dwc Posted February 22, 2022 Share Posted February 22, 2022 I had my first try at using a bahtinov mask last night, and whilst I think it was reasonably successful I wanted to check some basics to make sure I’m doing it right. Firstly, size. The mask I used was one I bought many years ago for an 8” SCT but never used, and subsequently upgraded to a 9.25” SCT. Apart from the obvious issue of getting it in place, will the 8” mask work ok or should I just pass it on and get a 9.25”? Secondly, installation. I’d already set up my dew shield on the scope before I decided to try it, so I put it on the end of the shield, which is about 14” long. It later occurred to me that maybe it needs to be close to the glass to work effectively, i.e. before fitting the dew shield, or removing the shield before using the mask. Is this necessary? Otherwise it seemed to do what I expected, refraction spikes that were picked up by the APT Bahtinov Aid and Bahtinov Grabber, that moved appropriately as I adjusted focus. It was a bit of a struggle to get the numbers to stay down. I guess a third question: collimation will affect focusing using a mask? I would guess that an imperfect start shape will alter the spikes. Collimation is on my list of things I need to learn …… 1 Quote Link to comment Share on other sites More sharing options...
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