Is a top notch APO really needed if using mono camera?

[ONIKKINEN]

11 hours ago, GTom said:

Paired with a 533mm, maybe even 294mm camera, that should be a great scope. Would not go much larger with sensors though.

This is a decent way to treat slower newtonians too. Mine is f/4.4 natively and a bit over f/5 with a paracorr and its not easy to get good stars corner to corner. However if i crop to a micro 4/3 sensor size (294,1600MM) then in 95% of the cases images are great corner to corner.

Newtonian + APS-C is quite demanding i would say. That is if one is a pixel peeper, if not then its workable for sure.

[GTom]

I pulled back last minute from a TS Photon 10" deal: my cameras are APSC and larger: the suggested GPU corrector vignettes 30%+ already on a 4/3 size sensor. That's still manageable with flats but gets useless quickly with anything larger. Upgrade would mean a 3"focuser AND a 3" corrector, each individually(!) costs around the same as the 10" Newtonian! Total cost would be near the price of a 140mm APO and we haven't even asked for a collimation-stable carbon tubing.

7 hours ago, Clarkey said:

Interesting that it quotes 'suitable for APS-C' but also says a 21.7mm image circle. Slight contradiction in my book. But I agree that larger sensors will not be good. I actually considered one of these for imaging but was put off by the small imaging circle (to pair with an IMX571). I do have a 150mm TS Photon F4 which I pair up with a 1600MM pro. I would certainly advise against this scope as it needs too many modifications to be acceptable for imaging - not least a new focuser.

 

26 minutes ago, ONIKKINEN said:

This is a decent way to treat slower newtonians too. Mine is f/4.4 natively and a bit over f/5 with a paracorr and its not easy to get good stars corner to corner. However if i crop to a micro 4/3 sensor size (294,1600MM) then in 95% of the cases images are great corner to corner.

Newtonian + APS-C is quite demanding i would say. That is if one is a pixel peeper, if not then its workable for sure.

 

[ONIKKINEN]

1 minute ago, GTom said:

I pulled back last minute from a TS Photon 10" deal: my cameras are APSC and larger: the suggested GPU corrector vignettes 30%+ already on a 4/3 size sensor. That's still manageable with flats but gets useless quickly with anything larger. Upgrade would mean a 3"focuser AND a 3" corrector, each individually(!) costs around the same as the 10" Newtonian! Total cost would be near the price of a 140mm APO and we haven't even asked for a collimation-stable carbon tubing.

 

 

My secondary is undersized so vignettes maybe 20% at 1x, but actually the paracorr makes this much better with its 1.15x barlow so there is less vignetting than native (reducers vignette more, extenders less).

Just some food for thought. The paracorr is more expensive though so always a compromise around the corner.

[Robert7980]

Optics matter the same regardless if you’re mono or OSC, there’s simply no substitute for premium optics. Refocus per filter can help disguise CA, but the overall quality is just far superior with superb optics. My Esprit 120ED absolutely destroys the performance of my budget triplet with FPL51 glass even though it has no CA, that’s with filter offsets in mono. The question is when is good enough good enough and the cost starts to outweigh the benefits. So there’s much more to it than just CA.