Deadlake

24 minutes ago, Highburymark said:

I remember you reporting this Martin - very interesting, particularly as the 3.3 TOE is my favourite of the line. I’d love to try a 3.4 HR. It’s probably a good sign that opinion seems to be split about the capabilities of the HRs and TOEs - but both have raised the bar in recent years for planetary eyepieces. 

I prefer the TOE 4 mm. Having said that the seeing was so good tonight I spent most of the time using the HR 2 mm that the 4 mm didn't get a chance. 
4 mm is usually most used when seeing is average on planets.

12 minutes ago, jetstream said:

Yes I get puzzled when some have to experiment to get colour unless the seeing is a major factor. Out H130 gives a deep ruddy colour and I use a NZ 3-6 zoom mostly in it. I really dont have a clue why seeing colour in Jupter is an issue. When its high up and very bright- highly contrasted here because of the very dark sky and overpowering, I do a couple of things. One is to use a slower scope to use the smaller exit pupil to advantage. The second is to use binoviewers where the beamsplitter halves the volume of light to each eye making detail much easier to see. The best view of Jupiter I have had was just over 300x in the 15" with the Binotron 27's. It was like looking at a good image , a very good image.

The third thing is obs at sunset and just after using the lighter sky to tame down Jupiters brightness. This is just me however but it does work for me.

In the UK really need the planets high up, last few years low down and large depth of atmosphere to peer thru..

I had the fortune to have a TOE 3.3 mm and HR 3.4 mm using with an LZOS 130 mm on a night of exceptional seeing when viewing the Moon.
Not much chance of looking at anything else this year due to the cloud cover. 😀

The one data point that the HR really showed it pulling away from the TOE was the level of shadow contrast visible within craters.
At one point I had to pinch myself at the detail. 
Also the dynamic range as well, noticeable more than the Vixen SD103S scope I used to have which I feel was still very good.

I also used a 2 and 2.4 mm HR, the scope just opened up with the level of detail on the moon, the limiting factor being I needed a guided mount to minimise vibrations.

Note: using a Baader moon filter took off the extra brightness the TOE adds.

Hoping for another good night, I'll try a BRAVDA and 10 mm UFF and see where that gets me.

4 minutes ago, jetstream said:

I am always very interested in reports of seeing colour in Jupiters bands or lack of. I see ruddy red in the bands with every scope I have and my reflectors do a great job and with the 15" really opening them up with very fine riffles in them. I really like observing Jupiter just at dusk and afterwards a bit. I tend to get the best views then but I only really obs it when well placed.

I'm always puzzled when some cant seem to get much colour out of Jupiter. Theres so much in there, white ovals, barges and the hooked purple spikes aka festoons.

I has to experiment with different EP’s and diagonals. However on nights of good seeing all is possible. 

Sometime best to have multiple scopes out to experiment with Barlow or BV’s side by side…

2 hours ago, jetstream said:

Yes, I believe it to be about MTF as well possibly. I hope through conversation here, ideas about it and how seeing can potentially affect these certain features as described by spacial frequency sheds some light on it. I think there might be something to it as the MTF graph describes optical quality in a different but related way to the idea of "diffraction limited or above" etc.

For planetary observations some of the best planetary views I had are by attaching a Barlow on the scope ahead of the diagonal (now running at F20) and using a 10 mm UFF EP or some BV's.

This helps with bring up contrast from observation and also brings out the reds on Jupiter.

It was not just me, one of the best nights for seeing for some time.

Why or why on a moon light night.....

 

1 hour ago, Mr Spock said:

Vixens are excellent too. But they do seem to be unobtanium these days.

4-9 Working days, 

https://www.bresseruk.com/Astronomy/Telescopes/Vixen-SD103S-apochromatic-Refractor.html

Actually quite shocked how much SD80 as gone up, when I bought my SD103S the SD80 was around £900, not just under £1300.

Well done government, this is not just global inflation.

4 minutes ago, jetstream said:

It is very possible the rest of the line will be well corrected for green and blue despite being corrected best in red. Its also possible that the 180mm tested had some issues stemming from a slip through QC.IMHO.

To me, the DPAC test and others, take bias out of the equation optics wise. No doubt many scopes from many makers will do well in these tests and some will not.  Time will tell as more and more scopes are run through the test, unless owners are scared they wont test well and therefore affect resale value. IMHO.

I am very interested in further SV tests and also scopes like the Starfield. AT scopes seem to be testing well and it will be interesting to see sample to sample variation in them, if and when more scopes become available.

I think the reason for little data is the hit on resale value, a theory but a reasonable one.

With regards to red line testing, I think the current theory is that the blue line will be more optimised than testing in the green and the green line will also not be as high.

