Ags

I just need a tripod to stick it on. For now I will try it out on my AZ3. It feels solid enough and the joints are smooth. I think I will have to buy the counterweight.

TS sent me this goody today. They also kindly included a free bag of Haribo vibration suppression pads.

I am looking to get a prism diagonal, and this one is pretty cheap: https://www.teleskop-express.de/shop/product_info.php/info/p2484_Celestron-1-25--90--diagonal-prism-for-refractors-and-cassegrains.html Is it a case of you get what you pay for?

Aperture is the solution to floaters.

A family member of mine has cataracts and I was wondering if anyone has experience of the surgery? What can you expect after the operation? How good is the vision post surgery? How does it affect stargazing?

Want one!

As a companion piece to the post of central obstructions and contrast, I did a similar calculation for contrast with cetnral obstruction fixed at 25% and vanes varying from 0 to 5mm. http://opticsandalgorithms.blogspot.nl/2015/05/animation-of-diffraction-of-spider.html Here is the graph corresponding to the C.O. graph in the previous post:

I created a graph showing the ratio of contrast to central obstruction size:

I added an animation of the effect of central obstruction size. This is a central obstruction growing from 0% to 50% by diameter in a 130mm scope. The generated image is 60 arc seconds across (one Jupiter, with a bit of black sky around the edges). http://i.imgur.com/UqEtSVv.gif http://opticsandalgorithms.blogspot.com/2015/05/animation-of-central-obstruction.html

I mustered the courage to post a new set of scope contrast data: http://opticsandalgorithms.blogspot.nl/2015/04/contrast-and-resolution-of-different.html I increased the precision of the resolution calculations slightly, but now calculate contrast as the ratio of intensity in a cental 1 arc second radius versus a circle representing a given target size - 10 arc seconds for Mars and 30 arc seconds for Jupiter and Saturn. so a elescope which got all the light within an arc second of the focal point would get a contrast ratio of 1.0, and a scope that just produces an unfocused blur would have a contrast tending towards 0. I hope i have not made any new mathematical errors, but i only seem to get time to work on this at 2am, so as in life there can be no guarantees.

I have been making slow but steady progress. I increased the number of samples per sub by a factor of 9, and also doubled the resolution of the final spot diagram to 1200x1200 pixels. I also found a way of detecting when the pattern is undersampled. I hope to put up some new contrast data tomorrow.

I finally figured out where my maths went wrong... It was a simple arithmetic error combined with a logic error; I have reconsidered how to calculate contrast and will redo the calculations accordingly.

Debugging the large newt issue is proving achingly slow, and I'm running out of ideas for the root cause...

The simulation is done at one wavelength (510nm) so an achro would do ok theoretically! But I believe the results would only be applicable to long-tube achros and to apos. I think I know what went wrong with the large newts - being very large, they are undersampled. I will redo the 300 newts too

Thanks for pointing that out 250/25% seems off. I'm running that one again...

I fed 28 telescopes through my telescope simulator and have some more telescope contrast/resolution data. http://opticsandalgorithms.blogspot.nl/2015/04/contrast-and-resolution-of-different.html Aperture rules!

Good to hear. I've been working on a more detailed report of various scopes, Newtonians 100 to 300mm, refractors 60 to 180mm, SCTs 150 to 280mm, plus more maks. For the Newts I give results for 25, 30 and 35% obstructions. I hope to post it tomorrow night.

What problem are you having accessing the source code?

It took all day, but I calculated the diffraction patterns of 20 different telescopes (mostly variations of Newtonian). It's too late to upload all the results, but I did make a start on publishing the pictures of the diffraction patterns: http://opticsandalgorithms.blogspot.nl/2015/04/refractor-diffraction-patterns.html

Yes, firstly I was relieved when my simulator matched the Rayleigh formula for refractors, and also that it showed the slight resolution boost obstructed instruments enjoy :-)

No, the Rayleigh criterion is simply miscalculated for scopes with a central obstruction. The formula typically given for the Rayleigh limit applies specifically to refractors, which have more energy in their airy disc, but it is slightly broader than the same disk in an obstructed telescope.

The convention is to use the peak sensitivity of the human eye which is ~510nm at night. http://en.m.wikipedia.org/wiki/Spectral_sensitivity At higher frequencies, the Airy disc gets smaller. I think observers in the 18th century noted color fringing in diffraction rings.

I've had a thread going in the Physics section for a few years regarding diffraction and Airy discs. I was trying to calculate telescope resolution and contrast for different optical designs. I eventually cracked the problem and spent today feeding some telescopes through my simulator. Because a lot of work has gone into this, and it needs more explanation than a forum post allows, I set up a blog for myself. http://opticsandalgorithms.blogspot.nl/2015/04/calculating-diffraction-patterns.html At the bottom of the page you can find a table of various telescopes and their resolutions and contrast levels for different targets. Of course even if my maths is perfect (and I can't believe my lovely SE4 comes out as badly as it does) I do not take into account manufacturing errors, so my results may be more applicable to high-end instruments like TMB apos than more affordable instruments like an ST80.

Spaceboy... you have too many EPs! Are those all filled with Naglers?