pete_l

It claims to have two versions that work with a wide range of scopes from SCTs to 60mm refractors. I'll watch with interest to see the experience of owners who bought one with their own money.

I sincerely hope you will still be able to enjoy astronomy when you are 90 - I hope I will, too! As for installing cabling that will last 30 years ... I would suggest that access would be a major consideration. Over that time there will inevitably be a need to do something. Even it is just to repair rodent damage. For that reason it might be worth considering having the cabling above ground in a suitably protected and visually acceptable conduit. That would also remove any problems with the channels getting waterlogged. To eliminate any regulatory problems with running mains voltages, you may consider a low voltage system, This would need higher currents and so thicker cables. But whatever you choose, I would suggest instaliing many more cables than you will need right now.

Trying to fit a rectangluar sensor into / over a circular field of view wastes an awful lot of something. Either of expensive sensor area or expensive image circle. The wider and flatter a sensor is, the worse the area of wastage. For reasons that will not become apparent I have been looking at sensors that would be the best "fit" (square peg / round hole type fit) for a Night Owl F/4 FR. This has an image circle of 16mm, so an image area of about 200mm² A ZWO533 is a pretty good match to this, being completely inside the circle, but that only uses 60% of the image circle. A 4:3 sensor that was the same height as the N.O's circle would be 21x16mm and have an area of 336mm² So being 68% too big. A 16:9 sensor with the same height is 28.5x16mm which is 456mm² so more than half the sensor area is unusable. The most efficient shape is therefore a square. What would be even better is if telescope optics produced a square or rectangular image, too

Get in touch with TS. Send them some sample images and annotate them with your observations. Presumably the scope is still under warranty. I have found them to be helpful and knowledgeable in the past.

For those wishing to stay away from the politics, the researcher's original article is available here.

Yes. So a fisheye lens of 1cm² in peak sunlight of 1,000W/m² would subject the 20μ square area of pixels to an irradiance of about 25kW/m² On that basis, a lens of twice that collecting area, that produced the same spot size would be getting close to levels which would damage the sensor. That puts the smallish lenses that I use (like this one) as being "ccd safe". But larger format fisheye lenses, such a CS types used on expensive Allsky cameras may concentrate too much light on the sensor.

Hi Antonio, I couldn't get the link to work. But while exploring I did find some research into laser damage on CCDs. Section 3.5 seems to me to be relevant. The question then is how much sunlight is captured by the allsky camera's lens and how tightly it is focussed onto the sensor. The paper suggests that damage start to occur with irradiance of less than 100kW/cm². If the lens is about 1cm², then peak sunlight would be about 100mW. However if that was focussed on just a few pixels, say 20μ square would that intensity exceed the damage threshold?

Hmmmm. I would question the data about laser induced damage. Simply because 50,000 Watts incident on a 1cm² sensor would vapourise it! The specific heat of Silicon is ~700Joules / °C / kg Assuming a 1gm sensor and plugging those numbers into the calculator [ link] gives a temperature rise of 70,000 °C per second. It is much more likely to be 50kW per m² - leading to a rise of only 7°C per second. But that is only going to be focussed on a small part of the sensor. Probably about a 4x4 pixel area - the size of the Sun on a 180° fisheye 2MP sensor. So the localised heating will be much higher. In addition there is the ambient temperature inside the allsky camera's dome due to electronics and solar gain. So the safety margin is already smaller than the same sensor in a nice cool lab.

IIRC the uploader is a python script. Has something in your Linux implementation been upgraded (possibly without your knowledge) recently? Or even just a duff USB cable?

Now we're talking! An astronomy camera with a sensible 1:1 aspect ratio. That still "wastes" a lot of the projected image from killingly expensive telescopes - only 64% of the light from a circular objective hits a square sensor, But it is a definite improvement over 4:3 and (worse) 16:9 formats, where even more photons slip past.

First, no there is no accepted convention for DIN style connectors. A problem compounded by not knowing if a diagram refers to the plug or socket when showing which pin is wired to what. Second, the simplest form of polarity protection is a single diode in the +ve feed inside the body of the mount. A diode in the plug is of no use at all! However, that diode contributes a significant voltage drop to the motors and the electronics. If your power supply is already a bit marginal, this will just exacerbate any problems and maybe introduce new ones. A better solution is to use a p-channel power MOSFET to prevent any damage. Again, this has to be inside the mount. The simplest implementation is this and for those who want an explanation, see here.

