Hi, I am doing sunspot observation right now. For our analysis software to to work, I need to take half Sun images i.e. the west and east side on top of normal full disk image. However, when I bring the Sun to either side, the image will saturate and have some stripes. The image is okay when the object is at the center of the frame. I suspects the cause of this is internal reflection. I did not have this problem with STF8300C and STL4020M. Any suggestion to overcome this problem? The details of the instruments are as follows: Telescope: TMB152 Camera: STF8050M FW : FW8-8300 Filter: Luminance Exp time: 0.08s The image of west limb attached below. I also tested this camera and FW with lunar. I got the same result i.e. images on either side will saturate.
The KAI-8050 sensor is an interline type sensor, not a full frame. It has a completely different design and it has different behaviour compared to the full frame KAF-8300 sensor. Reduce the exposure time or use an aperture mask or a neutral density filter. You may also wish to use black flocking material inside the focuser draw tube connecting the camera to the telescope. Also, if you'd like us to examine an image, we need a FITS file.
Thanks for your response. Attached is the fit file, Doug. Actually I did use ND 3.0 filter. The max value is less than 30k which is far from saturation. It is an interesting point when Colin mention about interline vs full frame. May you elaborate more on how interline affects the image produced?
Those "jail bars" typically happen on Kodak interline when the sensor saturates over a large area (as opposed to a few stars). It's possible that the sensor actually is saturating, even though you aren't getting 65,535. It depends on the analog gain setting and the substrate bias. Interline sensors use electronic shuttering, as opposed to full-frame sensors that need a mechanical shutter. The photosensitive pixels have blanked readout columns in-between them. The start of exposure happens when the sensor is cleared by momentarily changing the substrate voltage so there's zero well depth. The end of the exposure happens when the charge is transferred over to the opaqued readout columns. Then the readout progresses in the blanked columns, so there's no smearing caused by photons that continue to hit the sensor.
Hi Colin, I use Baader Astrosolar filter 5.0 for energy rejection filter. Hi Doug, attached is the Sun at the center fit file. It looks ok to me when the Sun is at center with the same exposure time. However, I will try play around with the exposure time later to be sure. Also, I can only upload one fit file per post. Can I upload more fit file at once (zipped file maybe)? What's the size limit for each post. Just to give better picture with more files. Thanks.
