Altair Lightwave 0.8x reducer with Evostar 80ED (& Equinox)

[ecuador]

Altair Astro has an inexpensive 0.8x reducer for refractors, but I had never seen any actual results with it, at least not with my SkyWatcher refractors (Evostar 80ED and Equinox 80ED), so I thought I'd get one and see. Turns out it works well with the Evostar, even giving you some advantages over the expensive matched 0.85x reducer, and it is not bad even at the corners of an APS-C sensor:

So people who can't afford the SW 0.85x should perhaps consider it.

It wasn't such a good match for the Equinox unfortunately. For more details and comparison with the TeleVue TRF-2008, you can read my blog post.

[ultranova]

A very nice write up on your blog, some very handy information so well done

Paul

[Chris]

3 hours ago, ecuador said:

Altair Astro has an inexpensive 0.8x reducer for refractors, but I had never seen any actual results with it, at least not with my SkyWatcher refractors (Evostar 80ED and Equinox 80ED),

 

 

Totally agree with your thoughts  here's my review of the Altiar 0.8 with the ED80 from a few years back, I'm a big advocate of them

http://www.insideastronomy.com/index.php?/topic/530-altair-lightwave-08-reducer-mini-review/

[ecuador]

2 hours ago, Chris Lock said:

Totally agree with your thoughts  here's my review of the Altiar 0.8 with the ED80 from a few years back, I'm a big advocate of them

http://www.insideastronomy.com/index.php?/topic/530-altair-lightwave-08-reducer-mini-review/

Ah, nice. I didn't come across your review because I was searching for results with the Equinox, for which I really wanted it. But, yeah, we agree on the Evostar, great bargain this reducer  

[Chris]

5 hours ago, ecuador said:

Ah, nice. I didn't come across your review because I was searching for results with the Equinox, for which I really wanted it. But, yeah, we agree on the Evostar, great bargain this reducer  

Yeah I think the Equinox at f6 is a bit fast for it, but It definitely did the trick with the Equinox ED120 I had @f/7.5.

 I've been meaning to pick another up for my ED100 f/9 which already has a fairly flat field but could do with speeding up a bit for when I fancy taking some pics. It will be interesting to see how they do with this scope.

The 0.6 also works very well with RC scope by the way

[Glimpse111]

So what works best for Equinox 80 ?

[ecuador]

3 hours ago, Glimpse111 said:

So what works best for Equinox 80 ?

The TRF-2008 works reasonably well for such a curved field (I have images in that blog post), but if you can find something better or cheaper do tell!

[Bagnaj97]

5 hours ago, Chris Lock said:

Yeah I think the Equinox at f6 is a bit fast for it, but It definitely did the trick with the Equinox ED120 I had @f/7.5.

 I've been meaning to pick another up for my ED100 f/9 which already has a fairly flat field but could do with speeding up a bit for when I fancy taking some pics. It will be interesting to see how they do with this scope.

The 0.6 also works very well with RC scope by the way

Do you know how well matched the 0.6 is with the ED100 f/9? The FoV would then be similar to ED80 with the matched 0.85x reducer, but faster.

ED80 with 0.85x = 510mm FL, f/6.375

ED100 with 0.6x = 540mm FL, f/5.4

[iwols]

daft question but do these improved speeds have the same effect with the dedicated  atik ccd cameras

[ecuador]

6 hours ago, Bagnaj97 said:

Do you know how well matched the 0.6 is with the ED100 f/9? The FoV would then be similar to ED80 with the matched 0.85x reducer, but faster.

ED80 with 0.85x = 510mm FL, f/6.375

ED100 with 0.6x = 540mm FL, f/5.4

I haven't tried the 0.6x personally, but from what I read, if you have a largish sensor like a crop DSLR, then the vignetting will be severe. Also I wouldn't expect a sharp field far from the center. For small sensors though it might work.

[ultranova]

7 hours ago, iwols said:

daft question but do these improved speeds have the same effect with the dedicated  atik ccd cameras

The faster F ratio would effect any image capturing medium, film / digital

If you were taking photos of a given exposure time of say 6 minutes with a F7.5

with a quicker system, say f6.25 you would get roughly the same image brightness

with 5 minutes, at f5 four minutes ,  these are only rough estimates for the explanation

and not actual figures.

 

[ecuador]

2 hours ago, ultranova said:

The faster F ratio would effect any image capturing medium, film / digital

If you were taking photos of a given exposure time of say 6 minutes with a F7.5

with a quicker system, say f6.25 you would get roughly the same image brightness

with 5 minutes, at f5 four minutes ,  these are only rough estimates for the explanation

and not actual figures.

 

Actually the f-ratio is logarithmic. In your example, if you need a 6 minute exposure at f/7.5 for a specific signal/pixel value, you only need 4.16 minutes at f/6.25, or, if you use the 0.8x reducer to go to f/6, just 3.84 minutes. You get the same light concentrated on a smaller, so more signal/pixel, less object size in pixels. 

Oh, and f/5 would be 2.66 minutes - f/5 is more than twice as fast as f/7.5