just like Moon of Venus phase , like hook , white in colorAt 15:55 suddenly I spot object at south direction from Sofia near the clouds . First I think that this was human craft but when I turn my binocular(20X60) towards the object under the magnification I saw white object looking just like phase of Moon or Venus or like little hook . At the moment I start our UFO-ALERT and take out all my optical arsenal , I telephone to few of the members but find only one of them and he was informed about the situation . The observation was hard because there are big clouds and for 25 minutes I was abble to see the UFO only for few seconds time . I try to fix it with 50Xpower spotting scope installed on a tripod but without any result . At 15:20 so many dark clouds enter all the sky that it was inpossible to watch the UFO and we stop the observation . There are no witnesses for this sighting ,the other member failed to track the UFO . This was my third UFO observation in my life but this type of UFO I saw for first time . Before I read about hook-looking UFOs in russian UFO webs . Here in Sofia we(few amateur-astromers) have UFO-ALERT system about situations like this today .