Which Eye Piece

[Bino Pete]

Any recommendations for a 2” eyepiece around 18mm to 20mm which would compliment my Celestron CPC800 XLT?

I do wear glasses.

Thanks.

[Stu]

Can you give an indication of budget Pete?

[Bino Pete]

Probably up to £150 (ish)!

[GavStar]

I think this would be a good option, 20mm eyerelief, quite compact and light, decent fov. I have the 15mm and 10mm versions for binoviewing and they work well imo. It’s 1.25 not 2 inch - not sure how important that is to you?

http://astrograph.net/epages/www_astrograph_net.mobile/en_GB/?ObjectPath=/Shops/www_astrograph_net/Products/AGAPMUF18

 

[Ricochet]

The 19mm Celestron Luminos (20mm eye relief) looks like the only option to me, assuming the eye relief is accurate. I don't know why you're limiting yourself to only 2" eyepieces though, that's probably the last criteria I would worry about.

[alanjgreen]

9 minutes ago, Ricochet said:

 I don't know why you're limiting yourself to only 2" eyepieces though, that's probably the last criteria I would worry about.

I agree. Get a second hand 17.3mm Delos. Its a "keeper" and will work in all your future scope purchases too.

If you only want 2" eyepieces to save hassle at the scope in the dark, then buy some of these Baader adapters

https://www.firstlightoptics.com/adapters/baader-low-profile-eyepiece-adapter-for-steeltrack.html

they are fastened to the 1.25" eyepiece via an "allen key" grub screw (you remove the thumb screw seen in the pic, its not needed) and make your 1.25" inch into a permanent 2" fitting. I have used several of these on my Delos and they are very solid!

[Bino Pete]

30 minutes ago, alanjgreen said:

I agree. Get a second hand 17.3mm Delos. Its a "keeper" and will work in all your future scope purchases too.

If you only want 2" eyepieces to save hassle at the scope in the dark, then buy some of these Baader adapters

https://www.firstlightoptics.com/adapters/baader-low-profile-eyepiece-adapter-for-steeltrack.html

they are fastened to the 1.25" eyepiece via an "allen key" grub screw (you remove the thumb screw seen in the pic, its not needed) and make your 1.25" inch into a permanent 2" fitting. I have used several of these on my Delos and they are very solid!

 

36 minutes ago, Ricochet said:

The 19mm Celestron Luminos (20mm eye relief) looks like the only option to me, assuming the eye relief is accurate. I don't know why you're limiting yourself to only 2" eyepieces though, that's probably the last criteria I would worry about.

Thanks for the replies. I admit, I don’t know much about eyepieces etc. I have the Baader mark3 zoom (1.25mm but has the 2” Adapter). I thought as I have the 2” diagonal I would be losing out on some of the light gathering using a 1.25mm eyepiece and a 2” one would be better. Is this not the case?

[alanjgreen]

12 minutes ago, Bino Pete said:

Thanks for the replies. I admit, I don’t know much about eyepieces etc. I have the Baader mark3 zoom (1.25mm but has the 2” Adapter). I thought as I have the 2” diagonal I would be losing out on some of the light gathering using a 1.25mm eyepiece and a 2” one would be better. Is this not the case?

No, its not as simple as that.

You need to take into account the total field of view (tfov) of the eyepiece.

A 2" eyepiece has a wider available tfov, so you can have lower power(lower magnification) and wider field of view.

 

A 24mm 68 degree Panoptic 24 is a 1.25" eyepiece that uses the full available tfov. Any eyepiece using greater fov (than 68 degree) will need to use more magnification to make up for the loss of fov. A 17.3mm 72 degree Delos uses the full available tfov of a 1.25" eyepiece by increasing the magnification. A 13mm 100 degree Ethos uses the maximum available tfov of a 1.25" inch eyepiece by increasing the magnification still further.

If you want an eyepiece in the range 18-20 mm then there is no need to go into 2" size unless you want wider than 72 degree fov. A 17mm 100 degree Ethos needs a 2" eyepiece as its tfov is greater than that possible in 1.25" format.

So its horses for courses, you only need 2" for wide (degrees) of sky in low power eyepieces.

