Help me choose: Tak FSQ-85 or RASA8

[TakMan]

May we see a pre-BlurXT Ollie - the RASA is also under consideration in cloudy Lichfield with a OSC !

Damian

Edited February 13 by TakMan

[GalaxyGael]

4 hours ago, Icesheet said:

Thanks for the informative, detailed reply. I guess my main interests at this focal length are nebulae, both in broadband and with a dual narrowband filter, and the dark dusty nebulae that have become more popular recently. As I write that, it’s  obvious I should prioritise signal over everything else. Especially, since I’m rarely collecting more than 4-6 hours on one target. Also, I notice I’m pushing my images too far when processing. The remedy to that is likely more integration time or something that collects signal faster. 
 

Interesting comments on the Tak star shapes. I was aware of the reverse lighthouse effect and it’s not something that bothers me in terms of an aberration or artefact (halos are my pet peeve). Hadn’t heard about cats eye bokeh though. Had a look online and see its inherent of the Petzval design. Is that what the new flattener was/is trying to correct?
 

I’m curious to hear of the other refractors that operate at f4.8 that you think are better than the FSQ-85. And those designed like the AP 110? (I’m in that lottery!).

 

I’ve learned that I’ll likely be a OSC man with dual narrowband filters. Tried the mono route and had so many unfinished images. I’ve also learned that weight and complexity of set up hinder me. Had an EQ6R and could never be bothered to take it out. Now have a Rainbow RST and with the Askar FRA400 I’ve never been so productive, albeit I feel I’m lacking something in my images.  

The comments here are largely pro RASA, or fast reflector of sorts. I think my main worry is that if the set up ends up being a nuisance I’ll give up. However, won’t know until I try. I think I’ll probably just sit on this until later in the year as come April the night will already be short. That gives me a chance to keep an eye on the market for a deal. 

 

 

Well, if nebulae and dust regions in wide to medium field are of interest, signal is key, and the case in particular for osc. 

Tak epsilons are among the easiest newts to collimate IMO and like Rasa, retain collimation long term. They are also almost impervious to temperature focus drift. My experience is with the steel tube epsilons, remarkable flat line hfr values all night long.

Any scope at f6 will reduce with 0.8x flattener to f4.8, whether 90mm f6 or the wide range of excellent 80mm f6 scopes.

Your fra400 can also be reduced to f3.9, just under 300 mm focal length and corrects out to aps c sensor size. Fast and wide, big chunky of sky. And it is smaller than the Rasa, so consider whether you lug it in and out for sessions, if that's matters to you. Unless the fov is a concern, can't see much better options than a reduced fra400 you already have really, apart from the f3.9 fsq85 with new reducer, but it's a big outlay for something very similar.

The TS 110flat f/4.8 is big and expensive, but slower than a reducer on your fra400, which might be the best option to see if wide field and speed is something that gives you the improvement you are testing the waters for?

The new reducer does t fix the aperture vignetting of inverse lighthouse beams on fsq85, nothing can formally as it's part and parcel of the optical design. It just shows more when reduced with modern sensors, but mitigated for narrow bandpass (3-5nm) NB imaging. The new 3 or 5 nm dual band filters might be good there if the star shapes matter, personal taste.

[Icesheet]

14 hours ago, GalaxyGael said:

Well, if nebulae and dust regions in wide to medium field are of interest, signal is key, and the case in particular for osc. 

Tak epsilons are among the easiest newts to collimate IMO and like Rasa, retain collimation long term. They are also almost impervious to temperature focus drift. My experience is with the steel tube epsilons, remarkable flat line hfr values all night long.

Any scope at f6 will reduce with 0.8x flattener to f4.8, whether 90mm f6 or the wide range of excellent 80mm f6 scopes.

Your fra400 can also be reduced to f3.9, just under 300 mm focal length and corrects out to aps c sensor size. Fast and wide, big chunky of sky. And it is smaller than the Rasa, so consider whether you lug it in and out for sessions, if that's matters to you. Unless the fov is a concern, can't see much better options than a reduced fra400 you already have really, apart from the f3.9 fsq85 with new reducer, but it's a big outlay for something very similar.

The TS 110flat f/4.8 is big and expensive, but slower than a reducer on your fra400, which might be the best option to see if wide field and speed is something that gives you the improvement you are testing the waters for?

The new reducer does t fix the aperture vignetting of inverse lighthouse beams on fsq85, nothing can formally as it's part and parcel of the optical design. It just shows more when reduced with modern sensors, but mitigated for narrow bandpass (3-5nm) NB imaging. The new 3 or 5 nm dual band filters might be good there if the star shapes matter, personal taste.

Ah, ok. Misunderstood you. I thought you meant there were native flat field f4.8 scopes. That TS110 looks interesting though if it corrects as well as it says. No, the reducer on the FRA doesn’t interest me. Although the stars are round, it bloats them even further so I’ll likely get an even softer image. I get this should be less of an issue than longer focal length galaxy type imaging but I see it and it bugs me 😆 So, if I’m staying refractor I would like something that has tighter, sharper stars. 
 

I think, I’m just about settled that a fast reflector is what will give me the results I want. Weight is a consideration for sure and I think the RASA is the upper limit. Worst case is two trips out but it’s literally just outside my door so should be fine. 

Edited February 14 by Icesheet