Is it worth spending 135 pounds on a reducer/flattener for imaging?

[Chris]

Hi folks,

I'm imaging with a WO zs66 on a mk1 HEQ5, and I'm wondering if its worth getting a 0.8 reducer/flattener? (135 quid from FLO). I think this would change my scope form f/5.9 to 4.7 which I know would make it more efficient at grasping light but is it a little difference in practice or a lot of difference? Or is there anything else I should be spending 135 pounds on to improve my imaging setup?

Also if I bought a reducer is there any other adaptors I need for this?, I ready have the t-ring and t-adaptor.

Any advice greatly appreciated,

Chris

[steppenwolf]

It is nice that you get an increase in light grasp (at the cost of a wider field of view) but what you are mainly buying into to flattening of the field which means better star shapes at the periphery of the frame and that is what is worth the money.

[Chris]

Thanks steve for the your advice:) I might leave it for now as I've got quite a good field of view as it stands, so much so that I've had to crop my images to some extent so far, I therefore would be paying to crop out rounder stars. I guess if I start imaging more wide field objects a flattener would be great to have. I see that you can buy an Antares 0.5 reducer (without flattener) from SnS for 25 quid on offer, so I could get one of these just to have a play with having a diferent f/ratio and FOV, but would the extra signal gained from a lower f/ratio outweigh the extra loss of resolution from having to crop the image more because of the increased FOV? I guess its 6 of one and half a dozen of the other:)

[paulk]

Surely you can sort out distortion in pp like you can with camera lenses?

[brantuk]

Steves advice is amongst the best you'll ever get - ignore at your peril lol

If you want to start cheap then either look for a flatener s/h or try the SW one for around £50. It works well in the fl=600 to fl=800 range. It made a vast improvment to my Meg72

[Psychobilly]

Surely you can sort out distortion in pp like you can with camera lenses?

Yes you can... using the lens correction tools can help with distortion and vignetting...

[Chris]

You probably can paul, it amazes me what people do in post processing:), I'm not too worried about the flattener at the moment though as I tend to crop my images anyway, I'm now trying to work out if a reducer on its own is worth having as these are quite cheap, i.e does the extra light grasp/signal produced by reducing focal length outweigh the loss of resolution caused by having to crop images more because of the increased FOV? in a nutshell will I get better quality images with a reducer in peoples opinion?

[jgs001]

I frequently use the lens correction tool to deal with the coma my 80ED produces around the edges... works a treat... I think if you can afford one, then go for it... you'll not have to mess so much in processing with the edges, the lens correction does lose some of the FOV. You'll also need shorter exposure times for the equivalent exposure level, as the imaging system is faster.

[Chris]

I wouldn't dream of ignoring Steves advice Bruntak:D I know you guys have way more experience with the imaging side of Astronomy than me:) a totally see that for wide field images a flattener would make a lot of difference, I'm basically trying to justify 135 pound for this item, and I can't because I've cropped all my images so far, not becasue of distorted stars (which I do have) but in order to increase the apparent size of the object I'm imaging. However, Bruntak, I'm VERY interested in this SW one for 50 quid, I certainly could justify that easier (please keep in mind I have to run all Astronomy pruchases past my wife ).

You say its worked wonders for your Megrez, Do they have then at FLO, I'll have a quick look:D

Cheers, Chris

[brantuk]

Hi Chris - all tongue in cheek buddy to make you smile lol. Yes FLO do stock it :

First Light Optics - Skywatcher Field Flattener

But it may have gone up a little since I got mine. Not the best but it works and can be sold of when you go up to the dearer one to offset the cost.

Here's a pic taken with the Meg using the flatener - eight 10 min subs with 30 flats and 30 bias guided on CG5GT - hope that helps.

[Chris]

Thanks John, I might be tempted by the skywatcher flattener, I'll check it out, but its good to know that I can sort out coma a fair amount using software:) I would like a faster system, as I'm working with fairly short subs, I'm not going to guide untill I've sorted out somekind of cheap shed-obsy to keep the kit needed in, so increased light grasp and FOV might keep me happy in the mean time:D

[Chris]

Know worries Bruntak I'm with you on the banter:D Thanks for the link it might be a good compromise, I'll let you know what I think:)

Cheers,

Chris

[Chris]

Right I see, the SW flattener has no reducing properties, so my scope would stay at f/5.9 however if I just wanted a flattener this would be a great choice as it is optimised for f/5.5 - 6 scopes. One reviewer said that they swapped a reducer/flattener for just the flattener because they found that the reducer made the scopes performance incredibly sensitive to having perfect focus? not quite sure if this is a common complaint?, if so its a bit off putting:( The SW flattener would be cool if there are many objects that benefit from my existing wide FOV, that you can image with 60 second'ish subs?

Does anyone have any experience with a reducer on its own like the one below?:

Astro Engineering Astro Engineering 1.25" focal reducer 0.6x (AC763)

Regards Chris:)

[Demonperformer]

I have (or had ... not sure if it is still in the box somewhere or if I sold it ... that should tell you something) a 0.5x focal reducer. I found the results to be less than inspiring, but that could just be me ...

[Chris]

Hi Demonperformer, I think that tells me all I need:) I guess you get what you pay for, so I might go for the 135 quid one from flow plus a Bahtinov mask, especially as I got 80 pounds more in my wages this month:D

[Demonperformer]

A quick tip ... don't buy a bahtinov mask, make a simple 'Y-mask' which is exactly like it sounds - three strips of black card, joined together in a 'Y' shape. Then some means of securing it to the front end of the scope/dewshield. You get the same diffraction spikes, use the same procedure of exactly bisecting the 'X' spikes, but as there is much less obstruction the image is a lot brighter. Cheaper and easier to use ... what more could you ask?

[Chris]

Hey Bruntak, yep thats a pretty flat image with nice round stars, definately worth 50 quid:) I take it with all that nebulosity you used your mod'd camera? You've got more stars than empty space as well:D

[Chris]

Hi DP:) I've only just read your message about the Y-mask, sounds great I'm going to make one despite just getting a Bahtinov mask cheap from the Astroboot.

I've also bit the bullet and just ordered the 0.8 reducer/flattener form FLO, thanks to everyone for their advice:)

Cheers,

Chris

[brantuk]

Yup - it was with my mod'ed 350P - not by me though unfortunately - but by a mate who was mentoring me

[Chris]

Cool, I've just picked up a mod'ed 350D, looking forward to giving it a whirl, might even have the 0.8 reducer/flattener by then. I'm quite excited about the prospect of imaging at f/4.7 with a flat field, less vignetting, sharper images (with the Bahtinov) and with a mod'ed camera, hopefully all this kit will help me to move up a level image wise:)