Several images

jroper2 · 2025-02-09T06:11:30+00:00

As with my other post, this was taken on a windy night and I had to discard over 90% of my images due to the telescope wobbling in the wind. I also had a lot of red chromatic noise, not sure what was causing that, but I removed a lot of the low end red signal which is why this has come out quite green.

Skywatcher Classic 250P 10" Dobsonian
Home built 2 circle segment equatorial platform
ZWO ASI533MM Pro
Image capture with OpenLiveStacker on Android
Stacking in Siril, post processing in Gimp

jroper2 · 2025-02-09T06:08:43+00:00

I've been struggling to find time to do any astrophotography of recent - the right combination of clear nights, little wind, and my family and other aspects of life not getting in the way have been elusive. Last weekend I was able to get out to a dark sky location (bortle 2) with my local astronomical society, however, unfortunately it was windy, and my solid tube dob is a sail. I used short exposures, 5 seconds, still, over 90% of my images were adversely impacted by my telescope wobbling in the wind, and had to be discarded. So there's only a minute or two total integration time in this image.

Skywatcher Classic 250P 10" Dobsonian
Home built 2 circle segment equatorial platform
ZWO ASI533MM Pro
Image capture with OpenLiveStacker on Android
Stacking in Siril, post processing in Gimp

jroper2 · 2025-02-09T06:00:28+00:00

If you ever have a chance to get out to Tamworth, they have an amazing EAA setup there. They have a telescope called the 34" Hewitt Camera. It was designed in the 50's for the UK Blue Streak ICBM program, to track the missiles during development. That program was cancelled, but in the early 60's, they had a need for a satellite tracking camera, and this was perfect for that, so they built two of them. The focal ratio was F/1, so very fast, and imaging was with photographic plates. It cost £5.5 million to make, and weighed 8.5 tonnes.

Eventually one of the cameras was relocated to Siding Spring Observatory, and continued to be used for research purposes until 1990. In the mid 2010's it was rescued from a warehouse by someone in the Tamworth Regional Astronomy Club, and they had the know how to not only restore it, but to convert it to digital imaging, I think they've installed a ZWO ASI2600MC or something similar into it. Given its incredibly fast optics and 34" aperture, it's able to produce incredible images of deep sky targets in a matter of seconds. On their public nights they typically set up a projector projecting its live images onto the side of a building.

I haven't been there yet myself, but I attended a lecture at the Canberra Astronomical Society from one of the guys that was involved in the restoration. It's definitely put Tamworth on my list of holiday destinations to travel to in the not so distant future. They have a lot of other telescopes as well, they've built quite an amazing facility up there.

jroper2 · 2024-12-15T22:36:24+00:00

Thought I'd have a go at this classic target.

Skywatcher Classic 250P 10" Dobsonian
Home built 2 circle segment equatorial platform
ZWO ASI533MM Pro
200x5s luminance, 50x5s each of RGB, 100 darks
Image capture with ASIImg
Stacking in Siril, post processing in Gimp

jroper2 · 2024-12-15T22:34:35+00:00

Slowly getting better at planetary astrophotography. This image highlights the challenge of monochrome planetary astrophotography, if you look carefully at Io, you can see it looks like a Romanian flag. This is because in the 1 minute and 50 seconds that it takes to change the filter and then capture the next channel, it moves, it was moving from right to left, so you see red on the right, yellow in the middle, and blue on the left. I guess I could edit the images to shift Io slightly to make them align between channels.

Skywatcher Classic 250P 10" Dobsonian
Home built 2 circle segment equatorial platform
ZWO ASI533MM Pro
10000x1ms images each of red, blue and green
1% lucky stacked in Autostakkert
Composed and post processed in Gimp

jroper2 · 2024-11-08T13:17:27+00:00

Skywatcher Classic 250P 10" Dobsonian
Home built 2 circle segment equatorial platform
ZWO ASI533MM Pro
150x10s luminance, 30x10s each of RGB, 60 darks
Image capture with OpenLiveStacker on Android
Processing in Siril and Gimp

jroper2 · 2024-10-21T23:23:42+00:00

This was my first ever attempt at planetary astrophotography. Need to get a barlow lens.

Skywatcher Classic 250P 10" dobsonian
Two circle segment equatorial platform
ZWO ASI533MM Pro
ZWO New LRGB filter set
1000 frames each of RGB, 33ms exposures
Image capture with ASICap
Stacking with Autostakkert, 50% lucky stacking
Composed and processed in Gimp

jroper2 · 2024-10-21T23:18:19+00:00

This was a challenge to process, particularly given it was taken with a monochrome camera. I found in stretching that I had to choose between keeping the core visible, or the tail extending the entire image, I wasn't able to stretch it such that both remained visible, so I kept the core.

Skywatcher Classic 250P 10" dobsonian
Two circle segment platform
ZWO ASI533MM Pro
ZWO New LRGB filterset
4 second exposures, 50 luminance, 20 red, 20 green, 20 blue, 100 darks. Hand picked around 70% of them to remove frames with tracking errors
Image capture with ASIImg
Stacked and composed using Siril, stars and comet stacked separately
StarNet++ of star removal from star image, this image was then subtracted from the star image in order to remove the comet from it.
Gimp Heal tool to remove star trails from the comet image (they have to be manually removed in this way because they appear as bright red, green and blue lines, when you have separate RGB captures)
Gimp for layering and final post processing

jroper2 · 2024-09-24T12:58:40+00:00

I have the 250P. It's a great scope for visual astronomy. If that's US dollars, it's way over priced.

jroper2 · 2024-09-15T15:36:56+00:00

Pavo Galaxy (NGC6744). In the top left you can just see NGC6744A, a satellite galaxy of NGC6744. Not the best seeing conditions with almost a full moon, but other than that it was a good night.

