Mandy D

The Moon in daylight at 07:30 today.

Skywatcher, 200P, Nikon D800, Explore Scientific 2x focal extender

Click and zoom in for full resolution image.

@MalcolmP Although Jupiter is nowhere near massive enough to ignite hydrogen, the planet does produce it's own heat in it's core, due, I think, to gravitational effects.

3 hours ago, Franklin said:

I was brought up to believe that Jupiter was "King" of the planets and after the Sun it dominates the solar system. I also read that if Jupiter was any larger it might even have "switched on" and become a star itself, making a binary system with the Sun.

Yes, Jupiter so dominates the planetary side of the Solar System, that it's barycentre with the Sun is outside of the Sun's body. It is the only one to do that. So, do we have to declassify Jupiter as a planet, as it is not technically orbiting the Sun, rather the pair orbit a common point? 😁

@badhex Sorry, for getting off track. Yes, it is the fact that L4, L5 are stable Lagange points that allows planetry mass bodies to exist there. L1, L2, L3 are like trying to balance a pencil on it's point.

@badhex it is well known that L4 and L5 are stable, whereas the other three are not. JWST is at the Sun-Earth L2 point beyond the Moon's orbit and has to orbit that point to avoid falling into the Sun's's gravitational well. This is known as a halo orbit.

9 hours ago, saac said:

 

That gas tap is real old school and identical to the ones we had in my school back in the 1970s and they were old then. I'm pretty sure Michael Faraday used ours ... 😁 The bench tops look simiar, too.

@CumbrianRed You should expect to be paying about £200 for a 200P and it should come with two eyepieces and the 1.25" and 2" extensions for the focuser at that price. Nobody keeps those eypieces when they sell these things as they are low end, although acceptable, especially the 25 mm, the 10 mm not so much. As @Ricochet has said the mirrors are excellent. If you are going to store the telescope assembled with the tube upright on the base, the 150P, 200P and 250PX all take up exactly the same floor space of 520 mm diameter. The only real difference in terms of handling is the weight of the OTA (tube) - 150P: 5.3 kg; 200P: 8 .5 kg; 250PX: 12.7 kg. The bases all weigh about 11.5 kg each. So, if you can manage the base, you can probably manage any of the OTAs. I struggle more carrying the base than I do carrying the 250PX OTA, because of it's awkward shape.

Another bonus with these telescopes is that they will all focus with most DSLRs, so you can do basic astro-photography (Moon, bright planets, etc) without buying expensive astro-cameras. I completely agree that you want to make sure the finderscope is included, as it is really not a bad piece of kit and is useful to have. I almost never use mine, though.

Unless you are going to get serious about astro imaging, the Dobsonian mount is very practical and extremely easy to use; much more so than an equatorial mount which will require polar aligning each time you set up.

As Ricochet says, check that everything works smoothly and is in good condition. However, dust on the mirrors is not something to worry about and even small scratches will not degrade the performance noticeably. I have a big (3 - 4  mm) black blob on my primary mirror and it makes no difference to performance. Don't worry too much if you cannot see anything through the eyepiece when you check it, as the mirrors could be hugely out of alignment, but that is very easy to correct. My 200P was bought secondhand and was so far out of collimation (alignment) that I could see nothing through it. 5 minutes with a Cheshire collimator (cheap) and it was working very well, although not perfect.

58 minutes ago, Paul M said:

Pluto had already been demoted before I tracked it down for myself.

By the time I had a scope big enough, its declination and distance had put it beyond visual observation.

 

I believe I was told my physics teacher in school that an 8 inch telescope was required for visual observation of it at the time. I now have a 12 inch and it is still not big enough, today. At least you have imaged it, whereas for me it remains on my list, having imaged all the planets in our solar system.

@badhex well, it's made for an interesting discussion. Yes, it has to meet all three criteria to be classified as a planet, but as you said, we were only discussing trojans at L4, L5. I'm perfectly happy for Pluto to be 'demoted' on this basis, but perhaps a little sad. I suppose the other thing up for debate, now, will be the satellites of the gas giants with Jupiter being expected to have 500 - 1000 or more. What happens when we get to that point? I'm fully expecting the 'planet' definition will be applied to bodies orbiting such large masses. I honestly cannot see anything that makes more sense. We really cannot go on adding pebbles to the collections of moons. There was similar debate around asteroids after the first few were found, so this is all following a rather predictable pattern.

