celestron 11 CPC eyepieces

[richard pokora]

Having recently purchased the telescope and opted for a Delos 17.3 for planetary and lunar observations.  The scope is f10 and taking into consideration the slowness of the scope what are the recommended lenses to purchase as I would like to get the best out of the telescope.

[Northern Soul man]

Hi Richard and a very warm welcome to the SGL mate, nice scope and nice EP, I tend to go up to around the 12mm focal length of EP for Planetary and Luna - it seems just about right but its more dependent on seeing conditions and the sky really, but as a rule I can get the Binoviewer and around the 12mm for the best views of Jupiter just this past apparition - but remember Jupiter was/is really high in the sky - so the atmosphere is much steadier here - I think this has the most impact on really good Planetary views - you can mention contrast/clarity of individual EP's, but at F10 and on axis there are a lot of EP's which will perform very well - with only very minor and I mean VERY MINOR differences with very small margins of excellence between them all - it just comes down to the usual things of good steady seeing, good local seeing and location of the scope whether it be in a field with just sky between the ground and object - whether your looking from a built up area over concrete/brick roof tops - all these factors help or hinder a good night under the planets - take Saturn now - very low on the Ecliptic - so no matter what EP's you have whether it be Televue or Celestron, Explore Scientific,Baader, Vixen to name but a few, the seeing will degrade Saturn far more than the aberrations in EP choice.

At F10 the majority of the EP's work well - for me around the 12mm gives the best combination of clarity and more important a nice bright image - some nights you will be able to increase up around the 9 or 10mm focal length - but at this magnification it starts to dull and blurr the image most of the time with very few seconds of steady air - these few seconds perhaps every minute or two allow you build a mental picture of more and more detail, the more time you spend at the EP on a Planet, the more detail you begin to discern - but the atmosphere can also change after time, you may get "windows" of steady air where the view becomes really nice - almost picture quality - then the whole thing goes down hill - as you can see there are many factors which make a good night the back of the scope - and there is just some nights, together will 11" aperture, steady air and really good local seeing that just make this hobby so worthwhile!!

Paul.

[richard pokora]

Paul, Thanks for the reply regarding the scope. Reaching the X200 magnification dependent on the atmospheric conditions and just how much more can be squeezed out of the scope with good collimation is my goal as I am 67 years old. Yes I did notice Saturn last week was difficult in the lower sky at 1am, Jupiter very nice to look at on the same night. I have spent awhile on Stargazers mulling over the eyepiece forum regarding lenses and wanted to wait before purchasing another lens, whether it be TV, Baader or ES.

[Northern Soul man]

Hi Richard, Thanks very much I intentionally didn't mention a particular brand of EP as this is a very individual choice - as you can see there are many different EP's out there going from pricey to really pricey!!

I think that the seeing conditions will "tell" you straight away if its going to be a good/great night or very poor night - the 11" aperture will give amazing Planetary/Luna views - within the first few minutes you can usually tell how good the sky is - even just doing a star test under moderate power - take the star in and out of focus, making the "doughnut" visible, the airy disk around the doughnut  will be nice and steady - a good night - or boiling and bubbling away - a bad night.

Regarding EP's, at F10 you can get away with spending a lot less than if you were buying an EP for an F4 scope, all the EP's mentioned will give very nice on axis views, with the scope tracking - you only need to look at the very centre (on axis) - the scope will track very well after initial alignment - here the differences between the most expensive EP and the least expensive EP will be small and just noticeable (RELATIVE to the amount you have to pay for each EP).

The old addage - you get what you pay for springs to mind - on here the Explore Scientific seem to punch well above their weight with excellence showing in comparison and again relative to more pricier offerings, also the BST EP's have an excellent following, I have the Baader Hyperions which work very well at F10, the Baader zoom is also very good, but EP choice is so individual.

Not sure if you have any clubs/Societies near you where you could meet up and "try before you buy" - this would be the best option, as with EP choice you have to take into account a multitude of things and the more you read - the more you realize just how an EP made for you would be not so for me.

I think that good collimation is also a factor in getting the best out of the scope - I tend to stick below x250 for the majority of the time as I like a slightly smaller brighter image with excellent detail, say in the belts of Jupiter showing differences when the seeing steadies, white ovals clearly visible, barges and festoons on display and the Great Red Spot this last 2 apparitions has been amazing, with the "hollow" before the spot giving very high contrast- not quite photo quality - but very close, also you can try to increase mag when the atmosphere allows, but this tends to make for a much duller image with the detail beginning to break down - so I just go back to a slightly longer focal length EP - I use the Baader Zoom to have a quick check at an increase of mag without having to swap out EP's, but for me, the best views have been through my WO Binoviewer over the last year or so, using the 20mm WO EP's which came with the set, using the 1.6 Barlow on the end of the Binoviewer, giving me an effective EP focal length of around 12.5mm giving a mag of x224, for me the two eyes are far more better than just using cyclops mode.

Hope that helps a little Richard - wait for a few more to chip in to the thread - and stick with that Delos - I think that the overall colour rendition in mine on the belts of Jupiter is a sight to behold!!

Paul.