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FORUMS Photography Talk by Genre Astronomy & Celestial Talk 
Thread started 19 Jul 2010 (Monday) 08:55
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How big should I be seeing stuff?

 
DonR
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Joined Dec 2009
Location: Georgia, USA
     
Jul 20, 2010 16:38 |  #16

swag72 wrote in post #10572577 (external link)
I was using an 8mm and 17mm eye piece. What you have shown is pretty much what I was seeing, albeit tiny in the eyepiece. And yes, it probably was about the same size as Saturn. I was expecting to see some kind of detail on Saturn. Jupiter, for example, when I see it, I have an idea in my head that I should be seeing some spot details ............... Won't be seeing anything if it's as damn small as Saturn!!

Star test ............... Mmm, looked at that ............... More confused. I think I'll put the scope away for a while and probably forget about it.

The 8mm eyepiece would be the one to use for Venus, 17mm is a little long. It does sound as if your expectations are a little off though. While all of the planets are going to be pretty small unless you have a very large telescope, you can still see a great deal of detail on Jupiter and Saturn when the atmosphere is calm. The detail on Saturn, though, is much more subtle than on Jupiter, and non-existent on a night with poor seeing. A classic visual test for optical quality, visual acuity and seeing conditions is to see the gap in Saturn's rings. Right now with Saturn's rings tilted less than 3 degrees, that would be possible but more difficult than at other times. A somewhat easier test would be to see the black space between the rings and the disk of the planet. You should be able to do that with your setup on a good night, but it will require some careful focusing and patience.

Jupiter's apparent size is about twice that of Saturn, or about the diameter of Saturn including the rings. You should definitely be able to see some detail on all but the worst nights. The most apparent detail will be different colored cloud bands. The great red spot will be visible most nights unless it's on the back side of the planet - in which case, waiting a few hours will fix it, because Jupiter completes a full revolution in about 10 hours.

The star test is the ultimate test of optical quality that can be performed without special lab equipment, but you do need an eyepiece that yields a magnification of at least 200X. Of course, you can use a barlow to achieve the high magnification. And you also need a night with good to excellent seeing.

Don




  
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swag72
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Location: Olocau, Spain
     
Jul 21, 2010 01:29 |  #17

Thanks for that info Don - I will have another go with Venus one night soon and check that I can see a difference between that and a star!!

My eyesight is good - Had them lasered in November last year, best money I ever spent!!!

I will keep my eyes peeled for when Jupiter is around at a vaguely reasonable time and see what I get then. Regarding Saturn, I did see a space between the rings and the planet. I guess my expectations are unrealistic and I thought that I'd be seeing stuff that filled at least half the eyepiece!! Best stick with the moon then!

Regards and thank you.


Catch my pictures on Flickr http://www.flickr.com/​photos/swag72/ (external link)

  
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Adrena1in
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Location: Winchester, Hampshire, UK.
     
Jul 21, 2010 10:00 |  #18

Not to put a spanner in the works, but I personally don't see the point of venus. I've tried it a few times, up to several hundred times magnification, and it's just a very bright blob...little detail at all, and the only significant thing about it being that you can see its phase, much like the phases of the moon. Another problem is it's usually quite low to the horizon, and seeing through all our atmosphere tends to introduce lots of chromatic aberration and a "boiling" effect. I don't bother with it myself.

Jupiter's rising just before midnight, so if you can be bothered to go out at about 2 - 3 am on a clear night I think you'll be pleased with the results...again, assuming it's clear and the seeing is good. You'll see loads of details, and the moons.

Something else you might want to look into is double-stars. They've never interested me remotely before, but lately I've been looking at a few and trying to split them, and it's actually quite rewarding. Albireo in Cygnus is lovely to look at because the two stars are such different colours. Nearby in Lyra you've got a couple of good Double-Stars in the constellation, and also the Double-Double, which will really test your optics. At low mag you'll see it's clearly a double, but up the zoom and you'll hopefully notice that each "star" is also a double, hence the name. (In each pair the stars are something like only 2 arc-seconds apart, but I split them easily the other night at only about 74x magnification.)


Canon EOS 450D, Sigma 18-200mm, Canon 50mm f/2.5 Macro, 2x TC, Revelation 12" f/5 Dobsonian, Mintron PD2285-EX webcam.

  
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trailblazer87
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83 posts
Joined Jun 2009
Location: Central, CA
     
Aug 08, 2010 23:53 as a reply to  @ Adrena1in's post |  #19

One thing that was only touched on. Looking at a map, you live a relatively populated area, and possibly reasonably low in altitude being that close to the med., for good viewing you may have to go up to a more mountainous region and try to get as high as possible. The other thing to think about this time of year is that it is summer and the atmosphere is really moving right now. I can't even get good viewing when I go up to 7000 feet in elevation. I live in a region of California with a similar climate as you. The winters provide wonderfully clear, still air, and awesome views of Orion. Wait a few months and point that thing at Orions Belt and see what you get. If you have a friend in the Pyrenees go visit him in November and take the telescope, you will be amazed at the difference.




  
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swag72
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Location: Olocau, Spain
     
Aug 10, 2010 05:19 |  #20

Brilliant - Thanks for that - I am looking forward to seeing Orions belt with the scope.


Catch my pictures on Flickr http://www.flickr.com/​photos/swag72/ (external link)

  
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How big should I be seeing stuff?
FORUMS Photography Talk by Genre Astronomy & Celestial Talk 
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