Imaging the full solar disc with Quark Chromo

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krakatoa1883
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Imaging the full solar disc with Quark Chromo

Post by krakatoa1883 »

Just my experience in imaging the full Sun with a Daystar Quark Chromo, might be of interest for someone else. As Quark chromo contains a 4.3x telecentric one needs, of course, a very short f.l. refractor plus a reducer. I have been successful by using of a 50 mm apo finder sold as a guide scope for deep sky photography (Skywatcher Evoguide). Actually there is no need of an apochromat but this one has a very fine focuser and can be used with either 1.25" or T2 accessories. It has 242 mm f.l. and once coupled with a Quark gives a f/20.8 system, which is certainly suboptimal however works, contrast can be further improved by slighly reducing the aperture to 40 mm in order to have a f/26 system. I inserted a H-alpha deep sky filter just in front of the Quark for protection, alternatively the objective can be covered with a similar 2" filter, just put it in the dewcap. A 0.5x reducer is needed on the nose of the CCD.

Such a small scope is not produced with very high mechanical tolerances so it is very important to check collimation adjusting it if necessary. This can easily be done by first determining which direction the objective is inclined and then removing a very thin layer of metal from one side of the front thread, where the objective cell is inserted, in order to compensate being careful not to ruin the thread itself. Collimation shall be almost perfect otherwise a such short f/l refractor will soften the solar disc on one side.

Second step is to find the focus position, this depends on camera and setup, mine is the picture below. Best to use self-centering holders and threaded extensions in order to avoid tilting.

Final results will largely depend on the used Quark, mine is only average but a very good one can produce finer images, certainly more uniform than with a tiltable etalon, for example. Double stacking would be possible with a front 50mm etalon.
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Last edited by krakatoa1883 on Tue Mar 02, 2021 2:45 pm, edited 1 time in total.


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Re: Imaging the full solar disc with Quark Chromo

Post by JochenM »

Interesting little experiment, Raf. That disk doesn't look half bad at all!

Might have to try that myself one of these days (should have all the necessary equipment lying around).


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Re: Imaging the full solar disc with Quark Chromo

Post by marktownley »

Good stuff! This is exactly what I with a 60mm/f6 technosky, 50mm lunt etalon, Quark, Baader 0.7x solar telecompressor - here's sundays disk

ImageHa-FD-DS50-bw by Mark Townley, on Flickr


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Re: Imaging the full solar disc with Quark Chromo

Post by krakatoa1883 »

Great disc, Mark, the additional etalon makes the difference.

Never used the 0.7 Baader Telecompressor, does it have a T2 thread for connection ?


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Re: Imaging the full solar disc with Quark Chromo

Post by marktownley »

krakatoa1883 wrote: Tue Mar 02, 2021 2:30 pm Never used the 0.7 Baader Telecompressor, does it have a T2 thread for connection ?
It has a SCT thread either end but just use a t2 step down.


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