Knight of Clear Skies

This article is worth a read, ALMA and the VLA have been looking at accretion discs in Orion. I appreciated the location map showing where the protostars are located.

Lovely. Finally a use for 4k TVs.

Nice job to capture the tail on our interstellar visitor.

I you have a clear horizon, you could try aiming at a light in the distance and take a long exposure with the tracking on. It should produce a clean arc, if it wriggles back and forth it's likely to be periodic error. I had my SA replaced and the new one seems to be fine, but I've had very little opportunity to use it.

Here's the same article on Medium, for better readability. As currently planned, Starlink is going to kill survey telescopes such as the LSST and Pan-STARRS.

Nice work. Hadley Rille pops out with the zoom, here's the view from the surface.

What camera did you use please?

Interesting stuff. I wouldn't expect a large increase in performance from these cameras, quantum efficiency of existing sensors is already very high. The question is what the noise profile looks like without cooling, the article suggests improvements are possible here. Potentially this could make large sensors more affordable but we'll see what happens.

Vintage equipment challenge? Most distant object?

Something I found in my archive, a 2 minute shot of the NA & Pelican. Just a quick colour balance, stretch and slight noise reduction. Might have a go at processing this properly if I can find the time. Here's a closer crop of the nebulae.

Star clusters would make a good target for this challenge. If it was taking place in the Autumn the Samyang 135mm would be hard to beat. This is 2 minutes on the NA & Pelican at ISO 800. The above is pretty much straight out of the camera, just a quick colour balance, stretch and very slight noise reduction. Something similar could be obtained in 30 seconds by bumping up the ISO and de-noising more aggressively. But at this time of year it's hard to think of many targets for it.

The batteries were new so should be OK, and it was warm outside. Now I've plate solved the image the image and checked the movement in RA it's running both fast and slow, which is good evidence the gears are the problem. I have two more 5 minute subs that look very similar.

Thanks for the suggestions everyone. I've plate solved the second image I posted to confirm the camera orientation, the seagulls are caused by uneven movement in RA. Looks like the mount is faulty as I'd need to take the exposure time below 30 seconds at 135mm to get reasonable star shapes. I also checked the weather that night, as I remembered there was very little wind. Yes, I sighted the polar scope on a distant tree and rotated the mount to confirm this. However, I just used the PolarisView app to check the where Polaris should be so I'm not concerned by the drift in dec. I'm going to talk to the supplier. While I'd like to run another test I'm now back in Hertfordshire without access to the mount.

What kind of star trails did you get though please? Did you get any seagull shapes?

I rechecked PA with the camera on, Polaris was still within the ring which shows the tripod hadn't shifted. It was just a rough polar alignment though, straight trails wouldn't have concerned me. I doubt my polar alignment was good enough for 5 minutes at 135mm pointing south, but the longer exposure makes it easier to see any misbehaviour from the mount.

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.

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?

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.

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.

No problem, I've added a few more details to my posts. There are also a few tips on using it in my first post to this thread.

@Rush - Are you sure that image of the Pleiades and California was taken with the Samyang? That looks more like a 50mm shot to me.