Obviously eyes and CCD are more sensitive to the green line wavelength.
 
At the same time if SV are forced to optimise in the green and red line then the produced lens will be made similar to how AP and LZOS produce their respective lens by testing with multiple wavelengths with an interferometer. 

Which is good for the quality on the lens, however will make them more expensive to produce.
 

6 hours ago, JeremyS said:

Don’t think that’s relevant John, or fair, considering this well documented, and unfortunate, saga.

His results clearly showed that SV methods were erroneous as they optimised lens performance in red, not in green - or even across a range of colours. Seems even SV admit that. The question that remains is whether this has affected smaller apertures than the one tested. Evidence from users is that they are fine.

At the moment there really is not enough data on SV's line up to call this one way or the other.

Actually the only data points I see on this are for SV's with LZOS lens cells that are tested on the green line 😀.

See:

https://www.cloudynights.com/topic/868125-dpac-testing-repository-of-tests-performed-on-refractors/

Even what SV are going to do is not firmed up, originally they where going to move to testing in the green line and then that statement was removed from SV's site.

Note: I've had to have Nic remove around 2 pages of comments around SV on a thread I have on CN as went off on SV tangent.

Gerry,

Does the mount need tracking or not?

If so I'd also look at the HAZ31. The weight is around 3.5 kg vs the AZ100 of around 10 kg.

Note: I'm planning on getting the motor upgrade for the AZ100 I have, I would just like a more portable and compact mount for dark sites visits etc or tree dodging in the back garden.

The HAZ31 is also a top loader which makes set up and tear down easier.

The only caution is earlier shipments appear to have issues with the mother boards. If you get a working version the tracking is meant to be superb.

The other gotcha here is balancing the scope. My tail heavy 105 mm LZOS needs a 1 kg counter weight on the lens end to balance when on the AZ100.

The harmonic drive in the HAZ31 makes the need for a counterweigh redundant, you can change EP's from a 30 mm UWA to a HR 1.6 mm without a rebalance.

I'm waiting on more reports but from the feedback I've seen very positive.

M

4 hours ago, Don Pensack said:

The APM Zoom requires only a bit of in focus when used as a 2" eyepiece.

When used as a 1.25", it requires massive amounts of in focus.

I regard it as a 2" zoom.

Unless the scope has a lot of in travel available, that means a zoom on its bottom end may likely strike the diagonal mirror in a star diagonal.

 

I think Sixela has work arounds with this for this (in the thread on CN) so the bottom of the Barlow is flush and will not hit the diagonal. 
 

However how much back focus is required, that’s an interesting question.

3 hours ago, Don Pensack said:

It's only a thread-on Barlow lens, though, which might be an issue in a star diagonal for all the 2"/1.25" eyepieces out there when used as 2" eyepieces.

It attaches to the bottom of the APM zoom, sold as a pack.

Needs push fit adapter for the 1.25" barrel.push fit adapter 

Gerry you might want to checkout the revised TMB APM Barlow, meant to give sharper stars at the edge then the VIP you are using, also very good used with Bino’s as well.

Did you mange to use the HR or TMB EP's at all?

8 hours ago, jetstream said:

You want to sell me the 1.6 and 2 ?My VX 10 could easily use the 2mm at 600x for lunar.

You still got your Doctor? 😀

14 hours ago, jetstream said:

One of the dumbest things Ive done is to assume the Vixen HR line would always be available. I should have bought them all.

Yep you want a full set, but not sure how much you would use them all…

If you have the 3.4 mm and either of the 2.0mm or 2.4 mm I think you have most bases covered..

A powermate and a 10 mm UFF works very well and with sensible eye relief.

On 24/03/2023 at 01:11, John said:

Apologies if I have missed some discussion on these but I wonder if anyone has them and, if so, what they think of them ?

I'm just "tyre kicking" really - pondering the option to move from my current mixed collection of Tele Vue and Pentax eyepieces to a simplified all Pentax line up of:

23mm, 16.5mm, 10mm, 7mm, 5mm and 3.5mm. I already have the 4 shorter focal lengths in the series.

Each time I think about "rationalising" my eyepieces I seem to talk myself out of it but I'm feeling a stronger will to actually make some moves now and a Pentax XW set, although not perfect (of course) would seem to be a pretty good compromise to happily live with based on my experiences with the XW's that I currently own.

I suppose the main thrust of my question is to find out if the new 85 degree Pentax's have any major issues that I ought to be aware of. I don't wear glasses when observing 

Thanks in advance for any feedback 🙂

 

Interested in why you would move from TeleVue to Pentax and not the other way around. 

