Hi,
I have a QHY5-III camera attached to a Celestron Nexstar8 telescope. I am trying to do some solar astronomy with a Bader filter. Through the eyepiece I can see the sunspots well, but when I try using my camera and Sharpcap I can only acquire a white image on my laptop screen--no matter how many adjustments I make to the different settings in Sharpcap. Any suggestions on what to initially set the exposure, gain, and other settings in order to view sunspots with this camera and Sharpcap. Any suggestions would be welcome. ty!
Need help with visualizing the sun :-)
Re: Need help with visualizing the sun :-)
Hello and welcome
What you see through your eyepiece and what is captured with the camera, is indeed different.
Through your eyepiece you have a field of view (FOV) that shows the whole sun.
The FOV that your camera has, is a lot smaller. So what you are seeing is a (small) part of the sun.
If you can give the exact name of your QHY5-III camera (the name of the sensor), I can give you the approximate FOV.
Or you can get it yourself over at https://astronomy.tools/calculators/field_of_view/: choose Imaging Mode there, set the Sun as object and fill in the details of your scope and camera.
In general: your telescope has a focal length of 2032mm. This is what they call a "slow telescope": with a camera attached, it will have a small(er) FOV. Perfect for planets and small(er) deep sky objects. Or with the sun a FOV with sunspots but not the whole sun.
To get the whole sun, you could use a reducer to get a bigger FOV. How much though depends on the sensor of your camera.
Menno
What you see through your eyepiece and what is captured with the camera, is indeed different.
Through your eyepiece you have a field of view (FOV) that shows the whole sun.
The FOV that your camera has, is a lot smaller. So what you are seeing is a (small) part of the sun.
If you can give the exact name of your QHY5-III camera (the name of the sensor), I can give you the approximate FOV.
Or you can get it yourself over at https://astronomy.tools/calculators/field_of_view/: choose Imaging Mode there, set the Sun as object and fill in the details of your scope and camera.
In general: your telescope has a focal length of 2032mm. This is what they call a "slow telescope": with a camera attached, it will have a small(er) FOV. Perfect for planets and small(er) deep sky objects. Or with the sun a FOV with sunspots but not the whole sun.
To get the whole sun, you could use a reducer to get a bigger FOV. How much though depends on the sensor of your camera.
Menno
Re: Need help with visualizing the sun :-)
Thank you so much for your response! My camera is the QHY5III485. An epiphany that I had last night is that I may have had trouble visualizing sunspots because the image may have been out of focus. When I look at a focused image through the 40 mm eyepiece, then remove the eyepiece and install the camera, I believe I have to rotate the focus knob about 8 times clockwise in order to regain focus of the image. I will think about purchasing a reducer, as you suggest, if it helps get a larger FOV.
-
admin
- Site Admin
- Posts: 14657
- Joined: Sat Feb 11, 2017 3:52 pm
- Location: Vale of the White Horse, UK
- Contact:
Re: Need help with visualizing the sun :-)
Hi,
just to add a few things...
1) The calculated field of view for your setup (485 camera, 8" SCT) is about 0.3 by 0.18 degrees - that's considerably less than the diameter of the sun (0.5 degrees). Adding a typical 0.67x reducer to the setup will increase the field of view 0.47x0.26 degrees - in that setup you would get nearly half the sun into view
2) If you are switching back and forth between the camera and eyepiece a lot, consider using a 'parfocalizing ring' - you put it round either the eyepiece or the camera and it locks around the 1.25" diameter barrel with a set screw. By adjusting the position, you can arrange that either the eyepiece or camera is held a little further out of the focuser than usual, meaning that both could be set up to be in focus at the same focuser position (or very close). The parfocalizing rings are typically very cheap (in fact, sometimes you get one with a camera).
cheers,
Robin
just to add a few things...
1) The calculated field of view for your setup (485 camera, 8" SCT) is about 0.3 by 0.18 degrees - that's considerably less than the diameter of the sun (0.5 degrees). Adding a typical 0.67x reducer to the setup will increase the field of view 0.47x0.26 degrees - in that setup you would get nearly half the sun into view
2) If you are switching back and forth between the camera and eyepiece a lot, consider using a 'parfocalizing ring' - you put it round either the eyepiece or the camera and it locks around the 1.25" diameter barrel with a set screw. By adjusting the position, you can arrange that either the eyepiece or camera is held a little further out of the focuser than usual, meaning that both could be set up to be in focus at the same focuser position (or very close). The parfocalizing rings are typically very cheap (in fact, sometimes you get one with a camera).
cheers,
Robin