I have a very similar setup. HEQ5. ED80, DSLR, QHY5 guider and a QHY6 widefield, so 3 USB cameras running together with no problems. Software wise I stay with Win7 and I don't use Stellarium, but Cartes du Ciel. Though all the rest .... yes. Flawless performance and more than adequate for the job. My Brix 2807 worked very well until I dropped it. But I replaced it with a BXBT-1900 and that is at least as good.

VATat 20% will be due on the combined cost of the goods and the postage. Depending on who delivers the package to you there will be an additional "administration" charge. How much that will be is difficult to say. But my experience (in the UK) is that it ranges from the unreasonable to the extortionate. You will also not have the protection of UK distance selling regulations.

Teleskop Express (a highly thought of German supplier - ships to foreign countries) suggests a variable length extension for this corrector. Used with a 10 or 15mm fixed extension would give you a range that should cover all possibilities.

Check the clearances of the mount and counterweights. Make sure there are no mount positions where one of the weights would collide with a corner of the top block.

Hopefully the Ali case will be like a FLIRC: passive cooling in direct contact with the CPU. Though that makes the onboard WiFi a bit tricky. Also, the 12 Volt outlets would be good if they were controlled on/off by the Pi4. I reckon the DSLR jack socket is for shutter control

There is a thing called Onstep which is a DIY controller kit that is intended to add goto to many mounts. One of those is the GP. I have the PCBs and connectors that I bought to replace the Skysensor 2000 on my GPDX. Although the charges to import this from the USA was almost as much as I paid for the parts and shipping. https://baheyeldin.com/astronomy/onstep-full-featured-open-telescope-controller.html

sounds good. I hope there's a large dollop of machine learning in there, driving an adaptive filter ........

Agreed. It seems to me that all you do by processing correlated noise is to broaden the point spread function. Essentially adding blur. That would definitely suppress the appearance of noise, but it would alter any "data" in the image, too. What I would like to see is that instead of a field of just noise, to analyse how this reacts with astronomical targets in the image.

There are no negative values for noise. Noise is a random additive component to the desired signal. So it follows that there can be no negative noise values. In all of this I am only looking at shot noise: the time dependent part of the total noise added to an individual pixel which comes from random photons that enter the telescope. Once you have read an image off your sensor, its parameters are fixed. There is a component of the final ADU value of each pixel which will be signal and another that will be the sum of all the various noise sources. Binning does not reduce the level of noise as your experiment above shows (the average noise level is still 25 counts). it reduces the spread of the noise, as you say. A binned image can be post-processed by subtracting the ADU value of the average noise from each pixel. And only then has the level of noise in the image been reduced. But going back to the original text, it says: There isn't any more data. The total number of pixels is the same - just allocated to 4 different subs. So I cannot see how the SNR can be improved to a better ratio than ordinary binning would produce.

I think that only holds true in a continuous system. With discrete data, such as that from an imaging sensor, noise adds arithmetically. An example of a continuous system would be where exposure time of a single image is increased. Then the noise component (being random) of two images would change with the square root of the exposure times. While the signal (being deterministic) with the simple ratio of them. However, once the image data is sampled, that becomes a discrete system with unchanging noise / signal parameters. The insert below is a snap from a spreadsheet which attempts to be a numerical model. Consider the 6x6 array of pixels labelled 'Signal'. This can be thought of a single "image" of a small object that has a centre in the outlined square, with a signal value of 17. The pale yellow squares around it suggest what might be seen, compared with a darker background. I have added some random noise values. So with both the signal and noise data for each individual pixel there are some SNR values. Of course in practice it is impossible to separate the signal data from the noise data for each individual pixel, so all of this is strictly theoretical

Sounds like a smoke detector would be a helpful addition for those intending to do remote solar imaging. As would a firefighting team on standby!

Can we have a shoot-out, please? A single, unprocessed sub from each of these scopes. Side by side. It would be great to see how they compare

You can buy a new mono QHY6 from a UK supplier for considerably less than that

No disrespect intended, but I would suggest the simplest possible set up. While there is no such thing as a computerised telescope that is ready "out of the box" there are ones that only require the minimum intervention to start using once it has been set up. I am thinking of the Meade LX850 Starlock system. It is as close as you will get to one that only requires switching on and it does its own alignment and automatic "centreing" and tracking ready to take images. You will still have to choose a camera for this. I would suggest staying with a "one shot colour" camera. This avoids the added complication of colour filters and having to take different images for red, green and blue light - then needing to use additional software to combine them into a full-colour end result. Furthermore, it would be worth your while contacting your local astronomy club. Not only can they provide local advice (which suppliers to use) and assistance in the initial setup and troubleshooting, but they may be willing to work with you for public outreach events too.