quality of eye pieces

[PaulCH]

Hi all,

as one of those newbies, I have recently bought a Celestron 127 SLT and am absolutly blown away by what i have been able to see so far, a couple of questions have come up.

Firstly, is there a YouTube post that takes one through the operation of the GOTO handset, the instructions are very good about how to align, but digging around in the dark to find out how to set slew rates, etc in the book is not easy, i would rather sit back and watch somewthing during the day before i go out - lazy i know!

Secondly, I am getting on fine with the low powered EP but am finding the High powered one more difficult to get used to, my question is is the EP of not as good quality as the lower powered one or is there something i could improve with my viewing technique - I know it is probably the later, but thought I would ask

cheers

Paul

[Reeny]

Lower magnification eyepieces are more tolerant.

If you magnify the image - you also magnify the errors in the optical path.

It is normal to struggle with higher powered eyepieces.

Those are the ones you will need to upgrade at some time in the future.

Check the collimation first, but don't rush into make any adjustments unless it is miles out.

Use these two guides to help.

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

http://www.umich.edu/~lowbrows/reflections/2007/dscobel.27.html

[hippie]

The standard lenses that come with most scopes are low to mid range starter EP's normally,

If your on a tight budget the look at BST's lenses they are very good from Alan at :- http://www.ebay.co.uk/usr/skies_unlimited,

Televue are one of the best lenses on the market but not cheap, 

There are others like Vixen, William Optics, Baader, Celestron, all seem to have reasonable reviews,  .

Read the reviews on differant lenses there are plenty and make your own mind up and what you can afford to pay! .

[michael.h.f.wilkinson]

Besides the point that high magnification requires good optics, other factors come into play. Usually, standard EPs are of the Plossl type (or related) and the 25-20mm types are quite easy to get on with. The eye relief if between 20 and 15mm which is fine for most. However, the 10mm or shorter ones have very tight eye relief (7mm and shorter). This makes viewing much less comfortable. Another factor is cooling down time. If you set your scope outside, there will be a temperature difference between scope and surroundings. This causes thermal currents in the tube, which do not generally cause too much trouble at low magnification, but completely trash the image at high magnification. You can see these currents by pointing the scope at a bright star or planet, and defocussing until you see the donut shape of the aperture. you will also see all sorts of whirling effects due to thermal currents (I frequently see a plume rising from the secondary, shown as a dark strand). Leaving the scope to cool for 30 minutes or so will help a lot.