Creates Uniform Flat Fields for Solar Imaging Spun Aluminum Mounting Ring for Durability High-Quality Polymer Diffuser Available for Telescope Tubes from 80mm to 209mm OD Fits Energy Rejection Filters (ERFs) from 63mm and up Description FAQ Specifications In the Box Downloads Warranty Daystar Flat Cap Diffuser for Solar Imaging The Daystar Flat Cap Diffuser for Solar Imaging provides a simple, robust solution for creating essential flat-field reference images, with sizes available to fit telescope or Energy Rejection Filter (ERF) outer diameters from 63mm all the way to 209mm. By producing an evenly illuminated field, this tool allows you to calibrate your solar images, effectively removing artifacts like dust motes, vignetting, and sensor imperfections for a clean, professional final result. Achieving Uniform Solar Illumination for Flat Frames In high-resolution solar imaging, optical train imperfections are unavoidable. The Daystar Flat Cap solves this by providing a uniform light source to record a "flat field" image. You temporarily place the cap over your telescope's objective or ERF, capture a reference frame of the even illumination, and then remove it to begin your imaging session. This reference frame is then used in post-processing to digitally subtract any fixed-pattern noise or uneven lighting from your final images of the Sun. Spun Aluminum Construction and Precision Sizing Built for repeated use in the field, the Flat Cap features a durable spun aluminum mounting ring that holds a specially designed polymer diffuser. This combination is both lightweight and rigid, ensuring it will not warp or degrade under sunlight. Sizing is critical for a secure fit; you must measure the outside diameter (OD) of the very front of your telescope or ERF housing. Do not use your telescope's aperture as a guide. Once measured, select the next largest Flat Cap size, and use the included felt pads to create a snug, light-proof fit. How do I choose the correct size Daystar Flat Cap for my telescope? You must measure the physical outside diameter (OD) of the frontmost component of your optical tube, which is usually the dew shield or an Energy Rejection Filter (ERF) cell. Do not use the telescope's aperture (e.g., 80mm, 100mm) for sizing. After measuring the OD, choose the Flat Cap model with the next largest inside diameter. For example, if your telescope's front measures 160mm, you would order the size that fits 160-169mm tubes. Why do I need to take flat fields for solar imaging with the Daystar Flat Cap? Flat fields are a crucial calibration step for any type of astrophotography, including solar. They create a map of imperfections in your imaging train, such as: Dust Motes: Small donuts or shadows caused by dust on your sensor or filters. Vignetting: Darkening of the corners of your image. Sensor Artifacts: Any non-uniform pixel response. By subtracting the flat field from your light frames (your actual solar images), you remove these distracting artifacts for a clean, scientifically accurate image. Can I use the Daystar Flat Cap for nighttime deep-sky imaging flats? While the Daystar Flat Cap is specifically designed to diffuse direct sunlight for solar imaging, it can be used for nighttime flats if paired with a separate, evenly illuminated light source. However, its primary design is optimized for the intensity and properties of sunlight, so results may vary compared to dedicated nighttime flat panels. I have a Coronado SolarMax II 90. Which Daystar Flat Cap do I need? The "90" in the telescope's name refers to its 90mm aperture, not its physical diameter. To find the correct Daystar Flat Cap, you must take a ruler or calipers and physically measure the outside diameter of the front of the telescope tube. Once you have that measurement in millimeters, you can select the appropriate size from the available options. How do the included felt pads work with the Daystar Flat Cap? The felt pads are self-adhesive strips that you can apply to the inside of the Flat Cap's aluminum ring. Since the caps are sold in size ranges (e.g., 100-109mm), the felt pads act as shims to create a secure, snug fit if your telescope's diameter is on the smaller end of a given cap's range. This prevents the cap from slipping off accidentally. Will the Daystar Flat Cap work with a Daystar Quark on my 120mm refractor? Yes, the Flat Cap is an essential accessory for any solar imaging setup, including one using a Quark. You would place the Flat Cap over the front of your 120mm refractor's dew shield or over the front of your full-aperture Energy Rejection Filter (ERF) if you are using one. Be sure to measure the outside diameter of whichever component is at the very front of the optical path to determine the correct size to order. Construction Spun aluminum ring with a polymer diffuser Available Sizes Fits telescope/ERF outer diameters from 63mm to 209mm across various models. Options include: 80-89mm (or 63mm ERF), 90-99mm, 95-104mm (or 80mm ERF), 100-109mm, 110-119mm (or 90mm ERF), 120-129mm (or 100mm ERF), 130-139mm, 140-149mm, 145-154mm (or 130mm ERF), 150-159mm (or 130mm ERF), 160-169mm, 170-179mm (or 150mm ERF), 180-189mm, and 190-209mm. Daystar Flat Cap Diffuser × 1 Felt Pads for Custom Fitting × 1 Set This product does not require software or have a dedicated manual. Daystar Filters Warranty
