|
JFYI, be aware that if you use a barlow, yes you will achieve focus, but....
1. you will double your f ratio which will mean 4 times the exposure length to achieve a similar image signal level (this is a big issue, ie a normal 5 min exposure will take 20 min to achieve the same result).
Taking shots of bright globs and open clusters might be ok but you will find that galaxies and nebula will be a challenge. For extended objects (planets, moon, sun etc) long focal length is important (using a barlow, ie; slow f ratio), for faint fuzzies with stars, aperture is more important (fast f ratio ie short focal length given the same aperture as above).
2. you will reduce your field of view
3. if you use a 1.25" barlow you will get strong vignetting around the edges and corners of your image, it may not be enought to encroach on the moon but any widefield images will be affected (assuming you are successful with them, see point 1). If you are going to use a barlow consider a 2" one. If you consider a 2" one try screwing off the lens cell of the barlow and screwing it to a Prime Focus Adapter. You may get enough focus movement without incuring the wrath of 1 and 2 too much.
|