John

Such a pity that the Pentax XO's have been discontinued. The 2.5mm pops up occasionally on the used market but I have not seen the 5.1mm for sale for ages now.

My other high power tool is a Nagler 2-4mm zoom. Not quite in the HD ortho / Supermono league but very good for a variable focal length eyepiece and having that "instant tweak" capability has proved very useful on a number of occasions.

Er, lets keep to the topic of time / daylight vs darkness / observing etc, shall we ?

Thanks

Old thread but maybe it still has some mileage in it ?

Sometime back I used to own a 5mm TMB Supermonocentric and a University Optics HD 5mm Abbe Ortho. I compared their planetary performance at some length over a number of sessions and concluded that most of the time the optical performance of the two was pretty much identical. During the time comparing them I had 2 sessions where the seeing conditions were very good. During those sessions I noticed that the TMB Supermonocentric delivered a little more contrast on the surface features of Jupiter and Saturn and that the most subtle features were just a little easier to spot with that eyepiece. These differences were only visible under the best observing conditions though and were subtle. 

Personally I felt that the smaller apparent field of view of the Supermonocentric made observing with it hard work (not that the 5mm UO HD ortho was exactly a relaxing eyepiece to use either ) so I didnt hang on to the TMB for too long. It was probably the best planetary eyepiece in pure performance terms that I've owned and used by a small margin though.

These days I'm happy and more comfortable using a 5mm Pentax XW in this niche

It's a very interesting topic I think. We all have different eyesight prescriptions and these will affect how eyepieces work with our eyes on a person to person level. The eyepiece designer has to produce a generic design that works with a wide range of eyes but in some cases falls short, unfortunately. This probably accounts for why eyepiece choices and preferences are very personal.

Tele Vue recognised this and has produced accessories such as the Dioptrx to help and those can be used with brands other than Tele Vue in some cases. I'm not aware of other eyepiece brands having developed such things but maybe they have ?

44 minutes ago, rl said:

Yes, but I guess I'm used to that....

Strangely enough not all eyepieces do that. Don't know why.

RL

With the 40mm Pentax XW, there is no lower lens set within the 2 inch barrel wheras with all the other XW's there is. So the field lens of the 40mm is a large heavily concave lens wheras with the 30mm (say) it's a convex lens further down the barrel. The field lens surface with the 40mm is also closer to the focal plane of the eyepiece / field stop position. This design difference may well explain why you can see these dust particles on the field lens of the 40mm XW when observing an extended illuminated target. With the other XW's that large lens surface is an internal one so not prone to picking up dust.

Put them on a good mount and with a half decent eyepiece in the drawtube and those old Japanese 60mm refractors give some fine views.

I have one that is practically identical to the one you have tidied up except that it has an 800mm focal length. It dates from the 1960's like I do

My brother and I invented the Space Shuttle back in the late 1960's. We glued balsawood wings on to our plastic model of the Apollo Command & Service Module to try and make it glide. It didn't work but the creative thinking was there.

Then darn me, both the USA and the USSR copied the idea ....... sort of

It seems to be around magnitude 18.5 according to the Sky Live data:

https://theskylive.com/289P-info

Isnt there a "super-apo" as well which gives 4 colour "crossings" as they are known ?

36 minutes ago, mikeDnight said:

They really are beautiful though, and you might not notice it so much if you buy one at a time. e.g. Add to basket, add to basket, add to basket.......etc, etc.

Adding them to the basket is easy. Paying for the basket full is the painfull bit !

They do have a place and I'm sure are excellent eyepieces.

I wont be getting them. I have used a 30mm XW in the past and liked it but I liked my 31mm Nagler a little more. As I said in my earlier post, I don't use the 40mm focal length enough to justtify spending £380 when my Aero ED is pretty good in that niche for 1/7th of the cost (used).

For other folks I can see that these 2 inch XW's might be just what they are looking for

1 hour ago, markse68 said:

What does this mean Jetstream? Keep hearing it but what does it mean? You can see deeper into space with it?

I'm sure Gerry will explain his meaning.

