ASI178MC-C and focal reducers

poobie

I've got a 178MCC, and I'm really happy with it, been having a bunch of fun playing with it. I got an inexpensive .5 focal reducer, and bring any of my OTAs to focus with the reducer mounted on the camera. I've tried it on a couple of cheap refractors and a C6 SCT.

is anyone successfully using a .5 focal reducer on the nosepiece of an ASI178MC-Cool? if so, what brand?

Sam@ZWO

do you mean cannot focus with the reducer?

usually the 0.5X reducer can focus with a refractor without diagonal

einari

What focal reducer do you have ?

If it's for example the agena 1.25" version you should have it 47.5mm from your imaging chip to get 0.5x reduction. By varying distance the reduction factor changes. If you have a 2" version of the reducer the distance is different.

Specs for 1.25" version:

http://agenaastro.com/antares-1-25-0-5x-focal-reducer.html

Anyway, you will notice that the quality of image in edges can be bad as these reducers are meant for small imaging chips. Don't know how quality changes is you use less reduction factor.

poobie

Sam - That's correct, I can't focus with the reducer in place, even with the diagonal removed. I'm probably 1-2cm of focuser travel from infinity; with the focuser cranked in as far as it will go, it's focused about a meter and a half from me.

The reducer is a junky off-brand model I bought on amazon, because none of the name brand products were in stock at the time. Oddly, it works OK for visual use with the 26mm Plossl Celestron ships with the NexStar 6SE.

I may try an Agena Astro one if I can find one in stock somewhere, and in the mean time, I've found that my 85mm and 180mm Nikkor primes produce a great image scale with this camera.

jsmithsd

I have used an Astrophysics CCD67T at 0.6x on a Pentax 100mm F/12 refractor and the 178mm-cool camera. Spacing must be precise to set the compression factor and you will need considerable in-focus travel. I noticed the 178mm-cool is blue sensitive and I got larger (blue bloat) stars when I used the telecompressor. The Pentax is an apochromat and is not color corrected, the telecompressor made it worse. A Baader UV/IR-Cut/L filter fixed the larger blue stars as it has an aggressive clip on the blue end of the spectrum.

Jason.

poobie

Jason - thanks for your input. I think the spacing must not be right; I simply can't get enough inward focus with either of the two nosepieces I've tried. I think the 178MC must be fairly blue sensitive as well, as my 85mm Nikkor creates enormous blooms unless stopped down to f4 or lower.

At any rate, I can live without it; I'll just keep using adapted camera lenses for now; I plan to hyperstar the C6 at some point, but no hurry. 180mm FL provides a really nice image scale for lots of stuff on this camera.