Bart, the idea of removing the coating of the secondary, or of having an MCM-like coating on the secondary, is not a good idea. This is because the secondary mirror support would get all the heat load. There would be no mechanical problem. This is just you will have the equivalent of a 40 Watts heat...

Hi Bart,
Testing the concept with a 200 mm F/8 mirror (indeed a 300 / F5.5 stopped to 200 mm) is on my to-do list. I think it should be OK.
Before that, I am working on another project related to very narrow band Ca K imaging.

Hello Bart, This is an interesting project ! This being said, and for Ca K - H imaging, and considering you have an F/8 mirror, another option would have been to keep the primary mirror coated. The setup would have been a litlle bit more complex because you have have needed the addition of a subaper...

Maybe a 150 mm F/8 (or 10) Newtonian telescope with a sub-aperture ERF in front of the secondary mirror is the way to go.

Nice images Valery ! There is a very distinct 3-D effect with the spicule field.

It is custom made starting from Baader 42 mm thread tube.

Hi Bart,
I have two of these tilt adapters (from Beloptik). I used them for testing Omega Ha filters. They work fine.
The tilt is rather easy to adjust. They stay tuned (there are two screws which can be tightened more or less).
Christian

Hello Alexandra, The first question is what is your Ha filter ? Indeed, the Ha solar filter sets the F/D, which in turn sets the size of the pixel, which in turn sets the sensor. If your Ha filter need F/30 or more, the short answer is the IMX174. Smaller pixel sizes won't make the job. In a nutshel...

BTW, the Televue X2.5 is not telecentric. It is much better to use a telecentric system.

Hello phil, There are 3 criteria which may help to find the center of the band : - measure the average intensity of the image => the darkest image is the one on the center of the band ; - the short dark "little things" coming in bunches are groups of spicules seen from above. They are at the border ...

Thanks Pedro :-) Mark, regarding the ASI290, the S/N max is 6.9 bits while it is 7.5 bits for the IMX174. So, in situations where there is a lot of light (e.g. use of an Hershel wedge), the IMX 174 will give better results. In Ca K, light could me missing. I had some good results with the ASI290 on ...

As explained by Mark, this is a bad idea. Make it simple and go for only one aperture. Here is a simulations comparing the effect on the figure of diffraction of full aperture, two and four holes : http://astrosurf.com/viladrich/astro/instrument/sensitivity/planche-obstruction.jpg http://astrosurf.c...

Hello Mark,
The focal length is close to 3000 mm.

Hello Mark,
The focal length is close to 3000 mm.

Thanks to all :-)
Christian

Thanks to all :-)
Christian

Dear All, I still have some images taken on 2018 waiting for processing. Here are some of them. The solar activity was not much higher than now :-( The seeing was quite good on July 1, 2018 : http://astrosurf.com/viladrich/astro/soleil/2018/CaK-1July2018-9h34mnUT-TOA150-IDS3370.jpg Here are close-up...

Dear All, I still have some images taken on 2018 waiting for processing. Here are some of them. The solar activity was not much higher than now :-( The seeing was quite good on July 1, 2018 : http://astrosurf.com/viladrich/astro/soleil/2018/CaK-1July2018-9h34mnUT-TOA150-IDS3370.jpg Here are close-up...

Beautiful !

This is a great idea ! Here are the links to some images. Newton 300 mm, G band, K-line, filigrees, faculae http://astrosurf.com/viladrich/astro/soleil/wl/2018/AR2720-25August2018-9h25min-N300-B1920-430nm.jpg http://astrosurf.com/viladrich/astro/soleil/wl/2018/AR2719-24August2018-11h43mnUT-N300-396n...

I am afraid sunspots are the effect of localized strong magnetic fields in the photosphere (and in the layer below).
They have nothing to do with comets.

Interesting info Raf :-)
I didn't know they have these small size Cassegrain scopes.They have quartz mirrors which is very nice. I have no idea of the optical quality.

Hello Bob, Here are the simulations for a re-spaced classic C8 : http://astrosurf.com/viladrich/astro/instrument/sensitivity/sensitivity-analysis-SC8-Plate.htm The diffraction limited flat-field increases by a factor of four when the Schmidt plate position is set 230mm ahead its nominal position. ht...

Hi Bob,
Is this the C8 or the C8 EdgeHD ?

Hi Bob,
I have done some simulations there for a re-spaced C14 :
http://astrosurf.com/viladrich/astro/in ... -Plate.htm
I can run some more for the C8 if it is helpfull.
Christian