Baader Solar Filter ASTF-100

Discussions of using SharpCap for Solar or Lunar Imaging
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Buckrogers
Posts: 78
Joined: Wed May 13, 2020 2:22 pm

Baader Solar Filter ASTF-100

#1

Post by Buckrogers »

Hey guys,

I have a Nexstar 4se and want to get into the hobby of solar imaging. Now I got this filter and when I attach to the scope and have it aligned to the sun, I see nothing through my Plossl 25mm eyepiece but black. However, if I attach my ZWO ASI224MC camera to it and us sharpcap, I see this.
Not sure what i'm looking at. I've tried to defocus, focus manually nothing seems to work for me. I've been playing around with the exposure and gain, see attachments and my histogram looks good, doesn't exceed 100% oh and I'm using a UV/IR cut filter too.
Attachments
Sun_00001.CameraSettings.txt
(1.06 KiB) Downloaded 58 times
Sun_00003.png
Sun_00003.png (565.77 KiB) Viewed 5915 times
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oopfan
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Re: Baader Solar Filter ASTF-100

#2

Post by oopfan »

Hi,

In that image, you are seeing dust donuts. The small donuts are on the sensor window. The large donuts are on the filter. I know you have the ASTF-100 on front of the scope around the dew cap. To the best of my knowledge, dust on the ASTF-100 will not cause the large donuts. There has to be some other optical element ahead of the camera, perhaps a filter. Are you doing "eyepiece projection". If so then those large donuts come from dust on the surface of the eyepiece.

However, at this time don't worry about the dust. Let's try to figure out where the focus is. I recommend removing the camera. Take a piece of thick white paper or cardboard and use it as a projection screen. Start by placing it at the back end of the scope where the light emerges from the scope. Move it back until you see a focused image of the Sun. If you can't see the Sun then the scope isn't pointing at it. I think that Astro-Physics (and possibly Baader) has a device that can help. It is essentially a pin-hole camera that projects the Sun's image onto a small projection screen.

Once you locate the Sun and are able to focus it using the projection method on white paper, take a ruler and measure the distance from the focal point to some reference point on the scope, say some mounting bracket. Insert your camera. Adjust the focus knob to the point where the camera's sensor is the correct distance from the reference point. If your focuser can't extend that far then you need to buy a tube extension. Let me know and I can help with that.

EDIT: Aah, reread your post. Now I see that you used an UV/IR cut filter. So then the large dust donuts are on that filter and the small dust donuts are on the sensor window.

EDIT: If you are certain that the scope is pointing at the Sun, then briefly remove the ASTF-100. This allows more light in, but please only do this using projection. Also, only do it briefly, because you never know if you are damaging your scope from heat build-up. When you finally find focus, take meticulous notes and measurements. You don't want to go through this headache again! Also, switch to Solar Tracking Rate on your mount's control paddle. Solar Rate is faster than Star Rate.

EDIT: Found it. Kendrick Sun Finder. https://www.astro-physics.com/ksf6000

Welcome to the wonderful world of astrophotography! Remember it's all about having fun :lol:

Brian
Buckrogers
Posts: 78
Joined: Wed May 13, 2020 2:22 pm

Re: Baader Solar Filter ASTF-100

#3

Post by Buckrogers »

Hey there,

Thank you for your comments. Interesting so I'll remove the UV/IR filter and clean it and will leave it off for now. I have tool for that. When you say projection method, you mean take the camera and including the eye piece right so there is just a hole and have the sun shine onto paper then measure. Already have mount on Solar tracking does a great job. Will be working on this on the weekend and will provide results. A sun finder that is cool will look into that also. Thank you.
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oopfan
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Re: Baader Solar Filter ASTF-100

#4

Post by oopfan »

You're welcome.

That's right. Let's find what's called "prime focus". That's where the image focuses without any intermediate optical elements, only utilizing the essential primary and secondary mirrors of the Nexstar 4se.

Brian
Buckrogers
Posts: 78
Joined: Wed May 13, 2020 2:22 pm

Re: Baader Solar Filter ASTF-100

#5

Post by Buckrogers »

Hey there,

So I followed all the ideas and they worked perfectly. This is my first attempt at capturing sun spots, so I'm a newbie :) Added some color as the Sun is not white :)
Attachments
Sun_May14.png
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oopfan
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Re: Baader Solar Filter ASTF-100

#6

Post by oopfan »

Hey, a win for the good guys! Congratulations. Here are some useful links. I like to keep an eye on the Sun too:

Solar Dynamics Observatory (SDO):
https://sdo.gsfc.nasa.gov/data/

SDO Visible light:
https://sdo.gsfc.nasa.gov/assets/img/la ... _HMIIF.jpg

STEREO (Look Ahead):
https://stereo.gsfc.nasa.gov/beacon/

Brian
Buckrogers
Posts: 78
Joined: Wed May 13, 2020 2:22 pm

Re: Baader Solar Filter ASTF-100

#7

Post by Buckrogers »

Wow, awesome thanks for the links..

Roland
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