markse68

no it doesn’t help with wobbliness John- only the dispersion colour smearing

5 hours ago, alanjgreen said:

It now lets 20% more light through the eyepiece than the vanilla plossl (as an added bonus).

my understanding of optics is pretty non-existent but I’m keen to learn. How can adding another lens at the eye end of an ep increase the light throughout of that eyepiece?

Agree with Robindonne Craig- I just sketched a rough model as per your dims and cost for 2 in printed nylon on fast 2day turnaround would be £14 from the printers I use. Are you sure the dims are right as it looks a bit different to your image. This SLS nylon is pretty tough stuff.

Mark

6 minutes ago, Paz said:

There are a lot of very helpful contributions to this thread that have got me wondering if I've been using my ADC optimally, next time I'm out I'm going to try some different approaches and pay closer attention to what I'm doing.

If I've been using it incorrectly that will be embarrassing but on the plus side it would also mean I've got some more improvements in the views to look forward to!

You did say what scopes you're using Paz but I can't remember but the other thing to bear in mind is they suffer quite bad distortions in faster scopes from what I heard- recommendation seems to be f10+ and in faster to use a barlow. Mines f8 and I'm using 2x barlow

i think 40mm

Edit- sure i read that somewhere and thought it was too high but looking at specs of the ZWO unit i think it must be closer to 60mm. They say the body height is 30mm but then you’re shifting the ep out further with the ep adapter. Strange neither of them spec for this

31 minutes ago, bomberbaz said:

HOW MUCH !!!! Just looked on APM website, are they layered in Gold 🙀

I expect you’d pay similar for a nicely engineered gear driven  Risley prism from an optical house- it’s really a luxury item that a few on the other forum seem to own. It’s USP apart from ease of use is the doublet prisms with planar faces that seem to mainly prevent image wander when adjusting but you’re putting another piece of glass in there too 🤷‍♂️ I have to keep nudging the dob anyway so simple prisms work fine 😉

2 hours ago, johnturley said:

Do you have the ZWO version (the Altair version appears similar), or one of the much more expensive Gutekunst versions.

Those Gutekunst ones are a bit erm pricey aren’t  they 😳
I figured I would have focus issues with any of them without major rework of my scope so I made my own.

54 minutes ago, DaveL59 said:

Came across this one, cambridge way but its the smaller Alcor (65mm) as Stu has (the peashooter). Even has the nice fully fitted wood case too tho the foam has had it and stuck to the tubes. Different design to the M but likely just as solid.

https://www.ebay.co.uk/itm/303623383926?ul_noapp=true

😍 the Alcor was my first scope- bought new from telescope house in person way back when for iirc £150! I still have it 😉 But thanks Dave- I might bid on this to give to one of my nephews- bit more manageable than the Tal-1s i’ve been collecting for them. It’s a lovely little scope. So solid- not a toy at all. Mines probably in similar condition now- hasn’t seen the light of day for decades...

11 minutes ago, Moonshane said:

Would it improve low doubles like Sirius and Antares?

yes- it really tightened up antares at the weekend and i “think” i split it but it was still noisy and i can’t be sure- need further confirmatory observation - if only it were summer...

15 hours ago, Paz said:

With mine I orient it so that the bubble level on the ADC is always physically on the top side and levelled and that is the orientation done

I don’t think a bubble level works with a newt as the image rotates depending on focuser/ota rotation? I could be wrong though

What is this sun thing you speak of? I seem to remember seeing something similar in the distant past 😉 

Beautiful sketch as always Achim-  full of hope

I guess if Don hasn’t come across this design in reality then it must be theoretical. I’ll try contacting the author of that website or maybe Chris Lord. There are a few archaic designs I’ve seen mentioned like the single solid element types that don’t seem to exist except maybe in museums-seems odd though when this one seems to offer real benefits 🤷‍♂️

11 hours ago, Paz said:

I've been using a ZWO ADC for a year or so.

I find atmospheric dispersion clearly noticeable on bright and low objects and the ADC can tune this out.

Here's my take so far on planets...

Saturn... It cleans up atmospheric dispersion but Saturn is quite dim and dispersion is not huge. I can't say I've seen more detail with the ADC, just a cleaner image.

Venus has fierce dispersion due to being much brighter but I find an ND0.9 filter usually turns in the best views of Venus for me, for whatever reason.

Jupiter is where I have found the ADC has provided the most consistent benefits. Recently the ADC made the difference between me being able to see the red spot or not.

It takes a bit of practice to be able to set it up quickly, at first it was quite a faff to use but now I've got the hang of it.

I use it on longer sessions and I don't tend to use it on short sessions.