Try the FLO field of view calculator with some of the eyepieces that I mentioned and you will see they all make a circle (fov) thats about the same sky. Then its just a choice of how much magnification you want (for the type of object you are trying to view)

http://astronomy.tools/calculators/field_of_view/

[rwilkey]

12 minutes ago, Bino Pete said:

 

Thanks for the replies. I admit, I don’t know much about eyepieces etc. I have the Baader mark3 zoom (1.25mm but has the 2” Adapter). I thought as I have the 2” diagonal I would be losing out on some of the light gathering using a 1.25mm eyepiece and a 2” one would be better. Is this not the case?

The light gathering is done by the telescope, not the eyepiece, all the eyepiece gets is the end result.  You will find that both 1.25" and 2" eyepieces will be useful to you.  One of the best 1.25" eyepieces out there is the TV Panoptic 24mm, giving the widest possible view for a 1.25" ep.  Good eye-relief, however, a little over budget, but well worth it. 

[GavStar]

8 minutes ago, rwilkey said:

The light gathering is done by the telescope, not the eyepiece, all the eyepiece gets is the end result.  You will find that both 1.25" and 2" eyepieces will be useful to you.  One of the best 1.25" eyepieces out there is the TV Panoptic 24mm, giving the widest possible view for a 1.25" ep.  Good eye-relief, however, a little over budget, but well worth it. 

I really like my 24mm pan. However i think the eye relief may be a little short for wearing glasses.

[alanjgreen]

11 minutes ago, GavStar said:

I really like my 24mm pan. However i think the eye relief may be a little short for wearing glasses.

@Bino Pete Gavstar is correct. I too have the Panoptic24 and it is a bit tight with glasses.

My prescription is -3.50 and I observe without glasses. So, do try observing without to see how you get on. I used to wear my glasses for the alignment stage of setting up the scope then put them away for the rest of the night. The scope knows where it is going and I can read/write without them so no problem.

If you do want to wear your glasses then buy eyepieces that offer "20mm eye relief" such as the Televue Delos & Delite (Celestron Xcel. You have to pay more for eyepieces with long eye relief   Some manufacturers can overstate their eye relief (Explore Scientific) and watch for eyepieces with curved upper lens as the measurement starts from the centre of the glass so 1-2mm can be lost in the curve. Dont buy any eyepiece with less than 15mm eye relief if you want to wear glasses.

If you dont want to pay Televue eyepiece money then the Baader Morpheus has decent eye relief

https://www.firstlightoptics.com/baader-planetarium/baader-morpheus-76-degree-wide-field-eyepieces.html

check the "specifications" tab for eye relief measurements...

[Bino Pete]

I have been quite happy with my Baader zoom eyepiece but thought I was missing out on even better views! How does the Baader zoom compare with the eyepieces you have all mentioned? Thanks again.

[alanjgreen]

5 minutes ago, Bino Pete said:

I have been quite happy with my Baader zoom eyepiece but thought I was missing out on even better views! How does the Baader zoom compare with the eyepieces you have all mentioned? Thanks again.

I used to own a Mk3 Baader zoom.

At 24mm setting its not very good due to loss of fov (see the tfov text I wrote above!)

I enjoyed mine and it will be okay in an f/10 SCT like the CPC800. After owning mine for 6 months, I decided to buy 10mm & 17.3mm Delos to replace it. I do prefer fixed length eyepieces but the zoom was great for finding out what magnification (mm) I found best for specific objects (galaxies, planetaries, planets etc)

After moving to Televue, the biggest difference is the "jet black" background, in my scope when I had both Baader Aspheric & Televue Panoptic the blackness (of the background sky) was astonishing and the difference it makes to seeing more stars was amazing. (It really stood out at the eyepiece). I have been Televue ever since.

The Panoptic 24mm cannot really be mentioned in the same sentence as the Baader Mk3 zoom. The Panoptic 24 is one of the best eyepieces ever made ... I would never sell either of mine - I have 2 for my binoviewer (which is a Baader by the way) [enough said]  

[Louis D]

11 hours ago, Bino Pete said:

Any recommendations for a 2” eyepiece around 18mm to 20mm which would compliment my Celestron CPC800 XLT?

