Which EP's for a C9.25?

[Johnboy2011]

I recently got a C9.25 and would love some advice on which ep's to get as a minimum. Warthog's sticky recomends 7.5, 12.5, 20 and 30mm for F10.

I was wondering if 7.5mm may be a touch too much power for our seeing?

Does anyone have any tips what spread of ep's to go for with this scope?

Any tips on manufacturer would be a great help too, I don't think I can afford to go straight to Naglers only!!

Thanks,

John

[Mr Spock]

I seem to have collected quite a few eyepieces for use with my C9.25, details in my sig. My favourites would be: -

Deep sky: 42mm LVW and 22mm Nagler

Planets: 9mm and 7mm Orthoscopics

Moon: 13mm and 8mm LVWs

[Merlin66]

John,

For an f10 beam the design of the eyepiece is not as critical as say for an f5 system.

Eye relief , wide field of view, having the eyepieces parfocal may be considerations.

I've been using TV plossls for the past 30 years - they do the job very well. Orthoscopic e/p are pretty good for planetary/ moon etc and even a Kellner (or the Edmund RKE) will work for lower powers.

You pay your money - you take you chance.

[Johnboy2011]

Thanks gents.

What is parfocal?!

[Merlin66]

The "Parfocal" eyepieces are designed to focus at exactly the same point.

That way you can remove one eyepiece and insert another without touching the focuser. Makes life that bit easier.

[jwr]

Parfocal means the eyepieces all focus at the same point. This means you can swap eyepieces without refocussing your telescope.

James

[Johnboy2011]

Thanks.

I am thinking then of may be going 8, 13, 20 and 30mm. Do you think that sounds about right?!

[cgarry]

8, 13 and 20 sounds okay. Though with my C9.25 I find my 8mm is often of no use due to bad seeing and drop back to a 10mm EP.

What type of 30mm are you thinking of getting? If you are going for a Plossl, then you should go for a 32mm as that will give you the maximum FOV for a 1.25" EP.

Have you thought about a nice 2" EP for widefield views?

Cheers,

Chris

[cgarry]

I use the attached spreadsheet to keep track of my EPs. It works well for me. You fill in the white boxes and the grey boxes are calculated for you.

ep_spreadsheet.zip

Cheers,

Chris

[Johnboy2011]

I would love to go 2" for the widefield. When I picked up the scope I saw the sellers Nagler collection, WOW! I think I know where my future lies!

I think for perhaps the two lower powers, around the 20mm and 30mm it would be worth staring out with the 2" rather than moving up from a 1.25"? I think for the higher powers I am going to start with good quality second hand plossls with a view to moving up to something high end like a Nagler further down the line when my collection is more full and funds allow!

John

[Merlin66]

A 20 year old 32mm TV plossl works well for me. I like it better than the 40mm version.

[cgarry]

The 32mm TV plossl is a highly regarded EP. Since the 32mm TV plossl shows about the same amount of sky as the 40mm TV plossl I have never quite understood why anyone would buy the 40mm.

Cheers,

Chris

[ollypenrice]

I use a 26 Nagler in a 10 inch SCT and find it excellent. There was a used 35 Panoptic on the for sale board recently. If it is still there, grab it!! I had one for a long time till it had an accident...

Olly

[cgarry]

There was a used 35 Panoptic on the for sale board recently. If it is still there, grab it!! I had one for a long time till it had an accident...

Olly

I second that. The 35 Panoptic is the EP I use with my C9.25 for widefield views. A fantastic EP that never seemed to come up second hand the whole time I was looking.

Chris

[Johnboy2011]

I knew I'd get tempted into something expensive!

The logic then would be 35mm with great FOV, 20mm for medium to low power (ideally 2" (ideally expensive televue!!)) and then perhaps 13mm and 8mm to cover high power?

I assume seeing would rule out the 8mm quite often meaning the 13mm would get a fair bit of use.

[cgarry]

You should consider the 35 Panoptic as an investment rather than a purchase! If you do a search on the for sale completed section you will get a good idea how much these EPs are worth second hand. That way you will not pay over the odds and will only lose the cost of the postage if and when you decide to sell it yourself.

In general EPs are 1.25" unless they need to be 2". So for plossls 32mm and below are 1.25" and above 32mm are 2". The 1.25" TV 40mm plossl is an exception to this and because of this only has the same actual field of view as the TV 32mm plossl.

Yes, you would have to fall back to 13mm when the seeing is not good enough for the 8mm so the 13mm would get a lot of use.

I find that only on a few nights is the seeing good enough to use my 8mm EP, mostly I drop back to my 10mm EP which sees much more use.

If the seeing is too bad to use the 10mm I either drop back to my 14mm or more likely give up on high power observing and look for some DSOs with the 35mm Panoptic instead.

Chris

[merlinxlm]

I'm about to place an order for a Celestron C9.25 OTA. And I'm buying a couple of eyepieces.

1 X WO Swan 40mm http://www.firstlightoptics.com/diag...t-adaptor.html

1 X Celestron Excel 10mm http://www.firstlightoptics.com/cele...-eyepiece.html

These are the two that Steve from FLO has advised me buying for a good all-round set.

Thanks.