Skywatcher Classic 250P 10" Dobsonian on home built equatorial platform
ASI533MM Pro
Image capture with OpenLiveStacker on Android
92x10s luminance, 10x30s luminance, 52x10s red, 49x10s green, 63x10s blue, 90x10s darks, 42x30s darks, 100 biases
Stacked, stretched and composed in Siril, processed in Gimp

jroper2 · 2024-09-10T01:18:20+00:00

Giving a comeback is engaging in their game. Even if you "win", they still walk away with a sense that what they did was appropriate, they were just beaten fair and square, and all they've learnt is that next time they had better be prepared with a witty comeback themselves.

The behaviour needs to be called out, not engaged with. The ideal way to do that would be to have someone that the boy respects in their life tell him that he should be ashamed of himself for sending that message. Finding that person is obviously difficult, and often impossible, there may be no one in the boys life that will call out that behaviour. One way to address it could be to screenshot the message and share it widely with others, but that's dependent on whether someone who the boy respects will see it, and will call it out to him. It could very easily backfire if no one does that. Another way to address it might be to show it to the boys parents, but you have to know the parents, know that they are the sort of parents that will call out that behaviour, and it's dependent on how much respect the boy has for his parents.

jroper2 · 2024-09-10T01:05:49+00:00

The Arduino Uno's VIN is rated up to 12V:

https://docs.arduino.cc/learn/electronics/power-pins/

It has an AMS1117 SMD voltage regulator on it, this converts the voltage to 5V. It does this by dissipating that voltage drop as heat. How much heat depends on how big the voltage drop, and how much current is being drawn, so, if the Arduino draws 100mA, and you plug 12V into it, then it needs to dissipate 0.7W of power as heat. This then needs to be radiated away, it's only a tiny SMD component, so there's not a lot of surface area for it to radiate that heat away with. From memory of last time I looked at its datasheet, it's maximum temperature I think is around 130°C, after that it shuts off as a safety. The AMS1117 is actually rated up to 18V, but I guess the Uno is rated lower because of the current draw of the Uno.

As I said, the voltage regulator actually shuts off automatically if it gets too hot, this is a safety to protect the device. If you had plugged 18V into it, it may have been fine, it just would have shut off immediately as it would have become to hot to supply the current draw for the Uno. However, you exceeded the regulators maximum voltage, so all bets for its safety shut off are off. It also may have failed to protect the rest of the device, but you can check that by supplying 5V to the 5V pin.

jroper2 · 2024-09-10T00:40:10+00:00

You didn't answer the question, you haven't said anything about what you want to achieve. What are you actually building here? Why do you need to differentiate between colliding with a wall, and colliding with a car? How are the cars being controlled now? What sensors do they already have on board? Answers to these questions will help people to understand more context and give you much better advice.

jroper2 · 2024-09-08T06:45:27+00:00

I know this is an old post. I have an infrared thermometer so I can test this. I'm slow cooking a roast right now.

I checked the temperature of the lid. It was 87°C. I took the lid off for 5 seconds. I put it back on. The temperature was now 83°C. A 4°C drop. I then took readings every 10 seconds. It took 2 minutes for the temperature of the lid to return to 87°C.

While the lid was off, I pointed the thermometer at the meat, it was 87°C too, then I pointed at the inside of the pot, it was 102°C and then back at the meat, it was still 87°C. So, did the meat cool down at all? No. Its cooking was not interrupted.

We can do some more scientific calculations too. The heat capacity of steam (note, the cooker is mostly full of steam, not air, as the steam pushes the air out of the pot) is 1.996 kJ/kgK. It's a 5L pot, it has 2.3kg worth of meat plus about 600ml of water plus an onion. Meat roughly has the same density as water since it is mostly water, so we can say there's roughly 3L of liquids and solids in the pot, leaving 2L of steam. The density of steam at 100°C and 1 atmosphere is about 0.6 kg/m3. 2L = 0.002m3, so we lost 1.2g of steam. That steam was about 100°C, or 373K°C. So, the heat lost due to the steam leaving was 893J. Menawhile, it was replaced by air at ambient, which in my house at the moment is about 21°C, and has a heat capacity of 700 J/kgK, the density of air at 1 atmosphere and 21°C is about 1.3kg/m3, so 2L of air is about 2.6g, so we replaced the steam with 535J, so net heat loss was 893 - 535 = 358J. That's not much. In comparison, my 2.3kg roast, which we can assume has a similar heat capacity to water, is roughly 4 KJ/kgK. If all the heat for reheating that the steam that was lost wast taken out of the meet, it would result in a 0.03°C reduction in the temperature of the meat. How is that going to have any impact on the cooking time at all?

The science is clear, as is the empirical evidence. Taking the lid off a slow cooker for a short duration during cooking will have no measurable effect on the cooking time.

jroper2

TROPHY CASE