Good to know i’m not the only one Paz

 Regarding setting up, what I do is set the prisms to max then rotate the whole thing to get the worst dispersion- max smear of colours. Then rotate it back 180 deg and lock it off then adjust the prisms symmetrically to get the best correction- i’m finding it quite straight forward really and there’s something very satisfying about tuning the image to max sharpness.

Mark

Looks interesting Dave- certainly looks like the sellers father was using it so not decorative junk! Love the fettled wooden mounting plate 😉 I’d probably take a punt 

1 hour ago, Doc said:

to get a good finish on wrinkle paint I found you had to warm up the mount with a heat gun first and then apply two heavy coats. Then gently warm the paint until it cures and leaves a wrinkle finish.

Looks beautiful Doc! Is it a special paint to get the vintage wrinkle finish?

33 minutes ago, jetstream said:

Maybe they should make some Pentax XO design eyepieces- are they patented?

it’s only one extra lens by the look of it 😉😂 very similar approaches to stray light control 👍

1 hour ago, John said:

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

I guess trying one would be the only way to know and yes maybe it is location or scope dependent (I’m using my 8” dob) but I really notice a difference even when Jupiter was really quite high last night between using it or not. Venus was extreme case and seeing so wobbly down there it was more an experiment than anything else

I’ve been playing with my Atmospheric Dispersion Corrector the last couple of nights and getting the clearest views I’ve ever had. I’m coming to the conclusion that it is an essential piece of equipment for planetary observing- at least while they’re low. Jupiter and Saturn were incredible last night with it-  very very sharp. Mars is looking more like a planet than an orange blob and the icing on the cake was Venus rising- without the adc a rainbow crescent but with it a tight crisp mini moon bar the wobbly atmospherics. It’s really been quite an eye opener! 

I guess the extra glass must take something away from the image but if the image is already blurred by AD then what it subtracts is more than made up for by what it corrects. Mine has uncoated prisms  so with my 18m bco on Jupiter I get 4 reflected jupiter’s around the edge but the glass being planar and angled these are off to the edge so don’t affect the important central image. I guess coated prisms would be better. shorter fl eps the reflections are out of view anyway. I’m using it with a 2x barlow.

Mark

11 minutes ago, John said:

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 ?

 

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

12 hours ago, jetstream said:

Ok youve hit a weak spot! I really want one of these... right up there with the ZAOII's

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

45 minutes ago, jetstream said:

This really does show why I like orthos- excuse me I better be specific- Abbe ortho lol! as we all know that orthoscopic is not a design but a condition

Even the beloved very narrow monocentric suffers "bigly" off axis. I'll take an Abbe any day.

would be interesting to see comparison plots for the Pentax XO design which appears to be a very carefully executed, corrected plossl (to my ignorant eyes )

5 minutes ago, johninderby said:

A pic or the Hi-Or 4mm.

yea but it’s not an h-ortho 😉 not the same thing at all from reviews i’ve read- they used a built in barlow to give decent eye relief as it would have been impossible to use at those fl otherwise- hi= high eyepoint (not highly orthoscopic)

2 hours ago, johninderby said:

Some AeroShell 33 airframe grease as recommended by Rowan for the AZ100. 

What colour is it and how does it smell?

1 minute ago, John said:

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

 

hi john, those were high eyepoint orthos with built in barlows- not this design i think

In another thread Gerry posted a very interesting chart of eyepiece optical designs and their ray tracing analysis taken from this webpage:

https://www.telescope-optics.net/eyepiece_raytrace.htm

Despite not really understanding what I was looking at (what do those ray trace patterns (splodges) mean- worst aberrations? need to do more research!) I noticed a schematic for a type of eyepiece i’d never heard of- #9 in the chart- the H-ortho.

This seems to be a variation on the Abbe design- still 4 elements in 2 groups but the triplet is quite different. The ray trace seems to suggest it is sharper for wider than the Abbe- if i’m reading it right, and presumably it is better corrected for distortions too, hence the name.

This is what the page has to say:

”9 - The "highly orthoscopic", or H-Ortho has somewhat different triplet configuration, resulting in a highly corrected field, similar to that of the monocentric eyepiece, only significantly wider. In part, this exceptional of field astigmatism correction is a trade off for the significantly curved best image surface. However, while the standard orthoscopic would also have astigmatism reduced with more strongly curved best field, it doesn't seem it could achieve the same level of correction.”

Anyway, google turns up a complete blank on this design. Anyone heard of it before? Is it just theoretical or do they exist? Maybe as a microscope ep? Did the curved field put the kibosh on the design?