150pds question.

[Andy R]

Hi

just recently acquired a used 150pds and just researching Coma Correctors for it, just a quick question if a CC is essential for imaging with a micro 4/3 sensor size. I’ll be using FF and APS-C Sensors too but mostly 4/3. Just curious from reviews I’ve been reading on certain CC’s

Andy

[ONIKKINEN]

Depends on how much you tolerate coma, which there will be a noticeable amount even quite close to the center at F5. I would definitely look into it, but take a few shots and decide whether or not it bothers you?  For very small targets where you crop most of the image away, like planetary will be mostly unaffected.

 

The full frame camera will have extreme vignetting with the 50mm secondary mirror of the 150PDS at F5 to the point of probably not being worth the effort. The APS-C will have vignetting too, but taking flats will deal with this quite well.

[Andy R]

40 minutes ago, ONIKKINEN said:

Depends on how much you tolerate coma, which there will be a noticeable amount even quite close to the center at F5. I would definitely look into it, but take a few shots and decide whether or not it bothers you?  For very small targets where you crop most of the image away, like planetary will be mostly unaffected.

 

The full frame camera will have extreme vignetting with the 50mm secondary mirror of the 150PDS at F5 to the point of probably not being worth the effort. The APS-C will have vignetting too, but taking flats will deal with this quite well.

Oh yes it would definitely bother me, Ive just read through reviews on different cc’s and they seemed to be varied in opinion (like most things). I will no doubt take the plunge but the baader mk3 is out of stock so was thinking stellalyra 2”.  

[ONIKKINEN]

I have this one: https://www.firstlightoptics.com/coma-correctors/ts-95x-maxfield-coma-corrector.html

This one does not quite fully correct coma/curvature on my F4.5, but i would be lying if i said it bothers me. From what i can tell most people would recommend the TSGPU, Explore scientific HR or the skywatcher aplanatic for well corrected fields. The stellalyra 2 inch is quite a bit cheaper than all of these, but i know nothing of the product (nor could i find much really) so not really able to comment on that.

Another thing you should think about is the length of the corrector. If it is long enough to obstruct your focuser you will have an extra diffraction spike, or at least some extra diffraction artifacts. The 0.95 maxfield (sold as both TS and sharpstar, same product) is shorter than most so it probably doesn't obstruct as much, if at all. The stellalyra looks pretty short too, so probably not an issue here.

[alacant]

33 minutes ago, ONIKKINEN said:

stellalyra 2 inch

Hi

It's the GSO. The only issue is that of its focus position, which is around 5cm further away from the tube as compared to the position without a cc. Great for the 150p, quite a turning force on a 150pds. 

HTH

[Andy R]

50 minutes ago, ONIKKINEN said:

I have this one: https://www.firstlightoptics.com/coma-correctors/ts-95x-maxfield-coma-corrector.html

This one does not quite fully correct coma/curvature on my F4.5, but i would be lying if i said it bothers me. From what i can tell most people would recommend the TSGPU, Explore scientific HR or the skywatcher aplanatic for well corrected fields. The stellalyra 2 inch is quite a bit cheaper than all of these, but i know nothing of the product (nor could i find much really) so not really able to comment on that.

Another thing you should think about is the length of the corrector. If it is long enough to obstruct your focuser you will have an extra diffraction spike, or at least some extra diffraction artifacts. The 0.95 maxfield (sold as both TS and sharpstar, same product) is shorter than most so it probably doesn't obstruct as much, if at all. The stellalyra looks pretty short too, so probably not an issue here.

indeed there is very little info on the Stella CC, even FLO said it hasn’t been tested on the 150pds. 
Yes the Ts option, it does tick the boxes, and keeps close to native focal length of scope, x0.8 is too much reduction tbh. I wasn’t keen on spending £250 or so on a CC but £189 seems reasonable plus only 10-15 day wait.

Thanks very much for your input. 
Andy

[Andy R]

26 minutes ago, alacant said:

Hi

It's the GSO. The only issue is that of its focus position, which is around 5cm further away from the tube as compared to the position without a cc. Great for the 150p, quite a turning force on a 150pds. 

HTH

What do you use on the 130pds al?

[barbulo]

What about the Sky-Watcher CC? Designed for same brand newts.

I went for the MPCC though, mainly for its slightly lower price. I read a lot of analysis and comparisons and those two were the candidates for a reasonable price. 

[alacant]

1 hour ago, Andy R said:

use on the 130pds

The GPU.

[Andy R]

2 hours ago, barbulo said:

What about the Sky-Watcher CC? Designed for same brand newts.

I went for the MPCC though, mainly for its slightly lower price. I read a lot of analysis and comparisons and those two were the candidates for a reasonable price. 

Ive read a few mixed reviews about them and having to shorten the focuser tube due to misshaped stars, sort of put me off them. 

Edited October 9, 2021 by Andy R
Autocorrected wrong wird

[alacant]

11 hours ago, Andy R said:

having to shorten the focuser tube

Hi

If you don't want to shorten either the focuser or the main telescope tube then perhaps best to go with the GSO. Specify Europoean shipping at the checkout.

Cheers

[Andy R]

4 hours ago, alacant said:

Hi

If you don't want to shorten either the focuser or the main telescope tube then perhaps best to go with the GSO. Specify Europoean shipping at the checkout.

Cheers

Having slept on it overnight I’ll ask the former owner if it’s been modified, I’ve had a look and Im not quite sure as I have no comparison. 
 

thanks

Andy