markse68

3 minutes ago, tooth_dr said:

Its losing 10 tonnes of this salty water per second.  Phenomenal

that is incredible! 😳 just how big is it?

it’s frozen sea water?

36 minutes ago, Barry-W-Fenner said:

Great stuff folks, real good to hear you all had such an enjoyable night's viewing.

I draged myself out of bed at 2.30am and got my 1st views of Mars, as John mentioned the southern polar cap stood out wonderfully, a real contrast in colour with the red planet! I spent about an hour looking at a few bits before it got light 😕

No joy with the comet as my NE is very obscured. What height is it at roughly, I might go for an early morning walk to see if I can get a glimpse!

 

Baz

 

Hi Baz, it wasn’t very high but clearing the roof tops for me at 3. when I first saw it at 1:30 it was through a gap between houses. Find Capella then diagonally down to the left the next bright star about 45deg down, then a bit further than same distance down again and there it was- quite faint naked eye here but when I knew where to look, easy to spot and it got much more obvious by 3 . But i’m further south in London. Forecast here is for another fine session tonight- hope you get it too

Oh and I had an epiphany last night too haha- Id wondered why Mars has looked so strange and elongated blaming it on atmospheric distortion but of course it has a phase and is not fully lit- doh 🙄😂 It looked splendid last night too- no obvious dark markings but very crisp polar cap and a feeling much more of an atmosphere shrouded planet than the red fuz Id seen before- it’s sharpening up and i’m excited 😃

Amazing night indeed 😄 My first comet! And it’s beautiful and strange. Really a wow moment. Earlier around 11 I think i split Antares 😳 it actually looked like a normal star it was so tight. Jupiter was stunning- I’ve been trying out my ADC (used on Antares too) and it brought out so much detail on Jupiter- etched details in the bands and around GRS though the seeing helped. I stood there at one point not quite believing every which way I looked there was something amazing to see! Fab  More than made up for the weeks of foul weather we’ve had! And yes those clouds!!

Looking great Dave   Such an interesting design too- I think i want one   Great to see you back at it

Mark

18 minutes ago, John said:

Out of production now but Takahashi used to do a 2.8mm and 4mm Hi-Or which might be that design ?:

Just found this that says the Tak Hi-Ortho was a high eyepoint ortho acheived by basically barlowing a longer fl ortho so not the H-ortho referred to in Gerry's diagram I think John

https://www.cloudynights.com/articles/cat/user-reviews/eyepieces/eyepieces-3mm-13mm/takahashi-28mm-hi-ortho-r329

Were does one find a Highly-Orthoscopic eyepiece (number 9)- is it just theoretical or were (are) they made by anyone?

This turned up in a fairly random ebay search  so i bid and was the only person who did. showed up today and it’s a monster- for some reason I thought it was going to be a tiny little thing but it’s a full blown 50mm finder with solid brass eye lens focuser and wow- massive afov! Needs a bit of cleaning up but i’m well chuffed with it for the grand sum of 4.99 plus shipping 😄 It’s a real beauty!

Great stuff Neil- a diy platform and a diy ep! (thanks for the link to the interesting ep- never heard of it before)

Good luck with your improvements!

Mark

53 minutes ago, Robindonne said:

I hoped for an answer like this🙏🏼   Ok so this is when an ADC? Comes handy?

yes! I tried mine out last night and have high hopes for it for just this purpose- was able to all but eliminate those colour shifts on Jupiter and Antares- like magic 😉

On 05/07/2020 at 23:21, Louis D said:

Look at the field lens end and see if it is near to the bottom.  Also look to see if the field stop is visible below it.  Most likely it has an internal field stop and is a negative-positive design like many more modern eyepieces.  Military eyepieces were often fairly cutting edge for their time because cost was not much of an issue.

Looking at this nice chart John posted in another thread I wonder if it’s a Galoc- it’s got the wide field and long er and is squat and wide like that. No i don’t think it’s got a negative lens if you mean like a barlow? I don't think it has a field stop as such either- seems to use the bottom of the housing as it’s stop. could be wrong though. 

