Focusing Masks Aren't Just For Imaging
I had my best view yet of Mars with my ETX-125PE last night and I think I stumbled upon a neat trick. One problem I've always had is fishing around for the best focus when using very high magnifications, it seems like I'm always tweaking it a bit this way and that trying to find the best focus. Just for yucks I tried an old imager's trick; using a focusing mask. Before slewing over to Mars I set my telescope up on Sirius and used a Bahtinov mask to set the focus precisely using a 5mm eyepiece (380x), and then slewed over to Mars and removed the mask. I was thrilled with the result and I was able to see quite a bit of fine detail across the martian disk. I used this trick before to help me set the focus when observing double stars, but this it the first time I've tried it prior to observing a planet. In the future a Bahtinov mask is certainly going to be part of m obsrving kit.
Have fun!
-John
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Last night was my best view
Last night was my best view of Mars yet, even better that what I described earlier. The weather was mild so it didn't take long for my ETX to settle down; just to be safe a set up a fan to blow over it for about 30 minutes as I waited for it to get dark. To help the air circulate I opened the eyepiece and camera ports and lowered the flip mirror. For viewing I used my binoviewers, a 2x Barlow, and a pair of 17mm eyepieces giving 224x. I set the focus of both eyepieces using a Bahtinov mask and that worked extremely well. This was the first time using the mask with my binoviewers and for the first time I was sure the both eyepieces were at their best focus. The results was a beautiful view of mars that was very sharp and had that 3D look you get when using both eyes. Overall, a wonderful evening.
-John
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Homebuilt scopes from 4.25-16.5"
Meade LXD75-N6/SN6/SC8, DSX-90, ETX-60BB, ETX-125PE, DS-2130
Orion StarBlast, BinoViewers, Coronado PST
Rebel XT/XTi, DSI Pro I, II, & III, DSI I & III, LPI, Electronic