The Grange Obs. laboratory, or GOlab, has developed several selected VIS, UV and Johnson UBVRI or Sloan u' g' r' i' z' PHOTOMETRIC FILTERS, and proposes them in the standard 1.25" filter thread (M28.5 x 0.5 mm).
The UV filters have a deep violet or fully black color and provide windows in the near UV (for sensitive CCDs) almost completely cutting the infrared part of the spectrum up to 1100 nanometers.
The proposed UV filter has a 3 nm FWHM centered on Calcium II H line solar continuum at (397 nm); the calculated filter transmission is published here.
This filter will be extremely useful for resolving details on the Venus atmospheric bands, and the 397 nm filter is ideal for imaging the Sun granulation and faculae but ADDING A FRONT MYLAR PLUS NEUTRAL DENSITY FILTERING.
The UV filters are also valuable for lunar or planetary imagery or terrestrial views since short wavelengths develop the best optical performance (Dave's formula resolution in arcseconds equal to 79/D in mm).
The 397 nm filter result on the Sun is shown herein
The 397 nm UV filter is offered at 250 euro for combined 2" and 1.25" eyepiece threads (not for filter wheels).
DO NOT TRY TO OBSERVE DIRECTLY THE SUN USING A TELESCOPE WITHOUT PROPER FILTERING TECHNIQUES. PLEASE ASK ASSISTANCE TO EXPERT PEOPLE BEFORE ATTEMPTING SUCH A DANGEROUS ACTIVITY, INSTANT BLINDNESS OF THE OBSERVER MAY RESULT IN CASE OF UNATTENDED OBSERVATION.
Another proposal is related to the PHOTOMETRY Johnson and Sloan system filters for the UBVRI and SSDS star calibration; the photometric standard is approximated with a good precision, for results with a proven accuracy of 0.01 magnitude or even better (it depends on the used telescope diameter and CCD response).
The glasses used come from Schott optical producer.
The UBVR Johnson photometric filters are 4 mm thick and I is 2 mm thick (not parfocal), whose minimum transmission curves are shown here below:
The V and R Johnson photometric filters calibration at the Grange Obs. 140 mm astrograph is shown here below; the calibration was done processing the ADU of the SXL8-P camera Philips FT12 CCD on reference stars:
The SSDS Sloan u' g' r' i' photometric filters are 4 mm thick and z' is 2 mm thick (not parfocal), whose minimum transmission curves are shown here below:
The SSDS photometric filters calibration at the Grange Obs. 300 mm telescope is shown here below; the calibration was done processing the ADU of the QHY6 camera Sony ICX259AL CCD on reference stars:
The photometric Johnson as well as Sloan bandpass filters are proposed at 160 euro each plus shipping, a cost apparently cheaper than any other optical producer known.
WHILE EVERY ATTEMPT HAS BEEN MADE TO VERIFY THE MENTIONED FILTER INFORMATIONS, IT IS STRESSED SINGLE OPTICAL ITEMS COULD HAVE SLIGHTLY DIFFERENT BEHAVIOUR DEPENDING ON SELECTED PRODUCTION BATCHES
Please contact Grange Obs.
for the available payment and shipping options plus delivery timing.
Ask also for custom filters for astronomy applications, Grange Obs. can help and provide assistance.
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