9 hours ago, John said:

Come to think of it, Vixen used a similar symmetrical design and called it an "orthoscopic" in the past.

apparently the original Plossl patent described it as an orthoscopic. I wonder if you can get less rectilinear distortion by limiting the field? The few i’ve looked at for it have a lot of rectilinear distortion. But then so do some of my Abbé orthos🤦‍♂️😂 But rectilinear distortion isn’t so important for astro I think- maybe more so for microscope eps

1 hour ago, Merlin said:

Quite a few military eyepieces are/where of the symmetrical  type. I had a big brass one that gave superb views of the Double Cluster with the 8-inch Newtonian.   The eyepiece was purchased  from  H. W. English the war-surplus supplier.

They were an Alladin's cave of surplus optical and other gear.

I think this one must be an erfle type as it has 80+deg afov. Not sure if that’s possible with a symmetrical?

i’ve just spent a very pleasant afternoon wondering around the gardens at Wisley with my mum on the first sunny day in what seems like ages! I was wearing sunglasses and the colours were so saturated and contrasty- very beautiful and kodachrome-like. When I lifted them the view was obviously brighter but the colours were more muted- everything looked greyer. It struck me that there was a similarity to the difference between my dob and the only refractor i’m familiar with- my little telementor. The telementor seems to present things in a richer more contrasty kodachrome way. But is it real? Or is it like wearing sunglasses? Does it matter lol- I have a uhc for the dob

1 hour ago, Stu said:

Indeed, I’m not saying it wouldn’t be without its problems; huge secondary required for a start (probably the same size as the primary 🤣🤣🤣), massive exit pupil, extreme coma etc etc. You would probably be able to use very tight photographic line filters though which might be fun.

My intention though was to illustrate the point that smallish, short focal length apos are the best way to get widefield views.

Mel Bartels takes it to extremes with his high  etendue scopes  25” f2.6  😳 https://www.bbastrodesigns.com/25/25 inch F2.6 Telescope.html 

Sounds like you could almost go for his philosophy Stu- one eyepiece, multiple scopes 😂

On 02/07/2020 at 17:07, Don Pensack said:

Note: most of these older military eyepieces had little to no rectilinear distortion to keep straight lines straight.

As a result, they had serious angular magnification distortion, with the edges usually having a lower magnification than the center.

That may make the eyepiece tough to use for astronomy, but it would be great for daytime use in a spotting scope.

I wouldn’t have wasted my time and money on it if I didn’t find it quite nice to look through with my scope Don 😉 It’s far from perfect but there’s something  really nice about it too

nice one! Looking forward to seeing your eyepiece case too 😉

The biggest problem is the minimum order of £40 but if you’ve got a few projects to do that’s not such a biggie. Price is based on bounding cube volume so you can stuff parts inside bigger parts and get them effectively free. I also had some eye cups and caps printed to replace the annoying rubber winged ones on my BCOs- these worked out about £1.50 each or so 👍

3 minutes ago, DaveL59 said:

looks great Mark.

Jeez what with Gina, you and others doing all these 3D parts, I more think maybe I need to go get one too. Could make up some replacement eyecups for some of the bino collection for a start. Have a feeling tho that it'll be another slippery slope financially that I don't want to be on at the moment, not to mention nowhere useful to put it here.

Thanks Dave  I got this SLS printed by a company- i don’t have my own machine. it’s nylon so really tough and they dye it black. can get quite pricey but I think quite reasonable for parts you really need or want. This was about £17 i think (ouch) but i’m pleased with it so that’s ok!

I was getting some 3D printed parts for some other projects done so I thought I’d have a little fun with this old ep- I present my “XW” ~25-30mm 😂 It did really need an eyecup as the er is quite long and eye position quite finicky so hopefully this will help

29 minutes ago, alan potts said:

what could Pentax have done if they set out to design an astronomical eyepiece.

wasn’t the XO range astro specific? they went to great trouble to minimise internal reflections in those I think

this is a weird statement- what could they be referring to?

40 minutes ago, johninderby said:

Interesting 🤔

https://astromart.com/reviews-and-articles/reviews/eyepieces/other/show/understanding-pentax-xl-and-xw-eyepieces

why would you do that ?!?😳

7 minutes ago, John said:

One interesting thing about the XW's is that they use special coatings on the cemented lens surfaces as well as the glass-to air ones to maximise transmission and minimise scatter. I think some others use this technique now. Not sure if the XL's did or not ?

 

well they mention “special coating” on all but the 40 in the data sheet I found so maybe- whether it’s the same though is anyone’s guess 

16 minutes ago, John said:

https://www.sciencecenter.net/hutech/pentax/ep.htm

thanks John!