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David Levi

From Sadalsuud

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I didn't have much time out last night, with a early start this morning, but thought that I'd better make the effort with clear skies. With the weather in this country you never know when you'll get the opportunity to stargaze again and I hadn't been out since last Wednesday anyway. I tend to plan my next observing session on the days when it's cloudy. As a beginner I'm using Turn Left At Orion as my guide to objects to view. There's so much in that book that I'll probably be using it for ever especially as it's always a delight to return to the old favourites. 

Last night I was going to try to observe the globular cluster M2 and then get to the Helix and Saturn planetary nebulae but I got distracted. I managed the first part ok. M2 is rather in the middle of nowhere with regards to bright stars by which to find it, so after finding Sadalsuud in Aquarius in my finderscope I headed north, starhopping using my 25mm eyepiece and Stellarium as my comparison. My modus operandi for finding objects has grown to be that Stellarium is on my computer in the kitchen and I go into and out of the house remembering star configurations that I have seen in the eyepiece and compare them with configurations that are shown in Stellarium. I've got a good memory and it's a good mental exercise as well. In the end the gobular cluster M2 was not that hard to find but I'm going to have to revisit it when I'm a bit more relaxed to appreciate it a bit better. What was upsetting me was my neighbour's, yes you've guessed it, security light. My blood pressure was up a bit as a consequence and I couldn't enjoy the experience as I would have liked to. M2 wasn't as spectacular as the great globular cluster M13 in Hercules but was pretty impressive. I didn't really notice any distinct stars just a general quite bright haze of light. I pushed the magnification up to 166x and it still looked really good.

It was at this point in proceedings that my plan went awry. I noticed in Stellarium, I had zoomed in sufficiently, that the asteroids Pallas and Eros were also in the vicinity. After observing Ceres last week it would be good to follow it up with a couple more objects in the asteroid belt. Pallas is, according to Stellarium, at magnitude 10. That's faint compared with the objects that I have been pursuing up til now and I wondered if I would be able to see it with my telescope. Starting at Saadalsuud again I made my way to the location of the asteroid Pallas via 16 and 15 Aquarii and HIP105075. A few faint stars later and I was looking through my eyepiece at the asteroid Pallas. I can see why William Herschel called these objects asteroids as Pallas appears just like a very faint star. I was observing it at 40x magnification but increasing the magnification to 100x and 166x didn't elicit any better view. It was still like a very faint star.

On to Eros next. Once again starting at Sadalsuud and navigating north via 21 and 20 Aquarii and HIP105534 I came to the area of sky where Eros is supposed to be at the moment. What did I see? Nothing. It seems like a magnitude 13 object is too faint for my telescope in the light polluted skies as seen from my back garden. I tried averted vision to no avail. Only my imagination was trying to conjure up Eros.

After this observing session I now have a new test to perform. How faint an object can I see from my garden? I'll have to plan this test for one of the next observing sessions when seeing conditions are good (relatively).

 

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Nice one David. Eros is somewhat low in the sky (not overly so, but it all counts), so it would be tougher than a similar object straight upwards at the zenith with less atmosphere in the way. Not sure what your light pollution is like (or whether it's better/worse in any particular directions)? You can also get a lot of variation from night to night - even when two nights both seemed good, one might simply allow fainter targets than the other with better transparency through the atmosphere. I've a slightly larger (250) scope than yours and a mag 13 star would be quite doable in some areas of the sky away from the direction of town, but difficult (impossible?) if it was in the direction of town. Try the test on a few different occasions and maybe in a few different parts of the sky to get a feel for it. High magnification darkens the sky background (but not the point sources of light like stars and asteroids) which can often make the difference in making these targets visible (and do what you can to hide from the security light of course!).

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Thanks for the encouragement Paul @Size9Hex . I have reasonable views of anywhere from south to west to north, buildings and a tree permitting. At least these are the least light polluted directions as I live quite far to the west of the city. The south to east to north half of the sky is very badly light polluted due the the bright lights of Cardiff. The overhead portion of the sky is as you say the best. I probably left it a bit late on Wednesday night to make a good attempt at seeing Eros, as Aquarius was getting quite low in the west by about 21.30hrs when I was attempting to view Eros. The forecast is clear again tonight and so I will try to get out earlier to give myself the best possible chance of seeing Eros when Aquarius is higher in the sky to the south. I will act on your magnification comment as well. I can't remember now if I tried higher magnification than 40x while looking for Eros. I don't think so. I'm pretty sure that because I didn't have anything to centre on, I didn't change the eyepiece.

