Focal Reducer - Should I or Should I not?

[Oldtimer (Alex)]

I've pulled the trigger on an ASKAR FRA 400 F/5.6 72mm refractor and I'm unsure as to whether I should lash out and invest in a focal reducer.
ASKAR has a 0.7X flattener/reducer which shortens the focal length from 400mm to 280mm and the focal ratio from f/5.6 to f/3.9 which retails for over $400.

Am I going to gain much by going down this path? Most of my imaging is carried out from my Bortle 6 - 7 backyard in Brisbane and I normally shoot with a guided ASI533 MC Pro cooled camera and an Optolong L Extreme dual band filter.


Comments/suggestions please.

[iborg (Philip)]

Hi


I don't really have a good answer, but, consider the angular size of the objects you wish to image.


You will get larger objects in a single frame with the focal reducer. It may save having to do mosaics.


Philip

[Bassnut (Fred)]

I recently got an ASKAR 500, and straight away the FR, gives soo many options !, havent used it yet but cant wait.
The ASI533 MC Pro doesn't have a huge sensor, so the extra FOV with the FR would be useful.

[bojan]

Maybe for that money ($400.00) you can buy a decent second hand 300 mm lens?
I don't know about the FR you are looking into, but my Celestron 0.63 (for C11.. yes, I am aware this is completely different animal, but still...) gave me some considerable headaches.. and I am still not 100% happy with its performance, but at least the cost involved was only $140.00

[AdamJL]

Not for that f/l personally. It really depends on what you want to shoot, but 400mm is plenty wide and you can build mosaics in the meanwhile if you want to shoot "wider" with the added benefit of having more pixels in the final image.

[BlakPhoenix (Rohan)]

There's two things to consider. Firstly is the FoV you get, 280 is very wide, but can create some beautiful views of the larger nebulae, or group multiple objects together into a single image. Of course, you do sacrifice resolution/detail since you have the wider FoV.



I would argue the bigger consideration is the increase in imaging speed you get. F/3.9 is a full stop faster than F/5.6, this means that 1 hour of imaging at f/3.9 is the same as imaging for 2 hours at F/5.6. I would argue that time is our biggest limitation with this hobby, and this allows you to either double the effective integration time of your images, or image twice as many objects in the same time.

[gregbradley]

My experience is reducers tend to be problematic and fussy. Fussy to spacing, fussy to tilt.

ASI533 has tiny pixels. At 280mm I think it is likely to exaggerate any tilt or spacing inaccuracy and be a pain.

But its only $400 so not a lot to risk. Typically high end reducers are more like $2,000-$3000 but that's for full frame.

For $400 its probably worth a shot but be prepared to chuck it.

Greg.

[Crater101 (Warren)]

I went through the same thought process with my Flourostar 91 a while back. I ended up going with the flattener rather than the reducer to maintain the focal length. However, while there's a lot out there about changes that happen with the reducer, there isn't a lot at all about using the flattener. I had endless issues establishing backfocus, and ended up sending an e-mail to William Optics for the answers. They were quite helpful. But I digress.

My point is that sometimes it's not just fitting the reducer or flattener. Do the research and make sure that you can integrate it easily into your imaging train. I wouldn't wish the little niggles I had on anyone.

[SeanB (Sean)]

I picked up a Meade reducer that I use on my 8SE. Allows me me to get ½° (Moon) without having to stitch images. Using a full frame Nikon D810.
If you can get a reasonable reducer at a reasonable price that then grab it. (I got. Mine at a garage sale and the seller had no Ide what she had, I offered $100 but she only took $20)

[bojan]

I have the same thing (?), see thread below:
https://www.iceinspace.com.au/forum/...ighlight=Meade
Not bad, but it would've be better if it cost me $29 :-)