Askar 65PHQ Reducer? Does it degrade stars? - Forums

Topic starter

Dec 19, 2023

Hi all. Im considering the Askar FRA300Pro or, preferably due to FOV, the Askar 65PHQ. Obviously if the 0.75 reducer does not degrade stars on the 65PHQ then its a no brainer. I can have the best of both worlds in terms of FL. I know it requires 55mm back focus when used I can live with that.

Has anyone had anyone had any experience with the reducer for the 65PHQ good or bad? Ill be using it with a 533mc Pro for now then on a 2600mcPro

Mark Twyman

Dec 19, 2023

I use the Askar 65 PHQ with and without the reducer. I have notice some slight aberration with the reducer, primarily out towards the edge of the frame. More noticeable with my 2600mcPro than it was with the 533 (I've used both). Nothing that can't be handled in post with PixInsight and Photoshop, but still. It may be a case where I have a little too much back focus. Once I can get my rig setup again, determining what's going on with that is job # 1

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Coolhandjo

Topic starter

Dec 19, 2023

I use the Askar 65 PHQ with and without the reducer. I have notice some slight aberration with the reducer, primarily out towards the edge of the frame. More noticeable with my 2600mcPro than it was with the 533 (I've used both). Nothing that can't be handled in post with PixInsight and Photoshop, but still. It may be a case where I have a little too much back focus. Once I can get my rig setup again, determining what's going on with that is job # 1

*** thanks. Yeah I figured it might be on the edges. Thanks for responding and be good to see if you can sort it out with spacing ***

Gilmour Dickson

Dec 19, 2023 · Edited: Dec 19, 2023

I have a ZWO FF65, so the exact same scope. With my 533mc the reducer is totally fine. But with my full frame Canons it is very poor in the corners. But I do need to play with backspacing which I haven't bothered to yet. My latest image on here of the Rosette nebula was with the 533 and reducer.

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Coolhandjo

Topic starter

Dec 19, 2023

Gilmour Dickson:
I have a ZWO FF65, so the exact same scope. With my 533mc the reducer is totally fine. But with my full frame Canons it is very poor in the corners. But I do need to play with backspacing which I haven't bothered to yet. My latest image on here of the Rosette nebula was with the 533 and reducer.

*** Thnaks. your rosette looks great. ***

Alex Nicholas

Dec 19, 2023

reducers and correctors will always degrade star performance, however, the 65PHQ has better star performance than the FRA300. I'd say with the reducer, the 65PHQ would still beat out the FRA300 for start tightness.

I use my 65PHQ at the native focal length and could not be happier with the results I get from it… I do however wish sometimes that it was either a little shorter, or a little longer… Sounds like I need a Redcat 51 and a 130PHQ ;)

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Mark Twyman

Dec 20, 2023

Alex Nicholas:
reducers and correctors will always degrade star performance, however, the 65PHQ has better star performance than the FRA300. I'd say with the reducer, the 65PHQ would still beat out the FRA300 for start tightness.

I use my 65PHQ at the native focal length and could not be happier with the results I get from it... I do however wish sometimes that it was either a little shorter, or a little longer... Sounds like I need a Redcat 51 and a 130PHQ ;)

*** I just wish it was a little bit faster at the native focal length. It's not terribly slow, for the quality of image you get ***

Alex Nicholas

Dec 20, 2023

Alex Nicholas:
reducers and correctors will always degrade star performance, however, the 65PHQ has better star performance than the FRA300. I'd say with the reducer, the 65PHQ would still beat out the FRA300 for start tightness.

I use my 65PHQ at the native focal length and could not be happier with the results I get from it... I do however wish sometimes that it was either a little shorter, or a little longer... Sounds like I need a Redcat 51 and a 130PHQ ;)

*** I just wish it was a little bit faster at the native focal length. It's not terribly slow, for the quality of image you get ***

Yeah, I agree... If we could have the same optical quality at F/5.6, it would be awesome.

Its always the way though, the faster the optics are, the lower the tolerance for any type of flaws... I also have a Sharpstar 15028HNT... 6" F/2.8 newtonian... When the collimation is PERFECT, and the seeing is PERFECT, and there is 0 tilt in the imaging train, and the focus is 100% spot on, that thing is incredible... The issue is that if ANY of those things are out by a tiny fraction, the images tend to look like mud...

My current setup is basically, I shoot narrowband from home with the 6" f/2.8, and when I go to dark skies, I'll shoot Lum through the F/2.8, and RGB data with a OSC camera on the 65PHQ on the same mount. That way I can get 6hrs of lum in and 6hrs of colour in 6hrs!

The 6" is a 420mm F/L, and the 65PHQ is a 416mm, both my cameras are IMX294, so its trivial to blend them together in pixinsight... I do want to do a comparison of getting say, 10hrs straight OSC with the 6" vs getting 10hrs L @ f/2.8 and 10hrs of OSC at f/6.4 and see if there's a benefit.. I think there is... but I've never done it on one target over 4 nights...

