My own cure for an aTak of quality fever

[Chris]

22 hours ago, nightfisher said:

After i posted about a Maksutov/Bino viewer it did start the cogs spinning, i bet a 150 pro with bino`s would be a hard act to beat

Yes that would be great, Jules, you would probably need to keep it at outside temp though, or face a good 70 minutes cool down time if brought from indoors as you know. I briefly had the 150 pro, not for as long as you, but long enough to notice that the corrector is as thick as the porthole on a deep sea sub! 

Mak's upto 5" and then switch to SCT's 6" and above if you ask me. Yes to less contrast with the SCT, but you get to use it cooled before it's time to pack away.

Lesser of two evils? 

[nightfisher]

10 minutes ago, Chris Lock said:

Yes that would be great, Jules, you would probably need to keep it at outside temp though, or face a good 70 minutes cool down time if brought from indoors as you know. I briefly had the 150 pro, not for as long as you, but long enough to notice that the corrector is as thick as the porthole on a deep sea sub! 

Mak's upto 5" and then switch to SCT's 6" and above if you ask me. Yes to less contrast with the SCT, but you get to use it cooled before it's time to pack away.

Lesser of two evils? 

When i spotted you had quoted me i thought it was for my other post about not being so impressed with the ED120!

Yes the 6" Maksutov is a cracking scope, if it had a shorter native focal length i would still have it, i dont care for SCT design, the C6 would be good with ts 1500mm F/L but its the wrong design for me, any way we are veering of the OP topic/thread 

[jetstream]

Sorry to go extremely off topic Shane. I hope its OK.

As the thread opens up more questions and comments it might be relevant for Cass users to understand what this graph shows. If it were me I would find the optimum mirror spacing, leave the focal length lie where it be and focus by some other means. I might look at an Intes Micro, hence my own pursuit for some understanding.

The reason why some Cass work so well is the same reason Shanes 150mm f11 works so well- they are at or above difraction limited performance as a system ie .8 overal Strehl. I also have a high respect for Horace Dall after learning a bit, the graph shows one of the reasons why.

 

 

 

[Moonshane]

It's no problem buddy. I actually think that my scope is like a stretched out Mak/SCT anyway!

[Stu]

10 minutes ago, jetstream said:

Sorry to go extremely off topic Shane. I hope its OK.

As the thread opens up more questions and comments it might be relevant for Cass users to understand what this graph shows. If it were me I would find the optimum mirror spacing, leave the focal length lie where it be and focus by some other means. I might look at an Intes Micro, hence my own pursuit for some understanding.

The reason why some Cass work so well is the same reason Shanes 150mm f11 works so well- they are at or above difraction limited performance as a system ie .8 overal Strehl. I also have a high respect for Horace Dall after learning a bit, the graph shows one of the reasons why.

 

 

 

Great point Gerry. How exactly do you go about finding that position, assuming the same rational applies to a Mak?

[Peter Drew]

An interesting comparison Gerry. The DK, having a 70% corrected parabola on the primary in conjunction with a spherical secondary is probably the least corrected of the three to achieve a good performance. This could be why inter mirror spacing is more tolerant.    

[jetstream]

No idea... personally if I buy one I'll ask Intes first if there is an optimum mirror spacing. I have wondered how some people get great views from SCT's in particular and I believe that there are a few things that can make or break the image.

This one shows a big contributing factor to Shanes 150mm f11 performance (CO %) and allows some wiggle room to keep the .8 system Strehl.

[jetstream]

1 minute ago, Peter Drew said:

An interesting comparison Gerry. The DK, having a 70% corrected parabola on the primary in conjunction with a spherical secondary is probably the least corrected of the three to achieve a good performance. This could be why inter mirror spacing is more tolerant.    

Great info Peter, understanding at least somewhat, how different scope designs work can be a benefit for us all I think. I still love newts