Eyepiece advice for a C925 Celestron.

The_bluester (Paul) · #1 22-09-2014, 08:16 PM

Firstly, my scope is not an Edge HD, just a run of the mill 925.

Over the few years I have had my scope I have managed to collect a bit of a ragtag assortment of eyepieces (Mostly from Ice Trade!) some 2" Celestrons E-Lux, a nice widefield Meade (68 degree 34mm (edited to fix the typo! it is not a 43mm) the original 40mm Celestron E-Lux 1.25" that came with the scope, a couple of TV Plossls and an 11mm Nagler.

I am starting to think about consolidating my EP family a bit. I have found myself gravitating towards wider views lately and the Celestron seems to spend the most time in the scope.

The basic question, has anyone had an experience good or bad with the ES 82 degree line, specifically in a C925? And has anyone used them with a focal reducer? I would love a couple of long FL Naglers but the budget just does not stretch to it. I am considering moving anything up to ALL my existing family and starting again (I might hang on to a couple of the shorter FL 1.25" jobs for planetary views) At the extreme end I would like to eeke out the greatest useable true field that my scope can provide. I could probably afford to snag myself a secondhand dob off the trader section, but I am not sure that the marriage would stand explaining why I need another scope!

Any suggestions or experiences with the ES line? I do like the combination of wide AFOV and wide TFOV.

Strawb (Dave) · #2 23-09-2014, 09:41 AM

Hi,
I find the LVW range just perfect for me - check them out

The_bluester (Paul) · #3 23-09-2014, 09:59 AM

I was hoping to get to the recent ASV star party at Heathcote and see if I could try a few other folks EPs but life got in the way as it does.

at 65 degrees the LVW are on the low end of the apparent field I am looking for, but certainly a step up from the Plossl types that make up my main group of EP's Even the 2" E-Lux are 56 degrees so a little wider than the Plossls but not by much.

casstony · #4 23-09-2014, 11:24 AM

Quote:

Originally Posted by The_bluester

The basic question, has anyone had an experience good or bad with the ES 82 degree line, specifically in a C925? And has anyone used them with a focal reducer? .

The ES eyepieces are generally very good performers and I've used quite a few of the 82 and 68 degree models. I'd avoid the focal reducer and just buy the appropriate focal lengths for your needs.

The_bluester (Paul) · #5 23-09-2014, 11:50 AM

The reason I was looking at the reducer is that with the long FL of the 925, anything not worth a fortune is still relatively limited in TFOV. All things being equal, a reducer would stretch the capabilities of the scope a bit further.

Buying a second scope would not be too popular at home :-b though it may nearly be feasible if I can snag a good secondhand dob cheaper than I can set myself up to get a comparable TFOV.

Merlin66 (Ken) · #6 23-09-2014, 03:38 PM

You'll find the reducer is for imaging rather than visual....
As said, get the focal length eyepiece to suit your needs...
(I find the 32mm TV the most used on the C9.25 and the C11. I have the 40mm but.....)

Amaranthus (Barry) · #7 23-09-2014, 04:21 PM

The f/6.3 reducer is also great for visual -- at least it is on my C8 (not Edge). I basically use it all the time for DSO observing due to the wider FOV and better edge correction, and only take it out when I'm doing planetary imaging. I get well over a degree of field with my 24 Panoptic that way.

Merlin66 (Ken) · #8 23-09-2014, 04:39 PM

Barry,
That's interesting to hear...I never did have the same level of success with the Celestron/ Meade original x0.63 reducer...
The NextGen x0.5 came close.....
(Note the latest Meade x0.63 reducer has a MUCH shorter focal length and hence a MUCH reduced spacing requirement....)

The_bluester (Paul) · #9 24-09-2014, 10:56 AM

Interesting to see differences of opinion on the reducer, but then a secondhand 40mm 68 degree EP is not a huge difference in mag to a 30mm with reducer, even if the loss of apparent field might be missed.

I do wonder how low I can go before I might start seeing the shadow of the secondary?

