Test for a Collimator/Reducer optic

[rsfoto]

Hi,

Continuing with the quest for using a Solid Etalon like DayStar or SolarSpectrum with a short focal length scope and getting the fullSun disk onto my CCD chip, or whatever other Solid Etalons are on the market, I made some calculations with some spare lenses I had laying around which I used for a flattener for a Mewlon 250.

Here is the drawing of the result

http://astroforo.net/astro/Sol/etalon/S ... -243-a.png

and here the calculated Spot diagram with 10nm wavelength having Ha in the middle

http://astroforo.net/astro/Sol/etalon/S ... a-spot.png

Last weekend I had a chance to build it using PVC pipe and hot glue :whistle:

http://astroforo.net/astro/Sol/etalon/RS-TeRe-04.jpg

Below some test images in Vis-NIR and Ha 12nm Deepsky filter. The towers are approx. 17km away

Vis-NIR http://astroforo.net/astro/Sol/etalon/T ... IR-F99.Jpg

H-alpha 12nm filter http://astroforo.net/astro/Sol/etalon/T ... nm-F99.Jpg

Now I need to get a Solid Etalon and squeeze it inbetween the 2 lens groups :silly:

[swisswalter]

Hi Rainer

promissing results, great mod :

[rsfoto]

Hallo Walter,

Thanks, Interesting exercise. Will now start and design the Aluminum parts for the 2 lens groups and play with different distances inbetween and from the rear element of the telescope.

Interesting to see how sometimes just a few 10ths of mm do change tremendously the spot diagram result :huh:

All this has been done due to NO Sun in the last days and weeks :S

[swisswalter]

Hi Rainer

even greater results if only done on the bench. I wish you sunshine, lots of sunshine to proof your design

[markthais]

There no mystery in what you want to do.
It is the same as ISOON or OSPAN or what they call it now.( they have what they use on there site)
The image goes through the filter and comes to focus. Near the focus point you have a positive field lens (+250mm). This lens helps with the outside rays. Then at the camera you use a camera lens that will focus at a close distance. You then focus on the image point. You can adjust the image size to fit any size camera chip.
I'm trying to remember, I wanted to fit the full disk on a 1/4" video chip. The image came to focus 200mm from the back lens of the telecentric, at 200mm the +250mm lens went there I think it was a 50mm lens that would focus at 100mm. You place this lens 100mm from the image and it come to focus on the chip.
You can make any size scope a full disk image with this approach, as long as the full disk will fits through the filter.
I have tried using telecompressors but they only work at about -2X any more and you run into problems.
I'll look for some other drawing and designs. This will make your system longer but you can get a full disk image.


I was thinking to shorten the system have the telecentric with a shorter back focus. Say 100mm, this way it is near the back of the filter add the field lens and now use a close focus lens to fit the image on your chip size.
Super circuits (on the web) have low cost lens you might try.
You may have to play around with some ray tracing but I know this will work

Mark W.

[rsfoto]

Hi Mark W,

Thank You :thanx: I know there is no mistery, but not being an optician it was and still is a bit of a mistery inside this Magic called Optics :woohoo:

[Spectral Joe]

This thread: http://solarchat.solarastronomy.org/ind ... do-etalons Has a discussion of field lenses in it.

[rsfoto]

This thread: http://solarchat.solarastronomy.org/ind ... do-etalons Has a discussion of field lenses in it.

Hi,

Thank You very much. Interesting reading. BTW I had some Sun through clouds and made some test images. Here you can see one.



The only problem I still have is to get the real focal length according to the calculation of the optical design software ¿?

[Spectral Joe]

Looking good! No apparent vignetting here.

[rsfoto]

Looking good! No apparent vignetting here.

The first 3 lenses have a diameter of 50mm and the last lens is a 40mm.

This http://astroforo.net/astro/Sol/etalon/T ... nm-F99.Jpg is a full frame image fom my Infinity 2-1RM and as you see there is no vignetting.