Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

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Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by arnedanielsen »

Dear friends,

Here are some FD images from July 13th.

First a FD image in H-Alpha using the Takahashi Sky-90II with Coronado 90mm/BF15, Coronado 2x CeMax and ASI 1600mm PRO.
Sun90FD_141036_Ha_(Coronado_90mm_BF15)_20210713_ZWO ASI1600MM Pro_lapl4_ap6013_Sharpened_Contrast_resize.jpg
Sun90FD_141036_Ha_(Coronado_90mm_BF15)_20210713_ZWO ASI1600MM Pro_lapl4_ap6013_Sharpened_Contrast_resize.jpg (456.33 KiB) Viewed 346 times
Sun FD in H-Alpha 13th of July 2021


For CaK imaging I've been using the ASI ZWO 178mm for a while now. This has produced nice, but undersampled, FD images at the native focal length of 360mm with the William Optics ZenithStar 61II stopped down to 46mm aperture. Using a 2 or 2,5x barlow to increase the focal length to 720-900mm gave a properly sampled image and much better results, but then of course I didn't get FD.

Wanting to get the best from both worlds I decided to buy an ASI ZWO 183mm. This camera has the same pixel size as the 178mm, but much bigger sensor allowing for FD images up till around 920-950mm.

For comparison I started out shooting using the William Optics ZenithStar 61II stopped down to 46mm at it's native focal length of 360mm.
SunCaK60_131118_CaK_(3934nm)_20210713_ZWO ASI183MM_lapl4_ap2795_out_Contrast_resize.jpg
SunCaK60_131118_CaK_(3934nm)_20210713_ZWO ASI183MM_lapl4_ap2795_out_Contrast_resize.jpg (265.57 KiB) Viewed 346 times
Sun FD in CaK 13th of July 2021

SunCaK60_131118_CaK_(3934nm)_20210713_ZWO ASI183MM_lapl4_ap2795_out_Contrast_Colorized_resize.jpg
SunCaK60_131118_CaK_(3934nm)_20210713_ZWO ASI183MM_lapl4_ap2795_out_Contrast_Colorized_resize.jpg (292.68 KiB) Viewed 346 times
Sun FD in CaK 13th of July 2021 - colorized



I then added a Coronado Cemax 2x to the imaging train. This turns out to multiply the focal length by 2,5 in this configuration and thus the focal length ends up at ~900mm. This is at the high end of the optimal sampling range for this aperture/wavelength and just fits the Sun within the field of view.
SunCaK60_135520_CaK_(3934nm)_20210713_ZWO ASI183MM_lapl4_ap9945_out_Contrast_resize.jpg
SunCaK60_135520_CaK_(3934nm)_20210713_ZWO ASI183MM_lapl4_ap9945_out_Contrast_resize.jpg (335.04 KiB) Viewed 346 times
Sun FD in CaK 13th of July 2021

SunCaK60_135520_CaK_(3934nm)_20210713_ZWO ASI183MM_lapl4_ap9945_out_Contrast_Colorized_resize.jpg
SunCaK60_135520_CaK_(3934nm)_20210713_ZWO ASI183MM_lapl4_ap9945_out_Contrast_Colorized_resize.jpg (364.52 KiB) Viewed 346 times
Sun FD in CaK 13th of July 2021 - colorized


Make sure to click on links for full size images.

It's so much fun to getting a properly sampled FD image like this without having to deal with mosaics.

Thanks for looking!
Arne


Best regards,
Arne
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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by Petrus »

Looking good as usual, Arne! Great CaK shots.


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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by Ivan »

Interesting description and wonderful photos, I learned a lot, thank you very much, Arne!

Ivan


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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by Ivan »

Arne, could you take a photo of the Takahashi Sky-90II with Coronado 90mm so that you can understand how the DS is attached to the telescope, perhaps you still have a drawing of the adapter? A friend of mine is now thinking about how best to connect Sky-90 and DS Coronado90. Thank you.

Ivan


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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by Carbon60 »

Good images, Arne.

Stu.


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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by MAURITS »

Beautiful images Arne.


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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by Montana »

Oooh that last CaK is an absolute cracker :bow :bow :hamster: just need to get rid of the dust bunny :)

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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by marktownley »

Very good indeed Arne! You could unscrew the lens off the Cemax barlow and screw it direct onto the camera nosepiece which would drop the magnification factor a bit, this is what I do...


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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by arnedanielsen »

Thank you very much for your kind comments Petrus, Ivan, Stu, Maurits, Alexandra and Mark!

Ivan: The front filter is the tilt-tuning version that came with the first version of the SolarMax 90. I ordered a custom adapter from ww.PreciseParts.com to fit the dewshield of the Sky-90II. It costed around $250 and was called:
Custom adapter, Coronado SolarMax 90 Solar Filter to Tak Sky 90 Dew Shield, L=10.8 mm

Alexandra: Will do :-) I unfortunately didn't have time for flats on this session, but have done so for later sessions.

Mark: Thanks for the tip. I will certainly try that. I wouldn't mind slightly more air around the solar disc.

Best regards,
Arne


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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by arnedanielsen »

Ivan wrote: Fri Jul 23, 2021 9:38 pm Arne, could you take a photo of the Takahashi Sky-90II with Coronado 90mm so that you can understand how the DS is attached to the telescope, perhaps you still have a drawing of the adapter? A friend of mine is now thinking about how best to connect Sky-90 and DS Coronado90. Thank you.

Ivan
Ivan,

Here's an image of the filter attached to the dewshield...
223280428_244130657542129_7718302961845748391_n_resize.jpg
223280428_244130657542129_7718302961845748391_n_resize.jpg (268.45 KiB) Viewed 272 times
Best regards,
Arne


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Re: Sun FD in H-Alpha and CaK 13th of July 2021 - CaK images with new camera (ZWO ASI 183mm)

Post by Ivan »

Thanks a lot, Arne.

Ivan


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