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Hello, Here is a post based on my own experience (RCC1 - UNC 200/800 FD4), can be helpfull for those who are using the same "setup" (or near) - standard RCC1 backfocus (BF) is 91,5 mm (connected on M42 corrector/ 94,5 mm -mechanical lenght- connected on M48 on corrector) - "standard" has no sens : real BF depends on F/D ratio and the same corrector will requiered different BF, depending on F/D ratio ... - After many (many many ...) tests, the BF RCC1 obtained on UNC 200/800 : 89,53 mm (on M42 -RCC1=optical BF) and 92,53 ( on M48 -RCC1= mecanichal lenght) On my setup : - M48 connection on RCC1 - mechanical lenght between sensor and RCC1 : 91,7 mm (74,2mm=rings + 17,5 mm asi071) - filter : IDAS 2,5mm--> 2,5/3=0,83 mm BF (approximatly) - total : 91,7+0,83=92,53mm RCC1 lenght "inside" crayford : 20 mm Here is a the result (the small default, slightly angular stars, is because the primary mirror was too tight, and not a BF problem. A pixinsight process was also applied on stars and made them a little blurry+few other stack problems... hope to publish a better picture next time ) |
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excellent picture. I use almost same equipment, but not used for so many DSO objects so far with reason of coma and focus changing - all issues is connected to temperature. My Orion Astrograph 8" F3.9 is changing all calibration every outdoor temp of 3-4 degrees.. 😊 That effect the RCC 1 vey much too. I now got a new callibration laser tool who do the work easier. I hope for the best this incoming season |
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Another (and last) picture , as promised a single light 360" (histogram/debayer/colors do not take care about noise, satellite ... --> only stars for example ) hope it will be usefull for those who (like me during a -very- long time ) are trying to find the right backfocus distance for RCC1 especially on an F/D 4 newton Clear Skies ! |