97 replies to this topic

[Astrojensen]

Gerd Düring, our designer for the APM 6" F/8 doublet  will do some design Ideas. He say with FCD 100 and LAF53 as matching glas, we should come out with the 6" F/6 similar or slightly better

 

soon I will show some design ideas

This begs the question of how much better the APM 152/1200 ED could be, if equipped with FCD 100 and LAF53... 

 

 

Clear skies!

Thomas, Denmark

[Moravianus]

I am struggling to see the VALUE in a 6" F6 refractor at the price level it will end to be with the inherent optical limitations. It will not be cheaper than the other 6" APM scope, rather with more expensive glass, I guess like more than $3,000.

 

Why spending this money, just for it to be a refractor ? Why not to go APM 152/1200 ED at slightly cheaper price ? Why rather not offer a PERFECT 8" F5 Quartz reflector with an IDEAL fan management and incorporated optical corrector (Markus has enough optical designer contacts) in a carbon fiber light tube.

 

Offer the

1/ reflector described above

2/ upgrade the APM 152/1200 ED as suggested by Thomas above

3/ split the APM 150 bino and offer an perfect correction  short f.l. "spective"

[Deadlake]

I can see the value of a 6" F6, it would be great to have a light weight APO which cools fast and can be mounted on an EQ6 class mount. The main aim is to have a scope which works directly with Bino's I presume. The 6" F8 LZOS is around $10000, so having a wide field scope which is cheaper is a plus and I guess the aim.

To get the scopes weight down a light weight Kruppax tube could be used, is this something KUO could manufacture or would this require a bespoke tube fabrication? I'd avoid carbon tubes as the thermal properties are great for mirrors but not for lens/len cells used in refractors.

Have you considered a 4" F6  doublet scope which would also be great for wide field and light weight. I'm thinking something that could go on a scope tech zero mount  (less then 7 kg) and hence be transported to a dark site with ease where a SQM > 21.5 would make up for the aperture lose. The last scope I can think of like this was the Vixen 4" F6.5 made some years ago. 

 

[lwbehney]

Gerd Düring, our designer for the APM 6" F/8 doublet  will do some design Ideas. He say with FCD 100 and LAF53 as matching glas, we should come out with the 6" F/6 similar or slightly better

 

soon I will show some design ideas

Hello Markus,

 

Looking at refractors merely from a seller's standpoint, I think fluorite is hot right now and has been for three years. Waiting lists for all the TEC and TAK DZ  refractors and likewise for the new Agema Optics too.  I would think about a fluorite doublet of any size you like. The demand is there, especially in any version > 100 mm. 

 

-Best Regards,

 

Larry

[ratnamaravind]

I want a ~130-150mm purely visual doublet not exceeding 6 kg.

[salico]

I want a ~130-150mm purely visual doublet not exceeding 6 kg.

I think, there was a Borg ED 150/1000 around 6kg...

Edited by salico, 15 January 2022 - 05:09 PM.

[djgilley]

Hey Markus, how bout this...take a standard 6 inch Chinese F5 achromatic lens, increase airspace slightly, then add a corrector downstream and ahead of a 3 inch focuser. There is lateral color, not sure how visible that would be in practice outside of a degree wide field since the energy seems to be concentrated in the airy disc. Though the corrector increases the focal length by 50% the tube length is the same as a 6 inch F6. Course there are the issues of alignment and glass cost for said corrector. The FPL element is equiconvex at least to ease fabrication a bit. This increases F/C color correction to ~1/6400 (about the same as a 6 inch F25 achromat) and more importantly reduces G line error 6.5 fold, down to just a bit over a wave of error. And almost ruler straight LSA lines. 

 

 

Edited by djgilley, 27 January 2022 - 02:53 PM.

[ThomasM]

Very interesting, I  had a look on the Oslo plots in your galery and I am impressed.

 

Thomas

[Alvan Clark]

There was an article years ago in S&T by Roland where he used a standard achro with 3 element corrector down the tube. I think he even came up with prescription for using it to correct the Yerkes. Don't know if he ever made these. Think he alluded to centering/tolerance

issues. Long time since I read that.

 

I doubt Markes is going to go for some exotic design.

[Astrojensen]

There was an article years ago in S&T by Roland where he used a standard achro with 3 element corrector down the tube. I think he even came up with prescription for using it to correct the Yerkes. Don't know if he ever made these.

He did. There's at least four or five in existence. 

 

 

Clear skies!

Thomas, Denmark

[SLight]

Since this is the type of refractor that isn't going to be used in a permanent set-up (observatory) please look into making it as light and compact as possible. Another vote for Krüpax as tube material 

[APM M.Ludes]

the prototype is prepaid and now started to go into production :-)

 

the ideas with correctors is great on paper but not in real live. In real live all companys are dealing with stability and collimation problems. we ship around the world and I want stable and simple design working out of the box without getting messages, hey my scope is not good , it need tweaking, aligning etc.......

 

so I go with the SD doublet :-)

[ippiu]

the prototype is prepaid and now started to go into production :-)

 

so I go with the SD doublet :-)

Hi Markus

Let me understand better...

Are you saying that in a quite short period, can we have an apo doublet fpl53 150 f6 scope?    

Edited by ippiu, 04 March 2022 - 10:11 AM.

[AstroPotamus]

Pretend like I forgot what this topic was about.  Is this thing designed for visual or AP use at this point?

[APM M.Ludes]

The 6“ f/6 is designed as visual Widefield.

however the correction for such a fast douplet is as good as in our 6“ f/8 ED … I am sure some of you will be able to make some not bad images with it

[AstroPotamus]

Thanks!

[Deadlake]

How do these compare?

https://www.cloudyni.../#entry11966488

 

[APM M.Ludes]

6" F/5 ED with FCD1 ( like FPL 51 ) against 6" F/6 SD with FCD 100 ( Like FPL 53 )..the first 2 samples arrive next week

 

the SD should have the similar improvement on CA then the ED over achromat

 

I will post pictures

[salico]

wasn't there a super light Borg ED 150/6,7? How was that visually? Maybe a reference...

[ABQJeff]

Can't wait to see test results for the 6" F/6 SD!  900mm is key to visual of 3 degrees (ie M31)...Put in a Pentax 40XW and you have 2.96 degree FOV with a 6.67mm exit pupil in a FCD-100 or FPL-53 doublet, not to shabby at all!!  Besides M31, put in some Nebula Filters and it should do excellent on Eastern or Western Veil, California, etc.

[jtpowers]

Looking forward to impressions of these first two samples. Are you looking for a minimum PV error from these lenses?

[APM M.Ludes]

I will tell you about quality when I tested the first samples. I always want the best of course :-)

[salico]

off course! (oh, one f too much)

Edited by salico, 23 June 2022 - 05:21 PM.