Quote:
Originally Posted by Suzy
Hi Luke,
I observe Omega Centauri regularly from my light polluted backyard and it's always been a good performer even in my 4" dob. You didn't mention what eyepiece you used that filled up the entire field of view but it sounds like you've used too high magnification. If I pop a 10mm plossl on which has a narrow 50 degree field (or is t 55?), it will fill up the eyepiece entirely and just look like a mud pie with strands running through it (much like you've described it). However, if I pop on a widefield 72 degree 10mm eyepiece, the view is incredible- the entire glob is visible with the black sky filling up the rest of eyepiece. Use lower power so you can see some dark sky around it; that will add to the contrast.
Also, don't stare at it. Roll your eye away (without moving your head) and roll it back to the glob- you should see it sparkle & some of it resolved into separate sprayed stars. If you stare at them they will just be fuzzy. It's to do with our eyes, they are not good at performing in the dark.
I am not talking about using averted vision here, just purely looking away.
However, using averted vision will make the views even better, and this is what we use for feint fuzzies to stand out. Though I don't class Omega Centauri as a faint fuzzy (I think you're using too much magnification). Yes, higher magnification can yield more contrast by darkening the sky background but it can also kill off many faint fuzzies like galaxies unless they are bright to begin with. In time, you will learn what magnification works best for these. And if the sky's transparency is poor, that high magnification will go against you too. Many people make the mistake of thinking they need to up the magnification.
How To Master The Art Of Averted Vision.
How To Hone Observing Sensitivity And Accuracy
Understanding Eyepieces
Luke, take your time and have fun. Don't worry, with some practice you will get good at this stuff!  |
The OP said he used a 9.7mm Meade Plossl. This is not a bad eyepiece and gives 123x and 0.42 deg. true field at 1200mm focal length. (Apparent field = 52 deg). I would think the Meade eyepiece is better than the 10mm Plossl supplied with most telescopes nowadays the latter eyepiece having poor contrast. The Meade would be no where as good in terms of contrast as the 10mm 72 deg eyepiece which you mention and I take to being the Pentax XW.
Note no matter what the apparent field is a 10mm eyepiece will still give the same magnification so seeing extra black sky around the object is a function of the larger apparent field, not lower magnification when comparing a 10mm Plossl to a 10mm wide field eyepiece.
Omega Centauri is a bright deep sky object and takes higher powers nicely. A magnification of 123x is not too much in an 8" telescope giving an exit pupil of 1.6mm, (apperture/mag = 200/123 or eyepiece f.l./f.ratio = 9.7/6). Anything from about 1mm to 2mm exit pupil is ideal for Omega Centauri in an 8" telescope and yes the larger apparent field eyepieces will give a more pleasing view because of the extra sky they show around the object and perhaps more so the extra contrast high quality wide field eyepieces will usually have.
If the OP has the 12.4mm Meade Plossl, try it. Other than that may I suggest an 11, 12 or 13mm Nagler as it would be ideal for Omega Centauri and many other objects. Note if wearing eyeglasses then only the 12mm eyepiece with better eye relief should be considered. Note for a bit less power and more pinpoint and tighter view of Omega, try a 16 to 17mm eyepiece of wide apparent field as the view will be very pleasing provided the eyepiece has excellent contrast.
Before buying extra eyepieces may I suggest first a visit to a dark site with the equipment at hand and see what works best and what gives the nicest contrast. Only then will you know if it is your equipment or sky conditions that is causing the poor contrast.