Why don't reflective telescopes work with mods or solar viewing?

[etatsolarchat]

I'll put cak on a newt, on my to do list :cheer:

sounds like a interesting project, a mirror that only reflects 656, start looking for some more shells with cash in them

[MapleRidge]

a mirror that only reflects 656...

don't tell me no one else has thought of this LOL

[colinsk]

I have thought this would be a good ERF used as a coelostat. You would have to polish the back and AR coat it or make it a wedge but it would be useful.

[sullij1]

Gee, there is Colin with dem big words again. :blink: Here is a link for those who dont know what a coelostat is (like me ).

http://www.google.com/search?q=coelosta ... 36&bih=799


Good idea, if you all could meke it work you might have a niche side biz.

[sullij1]

Here are some blokes that seem to be putting the foil covered big reflectors and coelostat variations to work for an outreach in far off lands. You will have to page through the photos to see all the different reflective set-ups.

http://web.williams.edu/astronomy/eclip ... roup1.html

[DavidG]

One needs to compare the same size aperture reflector and Cats to refractors before making judgments. Many time the refractor has a smaller aperture which is less effected by daytime seeing.
Having designed and built a number of h-alpha and white light systems, from an optical stand point reflectors have many advantages. One many one is that refractors even APOs have spherochromatism, that is spherical aberration as a function of wavelength. So an objective that is well corrected for visual use in the green, many times is not as well corrected in the red and almost aways is poorly corrected in the deep blue were CaK is done. While a reflectors do not have these problems. Commerical H-alpha and CaK units use specially designed objective that are fully corrected at the wavelength that the filter is designed for.
I built a 4.25" f/10 white-light solar newtonian that gives extremely sharp and contrasty image. http://www.considine.net/dgroski/wlnewt/

- Dave

[brianb11213]

from an optical stand point reflectors have many advantages. One many one is that refractors even APOs have spherochromatism, that is spherical aberration as a function of wavelength.
This is only approximately half of the story - unless you're imaging at prime focus, whatever you're using to increase the focal ratio will have its own aberrations and (given that it's going to contain light transmissive elements) the teleconverter will contribute spherochromaticism of its own.

In practice I've found that spherochromaticism is negligible in my William Optics FLT 110 triplet apo / Televue Powermate combination, at any rate across the visual range from CaK to Ha. When used with a 742nm cutoff infra red pass filter the resolution is less than I'd expect & I suspect spherochromatic aberration may well be a major contributory factor.

[colinsk]

Gee, there is Colin with dem big words again. :blink: Here is a link for those who dont know what a coelostat is (like me ).

http://www.google.com/search?q=coelosta ... 36&bih=799


Good idea, if you all could meke it work you might have a niche side biz.

I just wanted to make sure you got your Google on...

[sullij1]

Always good to learn somthing new Colin . :cheer:

[sullij1]

This IRIS solar scope thing is supposed to go into space on the 26th. Somebody mentioned coated mirrors. This maybe incorporating that kind of tech along with every instrument we have ever discussed and have a forum for. A good read if you are looking for a way to get to sleep.

I guess that answerers the why not a mirror question. Being in a vacuum at subzero probably helps (NOT TO MENTION DEEP POCKETS).

Here is the link with excellent drawings and information.

http://www.spaceflight101.com/iris-spac ... ments.html

[brianb11213]

Very interesting, thanks for pointing this out.

I guess that answerers the why not a mirror question. Being in a vacuum at subzero probably helps (NOT TO MENTION DEEP POCKETS).
Well the vacuum prevents the atmosphere absorbing the UV radiation they're interested in detecting. And helps cut out tube currents ... but forces the integration of technologies we really don't need at ground level, e.g. radiators to cool the optical components.

Very deep pockets are a great help in many ways. I guess the unit cost would come down if these things could be built on a production line & sold in hundreds or thousands instead of being hand built prototypes. Alas, launch costs plus the ground equipment required is going to restrict the market to the order of one binary digit.

[colmic]

Hi,

it's possible to make halpha imaging with a reflector with Big aperture:

- Find an Intes M703 Mak (180mm F/10 with secondary miror not glued)
- Buy a Baader 180mm ERF (about 1200 euros/dollars)
- Use PST etalon

As Vincent made (DSObserver) with full success with his 127mm F/10 Intes Mak, i saw in this mod and it works!

I'm thinking myself about this mod but my question is: will this mod be better than with my TOA130 mod????
180mm reflector versus 130mm APO refractor, that is the question :unsure: :S

[SolarJohn]

Michel - Ha scopes with 200mm mirrors have been made. Lunt started with the LS200, an eight inch reflector using a single etalon in double pass mode. The scope also had an option for CaK viewing/imaging as well. Lunt aborted the commercial project due to costs associated with making it a mass produced telescope, but I believe that an individual can make and tweak one on his own. I know of one individual that has made one, but have lost the web links and cannot find.
Posts on the LS200 may be found here, on CN, and the Lunt Yahoo forum.

SolarJohn

[colinsk]

I ordered a LS60DP before Lunt had delivered a telescope. I was given a LS60DS50 in trade because they could not produce the promised product. I am not sad about it because I have a great solar scope but I only ordered it to sort out the double pass optics.

[etatsolarchat]

Neo, I also tried what you did with very poor results, your WL looks great and others as well so I'll continue down that path, WL seems possible on the scts and other reflectors..

[etatsolarchat]

Neo, I see for WL you use different post filters 35nm ha, continuum, and astronomik red. Do you have any suggestion on which to use when or preference?