John

1 hour ago, jetstream said:

I must re frame this comment- there might be APM inspired LZOS lensed scopes out there around this aperture that compete.

I expect you will have seen this Gerry but it's a good article:

http://scopeviews.co.uk/FourInchBG2019.htm#_Toc26869850

Discovery scopes had an excellent reputation.

Rarely found on this side of the atlantic, sadly.

Used or new prices ?

I do know that the Baader 95 Travel Companion has a very, very long waiting list. So long in fact that Baader are not currently accepting new orders.

That sounds rather like the AP's so perhaps AP are involved ?

I find it odd that the mid range BST Starguiders are not working that well in the 300mm F/5 dob.

I've used those myself in my 12 inch F/5.3 dob and found them really rather good. The 8mm compared well to my 8mm Ethos for example with sharp stars, nice dark background sky etc, etc.

The 25mm is not so good with stars in the outer 30% of the field of view showing astigmatism but the 18mm, 12mm and 8mm were eyepieces that I was quite impressed with in my dob.

Dare I suggest that the collimation might be worth a check ?

I don't use one and my views of the planets over the past few nights have been pretty good with my ED120 and a small mak last night. Plenty of detail and no AD effects that I could see. I could see the Cassini Division and the main equatorial cloud belt with the 90mm mak last night plus 4 belts on Jupiter and festoons coming from the S side of the NEB. The ED120 showed quite a bit of detail on Mars and a nicely defined south polar cap. I had no issues with CA around Venus when it was well placed a little while back.

If I could borrow one I might give an ADC a go but I'm not exactly unhappy with the planetary views as things are

Maybe an ADC addresses more localised observing issues ?

21 hours ago, jetstream said:

.... Not sure if many know but Baader bought out Zeiss's inventory and design info when Zeiss left the astro world. This is how it was explained to me.

 

Steve at FLO explained this to me a couple of years ago. It is an interesting piece of information.

1 minute ago, markse68 said:

Or the TOE’s? Were they petitioned about the 2” XWs do you know John?

Don't know about the 2" XW's. Personally I don't think Ricoh are that bothered by the astro market and consumer demand from it

The TOE's do have a great reputation.

26 minutes ago, markse68 said:

don’t we all! 😉 Maybe we should petition Ricoh to re-release them 🤔

I think that has been done quite a few times by our friends in the USA. They are like hens teeth to find pre-owned, even the 2.5mm.

I guess the Vixen HR's are the nearest we have today that are at least vaguely obtainable ?

Love that Kerry

I find the binocular view of this comet the most engaging I think. Even more than the scope views. It's getting some clouds and other stuff in there that makes the view !

31 minutes ago, Ricochet said:

I don't think there is any need for a ~12mm if you've already got a 14mm. The two focal lengths are too similar to significantly change the views, unless you are hitting atmospheric limits, which I doubt with the telescope in question. For DSOs I subscribe to the theory that focal length steps of root 2 are as close as you should have, which corresponds to a doubling or halving of brightness for extended objects, and is what your eye sees as one "step" in brightness. I have 10 and 14mm XWs and have never needed anything else between the two (or anything between the similar 5-7-10-14 steps).

I agree. I often go 24mm (Panoptic) - 14mm (Delos) - 10mm (XW) and skip the Delos 17.3. Nothing wrong with the 17.3 though, it's just how observing seems to go.

Likewise with my dob I usually go 21mm Ethos - 13mm and skip the 17mm slot. Thats why I let the Ethos 17mm go - a big investment that was not getting much use !

I have now got a 17mm ES 92 in that slot in the 2 inch set - it's a fine eyepiece but if not used much at least it's a less expensive place filler than the Ethos !

Maybe I'm just not a "17mm person" with the scopes that I have ? 

Might have to be ruthless - I guess I have about £450 worth of eyepieces not getting much use in that slot but we know how it is - the moment it's gone, something crops up and you wish you had it

I'm not good at being ruthless when eyepieces are concerned ......

7 minutes ago, dweller25 said:

I had a 150 F/8 helios refractor on a Vixen GPDX and it was only just ok - an EQ5 would not be very stable whilst focusing at high power.

I also found CA was too much for me and none of the CA filters helped much...

 

I reached similar conclusions here eventually.