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Cool. 40x is definitely at low power end for the 200p scope and will show a bright sky background. You'll pull out fainter stars for sure with higher power. When you think you're on target, be confident and just zoom in on the empty space! Good luck!

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Clouds have just interrupted my observing session so I thought that I would update this thread while I am waiting for them to clear. It's supposed to be clear all night so I'm assuming it's only a temporary obstruction but it has halted an interesting investigation that I am carrying out with regard to the position of Eros. I managed to get out earlier tonight so Aquarius is higher in the sky than when I was observing in that constellation on Wednesday night. I was surprised to find that Eros has moved quite a bit according to Stellarium since Wednesday. My surprise is only because as a novice observer I haven't seen a faint object change its position before. My previous observations separated by a few days of Neptune and Uranus showed no noticeable change of position (they are of course a very long way from the sun and have large orbits - I know).

Anyway, tonight I believe that I have found Eros. I increased the magnification to 100x (and then to 166x) and can see a faint object in roughly the correct position. And that's the problem. I see all the stars as per Stellarium. I could only manage to get the setting of absolute scale to a maximum of 9 to show more stars. If I understand Stellarium correctly that's what you do to see more stars in the program. I can see more stars through my telescope (although very very faint) than Stellarium is showing even at this setting. I'm trying to get to the point but I want to state all the facts first before putting my case, which is: Stellarium is not showing the position of Eros correctly. There's a magnitude 10.40 star just to the south south west of the star HIP105212. According to Stellarium, Eros forms a nice obtuse angle (140 degrees say - where's my protractor when I need it) with these two stars. The distance from HIP105212 and Eros to the centre star is in a proportion that I have roughly measured as 2 : 3. According to what I can see in my eyepiece Eros is closer to the magnitude 10.40 star than Stellarium shows it. It's not quite 1 to 1 but closer to 1 : 1 than it is 2 : 3. That's how I see it anyway. Any comments on the accuracy of Stellarium would be appreciated as I want to know if I really have seen Eros.

Of course these observations only apply to tonight as the position of Eros is obviously changing quite a bit. I hope to get another opportunity to observe Eros in a different position to do another check on the accuracy in Stellarium.

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Nice report there, good luck with you spot the faintest object. My massive garden here is very dark and on a very good night I did see the centre star of M57 with my 12 inch which at 15.3 mag is very close to the limit, I have done it more easily though with my 18 inch on 3 occasions now.

Alan

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Just to tie up a loose end, I have revisited the search for the asteroid Eros tonight and I am now certain that I haven't seen Eros and don't think that at magnitude 13 it is possible to do so from my back garden. The object that I thought was close to the location of Eros as shown by Stellarium is still there and there is nothing to be seen at the position where Eros is supposed to be tonight. I'm not that surprised, as Eros is only 34km across at its maximum. No chance of seeing the NEAR spacecraft sitting on its surface then :icon_jokercolor: ! I don't have any problems in seeing stars of magnitude 10 but it is likely that I cannot see anything much fainter than this. After failing to see Eros I went to the Saturn Planetary Nebula, NGC 7009. Aquarius was by now quite low in the west and the almost first quarter moon wasn't far away. I could see that the nebula was slightly elongated at 100x magnification but I couldn't clearly make out the handles that apparently give the nebula its Saturn comparison.

I then turned my attention to the Triangulum constellation. As an attempt to test the capability of my telescope I tried to see the galaxy NGC 777 (magnitude 11). Nothing doing - the 2 stars magnitude 8 and 9 next to the galaxy were clear but I couldn't see the galaxy. I then went to see the Triangulum Galaxy. Or rather I turned my telescope to M33 as I couldn't see hardly anything of it. Only NGC 604 was just about visible but I couldn't make out any large scale structure of the galaxy itself. I was using my 25mm eyepiece giving 40x magnification. I tried higher magnification just for completeness but I didn't expect any better chance of seeing an object that's supposed to be as big as M33 by doing this and I didn't see anything either. The sky tonight and probably in general from my garden can't be clear enough to view objects like this. I'll find out more when I look for further galaxies in the future. Once again the magnitude 10 stars around where the galaxy should be were clearly visible in the telescope. 

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Lovely detailed report.

I often have the star chart a distance away as it helps keep my feet warm with a bit of movement. 

I often find my way to an object through memory after a few star hopping sessions although I have to admit something has to drop out before a new star pattern goes in the memory bank :icon_confused:

Never looked for the asteroids so one advantage of stellarium over the old star chart.

Damian 

 

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