Amaranthus (Barry) · #10 24-09-2014, 11:22 AM

The new reducer for the C8 has 105mm (nominal) backfocus, but it can vary from 55 through to over 200 mm - the distance affects the magnitude of the FR.

rrussell1962 · #11 24-09-2014, 11:22 AM

Hi Paul, Apologies if I missed something regarding your mount on the thread, but if you are thinking of a focal reducer it may be worth checking that you have enough clearance on the mount for the telescope to reach vertical with a focal reducer - particularly if you are using a 2 inch diagonal. I have a the Celestron focal reducer on my Nexstar 8SE and the diagonal hits the mount at about 80 degrees, not really an issue for me, I just set slew limits and wait a couple of hours for objects to swing into view. But I did have one of those "oh nuts" moments when I realised there was an issue.

Merlin66 (Ken) · #12 24-09-2014, 01:30 PM

Barry,
The new MEADE (not Celestron) x0.63 reducer has a focal length of 110mm and a "design" - for optimum performance - back focus of 45mm.
This really makes it's use for DSLR's very marginal....
http://www.iceinspace.com.au/forum/s...ad.php?t=88098

The_bluester (Paul) · #13 24-09-2014, 01:32 PM

I will have to recheck that. How deep is the reducer you use? I have a fair amount of clearance as things stand (I do have a 2" diagonal) so I would be surprised if a reducer would run me out of space.

The CPC925 has tall enough fork arms that even with the alt axis running through the rear cell the OTA can be parked facing directly down at the azimuth pivot point.

Tony_ (Tony) · #14 24-09-2014, 05:51 PM

Hello Paul,

I use an ES 18mm 82d with my c9.25".
Previously I used a WO 25mm 72d - the coma was fairly bad on this one so I got the ES.

I like the ES - there is still some coma in the outer 20% or so from centre - but overall the performance is very good. It gives good resolution of GCs and nebulae are quite good. I don't do a lot of visual observations - mostly imaging. I get used to the outer coma, mainly because it is so much better than the WO which I was also getting used to. If you aren't looking for round pin point stars to the edge then it is quite good.

There is a ES18mm for sale in the forums now - it is worth buying; even if you don't like it you can always sell it again. I think it is a good eyepiece for the price.

Regards,
Tony.

The_bluester (Paul) · #15 24-09-2014, 06:18 PM

Just had a look, with the OT pointed at the zenith I have around 100mm clearance behind the diagonal, so a reducer should not give me a problem.

Tony, thanks for the feedback and the pointer to the for sale section. I will have to have a look, the budget is pretty stretched this year though after we were bushfire impacted and a couple of other things and is only just starting to recover! This is more for planning for medium future. I will have to see how I go.

I should put the 2" E-Lux that I have in FS. They just do not get used enough to justify keeping them.

rrussell1962 · #16 24-09-2014, 09:42 PM

Hi Paul, with 100mm clearance you should be fine with the reducer. Just got in from work but I will measure the reducer thickness tomorrow and post just to be on the safe side. I will measure with the 1.25 visual back and also the 2 inch diagonal which attaches straight onto the reducer (or rear cell).

byronpaul (Paul) · #17 24-09-2014, 11:02 PM

Hi Paul,

I regularly used a Meade 0.63 focal reducer on the CGEM1100 with great results.

Admittedly it was an EQ mount so I had no clearance issues to be worried about, and I had zero problems achieving focus.

I also ran an SCT micro focuser in the image train and a 2" diagonal. My go-to eyepiece at the time was a 24mm Panoptic, but I also regularly used Type VI Naglers, Baader Hyperions, an ES 14mm 82deg, as well as 26mm & 32mm GSO Wide Views ..... all successfully through the focal reducer.

With this configuration I can recall some spectacular views of Eta Carina that have been engrained in my memory forever

Paul

The_bluester (Paul) · #18 25-09-2014, 07:01 AM

A question for people who might be more in the know.

When comparing eyepieces of the same focal length and field stop diameter (Meaning same TFOV) will an EP with a larger AFOV give a darker sky background due to spreading the same incoming light over a larger "area" or does it not work like that?

rrussell1962 · #19 25-09-2014, 09:45 AM

Hi Paul, the Celestron reducer adds around 26mm to the distance from the rear cell to the back of the diagonal. My 2 inch diagonal plus reducer measures 124mm from the rear cell to the back of the diagonal.

Amaranthus (Barry) · #20 25-09-2014, 12:25 PM

Quote:

When comparing eyepieces of the same focal length and field stop diameter (Meaning same TFOV) will an EP with a larger AFOV give a darker sky background due to spreading the same incoming light over a larger "area" or does it not work like that?

The scenario you suggest is not possible: AFOV(deg) = FSD/(Telescope)FL*57.3