You've had your TeleVue from some years not, why the Pentax EP's?

All the best, Martin

1 hour ago, Highburymark said:

For an $18,000 triplet, I agree. But the vast majority of scopes sold as ‘apos’ have varying degrees of CA and SA. It’s why we can buy pretty good ED doublets for £300+. We can’t expect perfection with such competitive products. The only loser in the long term if we expect too much from cheaper scopes will be the consumer.

But isn't this the discussion around marketing. For instance would you take a lower Strehl in green line or a higher Strehl in the red line. 

The lower Strehl in the green line gives better views, so in some way a marketing ploy has occurred.

A higher Strehl in the green costs more to fabricate by quite a bit.
 

Some more colour: Two years ago I was shopping for a fast 130 mm scope. I looked at several makes, I avoided SharpStar as I knew APM had moved production to KUO as they had quality issues with SharpStar. At the time I would of liked to know how Sharpstar where testing their lens.

One final point, some of those Technosky scope are DPAC'ing very well on CN, far better than you would expect for the brand.

Maybe we can eat cake?

4 minutes ago, Highburymark said:

I read the Suiter book, and have to admit half of it flew over my head. However I understand the basics, and for people like me, the simple star test, done properly, is enough to establish whether a telescope is doing a good enough job to be happy with it. Only one of my refractors has ever shown a near perfect star test - the TSA120. The others have shown some false colour at high powers, and clearly contrasting rings either side of focus. Yet I’ve been happy with their performance under the stars. 
So, for most amateur needs, I agree DPAC results are not needed. But I’m interested in what they can teach me about optics - that’s the attraction rather than trying to establish whether my scopes are perfectly figured. The hi-fi analogy is a good one - I sometimes wonder whether hi-fi buffs are too wrapped up in sound quality to enjoy the music they are playing. 

A scope's optics should get out of the way, however if not a change is needed.

37 minutes ago, jetstream said:

I dont know? how about this? Apparently from SV facebook page? Is this correct- I dont know

Since I posted the url has been updated, I've corrected the original post.

12 minutes ago, nicoscy said:

Some misleading facts: most color cameras have a RGGB matrix, so color cameras are more sensitive to green wavelengths. However, QE depends on each camera. If you are imaging in visible light, the 533MC is superior to the 585Mc due to high QE in visible light. If you go towards longer wavelengths (red, infrared, ha etc) the 585MC is a lot more sensitive. So, this assertion does not hold. It depends on the emissions you are interested to image in. Here’s a graph I created on some wavelengths - so, it all depends.

SV now states that they will have two types of scopes - visual optimized and imaging optimized. This is wholly unnecessary and is a marketing gimmick again. Very disappointing. AP, TEC, LZOS test in green. AP and APQ Zeiss check polystrehl (AP for Stowaway and AP110 clearly indicated this, APQ states this for their new range). Agema, a newcomer with long focal length fluorite doublets, also provides strehl info on all key wavelengths.

The implications of this - All scopes sold so far by Stellarvue  were supposedly optimized for imaging, so visual amateur astronomers can now start feeling disappointed and that they own an inferior (expensive and soon to depreciate more) product for their intended use. 

The “sweep under the carpet” moment: no discussion of zones, ripples and uneven polish of the lens assembly in question which was tested, which at $18k, only one word should have applied for the money: “flawless”. Which it is not…

I was hoping SV would just come up with a similar policy as the true Master Opticians of our times, stick to it, produce real high end scopes and be considered one of the great ones. Alas, it doesn’t appear so…

One last thing is cost. I know APM produced extra high Strehl lens for 105 mm scopes some years ago to celebrate 20 years of telescope production. The cost from moving from 0.95 to 0.99 was an extra $1000 per lens. How much for a poly Strehl lens?

Maybe Vic needs to come up with how much a poly Strehl optimised lens costs, the AP and APQ are really another level in costs compared with Taks etc...

 

3 minutes ago, John said:

That is just where I think things might be heading 😒

I hope not, I'd follow my eyes as I think a Strehl test do not cover full metrics required to describe the performance of a lens.

Here are some LZOS Strehl data points across the spectrum:



An AP110GTX as well:



Not sure why SV has gone after red, when the above do well in the red and the green...
SV is aiming to be high end so I've pulled these in.

Well Vic has responded

https://www.stellarvue.com/dvx-optics/

For AP null in red and for visual null in green.

Is it as simple as that?

1 hour ago, jetstream said:

You want to get your LZOS DPAC'd?

Both where tested in the green, thr interest would be the drop off in the red.

The only scopes with a high poly Strehl I can think of would be an AP110GTX and Zeiss APQ’s but I stand to be corrected…