The best "big achromat" experience that I had was with the Bresser 127L which is F/9.4 so not a lot of CA really and pretty well corrected.

10 hours ago, SiriusB said:

...Re ED120, if i were to spend >£1k I might as well splurge the extra for an ED150,unless i'm missing something?

 

Be aware of the size difference and therefore mounting requirements of the ED150. The gold scope is my ED120. An EQ5 is right at it's limit (even with the steel tube legs) of a 150mm F/8. I used a driven CG5 (EQ5 with 2 inch steel tube legs) with the 150mm F/8's that I owned (I've owned 3 or 4 over the years) and that was just about OK. Probably a motorised focuser would have helped keep vibration down more. The get the most from a 150m F/8 refractor something more substantial is needed really such as an HEQ5. The Celestron AVX is a bit more sturdy than the EQ5 and has 2 inch steel tripod legs.

I went with the Delos 17.3 and 14 because of the field curvature that I've seen reported frequently with the 14 and 20mm XW's. I've experienced FC in another Pentax eyepiece (the XF 12) and did not much care for it. Maybe the 14 and 20 XW's don't have as much FC as the XF 12 though ?

As the Delos are 1.25" format eyepieces, you don't need a 2 inch diagonal to get the full field of view from them.

Being able to use 2 inch eyepieces does give you wider options though.

It is still looking lovely and a bit higher up than it was last night. Not sure if it's brighter or not - probably around the same.

Sounds about right.

@cotterless45 gets some great views with his 150mm F/8 - look out for his reports in the observing section

This chart shows an assessment of the CA levels that achromats generate which might answer some of your queries:

It's not just about the CA with achromats. Quite a few also have spherical aberration, being either over or under corrected to some degree. Generally ED doublets (at least the ones that I've owned and used) are better corrected for SA as well has having lower levels of CA. SA impacts the scopes performance at higher magnifications.

Achromatic refractors can still be good  scopes to own and use though 

The "is it worth it question" is a personal one in my opinion. Each of us will have their own answer to that

3 minutes ago, Sunshine said:

You are correct, I could certainly use a 20mm for example, I just found that the 14 provided a wide enough FOV for targets like the double cluster. The Pleiades on the other hand, not sure if the 14 will do for that target.

This is a simulation of the 20mm Pentax XW in the Orion Eon 115mm F/7 on the Pleiades:

No XW's in 6mm or 12mm I'm afraid. The full range is 3.5, 5, 7, 10, 14, 20, 30 and 40mm. Last two are 2 inch eyepieces.

Delos are available in both 6mm and 12mm but they won't be par-focal with the XW's - they need around 8mm outwards focuser movement to reach focus. And they cost more than the XW's.

I find having choices at the higher magnification end very useful to find the "sweet spot" for a given target and conditions so I've gone for 1mm or even .5mm increments below 6mm in focal length.

To me, you seem to be missing a couple of longer focal length eyepieces ?

They are pretty good scopes. My first dob was the 8 inch (made by GSO which is who make Zhumell scopes) and I was rather surprised when it produced as good if not better views of the planets than the Celestron C8 that I had at the time could.

The 6" would be F/8 I think ? - they can be really good planetary and lunar scopes.

Takahashi used to have Hi-Or eyepieces of 2.8mm and 4mm I think.

Jupiter and it's moons (plus the odd background star) were a lovely arrangement last night. The Great Red Spot was right in the centre of the disk when I observed it as well.

Last night was a classic astronomy night - so many things to see, the hours just slipped by

12 minutes ago, RobertI said:

... Do you think they would also work with smaller scopes such as the ED100 or even the ZS66?

As Stu say, yes !

One of my favourite sights during the Summer months is of the Veil with my 102mm Vixen refractor, the O-III filter and the widest 2 inch eyepieces I've got. The whole thing is visible in the field of view then.

5 minutes ago, Fozzie said:

Haha Not going to let that one go are you, which is fair enough, i admit it's a shallow reason, not liking the look of something despite the obvious optical performance..

 

I was being serious Fozzie - if it's not what you want then thats a great reason for not going for it.

I feel similarly about some scope designs (SCT's for example). They are fine scopes but just don't do it for me

For rich field and refracting design I think the 152mm F/5.9's are really good choices. 32mm of aperture over the 120mm is not to be sniffed at (or licked ).