Achromatic imaging help

[robindurant]

Hi

What is the best way to get reasonable imaging results from an Achromatic 80mm telescope or is it waste of time. I hear so many bad things said about them that I wonder if its worth trying at all.

Robin

[Ant]

It is without doubt worth trying, I have imaged the moon and planets quite well through a 80mm F11 Achro.

I've seen some great results with the little ST80's.

What are you going to be imaging with?

Ant

[steppenwolf]

Robin, I have had some acceptable results with my ST80 Achromat although there is no getting away from the fact that they suffer for chromatic aberrations that imaging quickly brings to the fore! That said, there are some things you can do. One way to help with the problem is to 'stop down' the telescope by making an aperture mask - this is essentially a black cardboard insert in the lens hood with a nice round hole cut in the centre to restrict the light entry to the centre portion of the lens. Star with about a 10mm surround to the mask and give that a try and then experiment with larger surrounds (thus a smaller hole) until you get the best result. Clearly this will cut the light available too but there is a reasonable balance to be found. Secondly, take lots of subs. and stack them so that no star burns out too far accentuating the halos.

These are some of my earlier images taken with this telescope soon after I started in astronomy. Now, I have progressed from here but the 'scope itself did a reasonable job for me and these were taken without an aperture mask. You can clearly see the halos on the stars in comet image but it still made for an attractive shot and I even got it published!:-

[jgs001]

Robin, I saw three images taken with an ST80. One without a fringe killer and two with. They were all nice images, and the fringe killer did a nice job on the CA. I shall be purchasing a fringe killer filter of some sort for my 80mm scope.