70mm Petzval or 110mm triplet? Generic equipment discussions · Tareq Abdulla · ... · 7 · 328 · 0

Hi all,

I was thinking about buying a combo setup in future and i don't know which one out of two i should go with, one is so expensive while the other is cheaper, it will be like an add to another setup without details about that, so i don't know which one do you prefer to go with if you were in same boat?

1. 70mm Petzval with 350mm focal length, be it a Quadruplet or a Quintuplet, as long it is not a triplet anyway so i don't need to think about a separate flattener [a reducer is an optional], and i will pair it with a color camera i should buy of 294 sensor, so the scope aperture is smaller and also the sensor too and older model or gen of sensor, it will be for only color results of RGB [or dual band if i have to sometimes]

2. 110mm with 660mm focal length, i only saw one from two different brands but they are eventually the same, and this i have to pair it with a full frame mono camera that i don't have, and this is more expensive setup, and it will be used only for either Ha or Lum [not sure if i will use it with a color for RGB or dual band, also an optional idea].

As i mentioned above, one of two above choices will be added to another setup, they can all be used as individual, but it is part of say multiple or array setup i want to do, 2-3 years ago i was thinking too much about it and asked about it, but now i came across the above choices because i am tired of thinking about options, i could go with same setup i already have really, but i thought maybe i should have different setup but almost same FOV so i can have a variety in collection i have, and above two choices are still ideas and options only or just wish plans and not confirmed, i will decide later after i can see and read answers and reply by you.

Thank you

Mark Savan:
I have setups similar to both of the ones that you are considering.  They are both great but I view them as distinctly different in terms of their cost and capabilities.  In my opinion, your option 1 is, by far, the better "bang for your buck."  Depending on the specific hardware that you choose, your option 2 will be 2-3x more expensive than option 1.  I'm not sure if cost is a consideration but even from an ease of use standpoint option 1 will be better.

My suggestion would be to go to a larger sensor for option 1 - perhaps something like the 2600 or another APS-C sensor to take advantage of the larger FOV at 350mm.  I've found my Petzval (RedCat 71) to produce very nice stars all the way to the corners of an APS-C and it has a large enough image circle to illuminate the guide sensor on the 2600MCDuo

Thank you very much for your answer or reply, i was waiting that, so appreciated. 

When i mentioned that it will be an addition to another setup i tried not bring that another setup details, but i think i must mention that other setup so people can help better or answer better then.

The other setup i have is actually 3 setup, two of them are of TS Optics 90mm f/6 FPL55 triplet with 0.8x reducer, and both are paired with Touptek 2600 which is 571 sensor, and i also have a scope of Airy Disk 106mm f/6.6 with 0.92x reducer, I also have third Touptek 2600 i bought it recently, but i didn't use this scope yet and the new camera, so i already have three APS-C cameras and 3 scopes being two of them are identical, i was thinking about buying good 0.6x reducer for 106mm to give me 420mm which is close to the reduced 90mm at 432mm, but i am not sure if i have to buy that camera again as forth option, i can buy either a color or a mono, if color then i will use it with a dual band filter only, if a mono then i can use it either for SII or Lum or whatever but not RGB, so i was thinking about a different scope, 110m is larger than 90mm but close to 106mm so both can be together for tighter targets, while as you said if i buy 70mm then i can use it with APS-C sometimes for wider FOV, i already have 60mm both are doublets, but they are connected to the older cameras of 4/3" [1600mm and qhy163M], and i also have the Askar FRA400, but it is wider than 432mm but less wide than 350mm if i get that, i do have a Canon lens of 300mm.

The point is to match at 420-432mm as much i can, wider than 420 even only 10mm or longer than 432 even only 5mm could be not critical much but it might be easier in processing later, in all cases i was thinking to have either 106mm again or third 90mm triplet, but all 90mm prices are more than before even the one i bought first, i found 96mm and using with their 0.75x reducer will give me exactly same FOV of my two 90mm, and i can buy it and it is affordable and nice price, but 106mm is nicer and great price also, in fact i added 70mm as a cheaper option so i can use the remaining money for something else like accessories or even a small mount affordable, but i have to think about all options to see what is better, i am sure all people will say why don't i use only one setup or two, yes i know, but living under Bortle 8/9 and needing like 50-500 hours per target making to use one setup like a headache mission, in fact even with 3-4 setup i still take time, i don't like to spend like 1 month or 1 year on 3-4 targets for good results, and i really want very nice amazing results from B8/9 rather than just acceptable results, i prefer to spend $5k on additional setup than driving to dark skies, in my country it is very exhausted and not exciting at all, the view isn't worth risk and tiredness.

FRA400 with F/3.9 reducer and ASI294MM camera is a perfect combination when using bin1 or bin2 with drizzle x2. This kind of pixel scale is very near of optical limits. Very sharp astrophotos with 8288 x 5644 resolution!

Of course you get even better astrophotos with 110mm and full frame camera, but this option is much more expensive and far less cost-effective than the first one.

hi

first of all, you might consider the seeing in your location. You can check in astronomy tools site.

Riccardo