I do wear glasses.

Thanks.

Do you have astigmatism?  Check the cylinder (CYL) number on your latest eyeglass prescription.  If it's 0.5 or less, you can probably get away without wearing glasses at the eyepiece, especially at 20mm.  At 1.0 diopters, it might start to become visible.  At 2.0 or above (as in my case), you'll need correction except at the highest powers.  Televue's DIOPTRX webpage has a nice graph showing this relationship between astigmatism and exit pupil (which is proportional to eyepiece focal length).

My personal favorite at that focal length is the 22mm AstroTech AF70 which is the same as the Omegon Redline, TS Expanse, and Tecnosky Superwide HD.  Optically, the Celestron Ultima LX, Olivon 70, and SkyWatcher SWA 70 are the same, but in less ergonomic packaging.  Once the eyecup is screwed off, there is a true 20mm of eye relief and a true 70 degree AFOV corrected out to about 95% of the way to the field stop.  It's affordable and punches well above its price.

If you've got big bucks to spend, go with the 17mm Explore Scientific 92.  It's big, heavy, has 18mm of usable eye relief, a 92 degree field, and basically perfect correction across the entire field.

[Bino Pete]

22 minutes ago, Louis D said:

Do you have astigmatism?  Check the cylinder (CYL) number on your latest eyeglass prescription.  If it's 0.5 or less, you can probably get away without wearing glasses at the eyepiece, especially at 20mm.  At 1.0 diopters, it might start to become visible.  At 2.0 or above (as in my case), you'll need correction except at the highest powers.  Televue's DIOPTRX webpage has a nice graph showing this relationship between astigmatism and exit pupil (which is proportional to eyepiece focal length).

My personal favorite at that focal length is the 22mm AstroTech AF70 which is the same as the Omegon Redline, TS Expanse, and Tecnosky Superwide HD.  Optically, the Celestron Ultima LX, Olivon 70, and SkyWatcher SWA 70 are the same, but in less ergonomic packaging.  Once the eyecup is screwed off, there is a true 20mm of eye relief and a true 70 degree AFOV corrected out to about 95% of the way to the field stop.  It's affordable and punches well above its price.

If you've got big bucks to spend, go with the 17mm Explore Scientific 92.  It's big, heavy, has 18mm of usable eye relief, a 92 degree field, and basically perfect correction across the entire field.

Would this work on my CPC 800?

[Louis D]

6 hours ago, Bino Pete said:

Would this work on my CPC 800?

The 22mm AT AF70/Redline/Expanse/Superwide would certainly work very well in an f/10 SCT without any issues.  I'm using it in a Dob (and ED refractor) at f/6 without issues.  The 17mm ES-92, on the other hand, would probably tax the guide motors without proper counter-balancing.

[Bino Pete]

5 hours ago, Louis D said:

The 22mm AT AF70/Redline/Expanse/Superwide would certainly work very well in an f/10 SCT without any issues.  I'm using it in a Dob (and ED refractor) at f/6 without issues.  The 17mm ES-92, on the other hand, would probably tax the guide motors without proper counter-balancing.

Thanks, how would I counter balance a CPC800?

[alanjgreen]

14 minutes ago, Bino Pete said:

Thanks, how would I counter balance a CPC800?

You should not need to counterbalance the cpc800, it is not back heavy to begin with.

just don't add a rear crayford focuser whatever you do, then you will need to counterbalance. this just moves the weight of the diagonal and eyepiece away from the back of the scope increasing their effective weight  plus the weight of the hefty focuser.

my cpc1100 needed a counterbalance system, but it was very back heavy due to the large mirror to begin with!

If you hear the motors on the scope struggle to LIFT the scope while slewing by becoming louder then this is a sign that your balance is out.

you can test for yourself too, by holding the handle at the rear of the CPC and release the altitude clutch, the scope will drop down at the back. Now add all your accessories and repeat the test, it will drop down at the back faster than before (KEEP A LOOSE HOLD ON THE SCOPE HANDLE SO IT DOES NOT DROP IN FREEFALL).