Meanwhile, there is some interesting stuff here on eyepieces and deep sky observing from folks who use very big aperture scopes under very dark skies:

http://www.faintfuzzies.com/OR-Sept022011-OSP.html

Just out of interest, how much do the Zeiss zoom and Docter eyepieces cost new today ?

The Delos is £309 normally and currently £278 in the sale.

You could either flock it or paint it with flat black non-reflective paint. Don't make the aperture of the hole any smaller or allow flocking material to project beyond the sharp edge of the hole because that will reduce what is an already small apparent field of view and you will notice that your field edge becomes ragged.

Personally I'd probably go down the flat black paint route.

As above. Often these serve to provide the field stop for the eyepiece as well as keeping the lens elements in place.

Removing it will not increase the light throughput of the eyepiece. You might get a slightly larger apparent field of view with the eyepiece if it is acting as the field stop but the edges of the field of view are unlikely to be sharply focused.

Next step ? - put it back in the eyepiece and leave it in place I suggest.

Most of my eyepieces (all but 3 I think) were bought pre-owned over a period of 2-3 years. I doubt that could have afforded to buy them all new 

The used astro equipment market (certainly in the UK anyway) means that you can buy a decent eyepiece, try it for a while and then, if it does not quite suit you, sell it on for more or less what you paid less perhaps the postage charges.

With eyepiece choice being so personal (as this thread demonstrates) it is great that the used market is so active.

Peter makes a good point - have you actually tried using it ?

Saying that, I had an Omni 4mm plossl a few years back with just the same issue. It came with a scope that I bought.

I ended up chucking the eyepiece out. I figured it was worth about £10 on the used market when in good shape so not worth all the hassle of trying to split and re-cement the faulty doublet element.

Plossls and orthos have eye relief that is around 70% of the focal length. Its inherant to the design.

I've done that, swapping a Moonlite between my Vixen and Skywatcher refractors. As long as the flange is correct, no problem. You do need to remove the flange to get at the 3 fastening screws though.

46 minutes ago, davekelley said:

I don't find cool down a major issue in the middle of a British winter.  I can take the scope out to the shed for an hour before dark and bring it out to setup, half an hour and I think it's all good!  I was asking this question because I do desire a little more mag on the planets although it is true that often images are far better at lower powers.  In fact it's hard to beat the sharpness of a good 32mm super plossl on a lot of objects.  I just really like the Nirvanah ep's and looking at the moon (an easy target I know)  the scope was handling the 7mm with great ease.  I thought This thing can definitely handle a 5mm ep.  Sadly the Nirvana only do a 3.2.......I suppose I know that is just was too much and looking at planets is a different thing from looking at the moon.  In fact I've ordered an ND filter for the purposes of lunar observing!

regards

Dave

 

 

There is a 4mm Nivana eyepiece but it is probably still too much power to be useful:

https://www.harrisontelescopes.co.uk/acatalog/ovl4nirvana.html

The Skywatcher UWA Planetary eyepieces come in a good variety of focal lengths and are not too expensive:

https://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-uwa-planetary-eyepieces.html

40 minutes ago, jetstream said:

@Maniek the 20mm Lunt HDC is a very worthy contender in this focal length and compares nicely to the 21E...

Thats the same eyepiece as the APM XWA 20mm isn't it Gerry ?

I think this is fun - go as the solar system !:

My other half went to a party dressed as Halleys Comet - you can guess how long ago that was !

Welcome to the Stargazers Lounge forum.

Is your query actually related to astronomy equipment ?

Hi and welcome to the forum.

I owned the very similar Meade AR152 /1200 some time ago. It is a pretty substantial scope and for visual observing I felt that at least an HEQ5 mount was required. For imaging you really are going to need something like an EQ6.

This is the challenge with these big achromat refractors - mounting steadily them will cost more than the scope did by some margin !

Telescopes with very high optical quality seem to support high magnifications while maintaining good image quality. Although the maths still apply these scopes with premium optics do seem to be able to "bend the rules" surprisingly often.