@badhex I would say it is pretty clear that anything trapped at L4 and L5 are not obstructing the planet's orbit as they orbit the star with the planet. Hence, the planet's orbit is 'clear'. i.e. it cannot crash into bodies at those points as they have the same average angular velocity as the planet. Hence, I believe the modern definition of a planet is correct or, at least, acceptable.

59 minutes ago, MartianHill said:

@Nikolai De Silva
 

How spooky - we saw in the UK what you saw in Sri Lanka 😱

And right across North America, too.

I'm not sure what size thread we are looking at in your photo, but if it is supposed to go into a ball head, I suspect it will be 3/8" UNC. Your camera and tripod will usually be 1/4" UNC.  I think there are two options:

1.  Take the bolt out of the adapter and use a 1/4" bolt to secure it to the base of your ball head.

2.  Buy a new ball head with a 3/8" thread. It will probably be sturdier than one with a 1/4" thread.

3.  (secret option, not for the faint-hearted!) Drill and tap the base of you ball head to fit the adapater thread.

2 minutes ago, Xilman said:

29mm is microwave

Oh, yes, of course it is. 2.45 GHz is 12 cm, as used in microwave ovens!

Very interesting. So, it is basically a very high sensitivity infra-red sensor.

@Nikolai De Silva I just had a look outside and then photographed the same effect. I noticed that you have Jupiter on the wrong side of the Moon. Did you use mirror view on a mobile phone?

My picture is here:

https://stargazerslounge.com/topic/416373-moon-halo/

After reading @Nikolai De Silva's topic A Strange Ring Around the Moon, I went outside to take a look and it really was quite incredible, so I decided to photograph it. Not having much success from home due to lighting and unattractive foreground elements, I decided to wander up to the local church and see if I could get it's spire into frame with the Moon and halo in the background. Next to the Moon is Jupiter and above the spire we have a star.

Nikon D800, 14 mm f/2.8 prime lens, tripod and remote shutter release.

f/2.8, 12.1 sec, ISO-400

The exposure time is a bit bizarre and I have no idea how that happened as the camera was set to 13 seconds. Editing in GIMP. I think the processing could be improved a bit, especially in the deep shadow at the base of the Spire.

It looks like you've also captured Jupiter there, so potentially 5 moons in total!

I saw the same thing last night whenI was setting up. It is as others have described above. I've seen it many times, right from being a small child and it never gets old or less beautiful. You got a nicepic of it there! Enjoy it.

Awesome!

@900SL I think this might be the one at the Yangtse River show in China. @FLO posted about it a couple of days ago.

4 minutes ago, DaveL59 said:

I'd first ask how far away are you thinking?

Handheld binos will only do so much and once you get to >10x you really need something mounted on a tripod for stability unless you spend lots on stabilised ones.

Assuming 10 feet per floor, that is 300 ft vertically downwards and 300√2 = 425 ft at 45° would not be an unreasonable starting point. I think a bit more than 10x might just be required. A 300 mm lens on an APS-C sensor is not going to give much of an image size.

@Mr_Cat You do realise that you are measuring the outside diameter of the focuser tube? You need to turn the calipers over and measure the bore., which will come out much closer to 1.25".

1 hour ago, 900SL said:

Is there any preformed baffle in flexible sheets that can be cut and bent to shape?

 

I have a large roll of very thin ABS that is covered in dark blue velvet flocking that can be rolled into a 50 mm diameter tube. There is no reason to suppose that it is not available in black.

You most definitely succeded. That is a very nice Uranus.

The link, below, suggests that a 1 mW laser diode draws 20 mA.

https://botland.store/laser-diodes/15386-laser-diode-1mw-red-650nm-5v-velleman-wpm434-5410329725501.html

So, if you cannot measure the voltage when the battery is in the laser, connect a 150 ohm resistor across the battery and measure the voltage across it with your multimeter. If it falls over time, or drops immediately to low values the battery is no good.