Best ( cost effective !! ) field flattener for 80mm f5 refractor ??

[Craney]

Hello there,

I am a new member to these shores and although have studied the stars for many years  I  have only recently dipped my toe into some  low grade semi-serious astro-photography.

Mainly because the modern equipment is so much more productive than the wobbly scope and tank like Practika film camera I had 30 years ago.

I have a SW HEQ5 and recently bought an Opticstar AR80mm Gold  f5 (400mmFL) refractor. I took this picture of NGC 7000. I have noticed a bit of distortion on the top left of the image.  ( The image has been cropped a bit to centralise the nebula, but you can see the effect).

Is there an easy solution.  Could anybody recommend a cheapish device that could correct this.  

I have seen a SW field flattener at FLO

https://www.firstlightoptics.com/reducersflatteners/skywatcher-field-flattener.html

Would this work ?  (even though it is recommended f5.5 and above).

Malcolm at FLO suggested the Hotech device would be the better version, but it is over twice the price.

I was wondering if any experienced "short" refractor buffs could point me in the right direction.

Cheers,

 

Sean.

 

[ChrisLX200]

Because neither optic was designed to match your scope I doubt you would see complete correction with either flattener, you would in any case have to 'tune' the position of your camera (distance from the flattener) for best effect. I would definitely expect a degree of improvement though, I just wouldn't like to say how much!

ChrisH

[parallaxerr]

Agree with Chris. I recently had the same requirement for my WO ZS66 (F5.9), as the original FF is no longer available. I came across a post that suggested the Skywatcher flattener you've linked to won't come to focus with my scope (not to say it won't with yours) and that the Baader Multi-Purpose Coma Corrector (for Newtonian telescopes!) would work, which it does. I see a very small amount of distortion at the extremities but they mostly get cropped out in post processing, if they bother me I'll experiment with flange to sensor spacing, as Chris mentions.

Here's an image I'm working on that was taken with it,