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Messier 68 in Hydra - has it disappeared!!???


Moonshane
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My target for tonight was this globular cluster in Hydra. However it's low in the sky for me and I fear light pollution and poor transparency may have meant that despite it being described as 'easy' and a binocular/finder object I could not see it with 12" of aperture with the star field it sits in within my eyepiece field.

Is the above a likely reason or should I go to Specsavers?

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Poor seeing probably could have played a part, but light pollution or glare even could have shielded it (if you were looking through the light from a nearby streetlight. I doubt it's your vision ;).Speaking of vision impairments.. I've noticed that without my glasses on with my 26mm that Jupiter looks remarkably like a bright comet... weird huh?

Edited by Naemeth
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I don't know, but it could have something to do with hunting out a mag 10 object, so low on the horizon, a month away from the summer solstice, allegedly a real nasty one to star hop to, and along with M 83, perhaps the hardest Messier to find :p .

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It is a very anaemic globular, as I recall. Mag 10 it may be, but it is about 11' across. Compare that to mag 6 and 20' across for M13. 4 mags means a factor of 40 more light, over an area just under 4x the diameter. This means the surface brightness of M13 is more than ten times greater. M92 has an even greater surface brightness. Add low altitude and you have a tough object. In Sydney, I had it near zenith in clear skies and it was hard in 15x70 bins.

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Atmospheric extinction makes objects difficult near the horizon - add to that any light pollution and haze and the object becomes impossible. If the site is dark and the air is clear it's possible to view very near the horizon, though extinction still makes objects difficult and only the brightest are worth attempting.

The other night I viewed M83 with my 12". This is at almost -30 degrees RA, and only about 5 degrees above my theoretical horizon limit, but with a dark sky and clear air I managed it. My first view of it had been from Greece where it was much higher in the sky and visible with a 100mm scope.

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Shane because of your thread I decided to visit M68 last night. The sky cleared to the horizon in the southern direction so I went looking with the Ethos 21mm. I am pleased to say that the Glob is still there. In fact I had a very good view of it last night and switched to the 13mm Ethos for a closer look.

I also went looking for M83 but my fence got in the way. That is the problem with Dobs sometimes - I will try and revisit but this time I will put the 6" Newt on top of the SkyTee mount to get the extra height.

Mark

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cheers Mark - thank goodness for that :grin:

I think it must have been light pollution but I have since remembered that I was close to the top of my fence with the finder and therefore there's a chance I was losing a fair chunk of my aperture too :rolleyes: I'll have another look form somewhere dark and with a better southern view in the near future. at least I 'ticked' a new constellation - in fact two. I have never knowingly looked for Corvus or Hydra so there's something at least.

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Dobs are pretty low on the ground when looking near the Horizon. When I last went out looking at Jupiter, the Heritage was on a table, on my eyepiece case! Perfect height though.

Shane, you should put it on a big box (or make one) for near horizon viewing, as I'm sure the eyepiece height will be quite near to the ground.

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I also went looking for M83 but my fence got in the way.

There was also a fence in the way when I viewed M83 the other night - but it was a wire-mesh fence so I just looked through it, losing about as much light to it as I did to the secondary spider. :smiley: Last night managed some more objects close to my horizon, including globs NGC 6316 and NGC 6304 - but not viewed through a fence this time. Only problem is that my stool wasn't low enough so I had to go on my knees to look through the eyepiece of my horizontal dob.

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Only problem is that my stool wasn't low enough so I had to go on my knees to look through the eyepiece of my horizontal dob.

Aaah! The old praying to the Dob technique :D okay in warmer weather, not so good in winter.

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The praying technique is hard on my knees and neck. Think I might try Naemeth's suggestion of putting the dob on a box. Though with a 12" it needs to be a very big, very strong box. Think I've got something that will work - if it can take my own weight then it should be OK for the scope.

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saw this last week but it was very very faint due to the murky light polluted southern horizon and its low altitude.same aperture as you so likelyu i had slightly less skyglow.having major trouble finding m83 though,spent 2 hours one night with no joy

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I have two issues with a box, the eyepiece would be too high to observe standing and also the stability might be an issue depending on design - it would have to have three feet so be triangular to ensure correct weight transfer to the ground.

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I bought 3 tubular legs from B and Q and screwed them into the base of my 10" Skywatcher Dob. This gives me an extra 12/15" so I can look through the EP whilst standing when the scope is at the zenith. Its a much more manageable height although I can't quite get down to -30 Dec with the Dob because my southern facing fence is 7 feet in height.. However, this is not the thread for my DIY but the Dob is pretty stable and a much better height.

Mark

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