[QUOTE=bigjoe;1235242]
Quote:
Originally Posted by Tropo-Bob
I like the idea of longer focal lengths myself...but, they not always either available or practical.
Some years back I stopped down a 6" F8 reflector to 30mm (off axis, off course), which effectually made it F40. I split Epsilon Bootes so was very impressed. The other notable feature was that the depth of focus at this F Ratio was incredible; it seemed to be in sharp focus when I racked the EP in & out for over 5mm.
I often thought this was worth investigating further, but so far, have not....[/lengt
+1 for depth of focus from long focal length 
bigjoe |
Yep, another added bonus. When I first tried to contribute observations to the uneven doubles project all I had were a 10" and 14" dob. Sissy actually suggested stopping down the 14 with aperture masks. I never thought of it myself. Anyways, after a few very fun hours doing arts and crafts with my 5year old, I had a mask cut out of cardboard giving me 150mm and another 10 smaller masks to go on top of the big one to stop down further in 10mm increments. Please see attached photos.
The significance here is that if you have a big bore dob, you can participate as well.
By way of example, with HRG47 I was able to see the faint companion down to 120 mm direct and 110 mm with averted vision. For 3 Monoceros direct vision down to 130 mm, averted 110. Between 100 and 90 I call it a ghost zone where I think I see the fainter star, but not sure. By 80mm the faint companion is invisible for certain.
Like I said, lots of fun. Admittedly if you have a goto/tracking scope it helps a lot as you can play around with different apertures eyepieces etc.
Cheers all.
A