You want your scope to be slightly out of balance.

if you decide you want to balance the scope then you need an ADM Balance kit

https://www.firstlightoptics.com/adm-counterweight-kits/adm-mini-dovetail-counterweight-celestron-8-kit.html

but you should not need this on a cpc800, I used 2" diagonal and panoptic 41 with no issues.

Just listen to the motors, they will struggle if the balance is bad.

Alan

[Bino Pete]

21 hours ago, alanjgreen said:

I used to own a Mk3 Baader zoom.

At 24mm setting its not very good due to loss of fov (see the tfov text I wrote above!)

I enjoyed mine and it will be okay in an f/10 SCT like the CPC800. After owning mine for 6 months, I decided to buy 10mm & 17.3mm Delos to replace it. I do prefer fixed length eyepieces but the zoom was great for finding out what magnification (mm) I found best for specific objects (galaxies, planetaries, planets etc)

After moving to Televue, the biggest difference is the "jet black" background, in my scope when I had both Baader Aspheric & Televue Panoptic the blackness (of the background sky) was astonishing and the difference it makes to seeing more stars was amazing. (It really stood out at the eyepiece). I have been Televue ever since.

The Panoptic 24mm cannot really be mentioned in the same sentence as the Baader Mk3 zoom. The Panoptic 24 is one of the best eyepieces ever made ... I would never sell either of mine - I have 2 for my binoviewer (which is a Baader by the way) [enough said]  

Just to confirm (as they cost a lot of money - I want to get it right)!

Will the TV Delos work well in my CPC800?

Also, I do live in a semi-light polluted area, will I benefit from an expensive eyepiece?

Sorry if these are stupid questions!

[alanjgreen]

1 hour ago, Bino Pete said:

Just to confirm (as they cost a lot of money - I want to get it right)!

Will the TV Delos work well in my CPC800?

Also, I do live in a semi-light polluted area, will I benefit from an expensive eyepiece?

Sorry if these are stupid questions!

Televue Delos will work well in ANY scope. That's the point of buying one, you are future proof. They are superb and the 20mm eye relief will work well with glasses.

- your f/10 scope is not challenging for them, but you know that Televue test them down to f/4 and they are a lifetime purchase to take on to the next scope(s).

They have adjustable sides that unlock and then slide up/down, you will have some initial fiddling to get the height right for you then once it's locked in place - job done.

if you can find a second hand one, then you won't lose much if/when you come to sell. 

if you buy new then expect to lose 30% when/if you sell.

KEEP ALL THE TELEVUE BOXES, END CAPS INSTRUCTIONS safe as a buyer will expect to receive these.

I have two each of 17.3, 14 and 10mm that I use in my binoviewer. They are superb.

You will also save some weight over a hefty 2" eyepiece too.

Televue also seem to have sales every now and then, this is another good time to pick one up.

Place a wanted ad on this site (and astrobuysell) like this one and just be patient...

Alan

[John]

While expensive, eyepieces such as the Delos or Pentax XW's (in focal lengths from 10mm downwards) will work excellently in any scope you might ever own. Once you have them, they are with you for life while the scopes come and go

 

[Doc]

I couldn't agree more, I have the full set of Delos's and they are all great but the 17.3mm is the best.

[Bino Pete]

If my wife was feeling flush with the money and allowed me to get two eyepieces, what focal lengths would you advise that I should get that would give me the best coverage? Apart from my Baader zoom that I would probably sell to help fund the eyepieces I only have  a 30 and a 42mm both 2” revelations.

[alanjgreen]

The best delos range for your scope will be 10, 12, 14 & 17.3. The 10mm at x203 would be least used. You need to buy the size that will be YOUR MOST USED EYEPIECE, no point paying ££££ for the EP to sit in your case  

If you use the "buy one, skip one" theory then I would go for 12mm (x169 magnification) and 17.3mm (x117 magnification) as the first two.

Your scope has focal length 2032mm. Divide 2032 by eyepiece size to get the magnification. (2032/12 = 169)

[GavStar]

I agree that 170x and 120x are nice magnifications to have. I think I’d also like to have a 50x mag option as well for more extended objects. So I’d keep the 42mm eyepiece if you can (do you like this one?)