TV Plossls

Debash · Post by **Debash** » Thu Dec 07, 2006 8:23 am

Richard...will be at Tampines this weekend if Weixing is there..hope the weather is good

Post by **weixing** » Thu Dec 07, 2006 9:10 am

Hi,

Richard...will be at Tampines this weekend if Weixing is there..hope the weather is good

Err... this weekend or next weekend??

Have a nice day.

rlow · Post by **rlow** » Thu Dec 07, 2006 10:14 am

Hi Guys, I will be out-station this weekend. So I can join you guys only next weekend.

rlow · Post by **rlow** » Thu Dec 14, 2006 8:12 pm

Hi Weixing & Debash, is it still ON this weekend?

Robin Lee · Post by **Robin Lee** » Fri Jan 19, 2007 10:52 pm

So how's it? I would like to know whether TV Plossl beat the RKE. Does Ortho eyepiece better than Plossl in planetary as well?

Canopus Lim · Post by **Canopus Lim** » Fri Jan 19, 2007 11:00 pm

The on-axis (centre of the field) performance of orthos (UO and other better ones) and TV plossls are very close. The off-axis (off from the centre towards the edges of the field) performance, the TV plossls is better. I have tried the circle T ortho on my f/5 scope and the centre area of the field is sharp and good but towards the edges it gets 'blur'; that is where the TV nagler will just beat these eyepieces. A TV plossl is sharper towards the edges.

I have the Telescope optics book and have seen the sharpness of orthos, they are as what I have observed. Excellent for centre of the field but quite poor towards the edges in a fast scope (f/5 and below) scope. However, if you are using SCT or scopes that are slow (f/10), then the orthos would probably do fine from centre to the edge.

Canopus Lim · Post by **Canopus Lim** » Fri Jan 19, 2007 11:15 pm

Also about the RKE. I have not looked through one, but I can guess that off-axis (away from centre) the TV plossl probably will beat it in sharpness. On-axis, the RKE may win because it is a simpler eyepiece with fewer elements and hence if done correctly, it should have better contrast than the TV plossl. Also, there is no perfect eyepiece out there that does everything at the best. There is always a trade off in EVERY design. It also depends on the optical designer and how he balance the different kinds of optical aberrations like spherical, astigmatism, coma, field curvature, distortion etc. He has to balance them as all these cannot be corrected until perfect.

Robin Lee · Post by **Robin Lee** » Sat Jan 20, 2007 12:27 am

Is it still possible to get the telescope optics book? I am extremely interested in this. I have a full set of Meade Series 4000 Super Plossl eyepieces. I like to observe planets and star clusters most of the time. I will only observe galaxies and nebulae when the sky condition is good.

Seems like RKE and Ortho are good planetary eyepieces. Is Edmund the only manufacturer that make RKE?

Canopus Lim · Post by **Canopus Lim** » Sat Jan 20, 2007 12:44 am

TV plossls are good for planetary too.

Anyway, the book can be found here:
http://www.willbell.com/tm/tm6.htm

I am not too sure if you understand the optics physics behind it, but it is a good book to read for people who are interested in the different types of telescopes, baffling, eyepieces etc. I would warn first that it is not for casual readers because of the physics.

Robin Lee · Post by **Robin Lee** » Sat Jan 20, 2007 12:49 am

Thanks a lot for the link. I will try my best to handle the physics. The only difficulty may be the language. I learn physics in Chinese. By the way, is TV Plossl as good as Burgess Optical TMB Planetary Eyepiece?