc around the black hole, hope that clears things up.

Joking aside, the M87 jet probably is resolvable with a small scope and small-pixel camera like the 1600MM-Cool. So while we can't image the black hole itself we can confirm its existence, I'd like to know how the EHT image aligns with the jet. If I get a chance over Easter I'll probably have a go at it, I believe fairly short exposures are required to stop it getting lost in the core.