Using a barlow for Astrophotography

[Carole]

I have always been told this is a no no because of the increase of focal ratio, but take a look at this thread on SGL.  Makes very interesting reading:

https://stargazerslounge.com/topic/298212-julian-shaws-sombrero-with-a-surprise/

Carole

[Fay]

Thats very interesting Carole..

[MarkS]

That was an interesting read and I made on reply on that thread.

With low read noise cooled CMOS cameras I can see this approach (i.e. Refractor+Barlow) being quite viable.  It wouldn't work well for DSLR cameras though because the thermal noise would end up becoming dominant.

Although this approach does increase the versatility of a reflector, in the end you'll get the same quality image much quicker by using a large aperture reflector (Newtonian/SCT/RC)with the same effective focal length.

Mark