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Stephan Linhart

Dec 20, 2023 · Edited: Dec 20, 2023

Alex Nicholas:
reducers and correctors will always degrade star performance, however, the 65PHQ has better star performance than the FRA300. I'd say with the reducer, the 65PHQ would still beat out the FRA300 for start tightness.

From reading the replies in this thread, I doubt PHQ65 + Reducer performance is on par with the FRA300.
I only have the FRA300, so I do not have any experience with the PHQ.

However, the FRA300 provides me with a basically perfect star field with an ASI2600MC and ASI2400MC (Full Frame) camera.
And I honestly I don´t know how much tighter the stars can get, as I already have to drizzle the data to avoid blocky stars.

I would recommend you the scope with the native FL you desire, both scopes are great. Focal reducers often limit performance with medium to larger sensors and can come with tedious backspacing, and even worse, possibly tilting alignment.

Been down that route, no fun ;)

Best regrads,

Stephan

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tjm8874

Dec 20, 2023

I have both FRA300 and 65PHQ(and reducer), compared at full frame edge. x6 magnification.
You can see fat star on 65PHQ.

Quality : FRA300 >> 65PHQ
Versatility : 65PHQ (312mm and 416mm) > FRA300
Price : almost same

<- 6200MM 6200MC ->

Sean Mc

Dec 20, 2023

But at native fl, the phq is near perfect. It’s also petzval. The reducer ruins both if those things.

Coolhandjo

Topic starter

Dec 20, 2023

I have both FRA300 and 65PHQ(and reducer), compared at full frame edge. x6 magnification.
You can see fat star on 65PHQ.

Quality : FRA300 >> 65PHQ
Versatility : 65PHQ (312mm and 416mm) > FRA300
Price : almost same

<- 6200MM 6200MC ->

***Thanks! Is that with a reducer for the 65PHQ? or is this image without? ***

tjm8874

Dec 20, 2023

Coolhandjo:
***Thanks! Is that with a reducer for the 65PHQ? or is this image without? ***

With reducer.

in this case I took Ha+L on FRA300, RGB on 65PHQ+Reducer (so final quality follows FRA300).

Alex Nicholas

Dec 21, 2023

Coolhandjo:
***Thanks! Is that with a reducer for the 65PHQ? or is this image without? ***

With reducer.

in this case I took Ha+L on FRA300, RGB on 65PHQ+Reducer (so final quality follows FRA300).

Kind of moot if you were shooting through the Ha filter the FRA and OSC on the PHQ... even a mono Lum vs an OSC will show variance.
Same mount? seeing? guiding quality etc? focus 100% correct for both etc.

Not saying you're wrong, just that the evidence is anecdotal at best...

I put the 65PHQ optically as VERY similar to the Tak FSQ85 I used to own - except the Tak f/3.9 reducer was flawless! (but that reducer cost more than the 65PHQ)...

Either way - I think the best course of action is to always get a scope where the native, corrected focal length is the focal length you want... I have never had fantastic experiences using external correctors/reducers.. Petzval refractors, for me, have always yielded the best results... Followed closely by quality coma corrected newtonians (where the corrector is designed for the scope).

If you're buying a 400mm F/L scope, because with a reducer, it can run at 300mm and that's what you want - go and get a 300mm F/L scope...

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tjm8874

Dec 21, 2023

Alex Nicholas:
Kind of moot if you were shooting through the Ha filter the FRA and OSC on the PHQ... even a mono Lum vs an OSC will show variance.
Same mount? seeing? guiding quality etc? focus 100% correct for both etc.

I used FRA300/6200MM + 65PHQ(Reducer)/6200MC for this photo,

https://astrob.in/7t30rp/0/

StarAlignment (with distortion correction) can align images from different scopes.

Coolhandjo

Topic starter

Dec 21, 2023

Alex Nicholas:
Kind of moot if you were shooting through the Ha filter the FRA and OSC on the PHQ... even a mono Lum vs an OSC will show variance.
Same mount? seeing? guiding quality etc? focus 100% correct for both etc.

I used FRA300/6200MM + 65PHQ(Reducer)/6200MC for this photo,

https://astrob.in/7t30rp/0/

StarAlignment (with distortion correction) can align images from different scopes.

*** Thanks - nice image. The blue halos is what im trying to determine. Would the Fr300 give the blue halos as much as the PHQ in your opinion?***

tjm8874

Dec 21, 2023

Coolhandjo:
*** Thanks - nice image. The blue halos is what im trying to determine. Would the Fr300 give the blue halos as much as the PHQ in your opinion?***

The blue halos are mainly caused by heavy Ha / L processing but 65PHQ+Reducer can cause more blue halos than FRA300.

https://astrob.in/0kg0ux/0/

This is FRA300 only, sharper than 65PHQ+Reducer.

Your target FL = 300mm -> go to FRA300.
you are not sure between 300-400mm range -> go to 65PHQ. very sharp on 416mm.
If what you really want is actually 450mm -> you should go 80PHQ+Reducer. that is incredible.